Top Flite P51 - 65" span

[Peter Jenkins]

Hi Mike, I haven't got the plan with me in the house but if you look kn page 36 of the instruction book at steps 7 and 8 and page 37 step 9, it's fully covered there. As I said above, this is odd since the full size does not have any such structure! I suspect its just there on the model to stop the joiner wobbling around before you glue that in place to the 2 elevators.

Good luck with the H9 Mustang. I had an earlier.one with the full set of Robart air retracts and a Saito 200 Ti. Sold the lot to fund my aerobatics!

[Mike Mueller 1]

Peter. Been doing pretty good here in the colonies.....hahahaaa.....but have come up with a "problem", and wondered what you think. There is always something...............so my wing is a bit off. The right end sits about 1/3/4" lower than the left side..........some of it is that the wing itself is not "level, and I think I can take care of that with some spacers where you connect the wing to the fuselage. My bigger problem is that the wing is "warped' a bit. The right wing in the front is about 1/2" higher than at the root. The left is about 1 1/2" higher. The right wing in the back is about 1 1/4" higher and the left rear is also about 1 1/4" higher than at the root of the wing. . So the rear of the wings look pretty good, and the front of the wings are off about 3/4". If you consider the front and the back should be parallel, then the right wing should be about 3/4" higher, and the Left is about 1/4" too high..........does that make sense? I have the wing completely sheeted, and ready to cover. One more thing.......the left wing is level with the right about a foot out. Then it changes about 1/4" ever 6 inches out to the end of the wing, there it ends up being 1 1/2" more at the wing tip. I'm of the persuasion to just leave it, and work it out flying, adjusting aileron and rudder while flying. Some tell me that I need to steam the wings to being level........don't know how that might work with a wing that is already put together.........I'm not of the persuasion to remove balsa, and redo one of the wings.........what are your thoughts? Be nice now......Thanks!!! Mike Mueller

[Peter Jenkins]

Hi Mike

I'm slightly confused by the description of your wing. As designed, the wing is supposed to have a twist in it whereby the ribs twist nose down a little as you move from the root to the tip with the wing upright.

Could you confirm that when you built the wing, you kept the tabs on the wing ribs in place when you pinned the ribs to your building board. As the wing is built upside down, the tabs on the root ribs are much larger than those on the tip rib and that's how the twist is built into the wing. This is called wash out and reduces the incidence of the wing at the tip compared to that at the root. The reason is that as you slow the aircraft down and reach the stalling angle of attack, the root area will stall before the tips do. If the wing is built with a twist the other way, is is called wash in and is to be avoided like the plague. That's because the tips will stall before the root end and there will be a vicious wing drop. Washout is a standard technique on both full size and model aircraft where they are predominantly going to be flown under positive G. You don't find this on fully aerobatic competition aircraft as they spend half their life inverted so an untwisted wing is what you want.

With the wing upright, if you hold you wing on your building board with the root TE touching the board, you would expect to find that the tip TE is sitting off the board. With a 2.5 deg twist, you would expect to have the tip TE about 1.5 inches above the board (Tan2.5 x 32.5). The distance between the LE and the building board should be lower at the tip than at the root but don't worry about measuring that as if the TE measurement is correct it doesn't really matter about the LE measurement unless you've used some very odd ribs!

You should have the same amount of washout or twist on both wings otherwise you will have a built in roll as soon as you get airborne and will need aileron trim to sort out the problem.

You will also have joined the wings together with a set dihedral angle giving a very shallow V. This will also raise the tip of the wing relative to the root. When you join the wings you would have done so with the wings upside down and using 2 bits of balsa planks underneath the centre section to provide the correct joining angle. The wing tips should have the same amount of displacement upwards from level with the wing upright plus the wing section at the tip will be tilted down a bit relative to the root.

I don't know if I've answered your question or misunderstood you. Are you able to put up a photo of your wing? Did you use the same steps as I did when building my wing (see pages 3 and 4 of the build)?

Look forward to hearing from you.

Peter

[Peter Jenkins]

By the way Mike, I sent you a PM which you might want to take a look at. It's showing as unread in my Sent Box.

[Mike Mueller 1]

Peter...not sure I understand the wing fillet installation.......you have anything on that?

[Peter Jenkins]

Mike - Ah, wing fillets! Well, I got as far as putting them on and then taking them off as they weren't right first time! That's when the flying took precedence and the Mustang was parked. However, as we have just entered Lockdown 2 in England until at least 2nd Dec, I shall be returning to the Mustang build and tackling the.....wing fillet! Watch this space!

[Mike Mueller 1]

Peter. Here is an example of how someone has done the wing fillet.. https://www.youtube.com/watch?v=jTvJhEdYE-g

[Peter Jenkins]

Hi Mike

Thanks for the link. I did watch it but it seemed to me that he was experimenting in how thick to make his mixture and ended up with it setting before he could finish. I think he has the rear of the fillet wrong as it is too shallow. If you look at a photo of a Mustang the rear fillet is almost twice the size of the fillet at the front and his finished piece wasn't that close to the scale view.

I think I'll stick to the way I was doing it using sheet but make sure this time that the size of sheet I use is wider than before so that it takes up the right contour. I will also be wetting or steaming the sheet before hand to help it to bend to shape, I might use some filler to make good the odd bit but my feeling is that the resin route might end up being heavier.