Chambered 5'8 fish

I have shaped a 5’ 8 fish out of Eastern white, and western red cedar. This is the first wood board Ive ever made, so it is experimental. I then ripped it into quarters so I could use a router from either side to hollow the center pieces all the way through. My dilemma lies in the size and frequency of the chambers. I want to make the board as light as possible however I want the thing to take a lickin and keep on tickin. How thin can I make the top and bottom of the board? I was thinking a cm thick on the top would be strong enough, but I have no idea. How many ribs (not chambered area) do I need in order for it to hold up? I have two 8th inch red wood “stringers” milled up to lam in between the outer pieces and I have one 1/4 inch stringer for the center. Any advise is good advise. Thank you

That’s going to look so gorgeous. Sorry I can’t advise you any, but no doubt someone will be around soon enough with some pearls.

I’m no expert either, but I have chambered 5 balsa boards. The thickness of the deck and bottom depends on if you will glass the board or just varnish it. I can’t give you an exact thickness, or frequency of “ribs,” but here are some pictures of balsa boards glassed with 2x4oz on the deck and 1x4oz on the bottom. I would recommend doing a test piece, then jump on it. Cedar is quite strong, so I imagine you can get away with less than a cm thickness for the deck, especially if you plan to glass it. Try to stagger your chambers, even on the same pieces so they don’t all line up and cause a weak spot. You can save even more weight by chambering the stringers too.

As for chambering technique, I really like using a drill press with a good set of forstner bits. I used a marking gauge to mark a constant thickness on the deck and bottom, then used different sized forstner bits that matched the thickness of the board (2 inch diameter near the center, then gradually stepping down to 3/4 or 1/2 inch near the nose and tail). A drill press gives tons of control and will make a clean chamber if you make your plunges close together. Good luck and post pictures.


p.s. Here’s my 5’6-ish chambered fish:

It seems like that worked pretty well for you, those look great. I think I will try that technique and see how it works for me. I glued in the two 8th inch stringers today and faired them in. So I guess my next step is to plot out the chambers and get drilling. I will definitely be staggering them and hollowing the stringers. I am planning to laminate the board with a single layer of 4oz all around. Is it necessary to connect all the chambers and add a vent?

"Is it necessary to connect all the chambers and add a vent?

Deffinately, do both. You want one continuous air flow around the board, otherwise you’d get pockets where pressure could build up. I think this is the point of staggering the chambers, as wel as avoiding weak points. Never done one of these but been planning something similar for ages, hopefully start soon.

Post loads of pics as you go if you can.

I will be making the chambers continuous. I think that hollowing out the center pieces will be much easier than the rails. The only way I can think of chambering the rails is by taking a whole lot of measurements and using inside calipers. I’ll take as much out as I can with the drill press and from there maybe a chisel? I’m not exactly sure how its all going to work out. If anyone has any advise on how to do this I would appreciate it because the current method will take a long time and a lot of careful work. Pictures will come when I begin chambering