M4 Wing Re-Skin

n1264d · Post by **n1264d** » Tue Oct 16, 2007 4:05 pm

I am going to be re-skinning my wings here shortly. My plane will be in the experimental class when I get done rebuilding it. I am planning on using a wing jig similar to that of the Bearhawk. Basically two 4x4s mounted floor to ceiling with wing inbetween everything leveled and square. Wing root and tip end mounted securely to 4x4s to prevent movement. My question is, are there any dimensions I need to worry about or is everything supposed to be straight and level? Anyone use any other way to skin a wing. The top skin and leading edge is already off of one wing and the other wing is still complete.

Thanks!

MikeW · Post by **MikeW** » Tue Oct 16, 2007 7:41 pm

Are you putting a Bearhawk wing on your Maule or was your question just regarding the fabric work. What other mods are you considering to make it experimental? Poly-fiber has some really good instructional tapes/dvd's out there if you need a refresher before tearing in to your project. Also, I think there are some workshops available from time to time in Fairbanks and down in Anchorage, one was in the Anchorage paper last week.

MikeW

maules.com · Post by **maules.com** » Tue Oct 16, 2007 10:38 pm

Presumably you are reskinning the metal skinned Maule wing with metal.
Maule is now using a thicker top skin aluminium.
If you are going experimental, if it is for speed then keep the short length with the droop tip, but if going for slow speed landing then you might consider lengthening your wings and using the later flap system.

a64pilot · Post by **a64pilot** » Wed Oct 17, 2007 4:13 am

You might want to contact David Wright, he is in the middle of building a Maule wing jig for an experimental 300 hp., short winged Maule.
The one problem with keeping everything "square" is I assume there is washout, Keeping it "square" would of course remove the washout if there is any.

Hottshot · Post by **Hottshot** » Wed Oct 17, 2007 7:18 am

The Maule wing is built with NO washout built in.... that is done with the struts...

Please correct me if I'm wrong

maules.com · Post by **maules.com** » Wed Oct 17, 2007 8:43 am

M4 and M5 wings were built with no washout but later wings are built with washout I'm told by the factory.

Hottshot · Post by **Hottshot** » Wed Oct 17, 2007 8:49 am

Thanks Jeremy!

UP-M5 · Post by **UP-M5** » Wed Oct 17, 2007 9:10 am

my left wing is in a jig being reskinned right now. it is straight and square. and it is .020" on everything except the tank lids.

anyone here have any favorite primers for use on aluminum? anyone know what the factory is using? i like the boeing primer, but some are telling me not to use it on the external surfaces???? i already did the inside with it.

n1264d · Post by **n1264d** » Wed Oct 17, 2007 10:31 am

Thanks for all the info. I am doing an a metal wing. I want the speed but also some stol in the mix. Right now the fuselage is almost through silver (have a couple of pin holes to repair first) in polyfiber. I am making a new panel for it, vg's, going with extended gear, GAR Aero tailwheel, Bushwheels, 5th kid seat in cargo, patrol doors through cargo area and nomex honeycomb floorboards. It will be basic VFR with a lot of the interior panels tossed because it weighs a ton. It will have the Cont. I0-360 because that is what is on my shop floor right now along with a prop that is 0 since overhaul. That is the wishlist and so far the FAA sounds ok with it. The wing is an m4 wing converted to M5 with aileron, flaps and attach fittings. I had heard of a full mX7 wing for sale with everything in good condition and was/am still looking into that as being a good idea and saving time on the entire reskin project.

I went to a polyfiber week long course when I lived in Southwest AK but that was a couple of years ago. I saw the recent one advertised in Anchorage but won't be able to make it because of scheduling. Maybe next time.

UP-M5, anyway you could post some pics of the wing in the jig? I was thinking of going with .025, any reason you are using .020 on the wing? When reskinning are you doing the lower sking and trailing edge in the 11+ ft. sheets like the factory or breaking it up more? I was thinking I would have to separate out the trailing edge as I don't have a brake available to make the seam along a 11+ ft. piece. The reason for reskin is when I bought the project one wing had a leading edge and top skin off and the second wing was ready to go but had some cracks and repairs that I don't want to put back on a rebuilt airframe. I just can't do a good job on everything else and then leave several unsightly repairs on the wings.

flyer · Post by **flyer** » Wed Oct 17, 2007 6:26 pm

I am, once again, somewhat confused.

My M-5 wing calls for a washout of .5 degrees. If the wing is built square, will not bending it to .5 degrees washout cause wrinkling the skin? Would it not be better to build the washout in before skinning?

When I disconnect the struts, it appears to maintain the .5 degree washout. Maybe it maintains that because it has been bent that way for so long.

Flying is very complex. Maybe someone could simplify it for me.

flyer

maules.com · Post by **maules.com** » Wed Oct 17, 2007 10:28 pm

Most M4 and M5 wings with correct washout do end up with a little diagonal oilcan in the top skin. You could feed in the 1/2 deg when reskinning. Probably a good idea to go with next thicker top skin material to lessen cracking potential as seen in some worked M5's.
The M5 fuselage can be modified to take the later flap mechanism wings, MX7, M6 2nd generation though you'll need to change to the deeper chord rudder as well.

UP-M5 · Post by **UP-M5** » Thu Oct 18, 2007 9:09 am

n1264d wrote:

UP-M5, anyway you could post some pics of the wing in the jig? I was thinking of going with .025, any reason you are using .020 on the wing? When reskinning are you doing the lower sking and trailing edge in the 11+ ft. sheets like the factory or breaking it up more? I was thinking I would have to separate out the trailing edge as I don't have a brake available to make the seam along a 11+ ft. piece. The reason for reskin is when I bought the project one wing had a leading edge and top skin off and the second wing was ready to go but had some cracks and repairs that I don't want to put back on a rebuilt airframe. I just can't do a good job on everything else and then leave several unsightly repairs on the wings.

i used .020" because that is what was there. i wasn't aware that the factory had started using thicker material. but the thinner stuff has done fine for the last 25 years...
we have a 10' break to work with. so we just moved the factory lower skin splice one rib inboard. i thought about making the trailinig edge seperate, but moving the skin splice is easier for us.
i don't have any pics. but i could possibly get some in the next week or so.

maules.com · Post by **maules.com** » Thu Oct 18, 2007 10:43 am

The most common cracking points to look for are around the screws at the trailing edge of the inboard tank cover.
The other is spider cracks at the rivets attaching lower wing skin to the first trailing edge rib outboard of the wing root. There are only three rivets and adding two more stops the potential problem. Usually the right wing cracks first.

AK Mauler · Post by **AK Mauler** » Thu Oct 18, 2007 12:38 pm

I have a year 2000 MX7-180 and the bottom inboard wing skin has some slight rippling. It has always been that way since I have owned the plane. As far as I can tell, it doesn't effect the flying characteristics, but it just bothers me the way it looks. I am wondering if this rippling could be a result of the wing not rigged correctly with the struts? or could it be a slight manufacturing defect? The wing is not bent and there are no rivits that appear stressed. I was wondering if anyone else has seen this and had any luck correcting it with strut/wing adjustments. I really hate fixing something that isn't broke, but it just doesn't look right.

M4 Wing Re-Skin

M4 Wing Re-Skin

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