Boat Wrap

Share your thoughts, photos and general help to all builders

Postby Chappy » Thu Apr 16, 2009 12:41 pm

I picked up a huge roll of boat wrap on the cheap last fall from a neighbor that didn't need it anymore. I thought I would test a panel or two, but it sounds like it has already been installed on a Lazair and so far has worked well. I would be very appreciative of any technical information on the actual installs. Things that I'm interested in would be: product name and thickness, was it cleaned or degreased before tape installation, the actual tapes used, the process and tools used to shrink it and any special precautions, how long ago was the covering done and any issues that have cropped up so far (like tape creep, sagging, whatever). My immediate concern is how to handle it as it is very wide and folded, and will need splitting down to handle. It would be great if I didn't have to start from scratch. I'm old and have too many hobbies LOL.

Chappy
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Postby barrystrs » Thu Apr 16, 2009 11:46 pm

Some of the local lazairs have been using greenhouse plastic for years. The problem is keeping the tape stuck. The theory behind using shrink wrap was to get rid of the tape all together. This was not my idea or technique but I was so impressed I covered my lazair last spring. There are now 4 lazairs with shrink wrap.
None of the old tape needs to be removed! The wrap goes all the way around the wing. At the trailing edge, overlap the shrink wrap about half an inch. When you heat the plastic with an iron, it sticks to itself. We even covered the wingtips. There is no tape to fail and the only seem is on the trailing edge. The inboard end of the wing is also wraped and closed in.
The wrap is 7mm. I would prefer thinner, but that is the only thickness it comes in. I did not use capstrips on the top or bottom. The bottom of the wing is no longer concaved. Even at flying speed the air does not push the plastic up to the wing ribs. This different profile seemed to raise the stall speed 3 mph, but that is only an opinion , not documented. I flew 25 hrs last summer with this boat fabric, I have logged about 100 hrs in this plane previously.
I'm sure there will be many comments and concerns about the lack of capstrips. Before anyone gets too nasty I suggest you try samples and do destructive testing as the people before me did and I repeated for my own peace of mind.
I recommend this technique and cannot imagine going back to tape.
PS: total cost, $220 covers 4 and a half lazairs (fifty bucks each)
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Postby Chappy » Fri Apr 17, 2009 1:14 am

Oh yea, I bet this WILL generate some comments! But it's also very interesting. The idea of a big bag over the wings w/o any internal tapes is rather frightening to me. I remember when there were a couple fatalities in Easy Riser flying wings when the glued rib attachment on the top of the wings failed and lufted up. This caused them to become divergent in pitch at high speed, nose over, go inverted and tumble. Was a big deal at the time. Other aircraft that have utilized non-stitched wing covering have had cases of serious accident too when top coverings came loose.

So you can see that doing what you have done would NEVER have occurred to me. I really don't think I could bring myself to do it either, but I'm intrigued that it's working for you! I have seen Lazairs fly with missing top panels in the wing, and the pilot was unaware that they had blown a panel or two in flight until it was pointed out to them after they landed. I am very surprised that you haven't at least noticed a reduction in climb rate with your "loose" wings. Also, I would at least expect weird thing to happen at the low and high ends of the flight envelope.

The extreme width of the boat wrap I have would seem to lend itself to wrapping the wings like you did. The roll I have must be big enough to do 4 Lazairs, and I paid something like $50 for it! I think I can afford tapes, but please keep me informed as to anything else you learn about flying your Lazair with your extremely unconventional covering method. Of course, the original Mylar covered Lazair was considered pretty unconventional too. And be careful!

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Postby Shannon » Fri Apr 17, 2009 7:30 am

Hi Barry

I had never heard of this covering on Lazairs until now. Definitely sounds better than some of the things I've seen and heard about. Like anything new there will be lots of questions. For some reason I believe that people think asking questions and voicing concerns is being critical. A radical departure from the norm like no tapes or capstrips and changed wing profile is obviously going to spark some debate. If debating the pros and cons is a problem lets just stop right here. Remember that most questions are geared towards someone making the decision to use the wrap vs. people trying to poke holes in it. Sharing what has already been learned will help others so they don't have to start from scratch.

OK, two things I don't quite understand are this. First why would there be an aversion to capstrips placed on the bottom of the wings before shrinking to keep the concave shape (and at the same time add a degree of safety) ? I personally do not like the idea of free floating covering at all. Events from the past suggest that if your covering comes loose or off in the right area you will have bad situation. Maybe people aren't fully aware of the events of the past... i.e. needless tragic fatalities that could have easily been avoided.

Second what is the advatange of white wrap over clear-translucent ? Is there some difference in terms of lifespan, looks, or cost. Being able to see what's going on inside the wings is a big plus in my book. Reminds me of the guy who was flying with white painted Tedlar wings with severe rat damage to the ribs. He knew the ribs were damaged but couldn't really see the extent. When the wings were uncovered nearly all the ribs were ate to pieces.

I'd also love to know how this covering stacks up in weight against Tedlar and 1.7oz fabric. Maybe in the future someone can weigh an aileron. Lastly from what I've read some shrinkwrap films apparently have a 2 year guarantee for UV. What is the max expected lifespan on a hangar stored plane ?

Pic: Who owns this plane, anyone know ? Does it have Shrink wrap or is it covered with Fabric ?
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Postby lazairiii » Fri Apr 17, 2009 1:03 pm

Let me echo Chappy and Shannon and say that I too would highly suggest cap strips. If you have a tear or some other method of induced air into the wing covering envelope as they currently stand, you run the risk of complete failure. However, if you isolate the panels by the use of cap strips, then your risk is minimized.
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Postby Chappy » Sat Apr 18, 2009 9:17 pm

Barry,

I hope you haven't been scared off by our comments and concerns. I do have a question about your installation. You say that you used an iron to seal the overlapping pieces together along the trailing edge of the wings. Do you have any tape applied over that seam (belt and suspenders technique)?

One of my biggest concerns with this general covering technique is what George mentioned. If there is a failure of the covering material anywhere on the wing, since there are no rib tapes or capstrips, what's to keep the failure from propagating along the entire wing? I went out and looked at a piece of the boat wrap that I have, and it appears to be quite resistant to tearing. You can poke a hole through it with you finger easier than Tedlar, I think, but it seems very resistant to tearing, and that's the thing I would be most concerned with, so that is a GOOD THING.

The roll I have was made by XXXXX Supply. They have a pretty good website that includes a catalog and some tech info - how to install on your boat (duh). They offer a DVD instructional video for $20. Also, there are a bunch of videos on Youtube (of course). I hope that if anyone calls them, they know enough not to mention using it on an Ultralight!!!

The roll I have is 6 mil White 12' X 175'. It lists for only $120. It's a heavy roll, so shipping will add subtantially to that figure. They also sell an assortment of tapes made from the same material, some of which look like they would work well for capping the materials and attaching to the wing ends, etc. The same roll is available in clear (actually it's not, probably even more frosted in appearance than Tedlar). They even make it in Blue! The Blue would probably not be what you want in, say, Florida, as the interior spaces will get rather hot. White is supposed to result in the coolest structure. But Blue sounds neat. There appears to be a slightly heavier 7 mil product available too. Is this what you are using? Was there a reason you chose the 7 mil over the 6?

I think I'm going to order the DVD and a roll or two of tape and check them out. But this looks rather promising.

Chappy

Note about edit: I removed the name of the supplier just in case they do periodic Google searches of their name to see what hits they get. We don't want them to find out that their material is being used on , or considered for use on, airplanes. I'll post additional info on this wrap as I find it.
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Postby Chappy » Tue Apr 21, 2009 12:31 am

Chappy @ Apr 18 2009, 10:17 PM wrote:

I think I'm going to order the DVD and a roll or two of tape and check them out. But this looks rather promising.





I ordered the DVD and a roll of tape today, and asked for a couple samples of the blue and clear material. When I know more I'll post it.

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Postby bdiedenhofen » Tue Apr 21, 2009 9:22 am

Very cool idea. It is more economical than fabric, and should work well. I wonder about the capstrips though. If you simply rivet the capstrips through the plastic, will it still not be able to tear away around the rivets?
What about applying a strip of strapping tape over the plastic along the top of the rib, and then riveting through that? The capstip will cover the strapping tape, and the tape will give a little extra tear strength to the area if and when really needed.
Just a thought.
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Postby gdewsbury » Tue Apr 21, 2009 1:05 pm

I ran with the boat wrap for one season a few years back but had some problems and switched back to Dacron and paint since that was what I was most used to and wanted to be flying more than experimenting. 6 mil white. I may try again when recovering is needed but with some changes.
I realized as I’m writing that this is a bit long winded but hopefully useful.
The material is quite tough when new. I made a short wing section that could mount out the side of my truck and ran up and down a back road at 100 mph changing angle of attack to see what would happen. We poked holes and cut sharp slits with a razor knife as well. The material stood up very well. Even at extreme angles of attack there was not much change in shape of the covering and holes + slits did not propagate at all even when against the flow. There was no creep with the tapes at that time. We did discover that even with the best 3M tapes available that creep would occur over time and in fact released entirely from the under camber while still in the shop. Not much will stick well to polyethylene on its own. I discovered later that adhesion promoters (titanates) are available for polyethylene and other plastics but never got round to trying them. Installed rib battens top and bottom to keep the covering in place. Over time both the leading and trailing edge tapes were creeping. A separation at the leading edge between the root and first batten was the end of the experiment. I’m still kicking myself that I let someone talk me out of wrapping the covering completely over the leading edge so that there would be only one seam at the trailing edge. No big saving in weight or cost. Heat sealing overlapping edges of plastic seems to be the way to go. The material will fuse to its self completely with a little heat and a small amount of pressure. A friend is still working with the material on the ailerons for another type of plane. He has wrapped the ribs with strips of plastic instead of fibreglass tape and fused the covering directly to it so no adhesives are involved.
The coefficient of expansion is high for polyethylene. The creep of tape joints was exacerbated by heating and cooling cycles through the day. The adhesive being warmed through the day and the plastic pulling hard as the temperature dropped in the evening before the adhesive had a chance to cool completely. The plastic on its own does not heat up much in direct sunlight. It felt cool even at mid day in the open areas. Infrared seems to pass right through to the structure. Any place where it lapped over aluminum the plastic was getting baked. When the material was removed at end of season all areas over the structure were becoming brittle. Keep in mind that I did not have a hanger so the plane was in direct sunlight all day for 4-5 months. Attempts to shrink with an infrared heater suggested for Mylar or Tedlar proved a bit challenging. My first try was with a ruddervator. Watching one side only the material drooped 6-8” before shrinking. When done, both surfaces had been heated with the side I was watching starting to shrink first. The entire surfaces had fused together and shrank together as one surface. Not what I had in mind. In the end a heat gun was used since it could heat local areas and keep the surfaces apart. Heating over any structure where tape had been applied caused wrinkles that fused to themselves due to expansion and could not be flattened out without adding too much heat for the surrounding material. Any attempt to flatten wrinkles was likely to end with a hole in the fabric next to the rib.
The tape supplied with the plastic by a Marina called Hull Tape should not be used for anything structural. It is by design easy to remove so as not to leave marks on somebody’s boat. It will stick well enough as a good looking finishing tape but is intended only to hold plastic in place until shrinking is done.
Pros:
Easy to get in small quantities during the late summer or fall when Marinas are packing boats for the winter.
Dirt cheap.
Material is tough and can survive punctures and cuts until repair can be made.
Sections can be fused to themselves instead of using adhesive tape.
Attachment to structure can be accomplished by wrapping strips around parts like ribs.
Patches of the same material can be fused over punctures without adhesive.
No paint required.
Done in white looks very nice and stays clean. Not much sticks to surface.
Cons:
Process to cover plane is very different than what has been used in the past.
Don’t know useful life expectancy.
Done in white is blinding to look at during the day. LOL
Outdoor storage not good for long periods of time.

Cheers
Glen
Sorry. Did not take any pictures.
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Postby Chappy » Tue Apr 21, 2009 4:40 pm

Hi Glen,

Thanks for all the information! Hugely helpful! I guess we ran Barry off when we freaked out about his full floating covering on his wings. I just couldn't bring myself to try that. I've heard too many horror stories over the years about loose covering and problems like pitch divergence. But I must say that it seems to be working for him - so far. I bet there are aerodynamicists that would like to study what's happening with his plane! General wisdom says he should have hurt himself on the first flight.

Lifespan, if stored outside, sounds like it's rather similar to Mylar. How much sun/heat was your covering subjected to, as in Florida vs. Canada? I personally won't leave my plane out in the weather for more than a weekend if I have the option of breaking it down and putting it away in its trailer, so the reduced lifespan won't be a big issue for me. Reduced need for tapes would be a huge factor as they are very expensive and limit covering lifespan, typical with Tedlar covering. Did you degrease/wipe down the material before taping? Perhaps there are specific contact adhesive type glues that would work. I assumed you heat sealed the covering as the root and tips.

I'll have to learn more about adhesion promoters for this material. They might cause some damage to the material's strength over time. I have had products made from polyethylene that were basically impossible to get anything to stick to. They may have been polypropylene though. Man, it would be great to not have to deal with the job of removing old tapes and adhesive residue when doing recovering!

Perhaps the full wrap and heat seal at the trailing edge along with capstrips (for those of us that are big chickens) mounted through an extra strip of tape and the material would be all you need for attachment. I'm sure I would run a tape cap over the heat sealed seem at the trailing edge if for no other reason than appearance. The company my wrap came from offers tapes with 2 different adhesives. One like you mentioned that is removable w/o damage to paint, and a more aggressive one that is made for sealing and bonding the tape to itself (seaming tape). That is what I ordered. It is 2" wide. They also offer a 4" tape, but it's not clear from the description which adhesive it has; perhaps the DVD will make that clear. Their catalog does mention that this covering material does have an ultraviolet inhibitor added to it. This may turn out to be one thing that differentiates different brands of boat wrap.

I suspect that you could run into trouble with the capstrips if you used formed ones with the lip turned down against the covering. It seems to be much softer than Tedlar and run the risk of them cutting thru the covering eventually. Turned up (as Ultraflight recommended for Tedlar) should be fine, I would think.

That was pretty cleaver to wrap the ribs with the boat wrap so the covering would weld to it! That sounds like something to look at seriously .

Perhaps taping a sheet of Mylar or very thin foam over the spar first would act as an insulator to help protect the wrap material from heat and abrasion, and tape over the spar box, etc too.

It sounds like shrinking the wrap will require new skills/techniques, like when changing over from Mylar to Tedlar, but I guess that will just add to the challenge.

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