Heavily inspired ultralight

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rotax618

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Given the mission, quite a bit of weight could be saved if the wing was wire braced rather than cantilevere. A simple ‘A‘ type kingpost would take any negative G loads, D shackles would make for easy folding or disassembly.
 

BobDaly

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Regarding tail size, I believe the Skypup has low horizontal tail loading owing to the low moment coefficient of the NACA 43018 airfoil. Compare your proposed 4418 airfoil's -.09 Cm with -.013 of the 43018 airfoil. The 43018 allows for a cantilevered, low-drag, light horizontal tail and short-tail-arm fuselage. Comparing tail volume coefficients would be meaningless without taking the airfoil change into account.

If by "full wooden spar" you mean a solid plank the weight will be prohibitive. The Skypup spar really is a marvel. It's a composite beam with the flanges carrying the bending and the foam carrying the shear. Even a properly designed wooden box beam will likely be significantly heavier. You might check out what Victor Serda, Avión Experimental " El Canguro" - YouTube has done. Same mission goals.
 
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Taylor.S

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I was thinking of a I beam spar, however if that changes back to the foam spar that is not a big deal.
 

Jerry Lytle

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My eyes decieved me, I thought this topic was about a heavenly inspired ultralight. I wondered when it was going to get around to the inspirational part.

Not there yet by any definition.

20 years ago I paid 25 dollars for a set of ultralight plans. They had copied the Hi-max fuselage and Skypup wing, with ailerons borrowed from a Mini Max. Used a single wing struts typical of the Hi-Max design, the empennage was a copy of the Hi-Max. The coordinates for the wing section didn't match the plans, I don't know where they stole borrowed them from. Those plans like this thread did not appear to being inspired.
 

Taylor.S

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My eyes decieved me, I thought this topic was about a heavenly inspired ultralight. I wondered when it was going to get around to the inspirational part.

Not there yet by any definition.

20 years ago I paid 25 dollars for a set of ultralight plans. They had copied the Hi-max fuselage and Skypup wing, with ailerons borrowed from a Mini Max. Used a single wing struts typical of the Hi-Max design, the empennage was a copy of the Hi-Max. The coordinates for the wing section didn't match the plans, I don't know where they stole borrowed them from. Those plans like this thread did not appear to being inspired.
Would it make you happy if I changed the name to lightly inspired ultralight, what's your point? This design as of right now is still practically a sky pup, however it is smarter to make new design with inspiration than to significantly change an existing design that is the point of the design.
 
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Victor Bravo

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I know this has been said probably more than once already, but it deserves repeating: Sky Pup designer Steve Wood was a well trained and apparently very good engineer, specifically working in aircraft design. So please take it on faith that the Sky Pup had everything in the structure thought about and gone through to a pretty good degree, and that it would take an equal or better engineer to do as well or better (using the same materials he had available for the Sky Pup).

A decent engineer could come up with a lighter or stronger Sky Pup now, only because there are materials available (strong and cheap) that were not available previously. But even then, in order to make use out of these better materials, you need to have the capability of doing that same level of engineering with the new materials.
 

Taylor.S

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I know this has been said probably more than once already, but it deserves repeating: Sky Pup designer Steve Wood was a well trained and apparently very good engineer, specifically working in aircraft design. So please take it on faith that the Sky Pup had everything in the structure thought about and gone through to a pretty good degree, and that it would take an equal or better engineer to do as well or better (using the same materials he had available for the Sky Pup).

A decent engineer could come up with a lighter or stronger Sky Pup now, only because there are materials available (strong and cheap) that were not available previously. But even then, in order to make use out of these better materials, you need to have the capability of doing that same level of engineering with the new materials.
I couldn't agree more. I'm just using the pup as inspiration, with the direction it is going its definitely drifting away from being a sky pup.
 

Taylor.S

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I have been pondering and doing some price estimates and I think I am going to use the composite spar. If I am going back to the original spar I believe I will also use the sky pups airfoil.
 

Dewey Vicknair

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It seems that the Skypup already fits your mission parameters. Since your design seems to be morphing into a pup, I don't get the point. Is this something that is actually going to be built or is it mental masturbation?
 

Gregory Perkins

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The Volmer Jensen VJ-23 cantilever wood hang glider that was powered later on and fitted with wheels, had a sixteen inch thick top to bottom spar measurement at the wing root. I always thought that was amazing. There were not a lot of cantilever wing ultralights.
 

Gregory Perkins

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I know this has been said probably more than once already, but it deserves repeating: Sky Pup designer Steve Wood was a well trained and apparently very good engineer, specifically working in aircraft design. So please take it on faith that the Sky Pup had everything in the structure thought about and gone through to a pretty good degree, and that it would take an equal or better engineer to do as well or better (using the same materials he had available for the Sky Pup).

A decent engineer could come up with a lighter or stronger Sky Pup now, only because there are materials available (strong and cheap) that were not available previously. But even then, in order to make use out of these better materials, you need to have the capability of doing that same level of engineering with the new materials.
It could be abundantly appropriate that the SkyPup be reworked because the designer did not use the same empty max weight and performance max numbers allowed in FAR 103 ( because he designed the plane before FAR 103 existed ) and left quite a bit of performace on the table for us wishing to build to FAR 103 specs. More weight for the structure with better materials and bigger motors could really enhance the already legendary Skypup if designed optimally.
 

TLAR

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I will add a couple of items I would use on the Sky Dog, (Sky Pup improved).
The foam would be Dow billet, firmly secured for Hotwire.
The entire spar and ribs would be cut out of the billet in one piece. Align your templates accordingly. No epoxy used between ribs and spar. One piece.
Center section will require vertical epoxy joints, then chop out spar and ribs in one piece.
Wing attach.
Carbon tow as big as possible but must conform to the bend radi on the top corners of the spar.
You have to make a stay in place mold to contain the tow used to build uprights.
Fuselage must be on a rotisserie and center section jigged in place.
Add thixotropic compound to resin and start wrapping tow, start anywhere and wrap, up side through a trough in the foam, over spar, back down the side under bottom back up the other side over spar. Stop when you think you have enough.
Edit you will have three wing sections one center and two wings not one long ass wing
Tow one the bottom will be ward for landing gear and a place to support seat.
Leave the Tow uncut, continuous strand
 
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patrickrio

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Aug 15, 2020
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Make wing swing for storage and transport, like the wing on the backyard flyer.
swing wing.jpg
swing wing 2.jpg
Make the center section of the wing and spar in one piece 20 feet long. Design the tips for the wing portions longer than 20 feet without any ailerons and fold tips over the wing for storage so that it fits in a space 20 feet long.
 
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