I’ve been doing some drawings for my balsa/EPS 7’6 egg project and I’m getting confused with max beam and max thickness. On the outline, max beam is a bit ahead of center while on the rocker line max thickness gets behind mid length (more nose rocker than tail rocker). Is that normal ? Should these points be aligned ?
I’ve been doing some drawings for my balsa/EPS 7’6 egg project and I’m > getting confused with max beam and max thickness. On the outline, max beam > is a bit ahead of center while on the rocker line max thickness gets > behind mid length (more nose rocker than tail rocker). Is that normal ? > Should these points be aligned ? Hi Pierre, My rocker program allows me to tilt, flatten and extend the deck outline to fit the rocker in lots of ways. I programmed it for designing hotwire rocker templates. For your deck, I centered the fat part of the board by contorting the deck. The nose deck should angle away from the nose bottom at about the same angle which the tail deck angles away from the tail bottom. I put decks on most rocker templates which will allow the shaper a range of foil shapes. So it’s up to your artistic skill and preference to shape the foil you like from the resulting foam block. Like you, I believe that board foil should be loosely tied to width. First you will cut your outline and smooth out the bottom. Then you will mark the rail line, and shape the lower rail. After you cut your outline you will start shaping the midboard deck to your desired deck/rail form. From there you will use your eyes and tools to foil the deck into the upper nose and tail rails as you prefer them. This process will lead you in the general direction of a foil which thickens and thins with the width of the board. A whole lot foil design comes from rocker contour and rail design. For example, a board with lots of rocker and a flat rear deck will require you to make the midboard foam thick. If you wanted the same board to be thinner, you would have to curve the tail’s deck upward. I like thin nose boards because thick noses are heavy, and hard to throw around. I also like lots of lower rail curve in the nose. That means my nose deck/nose rails are pretty sharp. I prefer tails which are a little thicker than normal because I believe you don’t pay as much in performance to put some extra paddling floatation in the tail. However, you shouldn’t thicken a rounded pintail very much. As you said, foil should rely somewhat on width, and a rounded pintail gets pretty narrow. If you are installing a center fin box, make sure to leave enough tail thickness to accomodate the box and leave some foam and stringer material above it. Foil incorporates lots of design preferences. The preferences revolve around the surfing and paddling characteristics you are going for. I think it was Halcyon who said “think like water” below. I wish I knew more about designing foil for more types of boards. Maybe a pro can help us here.
Some boards have a wide point forward, thick point back. It’s hard to even tell usually without calipers. Also, lots of tails thicker than noses. Measure some boards and see. A thicker tail/dome deck kind of thing can work great. I’ve been seeing some pretty radical pinched forward rail/boxy tail rail set ups too which fly in the face of my old school “foiled rail” theories. I’ve seen guys ripping on em. My point is don’t get hung up on details. Glass it, ride it and figure out where the buttons are. With a couple pounds of torque applied to your back foot, it’s amazing what design “flaws” you can overcome.
My point is don’t get > hung up on details. Glass it, ride it and figure out where the buttons > are. With a couple pounds of torque applied to your back foot, it’s > amazing what design “flaws” you can overcome. I get your point John and it since I still have to try out the board I finished in december, what you said reassures me. Nevertheless I 've just started building boards because I’m eager to understand how it works and experiment. Also, the building technique I intend on using requires me to decide on each parameter (outline, rocker, rails, bottom and deck shape) right from the drawing board. With this technique I can pick the rocker I want but I can’t just shape it using my eyes and tools the way Noodle just said. Here’s the building process I used : 1. First I shaped a styrofoam core (recycled from an old epoxy/styrofoam sailboard) using a hand saw & surfoam : cut the outline and squared the rails. 2. I then glue on each rail a balsa plank (1 cm thick) that has been cut according to rocker line. I use a polyurethane yellow glue that dries using moisture within supports : it glues strongly and remains easily sandable. 3. Next I hotwire the deck and bottom rocker using the glued balsa as a guide. 4. With the two balsa “side stringers” the blank is now rigid enough to glue the top and bottom balsa planks (2 cm on top, 1 cm on bottom). 5. 3 cm more balsa is added on each rail as well as large tail and nose blocks 6. lots of sanding 7. Rails are then shaped using hand plane and sandpaper 8. Final sanding 9. Applied a water based sealant 10. Brought it to the glass shop (6+4 on top ; 6 on bottom - polyester) I’ve shaped my first (and only) board last december using this balsa/styrofoam sandwich technic. It took me nearly 50 hours … but I’m quite happy with the result : the balsa board looks great, it seems more dent proof and cost me less than if I had bought a foam blank !
Keep throwing shapes together and riding them. If you have preset design criteria, there’s a limited number of other changes you can make and still have a good performer. Trial and error are painful, but good teachers. I keep making stupid mistakes. Why should you be different? Because you’re French? Credit where credit is due… John Mellor wrote “think like water”. Thanks John.
Pierre - Wow! Sounds like quite an ambitious project! I flashed on Bob Simmons making one his plywood/foam composite boards as I read of your technique. Noodle - Thanks for the credit but I’m not sure I deserve it. I honestly don’t remember saying it.
Pierre - Wow! Sounds like quite an ambitious project! I flashed on Bob > Simmons making one his plywood/foam composite boards as I read of your > technique. Noodle - Thanks for the credit but I’m not sure I deserve it. I > honestly don’t remember saying it. I had heard of Simmon’s technic before but I didn’t really pay attention at that time. I got the idea when I saw Riley’s web site (www.riley.com.au). My son’s learning how to surf and wanted a board for Christmas. I couldn’t aford buying one off the rack and the idea of getting our garage/cellar with foam then resin all over didn’t attract me that much. But then with balsa it’s all different : I love working with wood, and since it’s biodegradable I could do all the planning and sanding outside in my back yard (not a bad idea, I found out that balsa dust is really a pain !) I found the technique quite easy once I had it figured out : - The fact that outline and rocker curves are made through bent planks mean that, as a begginer, I could be sure I would have smooth curves (templates had been drawn also using these planks to make sure the wood will bend all the way). - Balsa is harder than foam and I only used hand tools : it went real slow but I think I would have made more mistakes with soft foam and a power planner. - The rails are made of 4 planks (4 x 1 cm) and that gave me 4 permanent parrallel lines to guide me a little more while shaping rails. With respect to cost, it’s not more expensive than foam because I use way less balsa than building a regular balsa board. Using a traditionnal balsa technique mean using a large amount of wood, then take a lot of it out to cut the rocker and outline and finally take even some more out hollowing it inside. What’s left is then sort of a hollow “box” made out of larger plain “cube”. With the sandwich technic you just buy the planks needed to build the box : fewer wood (for the same result) and less than 5 % of waiste (the few bits left are used to make the tail and nose blocks). It is important to see that we’re not talking about a balsa veneer technic. The rails, nose and tail are shaped solid balsa and play an important role in the board’s strength and properties (the solid rails replace stringers for instance). Rather than wood veneer, I’d say it’s somewhere between chambered balsa (but even lighter and without need for pressure valves) and Blake’s plank on frame wooden board (where the frame is replaced by a styrofoam core). I can see 3 drawbacks to this method : 1. It takes longer to build : but I’m neither in a hurry nor doing it to make money. I don’t care if it takes longer, I’m having lot of fun doing this. 2. You can’t really get a domed deck or deep channels 3. You can’t shape the thing just with art, talent and instinct, you have to think it over right from sart. That didn’t bother me since anyway I had no shaping experience, talent or even good templates … I’ll also try to take some pictures from that first board I built and post them in the boards archive. I know it’s a long post and I hope I didn’t get anyone bored. I’ve learnt so much from this discussion board, I really appreciate all of you taking time to answer questions from begginers like me, therefore I felt that even though I still don’t know much about board design and building I had to share my little balsa experience. Pierre