Journey of two balsa compsands

I’m a backyard builder and a long time swaylock’s lurker, but don’t post here often… so many smart guys and craftmens around here that I feel intimidated!!

By the way I’d like to thank the sway’s crew for their stoke and willingness to share, and the compsand’s guys (especially Bert, and also of course danb, Benny1, Sabs, Silly, jjp, marjyv and the others…) for their creative and very inspirative posts.

Those are my first balsa compsands, but I’ve already played quite a bit with vacuum building (windsurf, kitesurf and surf boards with EPS, epoxy and PVC).

First board is a 5’816,521 1/8*16.5 big swallow tail, multi plugged (Chip’s inspired!!) twinzer/quad/twin convertible, flat continuous rocker (1.35"T, 3"N).

Second board is a 6’0*15.5(T)20.514.7(N) quad, double wingers, 80’s rocker (1.75"T, 4"N).

Both boards are very thin: 2"max, with concave decks so less than 1 7/8 in the middle.

A summer quiver… I’m a bit fed up with flat wide boards and swallows, so my next one will be a 6.6 round pin tail “barrels hunting machine”, 2.5" tail rocker :), balsa compsand of course…

Photos of the construction process in the following posts…

Core is 10kg/m3 EPS (0.65).

Outline and foil were cut with a hotwire.

Deck and bottom skins are 2mm balsa, density around 180kg/m3 (quite heavy for balsa), planks were carefully selected according to their flex and density, rails are 3*4mm balsa.

Fins reinforcements are blocks of 6mm balsa, balsa grain oriented perpendiculary to the board’s axis for maximum longitudinal flex and maximum lateral resistance. They are inserted and glued in the core with PU.

I used the offcuts of the outline to press the rails against the core.

I’ve used two slightly different methods: first rails then bottom skin for the twinzer, first bottom skin then rails for the quad. I prefer the second method (less possibilities of mistakes and a more beautiful result I think…).

I taped the balsa planks on the outside face for deck and bottom skins, and had no problem to remove the tape once the resine cured (cheap yellow tape for paint protection).

Tail and nose blocks are made with several layers of 2mm balsa, glued in a mould (lamellé-collé in french, don’t know the english term???).

My vacuum pump is the simplest you can build: a fridge pump, a tap, a fan. I inject oil before each use. No vacuum gauge, I prefer controlling everything by hand/eye… but beware, it’s very easy to crush 10kg EPS …

On both boards I glued the bottom skins before shaping.

I like to use a wet out table for vacuum building, but balsa doesn’t suck much resin so a wet out table isn’t necessary to achieve a good resin/fiber ratio (less than 0.5). I wet the fiber directly on the balsa planks. I heated the epoxy to allow a better fluidity and a maximum resin penetration in the wood.

Shape of the boards: after glueing rails and bottom skins it’s time to taper the rails. I like to draw the rails I want to shape on a paper sheet, take some marks and draw the bevel lines on the plank so that I can’t screw up the shape :). Rails are thin, very hard 0-16" from the tail, then down with a little tuck under up to the nose.

Rails were not finished, I let them squared (didn’t shape the lower/bottom part of the rails) to allow an easier balsa deck glueing.

Both boards have concave deck from the tail to 16" of the nose, max depth 6mm (1/4")

Then it’s time to glue the skin deck…

I bagged the outer layers. I tried without peel ly, only with release film and a drain and it worked pretty good.

The quad is 3ozbottom/2mm balsa/3oz/10kgEPS/3oz/2mm balsa/6oz deck

The twinzer is 4/2/4/10kg EPS/4/2/6oz deck

Weight so far: 1750g for the quad, 1950g for the twinzer.

A few logos…

“Caminante, no hay camino, sino estelas en la mar” = “Wanderer, there is no road, only the wakes on the sea”

From a poem by the spanish author Antonio Machado

" Wanderer, it is your tracks

which are the road, and nothing else. 

Wanderer, there is no road, 

walking makes the road. 

By walking, the road is made, 

and when glancing back 

you contemplate the trail 

which you will trample no more. 

Wanderer, there is no road, 

only the wakes on the sea." (Campos de Castilla, 1917)

And my tribute to Bert (for all his design and construction threads), Chipfish (for the multi-plugged board idea and his stoke), and all the swaylock’s members…

I have still some work to do:

…a bit of sanding


…set fcs plugs+vents

…build a bunch of plywood fins to juggle with fins configurations

I’ll post the final results and the test reports :slight_smile:

To be continued…

…and you think you got us impressed, Loïc?

Well, actually, yes, pretty much. Even if I had already seen them… Incredible…

That ‘other experience’ with vac building must have been quite extensive…either that, or you’ve got the magic touch. Maybe a little of both :slight_smile: Beautiful work. My first boards weighed what both of yours put together would weigh. Good thinking on the finbox inserts. Can’t wait to hear how they surf. Thanks for showing…

Beautiful boards, and some quality work indeed.

Each compsand thread I see, I pick up some new trick or technique for when I finally get around to building my own. Thanks for sharing.

Great boards. Great thread. Thanks.

I’m going to attempt my first vac bag project this summer. I’m presently looking for a pump set up. Just a few questions-

What is the fan for? Just to keep the pump from overheating? And you say you use a tap- do you mean a pressure release valve? What did you use to seal the hoses and bag?

I’m looking forward to seeing your next one. I’m a fan of narrower boards. Ilke being able to put them over on the rail when turning- hjarder to do on flat, wide boards.

Thanks again for the informative thread.

Thanks for your compliments, but 90% of the merit is for the swaylock’s community. With the amount of informations posted here, I was condemned to succeed :).


What is the fan for? Just to keep the pump from overheating? And you say you use a tap- do you mean a pressure release valve? What did you use to seal the hoses and bag?

Yep, the fan is to keep the pump from overheating. Fridge pumps don’t like to work non-stop. With a fan and some oil before use, it can last a few boards. I’ve built many kitesurf boards with similar pumps and never had any problem. The tap is a water tap/faucet, used as a pressure release valve. It is not perfect (too much sensitive), but it works. The hose is 8mm garden hose. I put the hose in the bag, and seal the bag with brown packing tape. I insert the end of the hose in a EPS block, so that the pressure is better diffused and the hose can’t get blocked.


great work

welcome to the club

Very nice work! I’m looking forward to doing a bit of vacuum bagging in the future.


I’m a bit embarassed , actually , to have my name associated with such fine craftsmanship, and next to bert burger’s name , and swaylocks …

… now , if it was a polyurethane blank , full of assymetrical rails , twisted bottom contours , unequal planshape , with an awful glass job …THEN , my name would ‘belong’ there , maybe !

Loic, thanks a lot for posting those photos , mate . Well, Balsa … I , for one , am very impressed !

Really nice looking boards …you are definately in the sabs and danB echelon , by the look of those photos , at least !

I’d like to see the fins , please ? … and , of course , to hear how they ride

cheers / salut !

ben “chipfish61”

Ben don’t feel embarassed, I’ve made a bunch of ugly boards myself and sometimes the ugliest boards work the best. “L’habit ne fait pas le moine” as we say in french :). Those balsa boards turned out pretty good, at least if they don’t work I could recycle them into lounge tables!! (but I’m pretty sure they will work OK…)

For the fins:

Still a bit of sanding to do, maybe a few more fins, and laminating. They are made with 10mm ply, 2 or 3 layers of 4oz each side, and tabs reinforcements (all fcs tabs, 3 tabs for the keels). I will have some hard work to try all the fins configurations!!


Those boards are beautiful! The fins are incredible,too. Let us know how they ride. Especially the two on the far right that look like they may be for a twinnie.Mike

mate , those fins look great !!

like rooster , I too would like to hear how the big twinnies go !!

" my next one will be a 6.6 round pin tail “barrels hunting machine”, 2.5" tail rocker :), balsa compsand of course…"

I hope it is a single fin with side fin options …bonzer runners , 2+1, thruster , big single fin / widowmaker side fins . [back fin box , PLEASE !]

then , we can compare notes … mine , of course , will be polyurethane foam , but hopefully glassed using epoxy resin …

cheers / salut !


p.s. - to keep you happy , I posted my 5’8 “multi plug option” fish at , a few of the fin options I have tried so far …to be continued , as I ride my way through a “few” fins [haha haha ]