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How to cover large compound curves

Old 05-26-2013, 10:24 AM
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harlanb
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Default How to cover large compound curves

I have posted this question before, but did not get an answer, so I thought I would try again.
I am fairly new to the hobby and have built and covered 4 kits so far.
Covering large compound curves (such as the front part of a fuselage) with out wrinkles is still a mystery to me.
I am faily adept at covering wings and am happy how those come out. My problem is with fuselages with large compound curves.
I have searched the forums and the internet, but have found nothing on covering large compound curves.
Minnflyer has a nice article on covering in the rcuniverse magazine, but it does not seem to cover large compound curves.
There are many write ups and videos on covering wings, but I have seen nothing on covering a fuselage with compound curves.
If anyone can post something about covering large compound curves I would be greatful. Sorry if I sound like a broken record with large compound curves, but when I ask about this, I just get a bunch of links on covering wings.
Please do not post anything on covering wings, I do not need any information on how to cover a wing.

Thanks.


Old 05-26-2013, 01:00 PM
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Gray Beard
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Default RE: How to cover large compound curves

Depends on what type of covering you are using, I have found Ultra easier to use them Mono but it's still the same way. You turn the heat up on the iron and have several extra inches of covering so you can grasp it, then holding the iron just over the top of the covering you pull and stretch it around the compound curves and iron it down as it stretches. Same thing for wing tips. A bunch easier to show someone then try to explain it. After you have done it a few times it becomes easy to do.
Old 05-27-2013, 10:28 AM
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harlanb
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Default RE: How to cover large compound curves

Thank you for your response grey beard.
So, if I understand what you are saying: You hold the covering up off the fuselage apply heat to the covering with the covering iron (Not heat gun?) then as the covering stretches, you pull it down to the fuselage and iron it down. Is that correct?

thanks
Old 05-27-2013, 01:59 PM
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Default RE: How to cover large compound curves


ORIGINAL: harlanb

Thank you for your response grey beard.
So, if I understand what you are saying: You hold the covering up off the fuselage apply heat to the covering with the covering iron (Not heat gun?) then as the covering stretches, you pull it down to the fuselage and iron it down. Is that correct?

thanks
Pretty much. As it heats the covering will stretch and you sort of lay it down over the wood as you go. Maybe Ken will make a video of it for gettingairborn ? If your using Ultra then it can be lifted if you see a wrinkle forming. Once it is covered a heat gun can be used to help remove any wrinkles you may have gotten. Practice is the key to any covering. There is even a special clamp for pulling the covering sold by Tower. I haven't used one but it may help?
Old 05-27-2013, 02:59 PM
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Default RE: How to cover large compound curves

Hi harlanb. Could you post some pictures of exactly what you're having difficulty with or tell us what kit you are trying to cover? Mostly I use the iron, but when I really need to stretch the material I reach for the heat gun. You have to be judicious in the application of the heat. How far you hold the heat gun from the area and length of time to apply the heat only come with practice. I always wear a cotton glove on the hand I use for grabbing the film, for obvious reasons. I also keep a damp cotton cloth handy to cool everything down quickly, especially the adhesive, and help prevent the film from sliding. If you can do a rounded, tapered wing tip a fuselage shouldn't present anymore of a problem for you. Be willing to waste some material, then practice, practice, practice, as Gray Beard has pointed out.
Old 05-27-2013, 05:03 PM
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Default RE: How to cover large compound curves

One thing not mentioned is securing the piece your working on, for the covering your pulling on is attached to the fuselage a bit farther back. To me this is the hardest part. Family members aren't interested in holding it so I generally need to get creative in securing the piece in all directions firmly without obviously damaging it. Sometimes between the legs works well with nose pointed up.. the bottom laying on something soft covering the bench. for example a rag, etc.

On that tower clamp.. it would be nice if wasn't straight across but curved like an arc to generally match the curve of our piece. For if your heating and pulling, the piece covering will generally have curvature.
Old 05-27-2013, 06:23 PM
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harlanb
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Default RE: How to cover large compound curves

Ptmac.
I am currently trying to cover a utter chaos 40, The front bottem part of the fuselage is all balsa and sanded to a compound curve. I covered it by doing ti from the bottem and up 1/4 of the sides with one piece. I started at the middle of the bottem and used a heat gun and stretching it up eithe side. It still came out with some wrinkles when covering around the sides. I wonder if I shold do it in smaller pieces.
I will try to post a picture.

Old 05-28-2013, 02:34 AM
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Default RE: How to cover large compound curves


ORIGINAL: KitBuilder

One thing not mentioned is securing the piece your working on, for the covering your pulling on is attached to the fuselage a bit farther back. To me this is the hardest part. Family members aren't interested in holding it so I generally need to get creative in securing the piece in all directions firmly without obviously damaging it. Sometimes between the legs works well with nose pointed up.. the bottom laying on something soft covering the bench. for example a rag, etc.
That's a good point. I have a [link=http://www.robart.com/store/hobby-tools/airplane-stands]Robart Super Stand #401[/link] I can secure the airframe to with rubberbands and an old comforter I place on the bench. But between the knees generally works the best.
Old 05-28-2013, 03:23 AM
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Default RE: How to cover large compound curves

Trying to cover the bottom and the sides with one piece of covering, although not impossible, is extremely difficult. Once you get up around the nose you have a lot of stretching and shrinking to do, as you have found out. Splitting it into multiple pieces simplifies the matter. Start with the bottom, then the sides, then the top, just like any other airframe. The seams aren't as apparent that way when sitting on a bench at the field for all to view. Now cover each section with as few pieces of film as possible. The sides can probably be done with one long piece each. Btw, are you using multiple colors?
Old 05-28-2013, 06:35 AM
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Default RE: How to cover large compound curves

I find Faye Stilley's books on contest grade covering to be very helpful and well worth the investment. I always go back to them before I start a covering project. You can find them used and I think the AMA or MAN carries them.
Old 05-28-2013, 07:49 AM
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Default RE: How to cover large compound curves

My stand is made from PVC with pipe insulation around it but I end up covering on my lap most the time. This time of year I'm in my summer uniform, just shorts and a tee shirt. When covering I always have burn marks on my legs from running the iron from the parts and across my legs repeatedly. I would make up a cowl and wing tip to practice on. With the Kaos I always covered the bottom first then went from the top and did the sides then tied into the bottom with the top piece. I have mentioned the brand of covering already but with Ultra the covering can be a bit loose and it will shrink very well with a heat gun. I have gotten some very tight covering over turtle decks just by ironing on the sides then shrinking down the top with a gun. I use Ultra for the main covering then Mono for the trim using Windex and my trim iron.
Old 05-28-2013, 08:33 AM
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Default RE: How to cover large compound curves

Gray Beard do you mean Ultracoat? I like Ultracoat because it has one temperature just to tack without shrinking and then a large temperature range shrinking the covering. Check out the link to Ultracoat tips on covering and don't forget to check YouTube for HowTo videos.

http://www.horizonhobby.com/article/...ote-tipstricks
Old 05-28-2013, 10:37 AM
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Default RE: How to cover large compound curves

[link=http://www.rcuniverse.com/magazine/article_display.cfm?article_id=726]RCU Review: Video How to Another Look at Covering[/link]


This will help.
Old 05-28-2013, 01:04 PM
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Default RE: How to cover large compound curves

Yes, Ultracoat is my main go to covering for almost everything. I first cover the plane then set it out in the sun to let the covering sag then shrink it again. I do this several times until the sun no longer sags it then I add all the trim. I use Ultra and Mono for the trim work. Mono goes on well with Windex then I just run the trim iron around it on the outside about 1/4 inch. This way the covering always stays tight without any sags or wrinkles. I do most of my building during the summer so I'm usually able to do this curing process. Winter builders not so much.
Old 05-28-2013, 03:38 PM
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Default RE: How to cover large compound curves

How long do you generally leave it out in the sun?

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