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  #11  
Old 11-26-2008, 03:59 PM
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Quote:
Originally Posted by tbzep
I've never tried basswood. How does it cut and sand relative to balsa?

Personally I like basswood. Some may argue that it's brittle but I haven't run into any problems with it.
It's a little harder to cut (especially on thicker pieces) but nothing a good sharp blade can't handle. I find it's very easy to sand (and somewhat more forgiving than balsa) and most of the grain can be filled with just primer.
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  #12  
Old 11-26-2008, 04:56 PM
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Quote:
Originally Posted by tbzep
I've never tried basswood. How does it cut and sand relative to balsa?


Trickier to cut, since it is denser (heavier, of course). I buy scalpel blades to replece a #11 Xacto blade, which helps. I have also used my tabletop bandsaw to cut a stack of 3 or 4 fins, and then take them down to the pencil outlines with a small Dremel belt/disk sander.

For smaller rockets, the basswood in 1/16" may be heavier, but it is such a small amount. I've used basswood on a upscale Orbital Transport, and you definitely feel the weight gain. I only did this for the main wings, and not the glider wings.

Basswood fills really fast, too, because of its tight grain. I only use sanding sealer these days, but on some basswood, you could almost go straight to primer with good sanding between coats.
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  #13  
Old 11-27-2008, 07:45 AM
Eagle3 Eagle3 is offline
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I find basswood much easier to work with than balsa. I'd never use it on a competition model, but for sport models it's great. It's slightly harder to cut and sand, but when I'm sanding basswood I feel I have a lot more control over the shape. You can sand a mistake into balsa a lot faster than bass. Bass has a finer grain, is much easier to fill n finish, and as mentioned earlier won't warp as easily as balsa. In the past when using 1/16 balsa I used tissue and dope to finish the surface, but I'm old skool.
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  #14  
Old 12-11-2008, 07:24 AM
micromeister micromeister is offline
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I'm with most of the other posters on this point: Bassswood is almost always preferred over balsa for my sport flying models. Particularly in 1/16" or less in thickness. the very small penelty in added weight is always overshadowed by the increased strength, stiffness and ease of finishing.
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  #15  
Old 12-12-2008, 02:14 AM
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Quote:
Originally Posted by tbzep
Next time you guys use 1/16" balsa for large fins, don't use thinned F-n-F to fill the grain. I made it thick as I could and still brush it on and it still warped the fins. I got them straight after the first application and I will after this one, but it is a pain in the butt to fool with. Just thought I'd vent a bit.



I use it on 1/16" balsa all the time.

before... Choose hard C-grain balsa if possible. A-grain is just asking for trouble anyway.
1. apply it BEFORE attaching to rocket
2. use it full strength and apply it with your finger (vinyl or nitrile glove recommended). rub it in.
3. apply it on both sides at roughly the same time (i.e. not one side and let dry, then other side)


from what I can tell in the picture, your fins were close to A-grain, and your F'n'F had a much higher water content than it needed to be.
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  #16  
Old 12-12-2008, 02:15 AM
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Quote:
Originally Posted by Doug Sams
I imagine the density was a key factor. It likely limited the absorption and thus minimized the warping.

I rarely use 1/16" preferring to instead upgrade most of my clones to 3/32" for the sake of durability. That said, I still use it on occasion and don't see many problems. I normally lay down a coat of Zinnser primer first, and I wonder if that averts the warping by limiting the absorption of the thinned FnF.

Doug...thinking out loud...

.



Could be, I usually brush on a coat of clear dope to limit absorption and it seems to work fairly well.
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  #17  
Old 12-13-2008, 09:32 AM
scigs30 scigs30 is offline
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I am finishing my Apogee II right now and it is an original so I used the balsa stock that came with the kit. I used Aerogloss balsa sealer, 4 coats and no warps. After 1 coat of grey primer the grain was all filled. Since I am building the original, I don't have the luxury of using basswood.
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  #18  
Old 12-13-2008, 10:30 AM
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I still mostly use balsa, but I pick the sheets with the hardest C-grain that I can find. I also use basswood on occasion, especially on larger rockets, but I'm thinking about using it more often. Thick basswood, like 1/4" or thicker, is A LOT of work to sand. (I use a a palm sander, and even then, it takes awhile.) Yeah, basswood is more forgiving than balsa to sand, in a sense, but that is because you have to make many, many more strokes (and go through much more sandpaper) to remove the same amount of stock. When you are making, say, 200 or more strokes to round one edge of a fin, as opposed to, say, making 30, it is easier to make subtle adjustments to correct minor errors.

I have used this stuff (see attached image) to fill the grain in balsa fins, and I have not seen any warping. Once the Delta Ceramcoat filler is completely dry, you can give it a light wet-sanding with 400-grit sandpaper to get a nice smooth surface. It may require 2-3 coats, depending on how coarse the grain is. I also use it on nose cones. You can find it in the crafts section at Walmart, and at Joanne's Fabrics and Michael's.

One other filler that has worked well for me is Pine-Pro Sanding Sealer, which I have only seen at my local hobby shop (in with the pinecar derby supplies), but you might be able to find it at Michael's, too. It is thicker and it fills faster than the Delta product, and it also wet-sands smoother. Unfortunately, I can only find it in small bottles, and it goes fast. (I used almost an entire 2 oz. bottle on my Golden Scout. ) Because of that, I mainly just use it on nose cones. But this stuff is truly great, and it is what I would use all the time, if I could get it in larger bottles. The Delta Ceramcoat filler and Pine-Pro are both water-based, but I have never had either one cause fin warping. They both just clean off my brushes with soap and water. Before you wet-sand either one, though, make sure that the coat has completely dried.



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  #19  
Old 12-13-2008, 11:02 AM
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BTW, I also think that FSI might have been on to something when they used 1/16" aircraft plywood for the fins in many of their kits. It is very hard, and if the fins aren't too big, there isn't much of a weight penalty. Tack the stuff on with gel CA, then give it some thin epoxy fillets, and the fins are bullet-proof! The birch aircraft ply that I have used was finished much smoother than regular plywood. It still needed to be sealed, but it usually just needed one light coat of filler to completely fill the grain. The downside? It was almost as hard to sand as basswood (almost) . I haven't tried make fins from 1/32" birch plywood yet, but it might work out that the slight extra weight would be offset by the much thinner aerodynamic cross-section.

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  #20  
Old 12-13-2008, 12:56 PM
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I also use the Delta Cream Coat, and really like it. I've tried both it and Aerogloss, and the Delta product seems to work just as well and isn't nearly as toxic and stinky. (When I use Aerogloss everyone in the house gives me grief.)
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