Open Bay Wingtip Covering Help

What is the best way to cover open bay wingtips??? I always get winkles in whatever I use, whether it be iron on film or silkspan.

Are there any simple tips onhow to do this??? Do I cover the tips first and THEN the main part of the wing??

Any help would be appreciated.....I want to avoid wrinkles on my next 2 planes that are coming off the board......

By a HUGE margin, I've had the best luck covering each bay individually. Most of my wingtips have 3 pieces on the top and 3 pieces on the bottom. Doing the aftermost 2 bays at once works alright on occasion, but the forward one or 2 definitely need to be covered individually (for it to work out for me).

I overlap the silkspan only the width of the wingtip rib.

Laminating the perimeter of the tip so that it's 3/16 thick helps also.

Doesn't really matter if I do it before or after the rest of the wing. I put the little triangle pieces on wet.

Hope this helps, would love to hear more about it myself.

Tools

Edit: in retrospect I guess most my tips have 3 ribs, therefore 4 bays. Front two individually, back two together. If a wrinkle forms, I cut it out and redo it. Only wastes a couple square inches and not much time.

if i understand this you do each bay on the wing tip separate. hey has scott started the flite streak yet. hey sorry about the dings on your planes i think the road trip put three years of hanger rash on my planes.

Try tearing the silkspan instead of cutting it, the overlap blends in better.

Wynn,
My method over the last 40 or so years has been to cover the entire panel at one time. I allow the silkspan to overlap in the center (if the wing is not yet installed) and work from the center out. At the tips, I just carefully pull/stretch the wet silkspan as I go working from the center of the tip towards both ends, and back and forth while keeping the edge wet with dope until I get the wrinkles out, and the SP doped down. I just dope down the perimeter of the wing, no ribs. Then I chew all the dried nitrate off my fingers! LOL!! First two coats of clear dope when the whole wing is finished is always Sig Supercoat (high shrink) making sure that I do one panel top and bottom then the other panel, never letting the opposite side completely dry before the side I am doping is done. After than the rest of the clear is Lite Coat, low shrink.
Of course, many think I am crazy, since i don't cover the tips seperately but I don't have any wrinkles.
Bill <><

I've done tips with silkspan both separately and just as a continuation of the wing covering. It depends on the shape of the tip, phase of the moon, etc. I think doing them separately would be easiest for a novice, and done carefully, it will look fine. The trick is to keep the silkspan wet and do not accept anything short of perfection. If you just can't get a wrinkle out, slit it and overlap the silkspan. Again, done carefully, this will look fine.

Not crazy Bill, just good enough to do it! Believe me, wouldn't be cutting all those wierd little shapes if I didn't have to!

Yep Brad, each stinking bay of the tip separately. I do the rest of the wing just like Bill mentions. I rarely do adjacent bays (of the tips) at the same time. As miserably tedious as it is, I do a bay, let it dry, do the next one, and so on. To speed things up, I'll do the first and third bays, then come back for the middle one.

I'm in training with Delta enough that I've covered several wings in my hotel room! Do a bay, go do a simulator, come back, do another, sleep, get up do a bay, goto class, blah blah. Will sometimes come back during lunch and hit a bay. Doing them separately hasn't caused a problem with warping, but I don't start doping them till they're all covered. I don't do entire panels like this.

Don't worry about the dings, REALLY, it's NOT a big deal. Hauling my dumb stuff all over the nation IS a big deal and I appreciate the effort. Glad to hear you made it home alright. All nighters are for college kids. Oh, and junior airline pilots, I hate them.

Later,

Tools

Edit: with respect to what Bill says below, I havn't had a problems feathering the edge of the silkspan IF it falls on top of a tip rib, and you can't tell it's separate pieces. Tearing it really does work super well though. cut it about a 1/8 large, then go along pinching off a 1/8 strip (or whatever, if it comes naturally, well, disregard). Trying to tear along a line isn't as easy as it sounds!

i guess this would work for ultracote too ?

Bill,

You just know the stretching, pulling, doping technique. It does take some time to acquire. It also takes a good bit of patience.

As good a time to start as any. Wasn't completely born with the technique myself.
C ya at Brodak's!
Bill <><

I use the same method as Tools. I tried doing tips in one piece and almost lost my religion. My hat is off to folks who can do it in one piece without wrinkles. I use as few pieces as possible, however I will use one piece per bay if necessary. It may take a little longer, but for me, it is worth the extra time.

Definitely, tear the silkspan, do not cut it. Tearing makes an edge that is much easier to blend in.

Wet tissue will stretch enough to do it in one peice if you really want to. Soak it for a while, perhaps with a tiny amount of detergent in the water to soften the fibres. It will stretch more in one direction than the other, so try each way and note which works best.

With film you need to use a heatgun or the like to stretch the film as you pull it over and around the tip. An extra pair of hands is very helpful.

I don't think it matters which you do first, but think about which side you want to have the exposed edges of the seams. Maybe bottom tips then top tips then bottom wing and top of the wing would give the nicest seam order with film. Depending on the shape and film you can do the whole wing in one peice with practice...
A.

Hi

Some coverings like tissue, silkspan and silk can be wet streatched to accomodate or nearly accomodate difficult areas. If you can't get the covering to accomodate the compound curves, you need to go with separate pannells as stated above but work from the rear forward so the overlaps don't lift.

Also just tack the corners first. Then tack the middle so the slack is the same on both sides. Keep doing that, averaging out the slack untill there is only a little slack between each tack. Now if it's a doped covering, let it dry, water shrink the slack out, then tack down the rest of the edge. If it is a heat shrink, time to use the heat gun and rub down with a soft cloth once the wrinkles are gone. If you can't head shrink enough slack, try streatching by pulling at 90deg to the direction you want it to shrink.

I like to cover the wing then the wing tips later. I run the grain of the silkspan length wise on the wing & cord wise on the wingtips.

I go with one sheet. At the tip, I make multiple radial cuts in the excess around the tip. This keeps it from bunching up.

Wynn.
Give me a call and we can arrange a demo night at my workshop for all the local guys. Tissue covering is easy if approached right, it's my preferred covering for all but a few types of model. Pic below is of a tissue covered model, white all over and some colour tissue trim.......

Standard Disclaimer:
Caution use at your own risk, results may vary, I am not a professional. I need to rely on smart people for their idea's, I don't have any of my own.

You can see my wing tips in the ARF Nobler post on this forum.

I had the same problems as you, wrinkles all over my wing tips. I cured my problems this year. With the help of Tom Morris and Bill Norman, problem SOLVED.

I find that it's easier for me to cover my wings panels in two pieces. The two pieces do not need to be the same grade either. I'll cover the tips first and then the wing.

Apply your dope to the wing as usual, however make sure that all surface structures, ie (Rib tops, cap strips and tip ends are completed filled with 60/40 dope (they shine).

My ARF Nobler wings & tips were covered in two different grades of silk-span. I used light on the tips and medium on the wing.

Now this is what I consider to be the best tip I have ever received and Thanks again to Bill Norman. Windex window cleaner.

You are ready to apply your tip silk-span. Cut the silk-span piece to allow for one inch overlap all arround the tip.

Now spray Windex window cleaner on the silk-span and apply the covering. The windex will wet the silk-span and the spray does not evaporate as fast as water which will give more time to work the silk-span, which means, less wrinkles. I don't know why but it seems to me that I can pull the slik-span a little tighter when using the windex spray.

As you dope is drying, don't forget to work the wing tip lines with your finger to help seal the silk-span to the balsa. Wrinkles can occur as the slik-span dries and pulls away frome the balsa frame.

The ARF Nobler I just finished did not have one wrinkle anywhere on the airframe and that in itself is, MIRACUOLUS.

I used light weight silk-span on the wing tipe and the fuse and medium on the wings.

I hope this helps.

Mike Clark
(MikeC)

Yes. A club demo night, featuring the covering of a wing in 'span, is exactly how I learned, in the late '50s.

We had a tiny clubhouse in Alexandria, Va, where the address was 4 digits, plus 1/2.

Tony neighborhood now, just The Hood then. We had numbers runners and Ho's in either side.

But we kept our minds on the airplanes, mind you.

I am not the most experienced modeler here - by far. However, I covered 6-7 wings when I was a kid and three more since coming back. So far, I have never had a wrinkle and have always covered the half spans and tips with the same piece. It sometimes takes some extra finger work around the tips, but using techniques already mentioned above, it is not that much of a problem and seems less labor intensive in the long run. Here's what I do:

1) Clear dope (I mix 50/50 Brodak dope/thinner) the open structure, sanding lightly after all coats but the last with progressively finer sandpaper (300 - 400) until there is a sheen and most grain is gone. You can just brush the surface of the last coat to memove any bumps or snags. Most folks say 3-4 coats, but 4 was insufficient last time, and the result has caused extra work after covering. You also want to minimize the opportunity for moisture to affect your balsa anyway.

2) Lay silkspan over a beach towel and spritz it with water until it is saturated.

3) Drape the silkspan over your wing (I do one panel at a time - e.g. bottom outboard - and overlap the silkspan an inch or two at the center line, making sure not to concentrate stresses at fuselage). Before any applications, gently stretch the silkspan along the span and chordwise until no wrinkles show - except for anything unavoidable at the tip. The silkspan clings to the structure and doesn't slide inward to slacken.

4) Only at the periphery and starting at or near the root t.e., I brush on thinner, which then bonds the silkspan to the smooth surface and requires no disturbing pressure. I follow this with a coat of dope - usually as I go, rather than afterward, but it usually is not needed to secure the covering. I alternately work the l.e. and t.e. as I work spanwise toward the tip. If a wrinkle appears, clear dope softens the bond, and fingers can be used to pull the silkspan over the edges to tighten it.

5) When I finally get to the tip, I work the silkspan (pull, stretch, redistribute deformation, etc.) to get it to conform as much as possible to the curvature imposed by tip ribs, blocks, etc. You can dampen more, if too much evaporation has already occurred. Often there is still some slack. I just cut or tear radially and overlap the silkspan. This can be done whether it is over wood or open bay. If the overlap is over wood, dope over it now, and expect subsequent sanding to make it completely invisible almost immediately. If your overlap seam is not over wood, dope only over wood to attach the silkspan at the periphery and allow the silkspan to dry; it normally shrinks tightly together, and subsequent doping over open bays will seal it to invisibility. Of course, if you are leaving the tip transparent, the cut may be slightly visible, although I have been reasonably satisfied with my results using plyspan (color darkens to opacity at overlap). You can minimize overlap by cutting out a sector. I don't think that I have yet needed more than one cut on a tip surface, but more than one works too. Avoiding sharp edges helps.

I have never (yet?) had cause to redo one of these tips. The dampened silkspan dries to a taut smooth surface. Subsequent coats of dope give it a nice ring when tapped. There should be less labor involved with one piece covering, and the very small seams from any radial cuts should be easier to smooth over than long ones between separate sheets.

Incidentally, I have noted that trailing edge sheeting on flapless wings seem sometimes to warp into a sort of reflex surface, due to asymmetrical stresses over soft, contest grade balsa. On mine, I have found that you can undo this tendency as you continue to dope your covering by stopping between (dried) coats to brush a small amount of thinner over the concave side of any affected area. This eases the tension on this side, releasing the surface to be pulled back straight by the tension on the dry side. Monitoring this progression and repeating the process as needed will ease the need for trim tabs. FWIW.