Quick Build Wing - guidance using the template?

[James]

Hi Guys,

so I went out this evening to drill off my aft tip rib and aft root section - the previous owner had drilled them off and then removed them for storage, so I thought it would be just a case of chucking in some rivets and on to wingtips :-)

1) My template doesn't hug the form of the upper wing. Sometimes there's up to 1/4" gap between the skin/ribs and the wood. Is this a problem? I've looked, but the back of the template seems straight, it hasn't warped.

2) When I use the template, I push it hard up against the nose, and then pull it down to match the ribs as best I can, and hold it with clamps. Or should I let it sit at its natural resting position?

3) When I temp-fit the tip rib / root rib, the trailing edges are a good inch short of the cut out in the template. I haven't hung the ailerons/flaps yet to see where they end.

Should I be worried? Or do I just drill everything off, and match up the trailing edges later?

In another part of the QB manual, it says to wait until you hang the ailerons.
Eric Newton's manual says to match the aileron trailing edge to the tips you've already installed. Which comes first?

Can anyone walk me through it?
Am I missing something really obvious?

Thanks,
James

[Mark Goldberg]

I am sure that wood template conformed to the airfoil shape when it was new. Many, many years later in different humidity etc - it has changed shape. You can always make another using the mylar transparency that came with your plans. Mark

[James]

Righto Mark - if it has bowed outwards, then that would explain both the gap under the cambered surface and the longer trailing edge.

I'll make another one and see if I have any more luck :-)

James

[PaulSA]

Couple of things:

I have found that either the rear spar flange has been slightly under-bent or (more likely) the flap cove stiffener has caused the skin aft of the spar to slightly bow out. I am going to have to run a piece of wood or something along it to get the correct profile and to fit the flap correctly. Secondly, I would hang the flaps and ailerons before fitting the wing tips. Get everything lined up (including the tip rib) and then trim and fix the tip trailing edge to match.

[Bcone1381]

My build is at the same point as you. I have no factory template, so I made one from plywood from the mylar airfoil to fit the top of the wing. Attempting to use it for flap and aileron alignment before riveting the wing closed was unsuccessful due to the issues talked about in Post #1 and #4. My wood jig seemed to magnify the irregularities. When I was doing this unsuccessful alignment the wings were mounted on the fuselage with the bottom skin unriveted.

My second jig (photos below) is made from two piece of angle AL. I fabricated 1" x .062 AL angle to exactly match the mylar airfoil shape, one for the top, one for the bottom. The angle is intentionally warped by striking the side that does not contact the skin with a hammer. I strategically struck it with care. It took about 15 minutes to fabricate each piece. I made two sets. The red line in the last photo should line up with the spar. The wings are sitting in the wing cradle with the leading edge facing the floor.)

The skin sits slightly proud just aft of the spar (due to the cove skin sighted ion post #4) by .045 inches. (1/16 = 062") mine is not close to .250 off.

I "believe" .045" is insignificant especially at this part of the airfoil. So I am pressing forward. "Believe" is the key work in that last sentence. No one told me that. It maybe its wishful thinking. But we most certainly have turbulent airflow this far aft. Also, I don't want my flight control alignment to be off by 1/16" nor do I want uncertainty, or have to wonder if its exactly right.

When setting up my jig, I
a) Make sure the jig is aligned over a wing rib.
b) Make sure the jig is not striking the control surface on a gusset.

I am happy dealing with this second jig because
1) I am able to check the flight control alignment from in relation to both the lower and upper surfaces at the same time.
2) The greater stiffness with the bottom skin being riveted closed provides a more stable platform for jig alignment.


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[James]

Yeah Brooks - thanks for the insights.
I was amazed that you had your wings on the plane with the bottom skins still unriveted - everyone I talk to here tells me unconditionally to have the wing on the level bench every time you measure or drill anything - not in a stand or on a rotisserie. I checked my existing template today, it doesn't conform to the mylar drawing at all, so the 1/4" discrepancy I saw reappears against the drawing. Good news, at least I know my wing profile is not deformed.
I've scrounged some clean MDF and a jigsaw... and amazingly I've managed to find some carbon paper to transfer the drawing line. Luckily the receptionist at work is old enough to remember what carbon paper is!

Some further questions - maybe you can help me again if you see this Mark -

1) Brooks mentions building a jig for the underside of the wing, as a second way of making sure the alignment is good - but the wing surface looks flat on the bottom. The instructions tell you to lay it on a table, and have the ailerons hanging down over the edge - should the bottom of the control surfaces align with the underside of the wing then?

2) The original factory template had a notch at the trailing edge - which is about 1.5" past the trailing edge on the mylar drawing. What's this notch for? I'll mark on the template where the termination of TE should be, but what's the extra chord length for?

Apologies if I've asked a question which is answered in the instructions - I still haven't got my head around all the process yet.
Thanks again for the input,

James

[Mark Goldberg]

I like to hang ailerons and flaps when the wings are already drilled to the fuselage and in place. That seems to me the way to get the best result. Although it can be done on a table. The bottom of the wing is not flat. That aft part of the wood piece is not important. Mark

[James]

Thanks Mark - great info, as always.
I think I'll go for the table option - I need to get my wings painted while I still have access to a paint booth :-)

I'm going to make a new template, put the wing on a level table, ensure the root rib matches, rivet on the tip rib, hang the ailerons and flaps, temp fit the tip rib aluminium strip with regards to the template, and then run a string line right along the trailing edge.

Sounds like a plan!

Cheers everyone,

James

[Bcone1381]

I concur the the bottom is not flat. I really like having both top and bottom references in view for the alignment. I would not go back to having only one reference.

I like to hang ailerons and flaps when the wings are already drilled to the fuselage and in place. That seems to me the way to get the best result. Although it can be done on a table. The bottom of the wing is not flat. That aft part of the wood piece is not important. Mark

Mark, can you be more specific with "Best results."

There is only one place to mount the hinges onto the flight control spar that will result in them being exactly right. We have some adjustment in two axis (left & right + up & down) to position the flight control hinge onto that spar. I don't understand how mounting the wing onto the fuselage will effect things. I'm thinking out loud now. (I hope I'm not sounding across argumentative.) My template in post #5 puts the hinges in the right spot in the vertical axis. I'm working on my wing tip mounting so ensure the horizontal axis is exactly correct. How would it change things if my wings were mounted on the Fuselage? I'll stop where I am and remount them if there is a benefit.

Brooks

[Mark Goldberg]

The reason I like doing everything on the fuselage best is mostly the cables and rigging. Just being able to check for no rubbing etc with the cables is a big plus. With your bottom skin still unriveted. The flap cables can sometimes present challenges. So having the wings mounted to the fuselage just allows more checking of what you got. Mark

[svyolo]

I am pretty close to closing my wings, and drilling the flap and aileron hinges. I already rigged the flap and aileron cables and it would be hard to make sure that was done correctly unless the wings were on, especially the flap cables. I don't remember the bottom wing skin being any issue for the flaps. There was a big issue with the aileron cable exiting the pulley and entering the strut. With the recommended pulley the cable was almost 1/2" outside the strut. I ended up using 1.75" pulleys, with Bobs approval. I am not sure if this is a B model issue. I could also make a different pulley mount and go back to the 3" pulley. I still might do that.

I have one wing on a big table, and one on a rotisserie. I will probably close the wings on the device they currently sit. I believe the parameters needed are flat, and not twisted when you drill the hinges. When doing it on the rotisserie, I will make sure the wing is adaquately supported in the middle so that it flat, and not twisted.

It seems to me that if you drilled the hinges with the wings hung, you would have to support the tips to keep the outer half of the wing from drooping a little from its own weight. That and working on a ladder.

I kind of like BCONE's setup of having the wings vertical in supports. Easy to work on. My left wing is on a rotisserie and should be similarly easy.