http://www.balsabill.com/ChamberingaBalsaBlank.htm
After spot glueing the rockered pieces together and rough shaping the blank I take some scrap balsa and a rubber mallet and start banging away.
Some of the pieces come apart pretty easily…and some are a little more difficult…
Unlike the last one I did, all the pieces came apart and now I’m ready to chamber.
I’m expecting a really light board. The roughed unchambered blank weighed about 20 lbs. This is what I call “fingernail quality” balsa.
fingernail?
Thanks for putting this up, Bill. How much glue? What kind? I thought you were going to use brown paper between the slices?
Can’t wait to see the rest of the story.
Lookin good bill.
Fingernail. I don’t weigh balsa sticks anymore. I stick my fingernail in the wood and I can tell the density hence the weight.
I emailed Jim the Genius while I was glueing this up concerning the paper. He advised against it. Unfortunately I had put some paper in the first couple of sticks and I won’t do it agian. Didn’t help with coming apart and I had to scrape it off the wood in a couple of places.
This wood was pretty straight so three spots worked for most of the sticks. I think five or six was the most I did on the most bowed pieces.
Elmer’s white glue.
I only had a couple of spots that were a little tough to get apart. One I had to beat pretty hard (see pic) and one it all came apart except one spot and I just pried it apart. Could be dangerous because the wood could split but it didn’t.
Get yer drill press ready. What's your choice of chamber shape/pattern?
Jim's the man for reference on all things chambered, nobody knows more about this process.
Don’t have a drill press. I use a drill for the pilot holes and a jigsaw with a stiff blade to connect for the chambers.
Chambers about 10-12" long with rounded ends. They should be a little stronger than straight up and down.
I’m adding three stringers made from some crate wood that my last shippment of balsa blanks came in. These make nice stringers. I needed a little bit of width because my outside pieces were just a little short. The width I get from adding the stringers will make it so my final template lays in just right. Here’s the centerpieces glued up with the stringers. The outside pieces are the pieces I use for clamping.
Very nice Bill. Thanks for posting. How thick above and below the chambers? How much do you stagger the chambers from piece to piece?
Working those stringers in there is key, I must admit I was shocked when I saw the first pic of the size of those chambers and thought of the structural implications. Do you remember you gave me a couple of pieces of that packing crate balsa a few years ago? It was supposed to be for a customer, but (long story left out) I ended up using it in a board for myself. It came out really nice as the center of a little T-band.
I'm sure you planned ahead in your rough-out for the thickness moving out to the rail when you add the stringers after chambering, but readers who might want to try something like this should take note.
This means I gotta stop by your place and check out another one of your projects, when I'm supposed to be in my shaping room trying to clear our backlog :)
This one should come out really light, keep the data (and photos) coming....
The only difference bewteen Bill’s approach and mine is, I do all my planer work first, true, rocker, turn rails, this way there are no suprises when I glue it back together. All that remains then is, clean up glue squeeze out and get down to the elbow grease of block sanding 'er out.
…hello Balsa Bill,
how much of Balsa did you let (left) to the deck and to the bottom?
thanks
Hey Jim! It looks like Bill took his rough-out nearly as far as I remember you doing it. Since he's adding those stringers, he couldn't really turn rail bands. Don't you usually leave just a little more square (for good clamping on the re-glue) in the rail, and then cut those last couple of bands after?
Or maybe you've advanced your ridiculous skills even further since the last time I saw you do one of these...
This is only the second one I’ve done like this. The first was the Waikiki Pintail which I documented last year. It’s in Hawaii now.
http://www.balsabill.com/GlueingupSomeBalsa.htm
On this one I spot glued the rockered pieces together, trued it up. cut a rough outline, foiled it to thickness from nose to tail measuring every foot, and put all the dome in the deck. I left the rails pretty square (1 3/4"). I’ve also put a slight roll in the bottom.When it’s glued back together I have to put on the final rail bands and then finish it off.
It’s amazing to me how Jim can take it as far as he does before he breaks it apart to chamber it.
I’m glueing it back together now and chambering as I go. The entire center section is glued including the stringers. One center and two offsets two sticks (5") off center.
I’ll chamber the last two pieces later today and then glue those on. I don’t think I’ll chamber the two rail pieces. They are pretty narrow and this thing is going to be pretty light. The wood is so light I could have left it solid and had a board as light as many chambered boards.
One thing I’ve learned pretty much by trial and error: When building a balsa board whether glueing up your own sticks or working with one of the commercially available balsa blanks, first, you have to make the wood look like a Clark or Walker or whatever blank. Cut a rough oversized outline, dome the deck and and foil it out to the same dims as a commercial foam blank. The balsa blanks you get from Shark Bay for example are true, have the rocker in and the thickness foil is pretty good. But you need to do a rough outlne and dome the deck before you actually start shaping. In other words: First shape yourself a blank and then shape a board.
Also, I build the blank with ALL the stringers in place, I just glue one side of them, then later keep assembling the blank with the spot glues.
I am never amazed on how much the wood will deflect from what is drawn as rockers and where it will be after cutting away the waste, but assembling it in pairs allows for the time of glue set and the struggle to keep the pairs even with each other.
I watched Curren and Velzy muscle a jazillion pieces of wood at once, a battle at the best, with many stciks out of alignement with the rest, slow and steady, I don’t want to go back and do it over
Balsa Bill, good post. Also I dig the trunks you make. Have you tried double stick tape in the lay-up? It only takes a small square for adhesion. I have always thought the “bridge truss” system would be better for chambers. It is a tried and true design in building where the chambers are spaced with 45 degree diagonal struts opposing in direction that separate one chamber to the next. (If I knew how to draw on this thing I would) So in essence you have a chamber and then two opposing “V’s” between the next chamber. This yields extraordinary strength. Also if in the lay-up, the chambers are staggered so they don’t line up perpendicular to the stringer. This distributes the load over the whole system and allows for maybe more chambering to lose the weight. This may sound waaayy too complicated, but it’s not. I make a template out of hardboard and use a pilot bearinged pattern bit or a spiral fluted bit with a collar on the router base. Once the template is made, It’s happy routing! I leave about 3/8 to 1/2 inch of material on the deck and bottom, but the struts can be whittled down to 1/4 inch allowing more removal of weight. Also the “V’s” can be inverted from piece to piece for even better distribution of load. (One piece “V’s”… the next piece would resemble having “A’s”). Does any of this make sense??? Or have I been in the shop too long?
How do you keep from damaging the rails during final glue up and still be able to draw the pieces together? Do you cut custom blocks that are the negative to the rails and then clamp?
Thanks Jim. That was good advice when you told me a long time ago. Never more that two pieces at a time. Once they are chambered it’s easier to force the rockers in too.
I know when you give advice you know from whence you speak.
I didn’t plan on stringers on this one until I got to the last rail pieces and realized they were about a half inch too short to get the width in the tail (or nose) that I wanted. So, rather than get more wood, shorten the board or raid the stash from the next project I decided to use these stringers that I’d had laying around for awhile. They gave me just the width I’ll need (7/8") to do the dims I want.
The next project, the one I emailed you about a while back, I’ll be adding the stringers in from the beginning.
tblank: Glad you like the trunks and thanks for the advice on the double stick tape.
On the chamber thing. Sounds great but, if I can’t do it with a cheap black and decker drill, jigsaw and a pocket knife it ain’t gonna happen.
On clamping up without denting the rail. Yeah. I’ve dented a few, On this one 
I cut the board down the center, added the foam stringer, then re outlined and re shaped since I’d lost too much width with the dent.
As to how I’ll do this one, I’ll post photos. One method is to use rubber bands (from inner tubes) but I’m not real good at that. Remember by using Jim’s two pieces at a time method there’s not too much left to glue when you get to the rail pieces. Yes sometimes I use the “bones” from where I cut the outline too.
I avoid the dents by, gluing the pieces with straight edge strong backs cut to the rocker and jointed flat on the inside edge, once I get the the outside rails sections, it is the old tried and true, bicycle inner tube strips, nothing fits snugger and doesn’t sink into the rail, unless you go hulk on it, but the clamping pressure is so much better than trying to use a dozen bar clamps, all digging into the rail
I just use a couple of pieces of 1x6 pine with rocker cut in for strong backs. Another tip I got from Jim’s DVD. If you don’t have one. Get one. Invaluable information. I know Jim uses hardwood but for the limited amount of work I do the pine works just fine.
I like the strap clamps but you have to be careful because they create a lot of pressure and one click too far can cause some damage.
JKP, do you use windlasses to tighten the inner tubes?
Next project: Balsa board with red foam and cedar t-bands.
