Shaping Ailerons or Flaps from Solid Balsa Stock.
 

I don't know how many of you have run into the same problem I have, that you can't find any online balsa distributor or LHS that sells strip ailerons much over 1.5" wide. If the you do find them online, then often one or two of the dimensions is way off. Very often I'm enlarging plans or I want to add flaps to a kit that was designed without flaps, and I run into this challenge. I suspect a lot of guys will just proceed with building barn door ailerons and flaps. But, I was born and raised in this hobby with every ARF or kit I ever built having strip ailerons, and I just prefer to stick with what has worked well for me. As they say "Necessity is the mother of invention" and I have devised this method for making nice uniform custom ailerons. (But some how I'd bet that somebody else has figured this out too. LOL).

Anyway, here's photos of how I make the larger sized ailerons or flaps. I'm currently building an old 95" Hobby lobby SR. Telemaster kit that has only the ailerons. The ailerons are 2" x 9/16" thick (it couldn't be a nice, normal 1/2" thick, right?! LOL) , and I want to add 20" flaps with the same dimensions to match. So I bought 3/4" x 2" x 24" balsa blocks from National Balsa when I ordered my supplies from them. (I had to buy 3/4" because they don't sell 9/16" or 5/8" thick balsa)

Essentially, you will start the job by using a leading edge and a trailing edge of the exact dimensions you want your flap or aileron to be. To match my Tele kit's premade ailerons, I wanted my 20" flaps to be 9/16" thick at the hinges, and 3/32" at the trailing edge. You can also use 1/8" wire which is easier to find at the local Home depot then is 3/32". I then sawed a piece of basswood (or any harwood) to 1/4" thick x 9/16" high x 24", and applied a piece of masking tape over it, and pinned it to the front of the 3/4" balsa block with T-pins. I then screwed the balsa block to a sheet of basswood (any sheet thickness is ok) with about a 1/8" hangover, so the 3/32" wire would have that 1/8" ledge to lay on and stay put. I placed the 3/32" wire onto that ledge and fastened the 3/32" K&S wire at both ends of the balsa block. This 3/32" wire will be used to make a trailing edge out of the balsa block. I then screwed the whole assembly to a 2"x4", and locked that 24" long assembly in my vice. I used thin scrap veneer or scrap balsa sheeting where needed to serve as shims to hold everything firm between the 2"x4" and the basswood sheeting so nothing budges. If you don't have a vice, then you might want to screw the 2"x4" onto a workbench to hold it still. This way you can use both hands to sand the balsa block without it sliding around with each stroke. Also, the 2x4" block holds the balsa up high enough to clear your work table surface when you sand.



You then use 60 to 80 grit sanding blocks to sand the balsa into the 9/16" x 3/32" flap or aileron. (or whatever size you chose) You avoid sanding the masking taped leading edge, or the wire trailing edge until you've removed 95% of the excess balsa. You will find it is easy to sand right down to the masking tape without actually sanding through the tape. By the time you are sanding the leading edge so that the masking tape is starting to sand off, you will have completed the job or are 99.9% done. If you sand through the tape, just add another tape on top and continue sanding very carefully until you're done. Of course, the 3/32" trailing edge (or 1/8" TE if you used Home Depot 1/8" wire) is easier to shape, because the metal wire will not allow you to sand beyond the thickness of it. You will see the wire get shiny and feel it too, and know you are done.



https://cimg5.ibsrv.net/gimg/www.rcu...7414f0e9f6.jpg

Photo above; A view of the underside. One end of the block with screws. Each end gets cut off and discarded later when the job is completed.


https://cimg7.ibsrv.net/gimg/www.rcu...cc3e817390.jpg
Above photo shows the small ledge or overhang of wood that the 3/32" trailing edge wire rests on. Also, the wire is held on each end with a screw.

https://cimg9.ibsrv.net/gimg/www.rcu...548b0dc13d.jpg
Photo above; 9/16" high hardwood leading front edge has a strip of masking tape the full length. The tape prevents the sanding block from going beyond the leading edge hardwood block.
I drew a pencil line to show how the balsa block will be sanded and shaped from the top of the leading edge to the top of the 3/32" trailing edge wire.

https://cimg5.ibsrv.net/gimg/www.rcu...90affdcb8e.jpg

Here I have the 3/4" x 2" block of balsa with basswood screwed to a 2x4",and locked in a vice to hold everything firm. This allows me to use long and controlled strokes with 60-80 grit sanding bar. There's also some scrap veneers or scarap balsa sheets shimmed between the basswood platform and the 2x4" to keep it from budging.
https://cimg6.ibsrv.net/gimg/www.rcu...df1244f756.jpg
Above photo; Everything mounted on a 2x4" and locked in a vice.. Close up of the masking tape covered hardwood leading edge, and the metal 3/32" wire trailing edge.

https://cimg9.ibsrv.net/gimg/www.rcu...c187011da3.jpg
Above photo;Just about done here and ready for 100 - 180 grit finishing strokes. That's the vaneer shims that you see under the basswood sheet. There are 2 screws on the underside of each end of the basswood sheet (which holds it to the balsa wood block) When you screw that whole thing to a 2" x 4" (so you can mount the 2"x4" in a vice), there is going to be a space between the basswood and the 2"x4" where the screw heads stick out . So just use scrap vaneer or balsa sheets stuffed into the gap wherever needed in order to keep things from wobbling around when you sand it. 60-80 grit paper really bites into that balsa wood, so just shim wherever you need to prevent shaking with each sanding stroke.

https://cimg3.ibsrv.net/gimg/www.rcu...fa23fcb574.jpg

Above photo; Here's the newly completed 2"x 24" aileron with one end of it cut off. (we cut off both ends to discard the ends with the screws) It is on the right, and the SR.Telemaster kit's aileron is on the left. Perfect match.

I like to tilt the table on my bandsaw and run the stock through to make mine. I do have to do a little clean up sanding afterwards to remove any saw marks.


carl

I have a large and tall standing cast-iron Delta bandsaw with an adjustable milled steel table. The thing weighs about 200lbs.... just to give you an idea of how serious a tool it is. LOL Still, I have never experienced it to be able to provide the long straight kind of a precision cut that you are describing. Over a long length of 24" balsa, I'm sure my band-saw blade would want to veer off course as it cuts through the wood and produces a very long wavy and uneven cut, basically trashing the balsa. I'm sure you are getting fine results with your saw or you wouldn't do it.. But, with all the years that I've owned mine, I can't imagine using my band-saw to produce a fine wedge shaped piece of wood like an aileron that only needs some "cleaning up" as you put it.

I suppose that I probably could use my band-saw to help remove a lot of the wood that I won't need. It could probably remove at least a 1/3 of the excess wood that I would otherwise have to sand off by sanding. That would save me a lot of time. Thanks for the tip. This thread was like crickets for the longest time, and it's nice to hear sounds of life. LOL

a well set up band saw will cut dead straight,...there are cabinet shops that don't even have a table saw because the have a good size band saw,....it will do just about any ripping and crosscutting a table saw will do with equal precision and less waste. you are either, feeding too fast for the tooth count or your guide blocks/ wheels are not set close enough to the blade, or one side of your blade may have lost some set in places, from the teeth hitting a guide block or wheel. it only takes just a touch of the tip of the teeth to completely wipe out the tracking ability of a blade. you might also try a bit more tension on the blade. depending on the age of the saw, you might also check the top wheel's bearing and tracking plate's pivots. play in either of these will produce a wavy cut, as the blade will try to steer the wheel instead of the wheel steering the blade. you should not be able to rock the blade side to side from front to rear of the saw. as you face the diameter of the upper wheel grab the left and right side and see if you can rock the wheel back and forth. if there is anything more than barely percievable play, that is your wavy cut. that rocking steers the blade left and right as it cuts.

I find what you describe as very enlightening. From your description of how accurate a cut can be with a band saw, and how very adjustable and capable it is, I've concluded that I must know little about it and have never utilized its full potential.
I basically use the band saw with the narrowest blade available to help me scroll through wood and cut out a rough jig-saw profile of the shape I need. If I'm not doing a fine precision cut, this 3/4HP band saw is stronger and faster then trying to use my small 16" scroll saw for that. It's also handy for cutting balsa sticks or sheet balsa into smaller sections real fast. LOL.

I'm sorry that I have never had the opportunity to learn of its full potential as you have. (Not being sarcastic. I really wish I knew how to use it like you do) I envy your knowlege of it. I have never used it for work, or had friends or family own a band saw for me to watch and learn about it's full potential. I'm embarrassed to tell you that I owned that tool for about 15 years before I realized that the miserable POS 5/8" wide blade that came with the saw out of the box was NOT the only size available to me!!! LOL I couldn't scroll any kind of small or fine shape with that thick 5/8" blade, and all it did was make straight cuts in everything. Heck, my table saw did that! LOL. I had wondered why a band saw was such a popular tool, being it was so limited! Only when I went to replace that worn out 5/8" thick blade 15 years later did I see smaller and finer sized 1/4" scroll blades hanging on the rack at Lowe's and finally realize it's potential and appreciate the tool. I put a new 1/4" scrolling sized blade in that band saw and suddenly I opened a whole world of shaping wood pieces that I couldn't do for the first 15 years.

Yes, I am quite aware of all the little knobs and adjustments for the blade..... but obviously I still don't use them to the band saw's full potential, and how to use it properly to the extent that you do. Wish I could witness you using that tool in the precision manner you describe. I'd love to see how you shape an aileron as you describe it. Thanks for the input.

I use steel at the leading and trailing edges. Usually rod of some sort for the trailing edge and what ever I have on hand for the leading edge. Place the stock down and tack glue the steel guides so the stock slips between them. This way I can use it as many times as needed. Use an exacto balsa plane to get it close then sand to finish.

That is similar to the method I'm describing. Except I'm using screws on each end to hold my 3/32" rod at the trailing edge, while you are using glue to tack it on. Your method of using metal at the front leading edge is preferred just like you are doing it. But the problem is that me and other guys don't have a source for obtaining long lengths of straight metal edges in the exact thickness needed. The aileron in the photo is 9/16" thick. Most of us have trouble finding metal strips in 9/16" , 5/8", or etc. So it is much easier for me to cut a length of wood in the exact leading edge thickness I need (or use a precut piece you might have on hand), and put a protective layer of masking tape over it and just use that.

Easy way to do the taller leading edge is to cut or form a lip at the front edge for what ever size wire you have on hand and glue in place. Make sure the wire and spacer block equal the height you need for the leading edge. Have shaped 4 and 5 inch ailerons this way.

Dennis

look for a book about band saw set up and use by a fellow named, Mark Duginski...... it is essentially the accepted Bible on band saw use amongst woodworkers. he actually lives about 15 or 20 miles from me, here in central Wisconsin. you can find his posts on a few of the more popular woodworking forums. one in mind is "SawmillCreek.com".

personally, as easily made as solid trailing edges/flaps and ailerons are, I prefer to build them up from sheet stock as top and bottom skins with the wing rib between or a small wedge in between for flaps and ailerons. I've seen a few times where the thin tapered edge of a solid aileron or flap warps and I don't like the glued butt joint between rib and trailing edge when using a solid edge. it's just a weak spot waiting to fail. if you're going to cover that butt joint with partial sheeting, why not just eliminate it by running the rib down between the top and bottom partial sheeting.......so much stronger and lighter aft of the C/G.

to add,....you can get blades even smaller than 1/4 inch wide as well. there are 1/8 in wide blades available from places like Rockler, Smc and other online suppliers that sell bandsaw blades. ( I have yet to see an 1/8 inch blade at a big box store, but I would suppose they could order one for a guy) I have a couple of them and they turn my 14 in bandsaw into a half way decent scroll saw. I use them when cutting gears for the wooden clock movements I occasionally make.

Sanding away half your material sounds wasteful and expensive to me. Not to mention needing a mask to guard against the dust and the clean up. If I can't purchase a shaped TE to do the job, then I frame up all my ailerons and flaps. It's not hard to do. And the weight you save!

i'm also not so sure it's all that important for the ailerons to be tapered,....shaped as part of the airfoil. I've seen and used 1/8 inch stock for ailerons all the time and never had any indicators that would point towards a problem because of their un-tapered shape . the key and more important aspect,..... is to get them tight at the joint between wing and aileron to minimize the turbulence from a gap..

I have solid 3 inch by 6 inch light balsa stock 48 inches long and mostly use my table saw set at a calculated angle and rip the ailerons. Depending on use I also use built up ailerons.

Dennis

Thanks for the post.

Just one (very small) point. It's difficult to see from the photo's and there may have been other reasons I can't see, however IF the grain (green lines) is/was what it looks like, I would have been really tempted to carve it to the red outline. While it's nearly impossible to buy thick C-grain wood to carve into a control surface, sometimes you can get closer to C-grain by choosing which side of the stock to carve. If I get a nice piece of C-grain I try to carve both sides.https://cimg2.ibsrv.net/gimg/www.rcu...6fc1b8209f.jpg

Yes, it's built up for most of what I build too.

I never really worried about grain (and density) until I built a Bubble Dancer RES glider and realised how much difference selecting the right piece of wood for the job makes if you're not overbuilding. If you are overbuilding you can can get away with anything as long as it's the right shape. Sometimes the piece of wood you need is buried deep in the sheet in your hand and is not necessarily aligned with the edges.

if you're building up ailerons, the best grain orientation would be from sheets that are as close to plain sawn as possible. the strength of this type of aileron comes from the type of construction, so the grain orientation of the component skin should be such that growth rings travel through as much chord of the aileron skin as can be had..