Gap Seal Tape - What is your opinion?
 

I just completed building the Polecat Thermal Dancer 3.1 M sailplane
http://polecataero.com/products/thermal-dancer

I am doing the final prep and asked some folks about the use of gap seal tape. I got mixed responses, so I thought I would ask the community its opinion of the use of gap seal tape.

1) If you use gap seal tape, tell me why. Any input would be appreciated. Do you use it only on top of the wing gaps or do you use it on bottom of the wing gaps too? I am talking hinge gaps on ailerons and flaps.


2) If you don't use it, why not?

Have you every tried it? Had a bad experience? Don't feel it helps? Feel it hurts? any input is appreciated. I am open to any comments at all.

If you don't know what it is, stay with the thread, you may learn something.

RE: Gap Seal Tape - What is your opinion?
 

I don't use it because using regular covering is so very, very easy. Of course, I cover with UltraCote and that may be one reason it's easy, but I doubt it. The technique ought to work with Monokote as well.

I cut a long strip that's slightly wider than necessary.
That is creased down the middle. The crease is probably the trick that makes this so simple.
Align that strip into the hinge gap and use a trim iron to tack it along it's length. Tacking it makes the rest go easier.
Iron down one side.
Iron down the other.
Use a new razor blade to trim the "flashing". It's surprising how quickly a sharp blade goes dull when cutting UltraCote. Those reinforcing lines must be made of some magic stuff.
Run the iron along the trimmed edge and it'll vanish.

I've never had a job make noise when the surface is moved when I used UltraCote. Not so with other brands.

RE: Gap Seal Tape - What is your opinion?
 

I've seen tape on other's airplanes and wouldn't ever try it simply because of a number of reasons.

One guy only taped the gap from one side. The exposed tape picked up grass, dirt, bugs, discarded cigarette butts, empty softdrink cans, an old license plate, a sweaty T-shirt (a RedMax Fuels one), and one of the club's lawn chairs. The good thing about only doing one side of the gap that was proven by that poorly done job was that the oil from his engine soon started killing the tape's stickum. Unfortunately, the first junk that came unglued was the lawn chairs and he was flying over the pits at the time. I would suggest that you not use tape unless you're going to tape both sides or your club has no lawn chairs.

Another guy taped both sides. His ailerons really needed the gaps filled, but the tape wound up popping. It might have been where it was stuck together well, and was trying to hold the ailerons rigid, or where it wasn't stuck together too well and was popping apart every time it was flexed one way, or popping together when flexed the other, or apart, or together or not.

Personally, I wouldn't want to use the stuff, in spite of the fact that the club now has no lawn chairs any more, at least intact ones.

RE: Gap Seal Tape - What is your opinion?
 

Well this is a pure glider, so there is not fuel or motor involved.

Lawn chairs?

RE: Gap Seal Tape - What is your opinion?
 

And I wouldn't use tape on a glider either.

Matter of fact, I've got an ARF that came with all the surfaces hinged with tape and it served as a lesson to me. It showed me why I wouldn't want to hinge surfaces with tape. Not one of the surfaces is actually in line with it's mate. And a flying buddy thinks tape hinges are great and his are no better. But that's just hinges, and you're focused on gap fillers. so.....

There are a number of tapes suggested by people who use it. I've yet to find any that works like people describe it working. First off, the technique is fairly difficult. Getting the sticky side into a gap takes some special skill or tools. The tape is hard to keep from sticking where you don't want it. It's hard to get it started straight. The unwatched end winds up sticking itself down while you're trying to get the other end aligned, deep enough, not too deep, etc. I suppose there are tricks, but it's not been worth it to me since ironing down UltraCote is dead simple and easy and I already got all the special tools.... the special tool needed.

I've yet to find a tape that's as light as iron-on. If I only fill one side of the gap, the exposed sticky side collects trash. Yeah, you can powder the sticky with talc or chalk, but I've yet to find powders that come in model airplane colors. White? no problem other than the fact that no matter how much powder, it hasn't been enough.

So I figured to always use tape on both sides. No joy......
Tape on both sides acts to stiffen the gap. So does UltraCote, but UltraCote is very flexible, and if it is stiffening (which I'm not sure it's doing) then it isn't enough to worry about. The tapes I've found that were very flexible were either heavy vinyls or very thin. The heavy didn't please me and the very thin weren't tough enough.

I've also seen tape that softened in the sun. Seen a model flying around trailing strips of tape that'd lost it's grip in the heat and hadn't blown off yet. Yeah, I've seen iron-on films coming off, but not off airplanes built by experienced builders who'd learned how to cover.

My personal opinion is obviously not in favor of tape. I categorize it with other labor saving things that are sold as saving the builder time when the amount of time in minimal and the results are questionable. I build my models to fly, not to build in 10 minutes less time. And with tape versus UltraCote in an installation time test, for me, the UltraCote is faster anyway.

I first tried tape on the spoilers of an OLYII back in the.... ???? 70s???? early 80s??? sometime back. I'm still flying that airplane (or would if there were any good glider sites around here) and have tried a number of different tapes. Why try different ones? The tapes tried either let go their adhesive or wore out. About 15 years ago I cleaned off the residual glue (for the umteenth time) and used ironon.

BTW, I used to fly gliders with an R&D guy who worked for 3M. He worked on tape mfg. He used dubro hinges on his OlyII. Everywhere, spoilers and all. And they looked to be a bear to use for the spoilers. If I remember correctly, the plans suggested tape, and he was one guy who always read the instructions first thing.

RE: Gap Seal Tape - What is your opinion?
 

You know, in spite of all those words, I'm looking forward to someone coming into this thread who likes tape.

I'd really like to know what to buy and how to apply it easily.

I've recently used some tape on a little foamy. Got the medical stuff and it worked good. But it looked like it wouldn't stand up to much stress under load. I couldn't tear it by hand across it's length, but it tore easily lengthwise. That's usually an indication that it won't stand flexing along that axis.

But would like to hear about what to buy and where to find it. It's always fun to find something new to try.

RE: Gap Seal Tape - What is your opinion?
 

I do, but it must be done right. I have seen a lot of rather sorry attempts to tape hinge lines causing a lot of control stiffness. For gliders I recommend using iron-on film for hinges. It is simple to do and surprisingly strong.
Check this link for a nice tutorial: [link=http://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/construction/film_hinges/index.htm]Iron-on film hinges[/link]

Also, presuming a top or bottom hinged control surface, you want to cover the V-shaped gap between the wing and control surfaces in order to minimize drag. IMHO, the best way to do this is to use [link=http://www.hobby-lobby.com/spoilers.htm#Gap]GR63 Graupner Control Surface Gap Tape[/link]. I know it is hideously expensive, but there is nothing like it (that I am aware of). The tape is thin, fairly stiff and has adhesive over only half its width. Also it is slightly curved width-wise in order to keep the non-stick portion pressed against the control surface even when it is deflected.

Some years ago I made a simple test to see if the gap sealing tape was effective enough to bother with. On my 3m glider, which has ailerons and flaps extending over most of the wing span, I put wing sealing tape on the left wing only. When gliding straight ahead there was a marked tendency for the glider to yaw towards the right, indicating that the drag of the left wing was less than that of the right wing. That was proof enough for me that the expensive gap sealing tape actually works.

/Red B.

RE: Gap Seal Tape - What is your opinion?
 

Darock,

I am confused as to what you are talking about. You seem to be describing how to make a hinge out of covering material, which has nothing to do with my question. The hinge is not in question.

If you are describing a gap seal process, I am unable to visualize this gap seal process you are using. If you could post a photo of this process, or end result where you seal the gaps I would LOVE to see it.

Thanks!





Thanks for the link. The graupner tape is similar to what I am using.

I especially appreciate your report on the test you did. Brilliant. I believe I will try that on my plane.

My plan is to get it all trimmed out without the gap seal tape first. Then I was going to apply the tape and see if I felt the difference, but I REALLY like the test you did. If the tape caused extra drag or loss of lift, it would tend to yaw or roll toward the wing with the tape. But yours showed the opposite. A terriffic idea.

Thanks so much! That has been the most helpful posting of all. :)

RE: Gap Seal Tape - What is your opinion?
 

Yes, that sentence is about the use of tape as a hinge. It was meant to do a number of things, one of which was to suggest that the tape I had wasn't up to hinging a foamy, much less seal the gap on an obviously much larger glider. People often use examples that are a stretch to the topic, sorry to confuse you. BTW, the mention of lawn chairs was a joke. However, the license plate wasn't...... hmmmm

RE: Gap Seal Tape - What is your opinion?
 

Red B.
Good info on the gap sealer. It's quite a different design than what is usually thought of when "sealing tape" is discussed. At least the picture and description show something quite different than using tape that sticks to both surfaces. And there would be no wear on the tape whatsoever. Interesting solution. Thanks

RE: Gap Seal Tape - What is your opinion?
 

It certainly is horribly expensive at $36.00 for just 16'.

I've seen flyers use a "flap of material" that was attached to the wing only, that reached beyond the hinge gap, effectively covering the gap. Positive pressure would cause the loose material to press against the movable surface as a seal.

It would be very easy to test the effectiveness of the "loose flap" concept just as you've done with the Graupner "tape". Take a wide tape and a narrow tape. Align one edge of each and "tape" them together, giving a strip of tape that has only part of it's width with exposed adhesive. Use that as you would the Graupner tape. Masking tape would be stiff enough to test. But if you wanted a springy effect like the Graupner provides....... hmmmmmmmmmmm That'd take some thought........

RE: Gap Seal Tape - What is your opinion?
 

I have done this, however the tape created in this way does not have sufficent stiffness and body to stay close to the wing. It tends to curl up over time, being as short as a few hours, especially if it sits in the hot sun.

http://www.hilaunch.com/Wing_tape.htm - 4th tape down. 10 foot roll X 1 inch wide is $5. Quite reasonable actually. More of a plastic roll rather than the film of clear packing tape. Much heavier than covering material.

RE: Gap Seal Tape - What is your opinion?
 

What a good list of tapes. It's good that someone else waded into the thread.

You know, seeing the Graupner "tape" triggered some looking around in my shop for something that'd work like the curved part of that gap covering material. Just about any semi-rigid plastic will hold straight enough in short widths. I cut some strips of 2Liter softdrink bottles. It would be glued along the wing side of the gap with the curve in the width of it giving adequate pressure to hold the gap sealed. In practice the wing is going to have positive or negative pressure above and below depending on the AOA of the wing. So having just one side of a aileron gap covered will only work "in one direction". But it's quite simple to find something that would work the same as the Graupner stuff for a lot less cost. It'd take a little more effort to make it look decent.

And in theory anything that bridges a gap with some degree of stiffness is going to actually have air pressure helping it seal. At least from one direction, when there is positive pressure from the "outside". So flaps would only need one side bridged. But it seems that ailerons would need both sides bridged or the gap sealed from the wing side of the gap to the aileron side.

RE: Gap Seal Tape - What is your opinion?
 

The simple solution is to use iron-on covering for hinging the surface (top or bottomed hinged) to provide a sealed hinge line, using the Graupner tape to fair in the V-shaped control surface gap. I have tried several different solutions, but so far the Graupner tape have produced the best result. It really sticks and no other tape I have come across have the cross-width springiness that keeps it pressed against the control surface. Considering it as simply "tape" it is horrendously expensive, but considering it a "hinge line gap sealer", the cost may be a little bit easier to accept.

/Red B.

RE: Gap Seal Tape - What is your opinion?
 

You asked for someone who likes gap seal tape. I do like it, but only for specific purposes. On a thermal plane, sport or contest, I believe it is more trouble than it is worth. On a slope racer it is definitely worth doing. I have used it on many different sailplanes, and also powered race planes. When you are looking for the highest possible performance, it will help. On my thermal duration planes I never felt it made much difference. I designed and built Saturn sailplanes from 1991-1997. I had quite a lot of success flying them in TD contests, most notably winning the Southeast Soaring Championships in 1993. If your plane is very light and flies quite slow, I wouldn't bother. If it is fast and covers a lot of sky, it might be worth your effort. Just my two cents worth.

David Layne

RE: Gap Seal Tape - What is your opinion?
 

This is an interesting thread so I'll chime in!

Years ago I had a Craftair Freedom (remember those?). I used plastic hinges with hing pins, so there was a roughly 1/16" air gap between the ailerons and the sub-trailing edge of the wing.

I made gap covers for the top of the hing gap out of monokote. One day during dive, about 1/2 way down, I saw one of the gap covers suddenly peel off. The Freedom immediatly yawed through about 30-40 degrees, oscillating back and forth and eventually returning to fairly straight flight (maybe 5 degrees off-heading?). She also slowed down noticeably.

So, yes they do have an effect, and it can be noticeable.

I made my gap covers out of a 3/4" wide strip of monokote. VERY lightly score down the length 1/4" in from one edge. Fold along score (adhesive side in) such that your strip is now 1/2" wide (1/4" wide area with adhesive plus 1/4" wide area that's folded over - so no adhesive. Run the iron along the folded section to seal it together. Lay the exposed adhesive side on the last 1/4" of the sub-trailing edge and iron down. The remaing 1/4" will seal the gap without getting grass/dirt/dust stuck to it. Hope that made sense, if not someone say so and I'll post a pic.

-E

RE: Gap Seal Tape - What is your opinion?
 

Well, I'll wade in here.. Hockey Tape or 3M #190. I've made a set of wipers out of the 3M #190 for a guys Destiny that didnt come with it, and we really wanted to get the in the air rather than return it to Soaring USA. You can get the #190 at most Ace Hardware stores. The display holds the 3/4" rolls of multi colored tape (red, yellow, green, white, and clear), plus they also have 1.5" wide.
I get the 3/4" rolls for $1.10 from the local "Tap Plastics" store.

I also use the 3M #190 on my John Higgins "Alias" as hinge tape and its a 70 ounce 60" screamer of a slope plane, and I replace the tape every couple of years. If you buy the white tape and wipe it down with acetone, you can paint Krylon right over it too. I should probably get around to making Goop Hinges on this plane, but I'm lazy....

To make gap seal, it kinda takes 2 sets of hands, but heres how it goes: Use the smooth back of a yardstick, Unroll about 30" of tape and apply it to the yardstick with half its width hanging off the edge. Dust the exposed sticky portion of the tape with baby powder, and use enough to kill the sticky. Carefully peel the length of tape off the yardstick and apply to the gap. Rub it down and get any tiny bubbles out. If you dont like how it turned out, just pitch it and try again. Cleanliness counts, so maybe vacuum the work area a little bit.

Some folks make gap seals out of thin mylar and use contact cement to hold it in place. I have a 10 year old Charlie Richardson "Raider" slope racer that has a home made set and it works really well. The only issue is finding thin mylar in that length, so that makes the tape attractive.

Hollow molded with skin hinges sounds more and more attractive, doesnt it?

RE: Gap Seal Tape - What is your opinion?
 

aeajr,

I use foamy hinge tape as a gap sealer both top and bottom. So far I have not had it peel off and it also does not seem to inhibit the movement of the control surface. If you apply it by deflecting the control surface full one way and wedge it into the gap, then rinse repeat for the other side, the surface movement is unchanged. Where I have seen the biggest difference is in the flaps on my Skybird. I get better response and actually had to dial in more elevator after I put the gap tape on. So I know it made a difference.

I think an argument can be made that the more high perfomance a plane is, the more you will get out of sealing the gaps, but it certainly will never hurt, (unless it's done wrong) and it goes so fast I can't see a good reason to not do it.

Just my 2 cents.


Tom

RE: Gap Seal Tape - What is your opinion?
 

I have made a wiper to cover the hinge gap using acetate sheet...the kind used for making animation cells. Cut a strip the exact length of the aileron and about 1/2-3/4 inch wide then stick double sided tape along its length but only covering half the width of it. If you can manage to score it to give a slight V shape or curve along the length so much the better. Stick it to the sub trailing edge and it will cover the gap and wipe against the aileron or flap as it moves. Its tricky to get it to work right but possible.

RE: Gap Seal Tape - What is your opinion?
 

Excellent suggestion. I was going to mention drafting mylar which will do the same thing. Actually, if it's going over a painted or opaque surface, the frosted side will take paint very well to match the wing/surface.

bob

RE: Gap Seal Tape - What is your opinion?
 

Hi,
Colin has the cheap and effective answer. I've used the same system for 6 years, just wish I'd got there earlier.
Dave.

RE: Gap Seal Tape - What is your opinion?
 

Yes gap seals work on the Bonanza they add about 7 or mph on the top end the is about 5 or 6 mph slower and roll rate is made soild in the real world made a new airplane out of the Bonanza . So with the fast models will be help the slower one maybe not so much if done right makes for a clener looking wing if nothing else.. On the Bonanza they are on the botton side Mr. Kite

RE: Gap Seal Tape - What is your opinion?
 

Colin,
Where in the UK do you buy this stuff?

RE: Gap Seal Tape - What is your opinion?
 

In light of being in the printing business for over 25 years, the first 10 of which were in a Silkscreen shop.......I can tell you without reservation, that you need 1 mil mylar over acetate.......mylar will just not tear like acetate will, and if you get the "permanent" adhesive on the clear film, you can heat set it so that it really is permanent !......where to get it ?......go to the local sign shop or the auto window tinting shop.......either of them should be able to at least point you in the right direction.....

In use, cover your wing and control surfaces like normal without any hinging......position the surface in the correct location and simply apply the tape like you would a normal pressure sensitive decal with dish-soap......I use strips with 3/8" on either side of the gap and keep the gap to an absolute minimum......ailerons taped on upper surface and flaps on lower surface...... works like a charm.......

RE: Gap Seal Tape - What is your opinion?
 

Hi, been some time. Well I've used both tape & film to do that job, not that doing so would improve the drag ratio (my flying skills are not good enough to notice that) but after reading countless articles in RCM by various authors who fly various types of aircraft. They ALL said that while sealing the gaps would improve the aerodynamics, their main concern for stressing to do so was to avoid 'flutter' . . . Where the airflow passes from one surface of the wing through the control surface gap to the side of it inducing a severe high Freq. vibration leading to sudden, catastrophic wing failure. I don't know if it was just a 'fetish' withen them but. . .

The other thing I noted: EVERY mid to higher-end Airtronics kit included the tape in the box. . . I guess you can draw your own concludsions from that.

Rick K