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Old Feb 05, 2013, 01:35 AM
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casor's Avatar
Boyertown, Pa
Joined Mar 2007
755 Posts
Wing sheeting

Hey Ken - looks like an enlarged plastic model Ken, very nice work. I think I am going to stop posting my stuff.

As long as we brought up the wings, without driving you too nuts, could you please loosely describe your sheeting process for a large model and what glue to use. Certainly I have done a number of small models, but doing the larger ones is a different ballgame since there is so much area. I don't like using CYA for this process as it dries too fast and it's too easy to get a section not affixed to the underlying ribs. I know you used jigs, but how do you keep such a large surface in true and not wiggling around/bending during the sheeting process....
Rob
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Old Feb 05, 2013, 06:16 AM
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Liverpool, England
Joined Jan 2005
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Hi Rob, I am afraid I use CYA, dont seem to have had any issues with it not grabbing the sheet, I always use 4"/100mm wide sheets and extra thick CYA so that it doesnt get a chance to dry up due to the relatively small area.

I try to plan the design so I have stringers at the correct distance apart to suit the 4"/100mm sheets.

With the wing still on the jig I sheet the top surface, this way the whole wing structure becomes very rigid and allows further sheeting without any problems
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Old Feb 05, 2013, 09:54 AM
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eye4wings's Avatar
Ware, herts. U.K.
Joined Sep 2008
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I'm trying something a bit different for skinning on the current design... foam!
I bought some 3mm art board which looks like depron inside with a layer of white card on both sides.

I found that if I stripped one side of the card off the board took on a curve that would be ideal for airofoil curves. Cyparis spar members and balsa (or possible foam again - haven't decided) rib strips a la 'mini-waste' system and the foam on top. All I have to do is cut the top to the right size - all in one piece so no joints to sand - and build onto it.

I think it holds promise - but I haven't actually tried it yet!
(but it's a lot cheaper than balsa!)
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Old Feb 05, 2013, 11:07 AM
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Quote:
Originally Posted by eye4wings View Post
I'm trying something a bit different for skinning on the current design... foam!
I bought some 3mm art board which looks like depron inside with a layer of white card on both sides.

I found that if I stripped one side of the card off the board took on a curve that would be ideal for airofoil curves. Cyparis spar members and balsa (or possible foam again - haven't decided) rib strips a la 'mini-waste' system and the foam on top. All I have to do is cut the top to the right size - all in one piece so no joints to sand - and build onto it.

I think it holds promise - but I haven't actually tried it yet!
(but it's a lot cheaper than balsa!)
I've done lot's of sheeting of build up wings with thin foam; it works great (and is cheap too!) Having paper on only one side concerns me as it might warp with changes in humidity, even if painted. Probably better to sheet the top and bottom to cancel any tendancy to warp. You'll get a much stiffer wing and can reduce the weight of the spar.

(Maybe I misread your post and you do plan to sheet both sides?)
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Old Feb 05, 2013, 11:38 AM
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United States, FL, North Port
Joined Mar 2004
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For sheeting large built up wing surfaces, i use the white "gorilla" wood glue.

I put a bead of the glue on all of the wing skeleton structure (ribs, spars, stringers, etc) then place the wing skin (its all glued together into one large skin) into position, and press it down so it makes contace with all of the wing structure frame.

Then while the glue is STILL WET, remove the wing skin from the structure and place on a table glue side up.

When you place the skin on the frame and press it into contact with the frame, the glue transfers to the wing skin. So when you remove the skin, you are left with a mirror image of the glue in the wing frame in the wing skin. Now you can go along all of the glue with your finger and smooth it out and spread it to any area that didnt transfer completely.


Now with the skin OFF of the structure, leave the glue to dry until it is no longer wet to the touch (about 45mins to an hour)

Now take your hobby covering iron and turn the heat as high as it will go.
Place the wing skin back into position in the wing
Then starting on the main spar, iron the wing skin onto the structure, slowly moving the iron down the spar. You will know you are moving at the correct speed when the balsa skin that was just ironed was warm to the touch and slightly discolored (the skin will also be bonded to the wing structure frame)

Continue with the main spar, then the ribs to the aft spar (or trailing edge if no aft spar) and then down the ribs from the leading edge.


I used this on my large Horton 229 project which has a 36" chord at its outer wing panel root and a spar of 62" along the main spar and it worked out great!
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Old Feb 05, 2013, 02:38 PM
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eye4wings's Avatar
Ware, herts. U.K.
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Quote:
Originally Posted by pmullen503 View Post
I've done lot's of sheeting of build up wings with thin foam; it works great (and is cheap too!) Having paper on only one side concerns me as it might warp with changes in humidity, even if painted. Probably better to sheet the top and bottom to cancel any tendancy to warp. You'll get a much stiffer wing and can reduce the weight of the spar.

(Maybe I misread your post and you do plan to sheet both sides?)
Thanks for the thought... but wherever there's a 'might', there's a mightn't!
I plan to give it a try with the card left on one side only (which will be balanced by the card left on the outside of the wing underside sheet as well) of the NACA 63A 417.5 (modified) section. It is only going to be half the centre section initially, and if it warps, then will be the time to decide what to do about it. It will have all the time it'll take me to get the retracts operative to acclimatise.

My 'mini-waste' system is here - for a balsa build... should be the same in foam/balsa....
http://www.rcgroups.com/forums/member.php?u=228170

I can't really get any lighter spars than 3mm x 12mm Cyparis top and bottom webbed with 1/16" balsa cross grain.
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Old Feb 05, 2013, 03:00 PM
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Quote:
Originally Posted by eye4wings View Post

I plan to give it a try with the card left on one side only (which will be balanced by the card left on the outside of the wing underside sheet as well)

Ahh, no worries then. I thought you trying to do an 3mm thick undercambered wing with ribs glued onto it!

Didn't mean to hijack the 129 thread. The build has been awesome so far!
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Old Feb 06, 2013, 01:17 AM
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Liverpool, England
Joined Jan 2005
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No worries about hijacking the thread I am still very much an inexperienced novice at this so any alternative methods of building are great to read about

Still slammed with Ofsted so no further forward this week
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Old Feb 06, 2013, 02:23 AM
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Ware, herts. U.K.
Joined Sep 2008
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Wow Ken! My admiration for your building skills just went up even further. I never could get a balsa skinned wing to look like yours (hence the planned attempt to use foam in one piece) but now I learn you're a teacher!

I have heard enough stories of pumped up little officials who can't teach but are more than happy to stand in judgement of those who can, and do, to know that I wouldn't be able to do what you do. I even wonder how it is we still have teachers....

So, great model - great modeller!
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Old Feb 06, 2013, 03:39 AM
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Australia, WA, Kalgoorlie
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I couln't agree more! Superb skill in both design and in execution.
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Old Feb 10, 2013, 06:27 AM
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Liverpool, England
Joined Jan 2005
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Persuaded my wife to give me an early birthday present, he is a 12" Dragon figure of a Stuka pilot - 'Johannes Patzer' dressed in a 1940 Norway campaign winter flight suit, close enough for the Russian front I thought. I added an Action man parachute harness, not quite the right colour but looks the part.

Really well made and fits great just propped into roughly the right position

I cut all the lead for the nose yesterday, I used the CAD drawing to make seperate stacked templates to cut the lead so its as far forward as possible and epoxied in place, was able to reduce the weight needed to just over 900g doing this. Was going to take her to the field today for some taxi tests but the weather is awful.

Starting the cowl plug today
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Old Feb 10, 2013, 06:39 AM
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Herr Patzer certainly looks the part, and looks determined to get a kill while he's at it too! I'm sure he will pilot the Panzerknacker in a most appropriate manner....
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Old Feb 10, 2013, 09:12 AM
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eye4wings's Avatar
Ware, herts. U.K.
Joined Sep 2008
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Did you allow for the extra weight of the cowlings in adding your nose weight Ken? - or do they perhap represent your 'safety margin'?
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Old Feb 10, 2013, 09:58 AM
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Liverpool, England
Joined Jan 2005
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Hi, I have only glued in place 750g for the time being will do the rest if needed after cowlings and paint are added

Ken
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Old Feb 10, 2013, 04:40 PM
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United States, WI, Fond du Lac
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The canopy frame and pilot look fantastic.
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