ptulmer

My Feedback: (5)

I'm almost ready to build this bad boy. Before I tried it, I thought I'd see if I was even close on the spar sizes. The LE is 1/8x1/8 square. So is the first and second spar.(these two are only on top. The Third spar is 1/8x1/4. I was thinking hard balsa should be enough. Would shear webbing be necessary? Any other thoughts? Soon as my engines get back tomorrow I'm going to start wearing out no. 11's. (wonder where they were?...hehe, One guess...bet their purdy now!)

rrragmanliam

My Feedback: (1)

Nice I like it!!! Any dehidral in the wing? If so I'd make the rudder a little more square. It'll make knife edge easier with less roll coupling.


Darren

BMatthews

1/8 sq for the leading edge is too small for two reasons. First it's not strong enough unless it's made from spruce. And second it won't support the covering for that critical to the stall first few % of the shape. I'd go for a 1/4 deep LE and make it wide enough to fit that 1/4 deep. Maybe 1/4 x 3/16 on edge?

If it's symetrical use the 1/8 sq turbulator spars on both the top and bottom so the airfoil will be the same shape on the upper and lower sides. Similarly use TWO 1/4 x 1/8 spars with one on the upper and the other on the lower surfaces. Lay them flat and then web between them. Either put the webbing between the spars or for this low stressed an application just glue the webs to the front or back sides of the two spars. Vertical grain of course. And even if it's not a symetrical airfoil still use the top and bottom 1/4 x 1/8's and web them. It looks like you'll be doing some serious aerobatics with this one and it'll need a proper I or sideways U shaped spar system for proper strength.

Otherwise it looks pretty good to me.

ajcoholic

My Feedback: (10)

Even 1/16th shear webbing will add LOTS of strength and negligible weight.

If you want to keep the spar sizes down, try some basswood. I like it better than spruce or pine.

AJC

ptulmer

My Feedback: (5)

2 degrees dihedral. I think that's about enough to make it neutral. I'll fix the rudder. I kinda took that one from looking at a pacer. (I thought it looked cool) But the pacer didn't have dihedral, so it may have needed it. I think this pic may show more of what you were saying Bruce. Is it better? I think I'm almost up to the same weight as a wing sheeted to the spar. Will 1/16 ribs be ok or do I need to upsize to 3/32?
A note on the airfoil: I used an airfoil similiar to the one used on the Electrostreak. I had converted one to glow with a .15la and it was the best dern plane I have ever flown. Better even than my one so-called sport/pattern .40 size. I'm not fixated on it tho.

Dukester

My Feedback: (31)

To make it easier to notch the fronts of the ribs, you might rotate the LE stock 45 degrees so that instead of cutting a square slot you are cutting a angled notch. Then you can sand down the sharp front side to create your LE.

Duke

Bipe Flyer

Here is my replacement built up version of an ACE mini foam wing. Hopefully it gives you some ideas.

I've used this on several planes, with and without shear webbing and it works great. I prefer using the shear webbing becasue it adds a lot of strength with little weight. I leave the outer 2 bays on each tip without shear webbing.

Leading edge: 1/4" balsa
Trailing edge: 1/4" balsa
Sub spars: 1/8" balsa
Main spars: 3/16" balsa
Ribs: 1/16" balsa
Sheeting: 1/16 balsa
Ailerons: 3/4" trailing edge stock

BMatthews

I'm with Dukster. Either make it a 45'ish V notch or make the leading edge stock taller and narrower so it just fits the full vertical nose of the rib. It's a lot easier to cut the ribs that way.

The new sketch looks fine structure wise other than the LE but I have to ask abou tthe airfoil. It looks like you pulled it from a plank style flying wing. There's a LOT of reflex in the rear of it. It's possible that it may even make the model fly quite a bit different upright to inverted.

Why not just go for a full symetrical? To make it easier to build use one with a straight line rear section like the one below that I'm going to use on an upcoming 1/2A project (it's a secret so don't ask... ). The rear part of the rib is flat top and bottom and note the trailing edge is angled as it's a piece of 3/16 sq that can then sit flat against the building board and the ribs but up against it. Well, actually the ribs will notch into the 3/16 sq by about 1/16 for a more solid joint.

If you like this airfoil I can send you a better jpg or a CAD file. It's not a brand name item but for a loose covered open frame wing it's all you need and will work as well as anything.

Bipe Flyer

If you do many built up wings I'd highly recommend building yourself a wing jig like on Howard Sullivan's web site. It really makes building wings a piece of cake. I couldn't find any arrow shafts, so I used steel rods from the hardware store.
http://webpages.charter.net/rcfu/Con.../WJConstr.html

Tower sells a Great Planes wing jig that is very similar, but I built mine in less than half an hour for only a few bucks.
http://www2.towerhobbies.com/cgi-bin...?&I=LXK258&P=7

zoomzoooie

ptulmer what do you want your plane to do? It looks like it would be a fast plane. I would use a symetrical airfoil with no dihedral for an aerobatic plane. What is the line towards the tips of your ailerons? Your ailerons should extent to the tip of the wing. This will make them more effective. Add small gussets to the inside corners for strength.

My little 33" SuperHots with a full symetrical airfoil uses 1/8" sq. spruce top and bottom spars with no webs. It has a 1" x 3/8" lite balsa leading edge rounded over. The wing uses 1/16" leading edge sheeting top and bottom from the leading edge to the spars. The ribs also have cap strips but are not neccessary. It has a 1/4" sq. rear tapered spare where the ailerons attach. 1,1/4" wide 1/16" sheeting. This is a very light but very strong way to build a wing. For added strength you could add webs. The tail feathers are 1/16" x 3/16" frame work covered with 1/32" sheeting to make very light but strong tail sections.

I agree with using bass wood or spruce rather than balsa for spars. It adds a whole lot more strength with no real gain in weight.

ZZ

combatpigg

My Feedback: (3)

3/32" ribs will stand up to heat shrink if they are 3" apart in a typical 1/2A wing. The shear web doesn't have to span the entire rib bay, I just glue 1/2" wide strips of left over 3/32" adjacent to each rib in a high stress application. A weak L.E. will not stand up to a rough grass field, 3/16" by 3/16" hard balsa is minimum. 3/16"by 3/16" spars do a good job of supporting a 36" span plane that weighs a pound or less, but my favorite is a single 1/8" thick spar that is 3/4" deep, and a 1/8" by 1 1/4" single sheet trailing edge, a simple notch in the ribs overlaps the T.E. sheet.

ptulmer

My Feedback: (5)

Well, I'm never too old to learn. I figured out why the first airfoil came out reflexed. Compufoil is a very powerful program. Sometimes you have to look for new ways of doing things. Based on all the advice I've gotten here is a new set of ribs. I'm not sure this is actually going to be lighter than a sheeted and capstripped wing. If it's strong and easier to build it would still be worth it.

I would like for the airplane to be capable of doing aerobatics. (even if I can't) But I don't think that the ailerons stopping 1 inch short of the wingtip will make them any less effective and would be less likely to flutter. Especially on a weak structure like this.

ps. When it flies I'll post a link to the plans.

ptulmer

My Feedback: (5)

Got my engines back. Man, Tim does a great job. Look at those little blue .020's! BEEautiful!!! I keep looking at that airfoil. I think I might thin it down a little. Opinions?

LS171Malibu

My Feedback: (16)

Just for reference... I have a small stick type plane I scratch built. All balsa in the plane is of the highest grade contest, very light. I made the spars by cutting four strips of sheet to 1/8x1/4x48, and laminated 0.007"x36 carbon matte in the center. Then cut down to 42" total length. The ribs are 2x8x1/16" and there are only 8 total. 3/8 LE. 1/4 TE. 1/16 Sheeting LE to spar, and center section. No cap strips. 1/16x3/4 sheet gussets on each side of rib at the TE. 1/16 vertical grain web except for out board bays. 3/32 ply laminated with carbon in the center bay web and another one inch forward for dowl support. Carbon laminated balsa for bolt support at TE. 1/4sq for aileron and wing tip frame work. Ailerons are 3 1/2 to 2 1/2 full length. Tips are 2 1/2 at widest point. Coverd with trans monokote. 2 225s and 2-56 rods. The finished wing weight is 8oz! The only thing I would do different is shrink the ailerons after hinging, or use heavier wood for the long runs, as they slightly bowed when shrunk.

OK... So, the planes finished weight is 2 1/2 lbs with fuel. Powered by a Saito 40a. This is a very strong wing. I have put it through vigorous flight test with no failure.

I feel that most planes are way over built. One thing is true though... this thing is a one crash plane. I would not expect to be able to fly it again if it was not landed on the gear.

BMatthews

Dang! Those deserve a thread of their own! They are GORGEOUS!

Thinner will fly faster but may not loop as tightly. Which you use is up to how you want to fly.

ptulmer

My Feedback: (5)

Here is a pic of the updated airfoil. The top one is 3/4" at the thickest point, while the bottom one is 7/8 at the thickest point. Both are 5 1/4 inches in chord. The aileron is 3/4" te stock. Bruce, I'll pm you my email address. If the offer is still open, I'd like to compare them.

Electricity has been down since Sat 'bout noon. (several trees too!) So, I sat down during daylight hours and started scratching a flat plate delta out for one of those .020's. Look's like they will get their own thread this afternoon!

Cad files will be available when I'm finished. (maybe a pdf also)

LS171Malibu

My Feedback: (16)

It looks to me like you plan on using shear webs on the fore and aft sides of the spar. In my opinion this is an over kill. I would suggest using verticle grain 1/32 in between (like an "I" beam) from the center to about 2/3 of the span. I know the balsa is light and it doesn't seam like much savings... but if you emply this type of building throughout the entire plane there is a lot of wood and glue weight to be saved. Just a suggestion though.

rrragmanliam

My Feedback: (1)

Hey Ptlumer, Did you start this yet? Check this sight out. Your plane looks like a prime cantidate http://members.cox.net/moorman1/ProjectJoss.htm

Darren

ptulmer

My Feedback: (5)

That dude was having too much fun freaking everybody out! I counted ten airplanes that he put anhedral in.
I'm finishing up the drawings. I should start cutting parts by monday.

rrragmanliam

My Feedback: (1)

Yea, I thought it was interesting. I have a simple 400 that I took all the dehidral out and squared the rudder on. It helped a little but it still wants to roll with rudder input. I'm going to cut the wing and try it. I'll let ya know.

Darren

ptulmer

My Feedback: (5)

It should work. The effect of dihedral and anhedral is to move the cg vertically. So on a low wing airplane with flat wings you already have an anhedral effect. By giving a low wing plane dihedral you bring it closer to neutrally stable. The opposite is true for a high wing. I wish I knew a formula for determining how much to use.

LS171Malibu,
I was looking back at your post. Hopefully, this will be an extremely light airplane. But yours sounds great! That engine is pretty heavy. Getting it on cg must have been difficult.