Two questions about chambering: 1. As a generalization, what is the usual thickness between the top of a chamber and the deck of a balsa board - say at the thickest point of a 3" thick board? 2. A site about balsa boards states that all chambered balsa boards should be fitted with vents. Since this was not done to the chambered balsas I have seen, at what point in the chambering process would this become a consideration? I realize that these questions are to some extent subjective, however I would greatly appreciate your opinions. Thanks. Patrick
Two questions about chambering: 1. As a generalization, what is the usual thickness between the top of a chamber and the deck of a balsa board - say at the thickest point of a 3" thick board? …I’m not chambering as I suspect you will be, but I’m thinking that 1/4" thick balsa with a good glass job (EPOXY) would be about as thin as I’d go…My hollows are 1/8" thick, but there is an underlying layer of Carbon fiber cloth…There is very little deflection, even with that thinness…With a chambered balsa, you’d better be pretty close with the rough shape before you split and chamber…You don’t want to be touching it a lot with tools after you’ve re-assembled it…There are few things as discouraging as shaping into air on a chambered board, trust me on this… 2. A site about balsa boards states that all chambered balsa boards should be fitted with vents. Since this was not done to the chambered balsas I have seen, at what point in the chambering process would this become a consideration? …On the chambered balsa I had it was unvented without any consequences…My hollows are another story… Hope this helps… Paul http://www.hollowsurfboards.com
Thank you, Paul. I needed to hear someone elses opinion about those questions. Sometimes when I am making something the internal dialogue starts to slow the whole process down. Looking forward to viewing your next board. Patrick
Patrick, You can reinforce key areas of the chambering, with minimal extra weight, with tight-fitting EPS stanchions. This also serves to displace a good portion of the trapped air. For some real fun, build a shaped and glassed (actual size, but short… like 2-3 feet long) section and then test to failure for applied weight, point-loading and impact. IMHO, my very limited experience with similar projects was usually closer to 1/2" top and bottom surfaces (at the thinnest), with the span of the chambers being about 12", the divisions between chambers about 1 1/2". The problem is that balsas density can vary radically depending on the wood you end up with... if at all possible, Id personally pick through the available lumber. Dale
Thanks Dale. I think your experiment is one I will definitely try. Another question just occured to me re mats and hollow boards: What would happen if a mat or hollow board surfer ended up in the wrong place and was buried under several feet of water? I assume the air in the hollow would compress much as ones lungs do while freediving, but I’m not sure. In any case, the mat being flexible like the lungs would probably have a greater chance of avoiding damage. Thanks again. I copied and pasted both yours and Pauls ideas. Patrick
I got some excellent surf Feb.‘03 …The swell was a clean 7’ @ 11sec…Winds were SCA from the east…4 guys total in the water… Clean peaks everywhere…5-6’ backs with the offshore fan pushing 30 - 40’ seaward… I rode my 10’2" hollow…A lot of board, considering the conditions, but it was a blast… I surfed it for about 4 .5 hours…Upon exiting the water, I thought the board felt heavy…REALLY HEAVY…You know where I’m going with this… Yeah, it leaked…It leaked where I lapped the rails and did a zip cut… I probably cut into the underlying layer of glass a bit, enough to weaken it and it to split right along the cut line…I’m thinking the compression of air while duck diving/ punching through forced the weakness to separate…Oh well… I realized the vent hole would never allow it to dry out …My remedy was to cut the rails off ( It took about 5 minutes with a utility knife)…That is the only way to be sure that the interior will fully dry out…and it dried fine overnight…I re-shaped the tail to be a round pin while I had the chance… I built out the rails with, 1/8" bending ply / cork like the 7’er, then 3 layers of glass overlapped onto the deck and bottom, and made pretty again… I will never do a cut lap on a rail again…lesson learned… …BTW, It surfs better with the round pin… Paul http://www.hollowsurfboards.com 
Patrick, FYI - saw a beautiful Billy Hamilton shaped chambered balsa without vents that was shipped (via air) to a local shop and was totally ruined due to implosions in many of the chambers probably caused by fluctuations in air pressure in transit. Just a thought if you plan to travel with your board. Pete
I’d leave 1/2" of material top & bottom if I were doing it.
Pete, I had Mike Brewer bring me Gary Mountfords board (VP FCS), it had done something in the cargo hold while on the way from Hawaii. At first look I thought that it had been creased by another piece of cargo, but upon closer inspection, it was delaminated. The solution was to sand the bottom really thin, then route out the culprit planks where the delam seemed to be. Once the bottom was open, I could see what had happened, the board was chambered to the point where the skin was only about an 1/8"thin and the chamber walls were only about a half inch. The culprit seemed to be where the balsa planks were glued together to get the thickness to do a functional gun rocker, the glue seams failed and the ribs popped near the skin. I liberally re-glued the broken struts and added vertical grain reinforcements to them, then I hand fitted new skins to the missing bottom planks, but made sure to make the route a half inch deep for them to sit in. This way the route intersection was near the center of the rail at nose and tail and didn’t have an unapealing look when reglassed. The topper to this story is, before Mike could come for the finshed board, it ws stolen from outside my shaping room. My wife and I had just had our youngest child and we were dead broke (you know how rich we shapers are), I felt like I was creating a story for Mike about where the board was, after all this Brewer gun was worth about 6 grand at the time. A year later Tom Eberly (shaper for Lopez and the famed Pipeline crew) was checking in on a friend who was strung out on the poop and noticed this really nice Brewer gun up on his wall. He gave me the heads up on this board (a police report had been filed on its dissapearance) and it was the same board. This fellow NOT wanting anything to do with the law, confessed he had gotten it from the Channin factory electrician for 600$ of blow, he felt he was owed more money for wiring the machine room and thought it was Channin’s board, not mine. Mike Brewer got the board back, I was vindicated, although no one ever said a word I had anything to do with it, but I had that fear over my head all along.
Once again, thank you very much. Since the one I am working on is a 6’2" classic fish I was thinking I might fly with it. Accordingly, the comments above have convinced me not to go any deeper/thinner with the chambers. While this is only my second balsa, the amount of work that goes into one, especially a repaired one, means the person who removed the board from the shop must have been very callus. Thanks Patrick