# A new idea for a UL Biplane for the UltraVair

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#### skyguynca

##### Well-Known Member
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OK, so now with some time I am sitting down with SolidWorks to design a new Biplane for the UltraVair.
Here are a few pics of the wing design. Just getting started, tube spars and ribs along with the trailing edge done. Weight is 13.43 lbs for the panel. Total estimated weight is 18.67 lbs for the the completed covered panel so I will feel good with all 4 panels weighing 80 lbs covered.

That leaves 174lbs for airframe, tail feathers and engine.....I think I can do that.

David

#### cluttonfred

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Neat! No ailerons…?

##### Well-Known Member
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Thats an odd airfoil? As mentioned no ailerons so going the CHEL or Sprat route?

#### skyguynca

##### Well-Known Member
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That is the one of the upper wing panels, ailerons are only on the lower wing. It is not aerobatic so two sets of ailerons are not needed.

The airfoil is an LM7610, been used on a few planes. Leading Edge used to sell them. Pretty efficient for low speed when not heavily loaded, on the powered EZ's you would see 11/1....on the Early Bird Jenny (very draggy) you would still see 8 or 9/1 with single pilot no passenger, on 48hp still climbed at gross of 800lbs 450fpm.

Addicted2climbing, I have the Raceair plans for the Skylite and the Zipster in my collection. I bought them from Ed before he sold the rights.

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#### BJC

##### Well-Known Member
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It is not aerobatic so two sets of ailerons are not needed.
FWIW, Robert Armstrong flew a flat wing two aileron Pitts is the World Aerobatic Contest.

BJC

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Using the Zipster or micro mong plans would be worth referring to for your design. Im very interested in your motor when its ready. Im swamped until October but plan to start a Skylite immediately when im free.

#### skyguynca

##### Well-Known Member
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Using the Zipster or micro mong plans would be worth referring to for your design. Im very interested in your motor when its ready. Im swamped until October but plan to start a Skylite immediately when im free.
Well, while I do like both designs alot, they are quite different from what I am doing.
As I post more of the design you will see that it takes no reference or similarities from either.

The Main Goal of this design is for it to be affordable for the average person and not a complicated build. I Fly's Aerolite 103 $13,000.00+, The Zipster welding required, coplicated fittings between the rib and spar and very very expensive tubing for the spars, well over$1500 just to buy the tubing for the spars.

My goal is to proof test that a nice ultralight with good performance can be built out of metal for less than $1500-2000 and simple enough for the average guy. The ultralight sport has mostly been forgotten. So the few models that are still out there cost around 1/3 of your annual salary or are completely beyond your disposable income. Or use so many off hand parts that you either have to pay a machine shop or metal shop to make your parts, or set up a wood shop.....making them un-affordable. I am trying for safe, inexpensive and mostly built or totally built using hand tools. I don't know if any of you knew Calvin Parker. I got acquainted with him when I built my Tennie Two. Great guy and became a good friend. He took so much crap from the homebuilding community when he introduced the T2. Well it was aerobatic, could be built for less than$2500 and used common everday tools. I loved mine and wish I had not been deployed to Europe and forced to sell it. He had the right idea and while I am late getting back to the game, I want to try and carry on the tradition of designing something so the every day middle income guy or gal can fly their own airplane.

thanks
David

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#### karmarepair

##### Well-Known Member
HBA Supporter
The airfoil is an LM7610, been used on a few planes. Leading Edge used to sell them. Pretty efficient for low speed when not heavily loaded, on the powered EZ's you would see 11/1....on the Early Bird Jenny (very draggy) you would still see 8 or 9/1 with single pilot no passenger, on 48hp still climbed at gross of 800lbs 450fpm.
Larry designed this airfoil, a modification of an Eiffel section, to use on the Easy Riser tailless hang glider - the reflex is there for pitch stability.

But reflex shifts the lift/drag polar down, so the lift/drag ratio is worse, as well and the maximum lift coefficient (although the advertised Cl Max of 1.8 is QUITE good).
Airfoil Design for Tailless Airplanes: 4 explains this better than I could.

Could you use a thin, cambered un-reflexed airfoil? The reflexed airfoil you've proposed WILL reduce the needed tail volume, true, and there is A LOT to be said for using something that has worked before in a similar application...but I wonder if there is a drag reduction to be had by getting rid of the reflex?

Some possible airfoils to think about:
GOE 265 AIRFOIL (goe265-il)
GOE 495 AIRFOIL (goe495-il) Gottingen airfoils are numbered in the order they were tested. Makes it a pain in the ass to find a particular thickness and camber.
E61 (5.64%) (e61-il) Eiffel
lrn1007 (lrn1007-il) low reynolds number, but laminar flow. I'm skeptical anyone can achieve the really nice lift to drag the X-Foil predictions promise for this.

I can't find polars for the LM7610...

I applaud what you're doing. Go, GO!

HBA Supporter
48" cord

Thanks
David

#### Lars Odeen

##### Member
I think this is an awesome idea. I like biplanes a lot, and will be following your project with great interest.

#### dew777

##### Active Member
@skyguynca

I like what you're doing with the ultralight biplane design!

#### skyguynca

##### Well-Known Member
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Super busy with work right now. I will progress on the project as time allows
Thanks for the interest

David

#### skyguynca

##### Well-Known Member
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Lightest possible, going to use 3/16 acft cable for Drag and Anti-drag, they are just not in the uploaded CAD rendering

#### Bill-Higdon

##### Well-Known Member
David, I applaud your efforts, Cal Parker took a lot of crap for things that are now common practice.

#### David L. Downey

##### Well-Known Member
Lightest possible, going to use 3/16 acft cable for Drag and Anti-drag, they are just not in the uploaded CAD rendering
Just curious, Dave: 3/16 seems massively over strength for crossed wires in that kind of a wing? Did you mean 3/32" aircraft cable?

#### skyguynca

##### Well-Known Member
HBA Supporter
Yes, sorry for the typo, was in an hurry. The wing structure is almost the same as the Early Bird Jenny.

#### David L. Downey

##### Well-Known Member
Thank you for the reply; that was the reason I asked! I always liked the earlybird solutions! If you get done before I die I will be one of the builders! Love biplanes and love fabric covering! (and then I can use the crest used for my avatar on the fuselage sides!!!)