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Building Tips and technical articles. => 1/2 A building. => Topic started by: minnesotamodeler on July 31, 2008, 04:21:37 PM
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Thought I'd post an update on this thing. I've been continuing to mess with it, more and more pleased all the time.
Pics: 1st, original traditional airfoiled Rumbler, viewed from LE--just for comparison.
2nd, "Droopy Diamond" (tall diamond-shaped ribs, interior spar, covering allowed to sag into round airfoil shape between)--Coverite "Microlite" film, very light.
3rd, I had to see what thicker film would do--so, this is Monokote, much heavier than the yellow Microlite. Sags just as well.
4th, ditto silkspan/dope. I thought it probably wouldn't sag; I was wrong. It's a sorry covering job, I about forgotten how to do it, but good enough to prove my point: Any kind of covering will work.
5th, all of them stacked for direct comparison.
6th, plan view just for reminders.
7th, profile of the D.D., again for reminders.
I believe the droopy diamond airfoil outflies the traditional...I plan to take both iterations out and fly them back-to-back for immediate impressions.
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You aught to try Doculam! I don't think it would sag as much. If you are interested I can send you some to try.
Robert
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Sure, send it on...the sag, though, is the desired trait; I would hope it would sag as much. But it would be good to know if it won't.
I'd just need about a 12" x 12" piece.
I'll PM you my snailmail address.
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Thanks friend. I will get some to you.
Robert
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...4th, ditto silkspan/dope. I thought it probably wouldn't sag; I was wrong. It's a sorry covering job, I about forgotten how to do it, but good enough to prove my point: Any kind of covering will work.
Careful with light silkspan. It sags best if applied chordwise but is not NEARLY as strong and will snag easily in weeds. Apply the silkspan spanwise and although less sag, you will be much happier.
With your experimentation, I'm sure you will determine the appropriate rib height to get the effect you want.
Your planes look really nice.
George
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Thank you George, rib height I'm currently using is 1.5" on a nominal 6.5" chord, that's 23%, sags to about 1", 15%...it's working really really well--the planes are very fast, track well, snap through turns with minimal speed loss, turn tight consecutive loops with no bogging, upwind maneuvers no problem, etc. An all-around good combat plane. A thorough experimenter would try taller ribs (shorter as well) to find the optimal. I'll probably get around to it eventually. Don't know how a guy could get much better performance than I already have though.
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OK, 1 more material type tried, to see how its "droop" measures up: 1.5 mil "Docu-Lam", donated by my good friend Robert McHam for my experimenting pleasure. As you can see, the droop of this stuff is again very much in the ballpark with all the others. Covering type doesn't seem to matter.
This Docu-Lam, by the way, is pretty good stuff. It requires higher temperature to seal, also to shrink, than the more typical plastic films, but it is much tougher. Shrinks up more, too, at temps I'd be burning holes in monokote, etc. And clear! It practically disappears, see second pic.
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Quote by minnesotamodeler:
"And clear! It practically disappears"
I know! Nearly like glass.
Robert
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Where do you get Docu-lam, and how is its weight? Also, is it paintable?
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Where do you get Docu-lam, and how is its weight? Also, is it paintable?
Hi Larry,
I got mine from Robert! I think it's the stuff used in laminating machines, for laminating documents...so should be available through any office supply house (Officemax, etc.). However, if that's the stuff, it comes in, like, 500' rolls or something, for big $$$. Somebody oughtta buy a roll and piecemeal it out to modelers in manageable quantities--somebody probably already does. Somebody oughtta research this (hint, hint).
It is extremely light, about like Coverite Microlite, but much stronger. Robert tells me it is paintable, on the outer surface if sanded lightly to get some "tooth", or on the under surface with no prep necessary--I don't know how that would affect the adhesion however. I'll probably be trying some of these things since Robert sent me a bunch of the stuff.
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Does this resemble the covering from Phil Cartier? I have not tried it yet , but seems the qualities may be the same.
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Ray,
I've been using this stuff since the late sixties, mainly on combat models back when. The stuff I use is called SEAL - LAMIN and you can google it and find it at a number of places. Here's a few:
http://www.teamphoto.com/products_lamsupplies.html
http://www.schooloutfitters.com/catalog/product_info/pfam_id/PFAM3911/products_id/PRO11777?sc_cid=shopping.com_GBC-3000004
http://www2.milwaukee.k12.wi.us/stock/AudioVisual.rtf
You're right about the high temp. You can actually scorch the balsa underneath the film and it doesn't melt.
Be careful if you sand prior to painting. I tried it a couple of times and let go when I lightly passed over a rib. I painted my wing tips on the old combat cats about 30 years ago and it hasn't cracked or peeled after all that time. Still tight as a drum too. For all of you that want to paint it I would suggest just wiping it off with a solvent to make sure its grease free and paint it as is. I used dope and like I said 30 years later and still looks fine. Build a test frame to try other paint. I think it will work well with Rustolium.
The laminates come in either matte or gloss. Both types look the same until applied. When heated the glue on the gloss melts and becomes clear.
Here's an example of wings covered using this stuff a couple of years ago. This was off the same 200' x 11-1/4" roll purchased in 1972 or thereabout. <=
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Thanks, Tom--looks like the same stuff.
Ray, I don't know if it's the same as Phil Cartier's stuff, it may well be.