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Author Topic: Covering undercambered wings  (Read 3215 times)

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Offline rogerandout

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Covering undercambered wings
« on: December 12, 2009, 11:17:58 AM »
I am currently building a BB Diamond demon which features an undercambered wing. The recommended covering is Solartex but how do you secure it to an undercambered wing section without it pulling off when heat shrunk??    $%&
Any suggestions gratefully received.

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Re: Covering undercambered wings
« Reply #1 on: December 12, 2009, 11:54:55 AM »
Errrm, very carefully....



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Offline RobC

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Re: Covering undercambered wings
« Reply #2 on: December 12, 2009, 12:08:03 PM »
balsaloc the bottom edge of the ribs, cover the bottom but don't tighten it, wick cyano along the covering where it contacts the ribs as insurance, cover the top and taughten everything up?  The only problem with that might be marking of the tex by the cyano.
If it uses cap-strips it will be easier and more secure.
flying's easy - it's getting it back down in one piece that's the hard part

Offline Michael_Rolls

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Re: Covering undercambered wings
« Reply #3 on: December 12, 2009, 12:08:57 PM »
I've heard claims that you can cover the underside first and use cyano to make sure the covering is stuck firm before shrinking gently and then covering the top when happy with the underside. never tried it myself and if there is a good solution I'd like to know it. The cyano idea may be OK if the wing is pretty rigid, but a lot of the vintage style designs to which this applies rely on the tautness of the covering fro a fair degree of their rigidity - obe of the reasons I've always used tissue or nylon for such models.
Mike
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alan c

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Re: Covering undercambered wings
« Reply #4 on: December 12, 2009, 12:44:28 PM »
Dont use tex,  its a lightweight structure, and it will pull,  do it the old fashioned way, with nylon,  then use balsa cement to adhere the nylon to the underside first,     if you want to use a heat shrink, try something thats not as agressive, like lightspan,  for this, balsaloc, or thinned down PVA will be good, 

Offline SWM

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Re: Covering undercambered wings
« Reply #5 on: December 12, 2009, 12:46:49 PM »
I am currently building a BB Diamond demon which features an undercambered wing. The recommended covering is Solartex but how do you secure it to an undercambered wing section without it pulling off when heat shrunk??    $%&
Any suggestions gratefully received.

I've done this with Tex and its quite difficult.

I did it with Balsa Loc and Ironed from the inward outward. Using a lower heat than normal, The Balsa Loc is best put on in minimum amounst and left to dry until the next day.

The less Balsa Loc the less the covering will slip about.

Try not to use to high a heat and leave the Tx slightly slacker than usual.

Having completed the covering, I then give the Tx 2 x 50/50 coats of dope - which seems to help it keep its shape. I know Derek Hardman of Solarfilm says you dont need to - but it works for me. Then Flexi Coat or Tufcoat and the jobs a goodn un.

I have tried cyno, but it marks the tex.

Cheers

Steve

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Offline steamysheep

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Re: Covering undercambered wings
« Reply #6 on: December 12, 2009, 13:48:45 PM »
staple gun....  ^-^
LOOK IF I AM EVER ON A LIFE SUPPORT MACHINE...... UNPLUG ME.....THEN PLUG ME BACK IN.........  SEE IF THAT WORKS....

Offline Pup Cam

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Re: Covering undercambered wings
« Reply #7 on: December 12, 2009, 14:11:10 PM »
Functional rib stitching :''

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Offline THEBOYBREWER

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Re: Covering undercambered wings
« Reply #8 on: December 12, 2009, 15:10:02 PM »
than usual.

Having completed the covering, I then give the Tx 2 x 50/50 coats of dope - which seems to help it keep its shape. Cheers

Steve



why would you want to dope your transmitter ??????????????
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Offline Patmac

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Re: Covering undercambered wings
« Reply #9 on: December 12, 2009, 19:51:41 PM »
My Junior 60 is Solartex covered. I donít remember having any problems covering the undercambered wings & the Solartex has stayed fixed since around 1986. In that time itís been used as a floatplane & the wings have been soaked a few times.
Earlier this year I built a Veron Deacon which also has undercambered wings & I covered it with Solartex.
I didnít use Balsaloc or any other extra adhesive on either model just applied the tex as supplied.

For the Deacon I first laid the tex on the underside tacked it to the tip & root of the mainspar then ran the iron along the mainspar. After that I followed the Solartex instructions to stick the outline in place then ironed it to each rib using the tip of the iron. I then went over all the stuck down fabric with the iron at a slightly hotter temp. The top surface was covered in the normal way then both surfaces were tightened with the iron at as cool a temp as would shrink the fabric.
I can't remember exactly how I tackled the Jnr 60 but it was almost certainly the same way.

Solartex doesn't shrink as tautly as nylon & remains more flexible so is less likely to cause warping.
It doesn't shrink as tautly as tissue either so doesn't stiffen the wings as much. The wings on my Deacon are a little more flexible than I would like.

The other non-shiny heat shrink alternatives Iíve used on different models are Litespan & Fibafilm.

Litespan remains even more flexible than Solartex but isnít as strong. I once covered a lightweight 100Ē glider with it but the wings fluttered when I applied some down trim to penetrate a moderate breeze. To get the rigidity I covered over the Litespan with doped tissue which was pretty unsightly so that had to be painted.

Fibafilm is rigid & strong but doesnít shrink very much. It tends to leave wrinkles that canít be removed around wingtips & any compound curves.

If I was doing the Deacon again Iíd cover first with tissue, watershrink, give a couple of coats of thinned dope then cover with Litespan. The tissue should give the right rigidity & the Litespan a good degree of puncture & tear resistance. Also the Lightspan could be in contrasting colours with the overlaps not necessarily on spars. Any colour trim could  also be done using Litespan. 
Pax vobiscum

alan c

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Re: Covering undercambered wings
« Reply #10 on: December 12, 2009, 22:47:32 PM »
thought the 60, and the deacon where flat bottomed clark y  :-\

Offline Patmac

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Re: Covering undercambered wings
« Reply #11 on: December 12, 2009, 22:48:45 PM »
thought the 60, and the deacon where flat bottomed clark y  :-\

Not the Junior 60 or the Deacon.
Pax vobiscum

Offline idigbo

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Re: Covering undercambered wings
« Reply #12 on: December 12, 2009, 23:16:29 PM »
The knack is to iron the Tex to the undercambered part of the ribs first, using a cloth to make sure the Tex is glued to the rib as it cools. Then work along the ribs to the leading and trailing edges, again using the cloth. Then do the outlines then finally the rib bays. Be careful not to get too much heat on the ribs though or the adhesive may release the fabric. If it does, simply heat the the rib area again and reapply using the cloth. I've done lots of undercambered wings and never had to use any other method, unless of course real rib stitching was called for.

Ian.
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Offline half throttle

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Re: Covering undercambered wings
« Reply #13 on: December 13, 2009, 14:25:39 PM »
The knack is to iron the Tex to the undercambered part of the ribs first, using a cloth to make sure the Tex is glued to the rib as it cools. Then work along the ribs to the leading and trailing edges, again using the cloth. Then do the outlines then finally the rib bays. Be careful not to get too much heat on the ribs though or the adhesive may release the fabric. If it does, simply heat the the rib area again and reapply using the cloth. I've done lots of undercambered wings and never had to use any other method, unless of course real rib stitching was called for.

Ian.

Me too  :af

The 4 or 5 Junior 60s I've built for myself and clubmates I've cap-stripped top and bottom and, using Solartex, I've never had any problems.

I found a nice, soft duster works well.
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Offline Michael_Rolls

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Re: Covering undercambered wings
« Reply #14 on: December 13, 2009, 16:55:21 PM »
This is all very encouraging. I've always chickened out of using 'tex or film on undercambered wings in the past and put up with tissue puncturing at the least excuse or the time and mess/smell of nylon. Next time. I'll take the plunge.
Mike
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Offline chris6

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Re: Covering undercambered wings
« Reply #15 on: February 01, 2010, 22:25:42 PM »
I am currently building a BB Diamond demon which features an undercambered wing. The recommended covering is Solartex but how do you secure it to an undercambered wing section without it pulling off when heat shrunk??    $%&
Any suggestions gratefully received.
Hi Roger

Fiba film, which is not self-adhesive and relies on balsaloc, worked fine on my Junior 6o which weighs 4lbs with 72" wing and narrow capstrips on the top and bottom of the ribs.

It has good fuel proofing and anti-puncture properties and is much lighter than solartex, and I reckon gives better stiffness too.

Regards
Chris

Offline Balsa

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Re: Covering undercambered wings
« Reply #16 on: February 02, 2010, 01:20:56 AM »
why would you want to dope your transmitter ??????????????

So he can have his wicked way with it...

Offline SWM

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Re: Covering undercambered wings
« Reply #17 on: February 03, 2010, 17:11:18 PM »
This is all very encouraging. I've always chickened out of using 'tex or film on undercambered wings in the past and put up with tissue puncturing at the least excuse or the time and mess/smell of nylon. Next time. I'll take the plunge.
Mike

I've done it Mike - Ironing out from the middle and not over heating. I know Derek Hardman of Solarfilm used to say doping the Tex was not needed - but I always did and it  ( 50/50 mix)seems to stabilise the slightly slacker Tex-  I know Fred (Ribstock) Webb says he always used thinned down dope on Text and his models do seem to last years without - slacking off. He uses Thinned down dope on his Lite Span models too. The reason he originally started doing this was Lite Span covered models hanging in the shop had hot temps/ cold temps in one day and the Lite Span would slacken - look aweful. Now his models last years on the shop ceiling and it looks like they were covered yeasterday.

On an aside. You will probably know getting nice tissue now a days is not as easy as it was in the 60's and 70's - I found out something yesterday but I havent tried it yet. We got some Chinese Lanterns from China - off eBay. The tissue looks like HW Model Span - now...I thought - they do these Lanterns in colours! What if they have tissue like this, on the coloured Lanterns....I'm going to try an order a couple of coloured ones. The Lanterns are huge - cost as little as £1.00 or less and might have £5.00 of useful tissue!

It's worth a look I guess,

I know we do have some tissue in at SWM, but it's never quite like the old Model Span.

Steve
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Offline Norfolk'n'Good

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Re: Covering undercambered wings
« Reply #18 on: February 03, 2010, 19:11:24 PM »
I had a SE5a years ago, always had the covering coming off the bottom wing even though I did the Sir Red method  :-\

I have recently done a test piece using Koverall, pva on the ribs 1st, laid the Koverall on it and waited for it to dry then heated it really hot to see if it would come off.  No problems at all and Koverall shrinks like a goodun so I would give this a go as and when I get an undercabered wing such as the 1/3rd scale Bristol I will be building later this year.

 

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