Ventus bT/cT comparison

At 03:36 18 April 2012, Bob Gibbons wrote:
-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first.

You've lost me somewhere.

Why does pilot weight stop you getting to max gross as long as the wing
tanks are big enough?

Assuming tanks *are* big enough to get to max gross without the engine then
it should be a piece of cake to get there *with* the engine.

PF

If pilot + other non-lifting parts exceeds 255kg, then you can't fly. If
you can fly, then you can water up to the 500kg limit.

Indeed, it should be beneficial as water in the wings reduces wing root
bending. It increses bending at the end of the tank area, but the
manufacturer should have taken care of that.........

At 08:43 20 April 2012, Peter F wrote:
At 03:36 18 April 2012, Bob Gibbons wrote:
-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first.

You've lost me somewhere.

Why does pilot weight stop you getting to max gross as long as the wing
tanks are big enough?

Assuming tanks *are* big enough to get to max gross without the engine
then
it should be a piece of cake to get there *with* the engine.

PF

On Apr 20, 2:56*am, Peter Purdie wrote:
If pilot + other non-lifting parts exceeds 255kg, then you can't fly. *If
you can fly, then you can water up to the 500kg limit.

Indeed, it should be beneficial as water in the wings reduces wing root
bending. *It increses bending at the end of the tank area, but the
manufacturer should have taken care of that.........

At 08:43 20 April 2012, Peter F wrote:



At 03:36 18 April 2012, Bob Gibbons wrote:
-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first.

You've lost me somewhere.

Why does pilot weight stop you getting to max gross as long as the wing
tanks are big enough?

Assuming tanks *are* big enough to get to max gross without the engine
then
it should be a piece of cake to get there *with* the engine.

PF- Hide quoted text -

- Show quoted text -

The Ventus (and nearly all gliders out there) fuselage is hanging from
the wings by four pins. On the Ventus they are about 15-20 mm in
diameter. The non-lifting weight limit is the maximum load those pins
can support and is unchanged by the extra weight water ballast adds.

Yes I know what max weight of non-lifting parts is.

If you can fly at all, you can fly at max gross.

I'm just confused by Bob Gibbons post (See quote below)

For his weight the margin on non-lifting limit is the same with or without
water the 28gals is irrelevant.

PF

Quote

-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first. For my weight and 28
gal of water, I hit max gross just before I hit the non-lifting limit.

End Quote

On Fri, 20 Apr 2012 02:59:15 +0000, Ventus_a
wrote:

'Bob Gibbons[_2_ Wrote:
.... text deleted

-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first. For my weight and 28
gal of water, I hit max gross just before I hit the non-lifting limit.
Bottom line, with the engine in place and ballasted to max gross, you
are at the same loading as without the engine, but you cannot dump
down to the same low loading as without the engine. With the engine
in, I can go from 10.1 lbs/ft2 max down to 7.9 lbs/ft2 min. Without
the engine, W/L ranges from the same 10.1 lbs/ft2 down to 7.2 lbs/ft2
(all with 17.6m span). The B model has the same issue and limitations.



Every Ventus cT manual that I have looked at says the max weight with
the engine in is 430 kg regardless of the span. With the engine out,
500kg at 16.6. and 17.6m respectively

Cheers
Colin

Colin, you are correct in quoting the handbook. Several of us actually
discussed this apparent contradiction with Klaus Holighaus on a visit
a number of years ago.

He agreed that it so long as the non-lifting limit is followed, it
makes no difference whether the engine is in or out.

The engine represents a fuselage (non-lifting) load on the airframe,
the cause of this non-lifting load should not be a factor in the
overall gross weight, so long as the non-lifting limit is observed.

Bob

On Fri, 20 Apr 2012 08:43:49 +0000, Peter F
wrote:

At 03:36 18 April 2012, Bob Gibbons wrote:
-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first.

You've lost me somewhere.

Why does pilot weight stop you getting to max gross as long as the wing
tanks are big enough?

Assuming tanks *are* big enough to get to max gross without the engine then
it should be a piece of cake to get there *with* the engine.

PF

PF, I agree this was a confusing way to state the situation. As you
correctly point out, if you satisfy the 255kg non-lifting limit, you
can ballast up to the 500kg limit irrespective of the pilot weight.

What I was trying to convey is that a lighter pilot can get more
margin under the non-lifting limit, and thus add more water ballast
before reaching the 500kg limit.

As I mentioned, at my weight, I am right at the 255kg limit with the
engine in place. I can add 28 gal before I hit 500kg.

If I weighed 20 lbs less, I could load in 31 gal before hitting the
500kg limit.

Or if I take out the engine, I can put in 40 gal before hitting the
500kg limit.

Sorry for the poor wording.

Bob

On Fri, 20 Apr 2012 08:43:49 +0000, Peter F
wrote:

At 03:36 18 April 2012, Bob Gibbons wrote:
-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first.

You've lost me somewhere.

Why does pilot weight stop you getting to max gross as long as the wing
tanks are big enough?

Assuming tanks *are* big enough to get to max gross without the engine then
it should be a piece of cake to get there *with* the engine.

PF

PF, I agree this was a confusing way to state the impact of the
non-lifting limitation.

What I was trying to convey is the impact of the pilot weight on the
amount of water ballast you can add before hitting the max gross
limit.

As I mentioned, at my weight, I can add 28 gal before reaching max
gross of 500kg. With the engine installed, I am right at the 255kg
non-lifting limit.

On the other hand, if I weighed 20 lbs less, I could add 31 gal of
water before reaching the 500kg limit.

If I took the engine out, I could add 40 gal of water before reaching
the 500kg limit.

Sorry for the confusion.

Bob

Interesting I have bT and my Manual says max. 270 kg for non lifting parts.

On Saturday, April 21, 2012 at 12:26:44 PM UTC+12, Bob Gibbons wrote:


Every Ventus cT manual that I have looked at says the max weight with
the engine in is 430 kg regardless of the span. With the engine out,
500kg at 16.6. and 17.6m respectively

Cheers
Colin

Colin, you are correct in quoting the handbook. Several of us actually
discussed this apparent contradiction with Klaus Holighaus on a visit
a number of years ago.

He agreed that it so long as the non-lifting limit is followed, it
makes no difference whether the engine is in or out.

The engine represents a fuselage (non-lifting) load on the airframe,
the cause of this non-lifting load should not be a factor in the
overall gross weight, so long as the non-lifting limit is observed.

Bob

Sorry, but I'm still confused.

To my mind, a non-lifting limit is a hard limit, defined by the mechanical limit of the four wing-root pins. If you remove the engine (and fuel tank and engine battery) then this limit should not change; you've taken weight off the pins so can add more pilot weight etc. (ignoring balance considerations for the moment).

What the flight namual seems to be implying (and thanks, Colin, for the discussions) is that there are some wing bending issues. The (non-turbo) Ventus was designed for a MAUW of 500kg and the wing will cope fine with a max non-lifting weight of 255kg (for example - it varies depending on the model). What the manual seems to be implying is that SH then wanted to put a turbo in but came up against the (true) load limit of the wing pins, as well as some bending moment limitations on the wing, but the market need for a turbo version was great so they put a 430kg limitation on the MAUW.

I know that there are cT/bT pilots out there who ignore the 430kg limit and ballast up to 500kg with no issues. I'm asking the Collective Wisdom of y'all whether:
a) my reasoning above is correct;
b) whether to take the numbers in the flight manual with a grain of salt, bearing in mind the discussions with Herr Holigaus; and
c) whether it's worth asking SH to revise the flight manual to clear up the confusion; or
d) to obey the flight manual at all times and loads.

Answers on a postcard...

DH
TX

Originally Posted by David Hirst

On Saturday, April 21, 2012 at 12:26:44 PM UTC+12, Bob Gibbons wrote:


Every Ventus cT manual that I have looked at says the max weight with
the engine in is 430 kg regardless of the span. With the engine out,
500kg at 16.6. and 17.6m respectively

Cheers
Colin

Colin, you are correct in quoting the handbook. Several of us actually
discussed this apparent contradiction with Klaus Holighaus on a visit
a number of years ago.

He agreed that it so long as the non-lifting limit is followed, it
makes no difference whether the engine is in or out.

The engine represents a fuselage (non-lifting) load on the airframe,
the cause of this non-lifting load should not be a factor in the
overall gross weight, so long as the non-lifting limit is observed.

Bob

Sorry, but I'm still confused.

To my mind, a non-lifting limit is a hard limit, defined by the mechanical limit of the four wing-root pins. If you remove the engine (and fuel tank and engine battery) then this limit should not change; you've taken weight off the pins so can add more pilot weight etc. (ignoring balance considerations for the moment).

What the flight namual seems to be implying (and thanks, Colin, for the discussions) is that there are some wing bending issues. The (non-turbo) Ventus was designed for a MAUW of 500kg and the wing will cope fine with a max non-lifting weight of 255kg (for example - it varies depending on the model). What the manual seems to be implying is that SH then wanted to put a turbo in but came up against the (true) load limit of the wing pins, as well as some bending moment limitations on the wing, but the market need for a turbo version was great so they put a 430kg limitation on the MAUW.

I know that there are cT/bT pilots out there who ignore the 430kg limit and ballast up to 500kg with no issues. I'm asking the Collective Wisdom of y'all whether:
a) my reasoning above is correct;
b) whether to take the numbers in the flight manual with a grain of salt, bearing in mind the discussions with Herr Holigaus; and
c) whether it's worth asking SH to revise the flight manual to clear up the confusion; or
d) to obey the flight manual at all times and loads.

Answers on a postcard...

DH
TX

Hi David

Too cheap to use a postcard but may I suggest a talk with Pat re his experience with OP if you haven't already. I'm sure he can add something

:-) Colin