So I have to bend balsa. 1/8x1/4 to be exact. I left the balsa soaking in water and attempted to bend it around the template I made. I managed to make one tip, a few splits, but it is strong with 3 pieces built up. How can I make this easier, I went through a few pieces just to mange one tip working out?
Well what I did was lamination, 3 layers of 1/4 inch. So hot water is a must. Also does windex even contain ammonia anymore? I also see there is different grades of balsa, clearly I need the more flexible type, but what I have at my LHS is what I have. The bend is essentially an arch. How much ammonia to water should there be?
I use ammonia with water as well. I have a 1" PVC pipe, about 4 feet long, capped at one end. I just put the balsa sticks in it, fill with the water/ammonia solution, and put a piece of plastic wrap over the open end, held on with a rubber band. For the thickness you are using, I'd probably let it soak for 48 hours, at least.
I think it would be stronger with more thin layers. So I am getting opposing times here. 30 minute got soak in tap water, 48 hours in water and ammonia and water, not sure how long. By the way I am bending by the 1/8 thickness, not by 1/4. I have three pieces, so total dimension are 3/8x1/4.
Hardness...it's just what my hobby shop has. It's either spruce or balsa. I can ask. Judging by it though, I would say medium in hardness, and I can feel areas of inconsistency where it gets harder. It's not the balsa that you can cut with your finger nail, but has give to it when dry. So can any balsa bend if it is soaked long enough? I may try adding boiling water in a bucket, when I get more wood that is, or maybe step up to ammonia and boiling water. The one wingtip is okay I feel; a split here and there, but the three pieces reinforce each other.
One thing i found with trying to make bends in balsa,is to do it gradually.What i mean is,put a slight bend in the piece,let dry under pressure,then soak and bend some more,etc.
It will take longer,but you waste a lot less wood.YMMV.
These days,if i need a rounded wing tip,i just cut pieces of 1/4 into a rough curve,glue them together ,then shape.Sometimes,i use thinner core,then add 1/16th top and bottom.That gives high strength for no weight increase.
The angle of bend is roughly what your rudder is. The wing tip I made was from letting the wood sit for an hour. I had work the next day, and pipeband practice the next, so the other pieces were sitting for 2 days, even with that, the wood still snapped. Would this mean that I need ammonia? I also tried doing little bends, giving a slight curve, then going back to the soaking.
Is that 1/16 squared, or does not matter, other than 1/16 being the thickness that is experiencing the bend? Also was that curved all at once, or for incredible bend of the fin, was it bent little bits by little bits? Is spruce better to bend?
HEAT - Hot, near boiling water, or steam works. You need to get the wood core around 200 deg F. Forget Windex or ammonia, stinky and not needed, you need HEAT.
Lamination. If you bend a hot wet wood pierce around a form and let it dry it will "springback" a bit when released. However say a lamination of four thin strips to equal single strip thickness glued up on a form will only "springback" a tiny tiny bit.If you search springback you can find a formula for % of springback Re lam #.
Yes, A grain balsa will wrap around a small mandel, but C grain (the kind with sort a freckled appearance) will not - C is great for flat sheet surfaces because it hates to bend/warp.
I don't know what grain I have, it is just what my shop has, and there aren't any other shops really. I can't say it looks freckled, more grain, although both sides are not smooth, guessing the pattern from cutting. Looking at pics, I'd say A to B. So boiling a ton of water, tossing it in a bucket and putting the lid on should do it? I did have spring back on the piece I made, but when I made two more pieces and laminated them, the piece had no springback at all really, seems strong, even with the slight splits in the wood. Would spruce work better though, as I can get spruce in the same sizes? Just wondering if the spruce bends better with moisture, as I am finding myself to be liking spruce for stringers, and I don't mind using it in the wingtips.
Spruce was used in my airplane because of the strength needed. You can bend almost any wood to a radius of appx 6X thickness with use of steam and ammonia. Some you can go down to a radius of 2X thickness.
The grain can make it harder to get the bend without splitting. Straight along the length of the stick bends best.
The whiter the balsa looks the lighter it is and the easier it bends.
Spruce tends to all be very straight grained. Its heavier than balsa and may not be appropriate for some purposes. For other purposes its better than balsa.
Without knowing the exact bend being done.... I can't say what to do. I can only point at the general techniques that work in most cases.
Thinner bends better.
Wet bends better than dry.
Ammonia softens a substance in wood that "glues" the fibres together allowing tighter bends.
Heat (steam or hot water) allows tighter bends than just wet or using ammonia.....
steaming ammonia lets you do the tightest bend (and is the most dangerous to your health)
Glue laminated bends can be more than 50% stronger than a single stick bend of the same final dimensions.
My plane is coming out pretty strong, it's a 60 inch wingspan Hurricane, the stabilizers are built up of multiple layers of cross beams. The fuse itself is built up of spruce stringers, resulting in a very stiff fuse. For the wings I'll be using spruce too for stringers...so maybe just going to spruce wing tips will be the best. I'll stick to 1/16x 1/4, in boiling water.