combatpigg

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Good evening, I have a little bit of progress to show. I mounted the sheeted wing to a long board and sliced the wing length wise [ on a table saw] in 2 places so I could sandwich in some spar lumber to give the wing some strength. I used standard local grown lumber [1/8" thick]. I know that SITKA SPRUCE is the superior wood, and some day when I build a full size plane that has to carry me I will get some. My spare time will be eaten up for a couple of days getting my car back on the road, but the next items to do on the wing will be final surfacing of the skins, and the wingtips.

der_steuermann

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Hi combatpigg,

cutting an already (balsa?) sheeted wing to add wing spars is new to me. [X(] To show a potential alternative I'll prepare a drawing tonight picturing the typical layout of my speed plane wings based on foam...

Seeya later!

bob27s

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On some of my F-1 and older QM wings, I used a good ole hardware store wood yard stick for wing spars. But the spar was trimmed, and glued to the cores first.......then the assembly was sheeted.

Cutting afterward...... probably will work as well. I recall folks doing that to reinforce damaged wings.

proptop

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Thanks HighPlains...Guys, there's something I've been wondering about...
Ever since reading about Jiro Horikoshi (sp?) and how he designed the Mitsubishi A6M Zero, I've designed my airplanes with the widest point of the fuse. about 1/3 back. He said he wondered why the guys at Nakajima designed the Oscar and Tojo (Ki-43 and Ki-44 respectively) with the engine as the widest point because that is draggier? (is that a word?, if not, it is now)
You know what I'm getting at, is why don't we design the fuse. (top view) to resemble an airfoil? That would also make packaging the radio easier.
Another thing...if so, should the widest point of the fuse. coincide with the wings airfoil high point, or should they be staggered?
Whadoya think?

daven

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Great thread, I will be keeping up with this one.

Great job so far.

Rudeboy

Using an airfoil shape for the fuse is the way to go IMO... even a simple NACA shape will be less draggier than a straight taper starting at the engine.

It may be a good idea to position the widest part if the fuse somewhere around the trailing edge of the wing.

Don't forget some nice wing and tail fairings.

HighPlains

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In quickie 500 by the rules we are not able to use wing fillets. The typical design of the past usually placed the widest part of the fuselage about where the thickest point of the wing was located and also the thickest part of the combined wing/fuse in height. About 1993 I built a quickie with the widest part of the fuselage moved back to the trailing edge. This tends to promote laminar flow down the fuselage to that point, after which the airflow goes turbulent. Without the expanding width of the fuselage, you tend to have flow separation at the wing/fuselage junction unless you build in wing fillets. In a quickie this was good for about 5 mph on the top end. Now nearly every new design uses this feature.

We also fly mostly high winged airplanes, as they seem to do a bit better in terms of drag at high lift than the low winged airplanes. Not too important for level flight, but a lot easier to hand launch if you are building without landing gear. Low wing airplanes are usually two handed launches unless you turn it over and launch inverted. Especially fun to do with the transmitter in one hand and the airplane in the other.

der_steuermann

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Here’s a schematic illustration of a strong and lightweight speed plane wing.

A wing spar is only recommended when utilizing balsa wood sheeting.

When covering the foam core (incl. spar) with fiberglass cloth all epoxy work must be done applying the “WET-IN-WET“ technique for best stiffness results. That means only one single work step is needed to finish ALL glass and wood coverings for both sides of the wing. For that use slow curing epoxy resin allowing several hours of work time...

The shape and the arrangement of the different glass cloth patches promote a uniform load distribution along the entire wing span. Stress concentrations as well as strain will be reduced to a minimum.

Wing tips: The smoothed wing tips are characterized by a sandwich construction consisting of balsa/plywood 1.5 mm/balsa for instance.

Finally the entire wing can be covered by 3/4 oz/sq yard glass cloth if desired...

-----

Stab and fin: Both surfaces should feature a sandwich construction of e.g.

3/4 oz/sq yard glass/balsa/plywood 1.5 mm/balsa/glass 3/4 oz/sq yard

3/4 oz/sq yard glass/balsa/ carbon fiber panel 1.5 mm/balsa/glass 3/4 oz/sq yard

carbon fiber panel 0.6 mm/balsa/carbon fiber panel 0.6 mm

...

combatpigg

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Another excellent lesson MR GETAWAY DRIVER[8D]! An equally great graphic to show how the wing is done. This thread has already turned into a pretty darn good "ALL YOU NEED TO KNOW TO GET STARTED" course in speed plane design and construction. I decided to go with full depth spars with the 1/16th inch balsa sheeting because the wing is so thin, I felt that I need that extra 1/8" of spar depth. Looking back, 1/64th inch ply would have been easier. The main draw back to my method is the labor intensive surfacing of the balsa/pine joints. I am hoping the plus side to this method will be some weight savings. I am making the wing smaller than the recommended area and I hope to make up the difference with weight savings throughout. I am going to use an ELECTRON RX and 300 NIMH batteries, total weight, 2 ozs. The [2] 225 servos , [1] HS 81and linkage , about 5 ozs. The engine, spinner, and exhaust system, 16 ozs. The bladder and balsa fuel cell, 1 oz. The total on board equipment package comes to 24 ozs. If this plane is to weigh 40 ozs RTF, you can see that I have [we have] a pound to play with for the airframe. So the budget for weight is 6 ozs for the wing, if I go over that then the wing will get used for a 1/2A twin engine bomber, and we start over!

proptop

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Just to get back to fuse. design for a few minutes...I was looking at some old designs a buddy and I used to sketch up some years ago. We designed some high speed fuselages by emulating fish. Take a good look at a Barracuda, or a Pike or Gar and check out the "laminar flow" airfoil (or hydrofoil ?) shapes. I am considering using the X5XX or X6XX series airfoils as a fuse. shape. If we use an airfoil (for the wing) with a finesse ratio of around 8-10% with the high point 50-60% back why can't we use the same basic shape for the fuse.? A 40" long fuse. would then be 3.2" wide at maximum with an 8% ratio. Only (?) problem is gonna be added bulk (weight [:'(] ) but with careful material selection it might not be too bad.

Another question for you guys with the knowlege...What do ya'll think about helical flow around a round vs. square cross section fuse.? The prop. pushes a donut shaped column of air back around the fuse. in (like a ) corkscrew path and I'm wondering if a tubular shaped fuse would be better, or one with squared corners that trys to straighten the flow as it moves back? (seems like that would cause more turbulence)
Another thing...what about dorsal AND ventral fins/rudders (the "fish" design again) of the same area to try to negate the yaw caused by the corkscrew propwash striking just the left of the vert. fin on a "conventional" design?

combatpigg

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HI PROPTOP, I'm not qualified to give an expert opinion, but gut instinct tells me that it is hard to improve on what GOD built, the fastest fish look like little airfoiled bullets. A perfectly round fuselage is possible with the electric planes, but for us fuel burners, mini turbines are not practical,[yet], so we will have to put a cowling around the cylinder and exhaust system. I suppose you could turn the form for a pretty sleek fuselage on a lathe. I think the turbulent air coming off the prop serves to break up air that wants to attach itself to the fuselage, so as long as the front view of the plane is as minimal as possible, that is all that matters.

I have decided to start over on the wing it weighs 6.5 ozs already and I haven't glassed it yet or cut in the aileron. OINK!! I am going to the hobby store to get some 1/64" ply, can I get you guys anything while I'm there? There balsa skin allows slight buckling where the skins are joined, and I don't want to be able to feel the slightest ripple. At least I have a good start on a wing for a 1/2A bomber or a .15 size MUSTANG.

HighPlains

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I would not use 1/64 plywood on the wing. It was tried a long time ago in F-1 and the results were usually the same. SNAP-BANG-WAP, where snap is the sound of the wing folding, and wap is the hole in the ground where it hits. Just not much strength in compression. Much better would be 3/32" for the top skins and 1/16" balsa with .007 x 1/2" carbon fiber for the bottom skin and tension member. Then glass over the sanded wing with 3/4 oz and several layers of 2 oz staggered at the center.

Your wing planform looks interesting, something along the likes of Steve Wittman's Tailwind. It should work quite well.

combatpigg

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H.P., Thanks for your input. I'm going remember what you said about the plywood collapsing. The wing explosions were probably due to some severe yanking on the sticks too. I like the balsa skin method and have never used plywood. The butt joint buckling wasn't going to sand out on this balsa skin job, the CA glue was leaving a ridge. I will keep trying, it might take 2 or 3 attempts, but there will be a "spec grade" wing done before the weekend is over[>:]! This planform is an even amount of taper, front and back. Structurally, it makes sense to reduce torsional moments.

HighPlains

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CA is just too hard to sand when joining balsa sheets. I use Ambroid model cement for joining wing skins. Still smells like modeling used to, fun to peel from your fingers, and about the only good use for it. But it does sand well. Fit the sheets well, tape up with masking tape, glue, weight, and wait.

combatpigg

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You caught me just in the nick of time with that tidbit, I'll pick up a tube while I'm out.

proptop

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Gee, and here I was thinking I was probably the only one still using Ambroid!

daven

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I don't use the ambroid, but I won't use CA either. You can never even out that stiff ridge at the joint. I use regular old wood glue, and tape the joint well. Takes a whil to dry, but you can sand it smooth.

I agree with Bob about not using 1/64 ply. I personally would use 1/16" contest grade balsa top and bottom with a 3/4" wide Carbon Fiberlaminate .007 under the skin at the high point. With the amount of glass you are looking to add, that would be plenty. Personally, I would only use a layer of 2 oz for the middle 1/3 of the wing, and 3/4 oz over the whole wing.

I am very doubtfull you can get to 6 oz with the 1/64 ply.

combatpigg

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Well, I just had to see for myself what kind of results I would get with 1/64th ply skins. I started with cores made from blue foam. Next I sunk in a pine spar, full depth, 80% of span. I also cut in a balsa leading edge and a functional aileron. Then I contact glued [with SORGHUM glue] the skins on. Then I vacuum bagged a layer of 2 oz cloth on both sides, with the reenforcing patches in the center. Final weight before painting or covering, 13 ozs[:'(]. This wing is nice and stiff, perfectly shaped, very nice looking, but it will weigh a pound if I paint it. Wing attempt #3 will be glass directly over foam. I am thinking about using .030" aluminum sheet for a spar. Now anybody interested in buying a couple of wings? From now on if I hear anyone talking about using 1/64th ply skin on a wing, I will quietly say OINK! to that, and keep on walking!

willflyforfood

Pretty neat wingtip fact... I have been doing a lot of research and found that a wingtip that angles back 60 degrees on the leading edge, and 30 degrees on the trailing edge, going to a point that looks rational is the most efficient. This allows the wingtip vorticies to escape off of the wing in the most efficient way possible. Thought this was pretty cool and would share. I have been designing a speed airframe myself and have found some pretty neat info. Would be nice to get something off the paper and on the boards, but for me designing it is half of the fun. We've got some pretty cool wind tunnels here at school and I plan on making full use of the facility, so this for me is a blast.


Joey.

Bob.R

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Joey,

Would you kindly post a sketch of this wingtip shape? Thanks.

willflyforfood

I could scan a sketch and put it on the computer or draw it in paint, but I dont know how to put it in a post, could you tell me? (sorry, you probably get this all of the time). Thanks.


Joey

willflyforfood

Here is something I sketched out.

willflyforfood

Here is another look, same tip on a wing that tapers . You have probably seen something sort of like this on gliders.

Bob.R

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Thanks Joey. Interesting stuff.

proptop

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Hey Joey, are those tips flat, or do they curl up like a winglet? They remind me of an APC prop tip or what some of the fast gliders have.