Looking to document my build from the get go and to say thanks for all the help on this site.
This is my second board, first epoxy board.
First was a wooden Simmons diamond tail. Soaked up a heap of water when our garage flooded so was only finished 75%.
I guess you could could say this isn’t even my second board then.
Anyway, here’s my tweaked drawings. Original outline, rocker and fin from blending curves.
I’ve added a grid over the file and some handy dimensions plus rail bands. Hoping this will help keep things consistent for my first build.
Dims: 6’6" x 21.5 x 3 - 7.5" greenough 4a fin - pretty flat rocker - rail bands are at 2" and 4" in at centre of the board.
Any advice is obviously more than welcome.
Thanks again.
I made several boards like this when I first started building boards back in 2001, some for myself and some for others. I surfed them regularly for years. I think my brother in law still has the one i made for him. Based on our experience with them:
6-6 is a little short for a single fin, one with that much curve in the template. Surfing a singlefin is all about the bottom turn and engaging the rail, so if you’re going to keep the rounded pintail (which is what I always used) you might consider adding a few inches to the length to moderate the curve a little more. I found 6-10 to be abut the lower limit in length in that design. Going shorter than that tends to slow them down too much because you’re not engaging as much rail on your bottom turns. If you are going to retain the shorter length then you might consider adding sidebites to compensate for the shorter rail line.
flat rockers will work well with the design. I was using 3.5" in the nose and 1.5" to 2" max in the tail. This template already has plenty of curve, so a flat rocker won’t feel stiff.
slightly rolled entry, flat bottom with some roll starting 3-4" from the rail and a mild panel vee (less than 1/4") starting forward of the fin is simple to shape and will be fast without being stiff or twitchy in the turns. The length is short enough that control isn’t a problem, so all I was looking for with the roll is to smooth the ride out a little.
I ran 10.5" boxes, mounted 5" from the tail and ran the fin more/less in the middle of the box. Best if your thickness at 5" is at least 1.1/4" so that you won’t completely break the stringer when you rout for the box.
There are other ways that people do these, but this is the combo that was most versatile and forgiving in the conditions I was surfing.
Im making my own blank with eps from the hardware store. Plan right now is no stringer and a heavier glass job. Id love to try some flax or different materials but im trying to keep it as simple as possible.
Huge thanks for all this info, ill be trying to work those bottom contours in for sure then and the side bites if it all goes to plan. Right now going glass on fin(s) for less tools and to learn the technique. I also like the idea of not having to buy a fin box. I was going with 7’ for the original template but if this board works out it’s going to be my girlfriends, she’s much lighter than me. Thanks again mate.
If your plan is truly to “keep it simple” I suggest just buying a PU blank with a stringer rather than going the DIY EPS stringerless route. There is nothing “simple” about that method, and your likelihood of getting a desired result is low. I imagine a single fin like this would benefit from a heavier PU blank anyway.
+1, especially with respect to the weight. You want to bear in mind that with singlefins the board is doing most of the work, not the surfer. You’re trying to be smooth and controlled so as to not interrupt the flow. You want to make the most of what the wave is providing. You aren’t trying to pump water through a fin cluster to produce drive.
I did a 7-0 some years back with a 1.5pcf EPS core, bamboo veneers top and bottom, and high density PU rails. It came out too light. I went back later and added another layer of glass (more weight) and that resulted in a very nice weight. Not too heavy and not too light. Of course, it was also overbuilt at that point, but we live and we learn.
A little weight is your friend on those boards. Letting them get to 2# per foot is a little excessive, but even that’s better than too light.
Thanks again for the input. I want to go with the eps diy core to keep the cost down, because of poor access to blanks and when I make a mistake I can start over at a lower cost. Im going to go heavier on the glassing schedule so the board doesn’t finish too light.
I’ve also edited the outline to stay wider out the tail and shallowed out the rocker in the front. All of this very closely matching the McTavish Diamond Sea which come in below 7foot: Shop Diamond Sea Available Online | McTavish Surfboards Byron Bay
Any thoughts on 50/50, 60/40 for this?
I ran your image up on Boardcad and what I got was about 2" in the tail and 2.9" in the nose. That rocker would surf, but you’d probably bury the nose a bit while paddling and you’d have to be real careful or your drops. If you added another 3/4" or so that would make things a lot easier for you. The tail is good at 2", or you could drop that to 1.5" for a little more drive. Your tail measurement is 16.35", which is what I would do in that design, but I like wide tails. A normal tail measurement for the design would be about 15.1/2" or so. But as i say the width you’ve got will work, too - you will just need to be assertive with your turns.
Anyways, the only change I’d suggest is bumping the nose rocker a little. And if you’re going to run a 16+" tail with a 14" width at the trailing edge of your fin you should plan on running a fin that’s at least 9" so you can keep the tip engaged when you’re banked over on the rail; I’d run 9.5" or 9.75". Which is actually what I do run in those designs.
With the core, try to get the heaviest EPS you can find. It’s not going to be that more expensive than the really light density EPS. The problem with putting a heavy shell over a light density core is that you’ll still beat up the core in the stress points. And you’re talking about doing a glass-on fin (which I’d actually advise against if this is your first time surfing a board like this). A glass on fin of that size will put a lot of stress on the glass and will try and pull the glass off your core. And you probably will get fin strikes with a 9+" fin, so the chances of losing a fin or tearing your blank up are higher than average. And once a light density EPS core gets exposed to a leak it will literally suck water up like a sponge.
You are 2 boards into building surfboards and you want to make a blank rocker etc. Do yourself a favor, give yourself a fighting chance to make a semi decent board, buy a blank…The DIY is a myth.
Your not saving any money when you have to throw away the crappy board and waste all the time making it.
Make simple rails, make a simple shape, follow the blank rocker. Learn
You have a lot of experienced people telling you just to buy a stringered blank (I am one of those people, though not as experienced as others). As resin head said, the economy of doing a DIY EPS blank is a myth. Not to mention, a heavy glassed light EPS core will surf like a Surf Tech. Certainly not suitable to a single fin as you envision.
