wing aerofoil

[Epitaph]

Hi peeps ^.^

I'm probably going to make a second wing for my 735mm Modelhob Coyote with less dihedral and ailerons. At the moment I'm listening to the podcast and playing with a 9g servo thinking how best to fit it, which I think I have that figured out. Now, the original plane came with a Clark-Y aerofoil, 14° dihedral and was a traditional 3ch trainer, I.E. no ailerons. I was considering going down to about a 5° dihedral and have more or less figured out the aileron mechanism for such a small wing (only 100mm chord), and a friend said recommended the E387 aerofoil for it when I asked what would be better than a Clark-Y to benifit the ailerons and still be a slow flier... so here I am asking opinions on a decent aerofoil for this plane.

 

[Epitaph]

Well, after a test of this aerofoil and a few others on the simulator, and no one had a better one to suggest, I decided to go ahead with the E387 model. I've already cut out the ply centre ribs and the central dihedral reinforcer which I have one of the washout halves gluing into place right now. The centre 3 will be in 1.5mm ply and all the rest in 1.5mm balsa. The centre one will have to lack the leading edge half though due to the servo mechanism for the ailerons, so will have to be reinforced with a little glass fiber.

Anyway, it's underway.

I'll post a couple of photos as soon as I can

 

[Epitaph]

New wing with ailerons

Well I managed to get hold of some 1.2mm ply, and it's tbe good stuff from Robbe in Germany! I had to make a plinth to sit on the fuselage sides as the wings new profile has a lower leading edge that has to be "molded" around the fuselage. Anyhow, just started gluing and already made a small booboo, as I forgot that the trailing edge on the centre is also covered in 1mm balsa the same as the entire leading edge... nothing that a little sandpaper can't fix though. Left the pieces gluing all night, and yes, it might take its sweet time, but white glue is the best there is for balsa and ply... hard as a rock now!

 

[Epitaph]

Here are the photos I've been meaning to upload...



And now some new ones... I've finished the plinth for the servo to sit on and have made up the front part ready to take the covering on the top. It's all been presented onto the fuselage and fits perfectly nto its place, which I was most worried about the servo as I hace the receiver at the same height on the "unocupied" side, but fits into place very nicely.

Now I can start placing wing ribs into place and start to think about hoy to make the ailerons and how best to snake the cable conduit to them.

 

[Epitaph]

Right... well, with what I have done since the last update, I'd say it's time to add something else, even if it is just one blurry photo...

I've added the fixed section of the trailing edge to one side of the total wing, adding all the ribs that go with it, and the last if the ribs being extra thick to take well the strain of the cut in for the aileron. I think I will go with a 150x20mm size aileron in the end, the total wingspan being 735mm. Still have to figure out exactly how to get the conduit to its position without adding too much weight or putting any nasty angles in it that the cable will not be very likely to appreciate.

Anyway, here it is for the moment!!

 

[earthsciteach]

Great work!

The undercambered airfoil will work nicely for a slow flyer. It will have more drag than a Clark Y, but that just doesn't matter at slow speeds. It will HATE to fly upside down, though, if that's a concern. Wouldn't be for me.

 

[Epitaph]

The plane itself is overpowered, because I made it out of bits and bobs I had lying around, so the drag isn't a problem as I will have the power to compensate if need be. As far as inverted flight goes, I'm not looking for that at all, hence why I still kept a little bit of dihedral on the wing, but it's only a very little. I'm not saying I won't make the odd loop and such, but this is a trainer, and I like a plane to fly as it should, not a "3D Cessna"!!!

I've been figuring out the conduit for the aileron control this evening, and right now have the starboard conduit drying in place... I was worried about the cable working well on the 90 degree turn it had to make in such a short space, but I just stuffed some vanilla lip balsm (which is basically vaseline) in the conduit hole before threading the cable through, and it works really smooth eventhough it's working more than it will as I haven't cut back to measure yet and is running through about 20cm of extra conduit, so I'm really pleased... I was worried most of the power of the servo was going to be wasted trying to push and pull the cable around that tight bend.

 

[xuzme720]

Why not go with a bellcrank? Not enough room or is it a weight issue?

 

[Epitaph]

A bit of both actually... Weight is already an issue because of the reinforcements where the ailerons are, but then I guess it's just as well I changed the aerofoil, which should help give the lift needed for the extra weight. I'm calculating the AUW to be about 300g in this version, which in scale weight is still within the limits, as the original 1430mm version has an AUW of 1500g roughly.

Anyway, I have the cable in place on the starboard wing, and it's running pretty smooth dispite the angle... I'm pleased with the outcome!!. I'll post a couple of photos later on tonight!!

 

[Epitaph]

Well... Just hooked up the servo to a servo tester and it's working great, but... I'm going to have to dial in some serious EPA figures

 

[Epitaph]

Ok... I think I'd better upload those photos...

 

[Epitaph]

Well... I've made a little more headway on the project, adding the balsa to the top of the wing and placing the aileron into its position... little trick: for sticking the aileron in place, I used a 3M medical tape which is like a sticky fiber. After putting into place, paint on a mix of 50% white wood glue with water and leave to dry. The mix is soaked up by both the tape and the balsa, turning it into a nice strong hinge.

So on this side all I have left is the leading edge and the wingtip... but I still have almost the entire port side to do yet, so that should keep me nice and busy!

 

[xuzme720]

The bend doesn't look that extreme. Or am I just missing the scale of this bird?

 

[Epitaph]

I tried to make it as nonextreme as possible... remember, the wing only has a 100mm chord in total, then from that you have to take off the aileron, then the horn movement, then a little for difference in angle... in total, that bend is happening in 50mm nothing more, and the cables are the tough ones!

I might have to take off the servo and reposition it to improve the lineal movement, but I'd rather do thatonce both ailerons are in place with their horns attached.

 

[xuzme720]

Ooh..yes it IS smaller than I was thinking...
I love the thinned glue on fabric tape tip. Seems much more permanent than blenderm!

 

[Epitaph]

Well I've now got the port wing with all the external structure in place, and half the ribs glued in so that's well underway. I also removed the servo and lowered the plinth to allow for the use of a smaller servo arm without affecting the lineal movement too much... -For those that don't really understand what I mean by this, a servo uses circular movement. When the arm is on a right angle to the rod it's moving, the movement transmitted to the rod is maximized because the circumference of the servo's circular movement is more or less in line with the direction of movement of the rod. But as the servo's circular movement reaches closer to getting the circumference perpendicular to the travel of the rod, the lineal movement reduces, eventually even becoming non existent or even reversed. This is seen in a cutaway fo a traditional gas engine, where there are 2 stages where the crankshaft can be seen as turning, yet there is no movement in the piston.-

Anyway, being the "Someday's dreamer" that I am, here I find myself making a MiniCoyote 2.0 wing, and thinking not only of a third version with flaps in the mix, but also the application of some of these things to a low wing design, as I was thinking about balsa scratchbuilding one from intuition and memory (no plans)...

First, I need to finish this though, and I am forseeing a problem with the oracover... Namely "iron problems"... I'll be happy anyway to chant victory by completing the structure for now... Covering is very straightforward...

 

[xuzme720]

A girl with iron problems. What is the world coming to?


I'm sorry, I said I wasn't and the damn traitorous fingers went right on ahead and kept typing. I am currently slamming them in the drawer for their insolence!

I am curious though, what's wrong with your iron?

 

[Epitaph]

Heating element inside burned out...

And I don't have an iron problem with clothes as I wear clothes that don't require ironing... Just a know how to peg them out to dry!

 

[xuzme720]

Ahh...new one on order yet? I know you aren't letting it keep you down!

 

[Epitaph]

That's not what's keeping me down...