U.S. Scale Masters
USSMA General Discussions => Scale Building Tips & Techniques => Topic started by: Skymaster on Wed, 10/31/12, 04:21 PM
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In the majority of our scale models, we see the fuse made out of wood, and some use fiberglass and composites. Wings are usually wood or balsa covered foam.
What is your preferance for construction materials and why?
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I prefer wood for the entire airplane. Beyond that it's covered in fabric or glass cloth depending of course on the subject. I've never liked foam wings, which is an unfounded bias on my part. I don't have enough experience with fiberglass to like or dislike it. I simply enjoy working on a wood model airplane. I do know from recent experience, when my Bird Dog splattered itself in the zucchini patch, I was able to rebuild it because it was of wood construction.
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Well, so much for never working with foam wings. I just picked a Sig Kougar for the glassed balsa over foam experience. I'm going to do some reading elsewhere in here on tips for adding panel lines and give that a try. If it turns out looking more like grout lines on a tile floor, no loss, I get the practice and a great flying sport plane in the end.The fuse is nothing more than a balsa box with a plastic turtle deck and canopy so I will probably silkspan and dope that part of it.
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Hey Dan,
If you have not done so already, check out www.rcscalebuilder.com (http://www.rcscalebuilder.com) it's about the best site on the net for getting anything info you want/need on scale building. Some of the best builders in the world post there. There is also a chat room for site supporters where several of us hang out. I'm GhostRider2110 over there...
See-ya
--Mitch
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Hey Dan,
I agree with Mitch that there is a lot of info out there on rcscalebuilder.com. BUT the intent of us doing a "build" forum here is to grow the passion for scale building and competition. To pass you off there is not the intent of what we are attempting to do here. I apologize that I or another seasoned builder hasn't responded to your post sooner.
As far as the Kougar is concerned..... Its a good flying plane. Are you gonna put retracts in or fixed gear? That's awesome your diving in and doing a foam core wing. I always found learning a new technique challenging and fun. I'm not sure how the instructions are now written. Back when I build those airplanes, they talked about using "Corebond" a Sig product that is similar to contact cement, but does not attack the foam.
Today most (NOT all) of the IMAC guys are using polyurethane glue to attach the balsa skin to the foam. There are advantages; One, you don't need to edge glue the balsa together. We've just taped them together, cut them to size, and when you spread the glue on the balsa, the polyurethane penetrates both the seams in the balsa, but the first couple of layers of the foam. This produces a much lighter and stronger wing. Typically after you have the cores and skins prepped, you'll spread a thin layer of glue on the balsa. Then you LIGHLY wipe the core down with a DAMP sponge, apply the skin onto the core and place it back in the shuck. Repeat the process on the other side of the core. Then you have to place a bunch of weight on top of core/shuck stack and allow to dry over night. The next day trim the balsa skins and add your edges.
I'll assume you've glassed an airplane before. Once the glass is on, and you've primed and sanded it, and its reasonably smooth, your ready to have some fun. To add panel lines of the over lapped type, like on my Skymaster, I used 2 layers of the GREEN 3M fine line tape. For filler I used Evercoat finishing puddy part # 421. Its light and sands easily. For the Kougar, one layer would work, but play with it. I taper from the tape out to around 3/4". we sand the puddy down to the tape, and the skin. When you pull the tape off..... you have a panel line. If you need a curved panel, the blue 3m fine line tape works great! I typically use 1/8" or 1/4" wide tape.
Let us know how your doing
John
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Hi John,
I just got back from my local hobby shop, while there I ordered some Core Bond. NO KIDDING! I assume you're talking about the Titebond or Gorilla Glue polyurethane glues. I'm sure he hasn't placed the order yet so I can always cancel the Core Bond if the PU glues are that much better/easier. Thanks for the tip on the panel lines I think it should prove interesting if nothing else. Yes, I've glassed before, my L-19 is glassed wood. By the way, the Bird Dog has flown again since I wadded it up. After proving to myself that it would still fly well after repairs it's getting stripped and repainted for next summers contests.
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Thats funny Dan! Yes I'm speaking of the Gorilla Glue Titebond I think it does make a better wing. Maybe not so much on the Kougar, but if your gonna build a larger plane with foam wings then absolutely!!!
So glad to hear the Bird Dog flew again! No reason why you couldn't throw some lines on it. I'd use one layer of tape on the both planes. 2 reasons; one weight, second the panels don't need to be that defined on planes that size.
John
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Thanks John on the Gorilla Glue idea. I have always used a thin epoxy coat to do foam cores will try next time.
Randy
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I build strictly foam wings glass fuses only, for about 20 years now, since I do scratch building only.I find it lot faster and stronger than building up from balsa. And it is much cheaper than buying a truck load of balsa wood. This is my two bits, I put in. Here is some pics of my next project. Jerry
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Very nice !!