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99lb/45kg primary glider

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jedi

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Back to the OP.

..........

I don't suppose any of you have put any pen and paper time into a project that might come close? Or have some great thoughts as to how to achieve a 99lb primary glider?
Yes I have considered the inexpensive floater you are proposing and the answer keeps coming back that there is not sufficient interest to proceed with the design.

Even the old primary glider designs are not viable in today’s market so innovation is required.

There is no clear development path for the innovation to follow until specific requirements and specifications are presented.

Storage, flying sites, life cycle costs, insurance and liability are examples of auxiliary issues that need to be addressed in the modernized primary glider development program.

Storage and disposable verses repairable parts are items that need resolution If this project is to proceed.
 
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Victor Bravo

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I have spent some time doodling on this type of concept, and my amateur approach is to start removing as many of the big heavy parts off of the airplane and shorten the load paths so some structure can be safely removed. So it looked to me that (compared to a conventional primary glider) the little Marske-ish flying wing I laid out could effectively remove most of the tailboom or rear fuselage, 1/4 of the forward fuselage, some of the horizontal stabilizer, all of the wing struts, and some of the seat. On balance, the wing ribs are a little longer and weigh a little more.
 

Hephaestus

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I have spent some time doodling on this type of concept, and my amateur approach is to start removing as many of the big heavy parts off of the airplane and shorten the load paths so some structure can be safely removed. So it looked to me that (compared to a conventional primary glider) the little Marske-ish flying wing I laid out could effectively remove most of the tailboom or rear fuselage, 1/4 of the forward fuselage, some of the horizontal stabilizer, all of the wing struts, and some of the seat. On balance, the wing ribs are a little longer and weigh a little more.
I still like that method... But I get overridden by 4 grey haired guys who are very averse to change 🤣

What we ended up doing was using a known (sandlin goat) deep diving for part/component weights. Knocking a third off of that, then running feasibility / costs to hit that number.

So now there's a spread, some parts couldn't reasonably be made lighter. Some could, and so we go from there.
 

jedi

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Notice that the primary glider had no landing gear. That is something that tends to be added weight. Don't do that!

Who can give numbers on the load limits for typical primary gliders of the 20s and 30s?

With respect to the 4 grey hairs of post # 63 are you designing for them or the kids. Do you want the old technology or will you innovate?
 
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Hephaestus

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Notice that the primary glider had no landing gear. That is something that tends to be added weight. Don't do that!

Who can give numbers on the load limits for typical primary gliders of the 20s and 30s?

With respect to the 4 grey hairs of post # 63 are you designing for them or the kids. Do you want the old technology or will you innovate?
We concluded it needs some ability for hang glider style launch sites. Because it definitely fits 2 different market segments, its attainable within the weight budget so why leave it out and have a sacrificial part that will need regular replacement?

As far as the grey hairs - bit of both. Not so much kid focused however. But they are representative of the target market. 4 guys (5total), 3 glider clubs, 3 instructors, one idiot who thinks why not? what else am I going to do this month? 🤣 (I'd be the bored idiot).

We've got the guy who thinks the SGU-22 is the proper design, the engineer thinks we're designing a 15m competition class aircraft, one who just wants it not to look like a Sandlin goat, one who is really pushing the hang glider market (probably related to his recent addition of a cane)
 

Jay Kempf

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Wing loads are making my head hurt.
Mocked up the root 3' of what was working in theory.
It's in the trash. No way that will survive handling. This is how you end up with heavy composite construction isn't it? Throw an extra layer or two on just to 'feel' right, even if the math says it's ok...
YES! Much worse in the certified world where you have to make composite FOS for the FAA and practical and then actually having to make the stuff in the mold where you can't reconcile every single piece of string and every molecule of glue. Lams are lams either prepreg or otherwise. Otherwise is heavier :)

If its any consolation boat guys are even worse.
 

Hephaestus

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YES! Much worse in the certified world where you have to make composite FOS for the FAA and practical and then actually having to make the stuff in the mold where you can't reconcile every single piece of string and every molecule of glue. Lams are lams either prepreg or otherwise. Otherwise is heavier :)

If its any consolation boat guys are even worse.
The exterior sheet seems nice now. Little bit of XPS foam went a long way (hotwired 5mm slices) that I'm happy with.

The root ribs and spar tubes... Not sure how buildable still, it's tempting to just go a bit block of foam but - weight penalty for that will suck.
 

WonderousMountain

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Followup, shown is scud II, The fuselage is stabilized with one verticle, empenage is all flying AND all interchangible, Elevator=Rudder, the second set of struts triangulates the upper longerons, which are Ash... Scud had two spars, whereas Scud II has a main spar construction. Wing was extended over 14 feet, Fuselage and subsequently weight by 5O#'s. Scud III was the first motor-glider, go figure. One crash resulted in fatality, involving an early era winch tow around 193X.
Ground handling used up to four flyboys. One still soars, one is on display, another replica was built. Original scud had corded trailing edge, maybe prototype only, I see no photos of that.
 
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