Pre-Preg

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

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

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?

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/

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

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

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.

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

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)?

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?