Wingtips (Building Questions and Suggestions)

[wirejock]

Originally Posted by Ralph Inkster

Actually probably a bit less ounces than your hinge attachment...

Consider installing a foam rib inside the wing tip to prevent cracking damage caused by the people leaning on the wing tip thinking it is stronger than it actually is.
Do all your wing tip fitting/aligning/nut plate/or hinge installments first before doing the foam rib.
I use 1/2" blue or pink foam to make a 36" airfoil shaped rib to support the aft 2/3 wingtip area where it is wide and flat, end the rib about 6" forward of the trailing edge. Wing tip forward concave areas tend to be more rigid & don't need extra support.
Rib attachment- position the rib inside the wingtip snug to the bottom skin, but spaced about 1/4" from the top skin. Use aerosol expanding foam to lock the bottom rib edge to the wingtip. After that is hardened up, remove the spacers and apply the expanding foam to the rib top edge and immediately install the wing tip to the wing while the foam is soft to let it harden in place, this establishes the final wing tip shape without distortions, and preserves your prior wing tip fitting/alignments.

Another good Tip tip. Thanks

[Reflex]

http://www.vansairforce.net/articles...mentphotos.pdf

The wingtips on my -14 were not as robust as I would have liked. My concern was folks touching or leaning on them causing the paint to crack. Also, they just seemed "flimsy" specifically on the bottom and I was concerned they they could deform at high speed and I'd never know it.

I used one top an one on the bottom that are 48" long. Used the method above. Fast, easy, light, added significant strength, and effective. Cost was 5 oz and two hours.

[DanH]

I cleverly reinforced parts of my tips, notably the flat aft areas, with pour-in-place expanding foam. They looked great...until some months later, changes in air pressure caused the foam to puff up in some places and collapse in others.

Don't do that.

[RV8JD]

The aft 1/3 of the WD-715-1 wingtips on my RV-8 do deform slightly at cruise speeds. It appears that the tip trailing edge area deflects upward and compresses the upper skin and thins the profile. I would assume the -7 would do the same (same wingtip) if it's not stiffened.

Deformed:



Undeformed:

[jcarne]

Originally Posted by Carl Froehlich

The exact reason to defer wingtip fit up until after the wings are on and rigging done (and checked by as many builder as you can find).

Carl

Carl I understand many people do this with good results but I feel it is solving a problem with another problem, drag. Vans intended for the aileron and flap to be in correct trail with the wing. If I run into an alignment issue it makes more sense in my mind to joggle/bend the flap skin protrusion to match the fuse (not drag free but I suspect less than the alternative). Either way both methods work I guess.

[Carl Froehlich]

Originally Posted by jcarne

Carl I understand many people do this with good results but I feel it is solving a problem with another problem, drag. Vans intended for the aileron and flap to be in correct trail with the wing. If I run into an alignment issue it makes more sense in my mind to joggle/bend the flap skin protrusion to match the fuse (not drag free but I suspect less than the alternative). Either way both methods work I guess.

Not at all, this prevents the problem as you fit the wingtips to properly rigged ailerons. Rig first, then fit the wingtips. Rigging is far more than just the single check of the aileron alignment tool.

Carl

[jcarne]

Originally Posted by Carl Froehlich

Not at all, this prevents the problem as you fit the wingtips to properly rigged ailerons. Rig first, then fit the wingtips. Rigging is far more than just the single check of the aileron alignment tool.

Carl

Let me throw out a scenario. Say your flaps contact the fuse before they should and you rig them there because it makes a nice transition with the fuse. Then you rig the ailerons to the flaps and the tips to the ailerons. Now you have an entire wings worth of trailing edge that is lower than it should be. This will increase drag. We are probably splitting hairs here as this method has clearly been used before; I just don't think it is the proper way. Van's says the ailerons are in proper trail when the trailing edge lines up with all of the tooling holes on the end of the wing. Therefore I think it best to rig them there.

As far as the aileron alignment tool you are referring I'm assuming you are talking about the bellcrank jig. This should have no bearing on aileron rigging, only making sure the bellcrank is in the neutral position when the ailerons are in the neutral spot. You are a smart dude for sure and I'm betting you are well aware of what the jig does, just wanted to make sure I am on the same page of what part your talking about.

P.S. Larry you and I have talked about this before, not trying to hijack your thread here.

[wirejock]

New question.
W-412 Wing Tip Rib
Wing tip hinge
How did you treat the rib and hinge where they will overlap?
I'm inclined to cut the rib flange off the tip rib to clear the hinge then tie them back together with a doubler.

[David Paule]

Just thinking (always dangerous; I'm not all that good at it and it hurts my head) but I bet you can stop the hinge before it interferes with the rib. You do need to allow sufficient room to get the hinge pin out. I'm betting that once the tip is sufficiently rigid, that last inch or three of hinge might not be necessary.

Caveat: I haven't gotten that far on my RV-3B yet.

Dave

[jcarne]

Larry, I trimmed the flange off of the rib. In my mind the hinge and wing are stronger than the rib anyways. It came out pretty sturdy.