Pre-Preg

[Jonathan St. Cloud]

Just wondering why glider are not made with pre-preg. Seems like it would save weight.

[Michael Opitz]

At 21:03 01 December 2016, Jonathan St. Cloud wrote:
>Just wondering why glider are not made with pre-preg. Seems like it
would
>save weight.
>
I think Sparrowhawk and Duck Hawk are pre-preg..

RO

[Tony[_5_]]

Yes the Windward gliders are carbon prepreg.

I guess the other manufacturers aren't that concerned about empty weight and don't want to have to deal with ovens for curing?

[Ron Gleason]

On Thursday, 1 December 2016 14:03:22 UTC-7, Jonathan St. Cloud wrote:
> Just wondering why glider are not made with pre-preg. Seems like it would save weight.

While I cannot speak for the glider manufacturers , I have a friend that designs and builds carbon snow ski's here in Northern Utah. They started using pre-preg but the types of weave, cloth weights and epoxy types are limited. This manufacturer now impregnates their own cloth.

For you snow skiers check out http://www.dpsskis.com/

[Jonathan St. Cloud]

They is exactly why I asked.
On Thursday, December 1, 2016 at 1:30:05 PM UTC-8, Michael Opitz wrote:

> >
> I think Sparrowhawk and Duck Hawk are pre-preg..
>
> RO

[[email protected]]

On Thursday, December 1, 2016 at 4:03:22 PM UTC-5, Jonathan St. Cloud wrote:
> Just wondering why glider are not made with pre-preg. Seems like it would save weight.

Some factors:
1 Molds have to be able to stay stable at curing temperatures and maintain their dimensions over a life of many cycles.
2 In the life of the glider, it will get broken. If the structure can't be repaired in a shop that does not have an autoclave(all the shops that I know of), it likely has to go to the factory for repair.
3 Most of the external structures in our gliders are over built to some degree in order to make them durable enough to live in the real world.
4 Pretty much nobody cares much about weight, except the little gliders. For all the rest we just want to know how much water can we get in it.
5 Prepreg materials obviously have storage requirements that add cost
6 They are generally more expensive and limited in choice of material properties.
7 Hybrid structures commonly used in modern gliders may well be limited by the availability of suitable materials. If you want your tail to stay on in a midair, you'd like to have some Kevlar in your tail boom. Or maybe you'd like some aramid in your cockpit to control where the catastrophically failing carbon goes. Tailoring the progressive failure of a nose is most commonly done with a mix of materials as well as laminating schemes.

FWIW

[Jim White[_3_]]

In Europe there is probability that it has much do with the cost of
certification of a new manufacturing process. Here where the weather is
often cr** people do go for light weight empty.

[Tango Eight]

On Friday, December 2, 2016 at 4:15:15 AM UTC-5, Jim White wrote:
> In Europe there is probability that it has much do with the cost of
> certification of a new manufacturing process. Here where the weather is
> often cr** people do go for light weight empty.

If it's good enough to fly, it's good enough to fly at 7 lbs / sq ft. Otherwise it's a better day for a bicycle, or hiking boots or maybe sitting indoors in the rain annoying the folks on r.a.s.

From the XC performance standpoint, there's little advantage to empty weight very much below 500# in a 15m sailplane. For self launching, well, weight is really important...

-Evan Ludeman / T8

[krasw]

On Friday, 2 December 2016 14:33:01 UTC+2, Tango Eight wrote:
>
> From the XC performance standpoint, there's little advantage to empty weight very much below 500# in a 15m sailplane. For self launching, well, weight is really important...
>
> -Evan Ludeman / T8

With lighter structure and materials you can build smaller wing and still have acceptable min. wing loading. Smaller wing -> higher aspect ratio -> higher performance (Diana-2 for example)?

[Bruce Hoult]

On Friday, December 2, 2016 at 3:33:01 PM UTC+3, Tango Eight wrote:
> On Friday, December 2, 2016 at 4:15:15 AM UTC-5, Jim White wrote:
> > In Europe there is probability that it has much do with the cost of
> > certification of a new manufacturing process. Here where the weather is
> > often cr** people do go for light weight empty.
>
> If it's good enough to fly, it's good enough to fly at 7 lbs / sq ft. Otherwise it's a better day for a bicycle, or hiking boots or maybe sitting indoors in the rain annoying the folks on r.a.s.
>
> From the XC performance standpoint, there's little advantage to empty weight very much below 500# in a 15m sailplane. For self launching, well, weight is really important...
>
> -Evan Ludeman / T8

Most gliders work out at about 6 (30 kg/m^2) dry with a 240 lb pilot, don't they?

[ND]

gliders are cured in an oven at SH anyway. i think it's most probably a cost thing. even though these new gliders are ridiculously expensive at face value, the profit margin the manufacturers are getting is very small, so they keep costs down wherever possible. that's part of the reason schempp-hirth (as well as many others) re-use fuselage designs. take the ventus 2 versus the V2X. you got a performance increase for only a new fin design, new horizontal tailplane, and new winglets.

On Thursday, December 1, 2016 at 5:55:38 PM UTC-5, Tony wrote:
> Yes the Windward gliders are carbon prepreg.
>
> I guess the other manufacturers aren't that concerned about empty weight and don't want to have to deal with ovens for curing?

[Luke Szczepaniak]

>
> Most gliders work out at about 6 (30 kg/m^2) dry with a 240 lb pilot, don't they?
>

An ASW27 would be about 40kg/m^2 with a 240lb pilot weight

L

[Craig Funston]

On Friday, December 2, 2016 at 6:28:43 AM UTC-8, Luke Szczepaniak wrote:
> >
> > Most gliders work out at about 6 (30 kg/m^2) dry with a 240 lb pilot, don't they?
> >
>
> An ASW27 would be about 40kg/m^2 with a 240lb pilot weight
>
> L

Cost and repairability are factors with pre-preg although power aircraft like the Lancair use prepreg extensively. Newer spread-tow pre-pregs are amazingly light and stiff.

From a performance standpoint, span loading is a significant factor. For an equal wing loading and span, the lighter sailplane with the lower span load has lower induced drag. Reynolds numbers also play a factor when the chords get so small, but the aero community seems to be getting better at developing profiles that aren't hurt too much by this.

Cheers,
Craig

[Ross[_3_]]

On Thursday, 1 December 2016 22:03:22 UTC+1, Jonathan St. Cloud wrote:
> Just wondering why glider are not made with pre-preg. Seems like it would save weight.

Having done 10 years working in Formula 1 making the cars solely from Prepreg and then another 6 years in aerospace making a payload fairing for a well know rocket launcher, I can say that the preconceived idea that prepreg is expensive is wrong.
You also don't need an autoclave to cure it

If you were willing to invest just a little money your raw material usage, and you reproduce-ability would increase no end.
Also, you could happily do a post cure on the parts and paint them any colour you like, just like in Formula 1.

[Casey[_2_]]

On Friday, December 2, 2016 at 1:25:16 PM UTC-5, Craig Funston wrote:
> On Friday, December 2, 2016 at 6:28:43 AM UTC-8, Luke Szczepaniak wrote:
> > >
> > > Most gliders work out at about 6 (30 kg/m^2) dry with a 240 lb pilot, don't they?
> > >
> >
> > An ASW27 would be about 40kg/m^2 with a 240lb pilot weight
> >
> > L
>
> Cost and repairability are factors with pre-preg although power aircraft like the Lancair use prepreg extensively. Newer spread-tow pre-pregs are amazingly light and stiff.
>
> From a performance standpoint, span loading is a significant factor. For an equal wing loading and span, the lighter sailplane with the lower span load has lower induced drag. Reynolds numbers also play a factor when the chords get so small, but the aero community seems to be getting better at developing profiles that aren't hurt too much by this.
>
> Cheers,
> Craig

I've heard conflicting sides about pre-preg repairability. Greg said its a misconception and can be repaired fairly easily and I have seen a Sparrowhawk that has been repaired by him.

https://www.youtube.com/watch?v=JYcHDPzx1ao

[Ross[_3_]]

Easy enough to fix if you know what you are doing.
Not quite as easy as wet laminate that the gliders are made of today

[Kevin Brooker]

run of the mill pre-pregs are heavier then a careful wet layup but the pre-pregs allow for a less skilled labor force. When reducing the amount of material, the orientation and wetout become super important. With prepregs the resin/matrix ratios are more predictable and variations in skill are all but eliminated, The shape of the pieces is also more fixes as the resin holds the fibers in place and there is much less distortion. Pre preg is also much faster to construct. If sailplanes were to be wet layup the costs would be in the range of 15-20% more.

[Ross[_3_]]

So what you are saying is that if we all move to pre preg sailplanes we save 15-20%? Why is no one in Europe doing it?
I personally see no reason why a wet laminate would be better or lighter
Based on the square meterage of the material vs the time saved you would probably save a little on prepreg, and open a whole new window of opportunity in other areas.

[Bob Kuykendall]

Here's the key thing: Glider structures are bound more by stiffness than by strength. True, pre-pregs can be much stronger than more conventional laminates. However, they allow only a rather modest premium in stiffness.

Think of it like this: Suppose you have a magical material to make wing spars out of that just as stiff as what we use now, but is is twice as strong. Then you use half as much. The result is that you'd have twice the wing deflection per unit g. Your new wing at 2.5g looks like your old one at 5g. And 4g looks like 8g.

That might work out OK, and it would have a pretty soft ride, but the aero effects can be unpredictable, and it gets pretty hard to make control surfaces that work smoothly while following the curvature of a g-bent wing.

Furthermore (and probably much more importantly), stiffness is much more important than strength when mitigating elasticity. So you'd end up using way more of your magic material than dictated by strength just to get the stiffness up where you need it to have Vne with a usable margin against flutter..

And, as others have already touched on, extra mass often results in a structure that is more resistant to handling, assembly, and operational damage. And gliders aren't much fun unless they are operational.

The full sermon on these topics runs around an hour. If you want the whole thing, come to our 21-27 January 2017 Akaflieg:

https://www.facebook.com/events/335703193452266/

Thanks, Bob K.
https://www.facebook.com/pages/HP-24-Sailplane-Project/200931354951

[J. Nieuwenhuize]

Op zondag 4 december 2016 18:14:46 UTC+1 schreef Bob Kuykendall:
> Here's the key thing: Glider structures are bound more by stiffness than by strength. True, pre-pregs can be much stronger than more conventional laminates. However, they allow only a rather modest premium in stiffness.


Bob,

I don't follow. Assuming one type of fibers, both stiffness and strength are only driven by fiber straightness and fiber volume fraction, so you'd expect both to rise comparably. Obviously, pultrusions and unwoven (UD, BIAX, TRIAX) are better at both.

So aside from moving to unwoven fibers, fiber fraction is the big elephant in the room.

If we compare our typical 200 g/m2 carbon cloth, these are typical weights for the full laminate:
Hand-laminated, 32% fiber volume fraction, 520 g/m2 total areal weight.
Vacuum-bagged; 40% fiber fraction, 415 g/m2 total areal weight.
Infusion/prepregs, 55-60% fiber fraction, 325-300 g/m2 total areal weight.

Getting very light weights with prepregs can be tricky, once you formulate resin fraction approaching or below 40%, the laminate gets very dry. Even with an autoclave and de-bulking in the process, getting voids is a risk. With infusion, as long as you have wet-out you're fine. In practise both are in the 55-60% Vf range.

Prepregs are a no-brainer for small parts. For big parts, it quickly gets prohibitively expensive. Even for modest amounts of fabric (a few hundred square meters/yards), expect to pay hundreds of US$/Euro's per square meter for a typical aerospace qualified combination, like T700 or T1000 plus a qualified resin.

Both also yield extra weight reductions since the adhesive joint to the core is way lighter.

Bottomline, using either technique can spectacularly reduce empty weight and weight reductions up to 1/3rd of the structural weight are possible.

[kirk.stant]

On Friday, December 2, 2016 at 6:48:16 AM UTC-6, Bruce Hoult wrote:
> Most gliders work out at about 6 (30 kg/m^2) dry with a 240 lb pilot, don't they?

My LS6 runs around 8psf (39 kg/m2) dry with me in it (240 on a good day). I would think you would have to get into open class or older std gliders to get as low as 6 psf...

Works great for no-ballast (Beer ballast?) contests...

Kirk
66

[Jonathan St. Cloud]

For the guys with an engine weight does make a difference. Imagine if the 100 pounds of engine and fuel were offset by construction methods that lowered the empty weight of the glider by even 50-70 pounds. YOu would functionally have the same wing loading range as a pure glider.

Just saying.
On Thursday, December 1, 2016 at 4:09:14 PM UTC-8, wrote:
> 4 Pretty much nobody cares much about weight, except the little gliders. For all the rest we just want to know how much water can we get in it.

[Casey[_2_]]

On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud wrote:
> For the guys with an engine weight does make a difference. Imagine if the 100 pounds of engine and fuel were offset by construction methods that lowered the empty weight of the glider by even 50-70 pounds. YOu would functionally have the same wing loading range as a pure glider.
>
> Just saying.
> On Thursday, December 1, 2016 at 4:09:14 PM UTC-8, wrote:
> > 4 Pretty much nobody cares much about weight, except the little gliders.. For all the rest we just want to know how much water can we get in it.

Different building methods in same factory brings several issues I could think of.
Cost of buying and storing different materials, cost of process, possible mistakes in manufacturing, return on investment, different flying characteristics. Just throwing this out there.

[Casey[_2_]]

On Monday, December 5, 2016 at 4:58:14 PM UTC-5, Casey wrote:
> On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud wrote:
> > For the guys with an engine weight does make a difference. Imagine if the 100 pounds of engine and fuel were offset by construction methods that lowered the empty weight of the glider by even 50-70 pounds. YOu would functionally have the same wing loading range as a pure glider.
> >
> > Just saying.
> > On Thursday, December 1, 2016 at 4:09:14 PM UTC-8, wrote:
> > > 4 Pretty much nobody cares much about weight, except the little gliders. For all the rest we just want to know how much water can we get in it.
>
> Different building methods in same factory brings several issues I could think of.
> Cost of buying and storing different materials, cost of process, possible mistakes in manufacturing, return on investment, different flying characteristics. Just throwing this out there.

Maybe this is why GP decided to put the batteries in the wings. Removal for light days without changing CG. All other FES gliders have batteries behind cockpit and have to fly with batteries.

[Dan Daly[_2_]]

On Monday, December 5, 2016 at 7:59:28 PM UTC-5, Casey wrote:
> On Monday, December 5, 2016 at 4:58:14 PM UTC-5, Casey wrote:
> > On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud wrote:
> > > For the guys with an engine weight does make a difference. Imagine if the 100 pounds of engine and fuel were offset by construction methods that lowered the empty weight of the glider by even 50-70 pounds. YOu would functionally have the same wing loading range as a pure glider.
> > >
> > > Just saying.
> > > On Thursday, December 1, 2016 at 4:09:14 PM UTC-8, wrote:
> > > > 4 Pretty much nobody cares much about weight, except the little gliders. For all the rest we just want to know how much water can we get in it..
> >
> > Different building methods in same factory brings several issues I could think of.
> > Cost of buying and storing different materials, cost of process, possible mistakes in manufacturing, return on investment, different flying characteristics. Just throwing this out there.
>
> Maybe this is why GP decided to put the batteries in the wings. Removal for light days without changing CG. All other FES gliders have batteries behind cockpit and have to fly with batteries.

Aren't the light days the ones where you most need the batteries?

[Fraser Wilson[_2_]]

Three further points with pre preg;-
1-Uni directional (UD) pre-preg, which is extensively used in wings, is
difficult
to form into compound curves;- it wrinkles
2-stray fibres, with pre-preg stray fibres can puncture the vac bag. The
wing
skins don't come out of the moulds until after the wings have been fully
glued
together. It's a bad day to discover a single stray fibre has killed the
vacuum
during the cure of a skin and you've just glued it to a good
spar/skin/installed
controls etc
3 - wet lay up wings post cure at 60C, normally out of mould. Pre-Preg
cures
at least 80C maybe hotter but this must be done in the mould. This means
the part and mould thermal expansion must be closely matched and the
longer the part , the more compound curves, the more difficult this
becomes.

Dry fibre resin infusion probably offers the best way forward as it can
provide
similar fibre fractions to pre preg but without the above and earlier
mention
drawbacks.

Fraser

At 21:58 05 December 2016, Casey wrote:
>On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud
wrote:
>> For the guys with an engine weight does make a difference. Imagine if
>th=
>e 100 pounds of engine and fuel were offset by construction methods that
>lo=
>wered the empty weight of the glider by even 50-70 pounds. YOu would
>funct=
>ionally have the same wing loading range as a pure glider.
>>=20
>> Just saying.
>> On Thursday, December 1, 2016 at 4:09:14 PM UTC-8,

>=
>wrote:
>> > 4 Pretty much nobody cares much about weight, except the little
>gliders=
>.. For all the rest we just want to know how much water can we get in it.
>
>Different building methods in same factory brings several issues I could
>th=
>ink of.
>Cost of buying and storing different materials, cost of process, possible
>m=
>istakes in manufacturing, return on investment, different flying
>characteri=
>stics. Just throwing this out there.
>

[Ross[_3_]]

On Tuesday, 6 December 2016 08:45:13 UTC+1, Fraser Wilson wrote:
> Three further points with pre preg;-
> 1-Uni directional (UD) pre-preg, which is extensively used in wings, is
> difficult
> to form into compound curves;- it wrinkles
> 2-stray fibres, with pre-preg stray fibres can puncture the vac bag. The
> wing
> skins don't come out of the moulds until after the wings have been fully
> glued
> together. It's a bad day to discover a single stray fibre has killed the
> vacuum
> during the cure of a skin and you've just glued it to a good
> spar/skin/installed
> controls etc
> 3 - wet lay up wings post cure at 60C, normally out of mould. Pre-Preg
> cures
> at least 80C maybe hotter but this must be done in the mould. This means
> the part and mould thermal expansion must be closely matched and the
> longer the part , the more compound curves, the more difficult this
> becomes.
>
> Dry fibre resin infusion probably offers the best way forward as it can
> provide
> similar fibre fractions to pre preg but without the above and earlier
> mention
> drawbacks.
>
> Fraser


I tend to disagree with most of that.
UD is difficult on complex shapes yes, but what is complex about a wing? It is basically straight. If you can laminate it with wet laminate, you can do it with prepreg.

You would cure the skins then glue the rest in. Well, this would be my approach. The spar can be co-cured in there if you like. Makes for easy small steps in manufacturing.
Similar way to the concept behind a F1 car. Outersking, honeycomb and inserts, innerskin.

Don't see the issue with postcure. No need for it to be done in the mold with Prepreg. We were postcuring suspension to 180-220 deg C out of the mold and had no issues. They were cured at 130 to start with.
As far as thermal expansion goes, why not make your molds out of tooling prepreg? Works like a charm, and if you have a decent glider you will make plenty of gliders out of the mold and you will always have the same shape. Beats having to rework your molds every couple of years

[Casey[_2_]]

>
> Aren't the light days the ones where you most need the batteries?

I was thinking of a comp. Motor only used to prevent land out and longer day. But I suppose on a rec flying day one could take out on a light day as well. I would think that flying a light day and booming day are no different other than more turns and less aggressive speed, but a lighter craft would benefit. I'm not even sure what the GP batteries weigh.

[Luke Szczepaniak]

On 12/5/2016 7:59 PM, Casey wrote:
> On Monday, December 5, 2016 at 4:58:14 PM UTC-5, Casey wrote:
>> On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud wrote:
>>> For the guys with an engine weight does make a difference. Imagine if the 100 pounds of engine and fuel were offset by construction methods that lowered the empty weight of the glider by even 50-70 pounds. YOu would functionally have the same wing loading range as a pure glider.
>>>
>>> Just saying.
>>> On Thursday, December 1, 2016 at 4:09:14 PM UTC-8, wrote:
>>>> 4 Pretty much nobody cares much about weight, except the little gliders. For all the rest we just want to know how much water can we get in it.
>>
>> Different building methods in same factory brings several issues I could think of.
>> Cost of buying and storing different materials, cost of process, possible mistakes in manufacturing, return on investment, different flying characteristics. Just throwing this out there.
>
> Maybe this is why GP decided to put the batteries in the wings. Removal for light days without changing CG. All other FES gliders have batteries behind cockpit and have to fly with batteries.
>
Probably has more to do with allowable max weight of non-lifting parts...

Luke Szczepaniak

[[email protected]]

On Monday, December 5, 2016 at 7:59:28 PM UTC-5, Casey wrote:
> On Monday, December 5, 2016 at 4:58:14 PM UTC-5, Casey wrote:
> > On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud wrote:
> > > For the guys with an engine weight does make a difference. Imagine if the 100 pounds of engine and fuel were offset by construction methods that lowered the empty weight of the glider by even 50-70 pounds. YOu would functionally have the same wing loading range as a pure glider.
> > >
> > > Just saying.
> > > On Thursday, December 1, 2016 at 4:09:14 PM UTC-8, wrote:
> > > > 4 Pretty much nobody cares much about weight, except the little gliders. For all the rest we just want to know how much water can we get in it..
> >
> > Different building methods in same factory brings several issues I could think of.
> > Cost of buying and storing different materials, cost of process, possible mistakes in manufacturing, return on investment, different flying characteristics. Just throwing this out there.
>
> Maybe this is why GP decided to put the batteries in the wings. Removal for light days without changing CG. All other FES gliders have batteries behind cockpit and have to fly with batteries.

Putting the batteries in the wings reduces the weight of non lifting parts which means the wing spars and root area don't have to be made as heavy.
UH

[Per Carlin]

On Tuesday, December 6, 2016 at 6:15:46 PM UTC+1, wrote:
> On Monday, December 5, 2016 at 7:59:28 PM UTC-5, Casey wrote:
> > On Monday, December 5, 2016 at 4:58:14 PM UTC-5, Casey wrote:
> > > On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud wrote:
> > > > For the guys with an engine weight does make a difference. Imagine if the 100 pounds of engine and fuel were offset by construction methods that lowered the empty weight of the glider by even 50-70 pounds. YOu would functionally have the same wing loading range as a pure glider.
> > > >
> > > > Just saying.
> > > > On Thursday, December 1, 2016 at 4:09:14 PM UTC-8, wrote:
> > > > > 4 Pretty much nobody cares much about weight, except the little gliders. For all the rest we just want to know how much water can we get in it.
> > >
> > > Different building methods in same factory brings several issues I could think of.
> > > Cost of buying and storing different materials, cost of process, possible mistakes in manufacturing, return on investment, different flying characteristics. Just throwing this out there.
> >
> > Maybe this is why GP decided to put the batteries in the wings. Removal for light days without changing CG. All other FES gliders have batteries behind cockpit and have to fly with batteries.
>
> Putting the batteries in the wings reduces the weight of non lifting parts which means the wing spars and root area don't have to be made as heavy.
> UH

And this is exactly why retrofitting an older glider to FES is impossible. With an max weight of non lifting part typically in the range of 230-250kg is it not enough marginal to put in an extra weight of 40-50kg for motor, electronics and battery in the fuselage unless you are a really light weight pilot.
I have asked the FES guys several times if it would be possible to get batteries suitable for wing installation and the answer is no.

[ND]

On Wednesday, December 7, 2016 at 1:49:59 AM UTC-5, Per Carlin wrote:
> On Tuesday, December 6, 2016 at 6:15:46 PM UTC+1, wrote:
> > On Monday, December 5, 2016 at 7:59:28 PM UTC-5, Casey wrote:
> > > On Monday, December 5, 2016 at 4:58:14 PM UTC-5, Casey wrote:
> > > > On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud wrote:
> > > > > For the guys with an engine weight does make a difference. Imagine if the 100 pounds of engine and fuel were offset by construction methods that lowered the empty weight of the glider by even 50-70 pounds. YOu would functionally have the same wing loading range as a pure glider.
> > > > >
> > > > > Just saying.
> > > > > On Thursday, December 1, 2016 at 4:09:14 PM UTC-8, wrote:
> > > > > > 4 Pretty much nobody cares much about weight, except the little gliders. For all the rest we just want to know how much water can we get in it.
> > > >
> > > > Different building methods in same factory brings several issues I could think of.
> > > > Cost of buying and storing different materials, cost of process, possible mistakes in manufacturing, return on investment, different flying characteristics. Just throwing this out there.
> > >
> > > Maybe this is why GP decided to put the batteries in the wings. Removal for light days without changing CG. All other FES gliders have batteries behind cockpit and have to fly with batteries.
> >
> > Putting the batteries in the wings reduces the weight of non lifting parts which means the wing spars and root area don't have to be made as heavy.
> > UH
>
> And this is exactly why retrofitting an older glider to FES is impossible.. With an max weight of non lifting part typically in the range of 230-250kg is it not enough marginal to put in an extra weight of 40-50kg for motor, electronics and battery in the fuselage unless you are a really light weight pilot.
> I have asked the FES guys several times if it would be possible to get batteries suitable for wing installation and the answer is no.

nothing is impossible.

[Justin Couch]

On Wednesday, 7 December 2016 17:49:59 UTC+11, Per Carlin wrote:
> And this is exactly why retrofitting an older glider to FES is impossible.. With an max weight of non lifting part typically in the range of 230-250kg is it not enough marginal to put in an extra weight of 40-50kg for motor, electronics and battery in the fuselage unless you are a really light weight pilot.


Not really a problem. Look at the old TOP installs on LS3s and 4s. An AD was issued that increased max weight of non-lifting parts. The tradeoff was a reducing in Vne and other airspeeds. So long as you stayed within CofG limits, then tradeoffs of weight for speed can always be done.

[Per Carlin]

On Thursday, December 8, 2016 at 1:22:15 AM UTC+1, Justin Couch wrote:
> On Wednesday, 7 December 2016 17:49:59 UTC+11, Per Carlin wrote:
> > And this is exactly why retrofitting an older glider to FES is impossible. With an max weight of non lifting part typically in the range of 230-250kg is it not enough marginal to put in an extra weight of 40-50kg for motor, electronics and battery in the fuselage unless you are a really light weight pilot.
>
>
> Not really a problem. Look at the old TOP installs on LS3s and 4s. An AD was issued that increased max weight of non-lifting parts. The tradeoff was a reducing in Vne and other airspeeds. So long as you stayed within CofG limits, then tradeoffs of weight for speed can always be done.

Well, for us Europeans that fly certified gliders is this not easy. The Type Certificate Holder has to release an AD and for older gliders is this not likley, not unless that you pay for it.

[J. Nieuwenhuize]

Op dinsdag 6 december 2016 11:58:23 UTC+1 schreef Ross:
> I tend to disagree with most of that.
> UD is difficult on complex shapes yes, but what is complex about a wing? It is basically straight. If you can laminate it with wet laminate, you can do it with prepreg.
>

Not really. Wing skins need 45/-45 fibers. Easy enough to put in a single tapered wing, but multiple tapers, fairings or wing tips are pretty awkward for either prepregs or thick BIAX/TRIAX.
Fuselage is worse.

> Don't see the issue with postcure. No need for it to be done in the mold with Prepreg. We were postcuring suspension to 180-220 deg C out of the mold and had no issues. They were cured at 130 to start with.
> As far as thermal expansion goes, why not make your molds out of tooling prepreg? Works like a charm, and if you have a decent glider you will make plenty of gliders out of the mold and you will always have the same shape. Beats having to rework your molds every couple of years
Pretty expensive to make such a mold since you need a plug that can withstand that temperature too. Solid aluminium requires major adjustment (thermal expansion during cure), inconel is $$$.
That's one of the biggest advantages of infusion. Cure at 30C or so, join parts etc and pull from the molds. Then, with a very slow ramp-up (<5C/hour) you can postcure to 100-120C and you have a plane that can be painted any color and won't need rework for spar bumps and other annoying issues.

[Fraser Wilson[_2_]]

At 18:43 08 December 2016, J. Nieuwenhuize wrote:
>Op dinsdag 6 december 2016 11:58:23 UTC+1 schreef Ross:
>> I tend to disagree with most of that.
>> UD is difficult on complex shapes yes, but what is complex about a
wing?
>=
>It is basically straight. If you can laminate it with wet laminate, you
>can=
> do it with prepreg.
>>=20
>
>Not really. Wing skins need 45/-45 fibers. Easy enough to put in a single
>t=
>apered wing, but multiple tapers, fairings or wing tips are pretty
awkward
>=
>for either prepregs or thick BIAX/TRIAX.
>Fuselage is worse.
>
>> Don't see the issue with postcure. No need for it to be done in the
mold
>=
>with Prepreg. We were postcuring suspension to 180-220 deg C out of the
>mol=
>d and had no issues. They were cured at 130 to start with.
>> As far as thermal expansion goes, why not make your molds out of
tooling
>=
>prepreg? Works like a charm, and if you have a decent glider you will
make
>=
>plenty of gliders out of the mold and you will always have the same
shape.
>=
>Beats having to rework your molds every couple of years
>Pretty expensive to make such a mold since you need a plug that can
>withsta=
>nd that temperature too. Solid aluminium requires major adjustment
>(thermal=
> expansion during cure), inconel is $$$.
>That's one of the biggest advantages of infusion. Cure at 30C or so, join
>p=
>arts etc and pull from the molds. Then, with a very slow ramp-up
>(<5C/hour)=
> you can postcure to 100-120C and you have a plane that can be painted
any
>=
>color and won't need rework for spar bumps and other annoying issues.

I definitely would not take Ros's recommendation of co curing the wing
skins
and spars in one operation . This is just what SH got badly wrong on the
Discus wings when they tried to co cure the caps to the wing skins but
found
they couldn't ensure a satisfactory bond to the spar web when they bonded
the skins together;- was it 70 odd wings sets scraped?

As for a partial cure on a wing cover, remove from mould and final cure at

high temperature, I'm very dubious. In order to assemble the wing skins
together to get the right twist and fit the wing skins must be held to a
high
level of precision. Added to this an individual wing skin is an unbalanced

layup I.e two thick 45's, foam, and one thin bid so its ripe for thermal
distortion. However when the top skin and bottom skins are bonded it
becomes balanced across the wing section. As for the justification that it

works on a 30 (or so) cm part therefore it must work on an 8m I will make
no
further comment.

Yes of course it's possible to build a wing in pre-preg but why? The mould
has
to be made from a more expensive material, more expensive energy is
required to heat it to higher temperature and more expensive manhour time
is required to do all the inter leafing so as to avoid the wrinkling.

Fraser

[[email protected]]

On Thursday, December 8, 2016 at 6:15:05 PM UTC-5, Fraser Wilson wrote:
> At 18:43 08 December 2016, J. Nieuwenhuize wrote:
> >Op dinsdag 6 december 2016 11:58:23 UTC+1 schreef Ross:
> >> I tend to disagree with most of that.
> >> UD is difficult on complex shapes yes, but what is complex about a
> wing?
> >=
> >It is basically straight. If you can laminate it with wet laminate, you
> >can=
> > do it with prepreg.
> >>=20
> >
> >Not really. Wing skins need 45/-45 fibers. Easy enough to put in a single
> >t=
> >apered wing, but multiple tapers, fairings or wing tips are pretty
> awkward
> >=
> >for either prepregs or thick BIAX/TRIAX.
> >Fuselage is worse.
> >
> >> Don't see the issue with postcure. No need for it to be done in the
> mold
> >=
> >with Prepreg. We were postcuring suspension to 180-220 deg C out of the
> >mol=
> >d and had no issues. They were cured at 130 to start with.
> >> As far as thermal expansion goes, why not make your molds out of
> tooling
> >=
> >prepreg? Works like a charm, and if you have a decent glider you will
> make
> >=
> >plenty of gliders out of the mold and you will always have the same
> shape.
> >=
> >Beats having to rework your molds every couple of years
> >Pretty expensive to make such a mold since you need a plug that can
> >withsta=
> >nd that temperature too. Solid aluminium requires major adjustment
> >(thermal=
> > expansion during cure), inconel is $$$.
> >That's one of the biggest advantages of infusion. Cure at 30C or so, join
> >p=
> >arts etc and pull from the molds. Then, with a very slow ramp-up
> >(<5C/hour)=
> > you can postcure to 100-120C and you have a plane that can be painted
> any
> >=
> >color and won't need rework for spar bumps and other annoying issues.
>
> I definitely would not take Ros's recommendation of co curing the wing
> skins
> and spars in one operation . This is just what SH got badly wrong on the
> Discus wings when they tried to co cure the caps to the wing skins but
> found
> they couldn't ensure a satisfactory bond to the spar web when they bonded
> the skins together;- was it 70 odd wings sets scraped?
>
> As for a partial cure on a wing cover, remove from mould and final cure at
>
> high temperature, I'm very dubious. In order to assemble the wing skins
> together to get the right twist and fit the wing skins must be held to a
> high
> level of precision. Added to this an individual wing skin is an unbalanced
>
> layup I.e two thick 45's, foam, and one thin bid so its ripe for thermal
> distortion. However when the top skin and bottom skins are bonded it
> becomes balanced across the wing section. As for the justification that it
>
> works on a 30 (or so) cm part therefore it must work on an 8m I will make
> no
> further comment.
>
> Yes of course it's possible to build a wing in pre-preg but why? The mould
> has
> to be made from a more expensive material, more expensive energy is
> required to heat it to higher temperature and more expensive manhour time
> is required to do all the inter leafing so as to avoid the wrinkling.
>
> Fraser

I am aware that some SH wings required inspection of the glue joint between the shear web and the spar cap, and some required repair. I never heard of any being scrapped. They did a great job of dealing with a quality problem caused by a supplier.
SH uses the method of building the spar caps into the skins to this day with good results.
UH

[Ross[_3_]]

On Friday, 9 December 2016 00:57:51 UTC+1, wrote:
> On Thursday, December 8, 2016 at 6:15:05 PM UTC-5, Fraser Wilson wrote:
> > At 18:43 08 December 2016, J. Nieuwenhuize wrote:
> > >Op dinsdag 6 december 2016 11:58:23 UTC+1 schreef Ross:
> > >> I tend to disagree with most of that.
> > >> UD is difficult on complex shapes yes, but what is complex about a
> > wing?
> > >=
> > >It is basically straight. If you can laminate it with wet laminate, you
> > >can=
> > > do it with prepreg.
> > >>=20
> > >
> > >Not really. Wing skins need 45/-45 fibers. Easy enough to put in a single
> > >t=
> > >apered wing, but multiple tapers, fairings or wing tips are pretty
> > awkward
> > >=
> > >for either prepregs or thick BIAX/TRIAX.
> > >Fuselage is worse.
> > >
> > >> Don't see the issue with postcure. No need for it to be done in the
> > mold
> > >=
> > >with Prepreg. We were postcuring suspension to 180-220 deg C out of the
> > >mol=
> > >d and had no issues. They were cured at 130 to start with.
> > >> As far as thermal expansion goes, why not make your molds out of
> > tooling
> > >=
> > >prepreg? Works like a charm, and if you have a decent glider you will
> > make
> > >=
> > >plenty of gliders out of the mold and you will always have the same
> > shape.
> > >=
> > >Beats having to rework your molds every couple of years
> > >Pretty expensive to make such a mold since you need a plug that can
> > >withsta=
> > >nd that temperature too. Solid aluminium requires major adjustment
> > >(thermal=
> > > expansion during cure), inconel is $$$.
> > >That's one of the biggest advantages of infusion. Cure at 30C or so, join
> > >p=
> > >arts etc and pull from the molds. Then, with a very slow ramp-up
> > >(<5C/hour)=
> > > you can postcure to 100-120C and you have a plane that can be painted
> > any
> > >=
> > >color and won't need rework for spar bumps and other annoying issues.
> >
> > I definitely would not take Ros's recommendation of co curing the wing
> > skins
> > and spars in one operation . This is just what SH got badly wrong on the
> > Discus wings when they tried to co cure the caps to the wing skins but
> > found
> > they couldn't ensure a satisfactory bond to the spar web when they bonded
> > the skins together;- was it 70 odd wings sets scraped?
> >
> > As for a partial cure on a wing cover, remove from mould and final cure at
> >
> > high temperature, I'm very dubious. In order to assemble the wing skins
> > together to get the right twist and fit the wing skins must be held to a
> > high
> > level of precision. Added to this an individual wing skin is an unbalanced
> >
> > layup I.e two thick 45's, foam, and one thin bid so its ripe for thermal
> > distortion. However when the top skin and bottom skins are bonded it
> > becomes balanced across the wing section. As for the justification that it
> >
> > works on a 30 (or so) cm part therefore it must work on an 8m I will make
> > no
> > further comment.
> >
> > Yes of course it's possible to build a wing in pre-preg but why? The mould
> > has
> > to be made from a more expensive material, more expensive energy is
> > required to heat it to higher temperature and more expensive manhour time
> > is required to do all the inter leafing so as to avoid the wrinkling.
> >
> > Fraser
>
> I am aware that some SH wings required inspection of the glue joint between the shear web and the spar cap, and some required repair. I never heard of any being scrapped. They did a great job of dealing with a quality problem caused by a supplier.
> SH uses the method of building the spar caps into the skins to this day with good results.
> UH

Use TB650 as we do in the Formula 1 for tooling.
Most F1 parts require UD and there are no more complex shapes than on an F1 car.
I think a glider would be pretty easy having made about 200 of them whilst working in one of the good Germany manufacturers.

And no, they never scrapped 70 wings. Not sure they scrapped any at all. Not 1 in the entire time I was there

[Soartech]

On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud wrote:
> For the guys with an engine weight does make a difference. Imagine if the 100 pounds of engine and fuel were offset by construction methods that lowered the empty weight of the glider by even 50-70 pounds. YOu would functionally have the same wing loading range as a pure glider.

Jonathon is describing my Apis M 15 meter! Only 500 lbs. total including the engine, prop, starter, battery, etc. Has carbon in the wing spar and other areas.

[Ross[_3_]]

These guys seem to think this will work

https://www.facebook.com/NixusProject/

[Bob Kuykendall]

On Thursday, December 15, 2016 at 12:20:27 PM UTC-8, Ross wrote:
> These guys seem to think this will work...

Well, of course it will work. When you have a billionaire footing the bills, you can make anything work. The real question is, does it make enough difference to justify the extra expense in the absence of such extraordinary measures?

[[email protected]]

I wonder if anyone said the same thing about computers in the early days, Bob!

[Jonathan St. Cloud]

Who is funding this project. looks very interesting.
On Thursday, December 15, 2016 at 12:20:27 PM UTC-8, Ross wrote:
> These guys seem to think this will work
>
> https://www.facebook.com/NixusProject/

[Martin Gregorie[_5_]]

On Thu, 15 Dec 2016 20:57:17 -0800, roel.baardman wrote:

> I wonder if anyone said the same thing about computers in the early
> days, Bob!

Unlikely that anybody did.

The very first electronic computers were built for code-breaking and to
calculate artillery range tables. Yes, these tasks could be done
manually, but not nearly as fast. Colossus played a major part in winning
WW2 while ENIAC went on from generating range tables to help design
second generation nukes: the Fat Man design calculations were done using
a roomful of IBM card equipment. See Richard Fyneman's books for more
detail.

The first commercial computers were built by Lyons in the UK. Lyons was
the Starbucks of its day, and used the first machine to streamline bakery
production for the next day's teashop requirements. That was a success
from day one, at least partly because they knew exactly what they wanted
the machine to do and the company already had a solid background in
process optimisation.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[[email protected]]

On Friday, December 16, 2016 at 5:24:30 AM UTC-6, Martin Gregorie wrote:
> On Thu, 15 Dec 2016 20:57:17 -0800, roel.baardman wrote:
>
> > I wonder if anyone said the same thing about computers in the early
> > days, Bob!
>
> Unlikely that anybody did.
>
> The very first electronic computers were built for code-breaking and to
> calculate artillery range tables. Yes, these tasks could be done
> manually, but not nearly as fast. Colossus played a major part in winning
> WW2 while ENIAC went on from generating range tables to help design
> second generation nukes: the Fat Man design calculations were done using
> a roomful of IBM card equipment. See Richard Fyneman's books for more
> detail.
>
> The first commercial computers were built by Lyons in the UK. Lyons was
> the Starbucks of its day, and used the first machine to streamline bakery
> production for the next day's teashop requirements. That was a success
> from day one, at least partly because they knew exactly what they wanted
> the machine to do and the company already had a solid background in
> process optimisation.
>
>
> --
> martin@ | Martin Gregorie
> gregorie. | Essex, UK
> org |

Very unfortunate that these early UK computers never caught on, Martin. I hear rumors that you guys couldn't figure out how to make them leak oil?

[Dan Marotta]

Ouch! Since my first motorcycle was a BSA (bolts, screws, and
adjustments) I'm conversant with oil leaks...

On 12/16/2016 7:53 AM, wrote:
> On Friday, December 16, 2016 at 5:24:30 AM UTC-6, Martin Gregorie wrote:
>> On Thu, 15 Dec 2016 20:57:17 -0800, roel.baardman wrote:
>>
>>> I wonder if anyone said the same thing about computers in the early
>>> days, Bob!
>> Unlikely that anybody did.
>>
>> The very first electronic computers were built for code-breaking and to
>> calculate artillery range tables. Yes, these tasks could be done
>> manually, but not nearly as fast. Colossus played a major part in winning
>> WW2 while ENIAC went on from generating range tables to help design
>> second generation nukes: the Fat Man design calculations were done using
>> a roomful of IBM card equipment. See Richard Fyneman's books for more
>> detail.
>>
>> The first commercial computers were built by Lyons in the UK. Lyons was
>> the Starbucks of its day, and used the first machine to streamline bakery
>> production for the next day's teashop requirements. That was a success
>> from day one, at least partly because they knew exactly what they wanted
>> the machine to do and the company already had a solid background in
>> process optimisation.
>>
>>
>> --
>> martin@ | Martin Gregorie
>> gregorie. | Essex, UK
>> org |
> Very unfortunate that these early UK computers never caught on, Martin. I hear rumors that you guys couldn't figure out how to make them leak oil?

--
Dan, 5J

[[email protected]]

Lucas: Prince of Darkness

Lucas 3-position switch:

Dim
Flicker
Short

[Jonathan St. Cloud]

I would have thought the electrical systems of those first UK computers would have been the downfall. I have found the Italians' are great for self rust inhibiting (oil leaks, Agusta). All kidding and references to British cars and motorcycles aside, the Brits have a rich history in innovation. A few military innovations come to mind, radar, angled carrier decks, steel carrier decks, tanks (think M1A1 type)...

Thanks for the history on early computers.

[Dan Marotta]

....And why do Brits drink their beer at room temperature? Because
their refrigerators are built by Lucas, of course.

On 12/16/2016 8:37 AM, wrote:
> Lucas: Prince of Darkness
>
> Lucas 3-position switch:
>
> Dim
> Flicker
> Short

--
Dan, 5J

[Pete Smith[_6_]]

Not room temp but cellar temp, 12c

At 16:31 16 December 2016, Dan Marotta wrote:
>....And why do Brits drink their beer at room temperature? Because
>their refrigerators are built by Lucas, of course.
>
>On 12/16/2016 8:37 AM, wrote:
>> Lucas: Prince of Darkness
>>
>> Lucas 3-position switch:
>>
>> Dim
>> Flicker
>> Short
>
>--
>Dan, 5J
>