Foilboard volume formula?

Anyone have any rules of thumb for what volume to ride and for sizing a foilboard in general? I was never really a shortboarder so the most common answer (same as your shortboard) doesn’t really tell me much. It feels like dimensions across brands and models have gotten even more diverse. At 6’5, 225 lbs I got a 4’7" 20.75 @47L board to learn on, but I have no idea where to go next.

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Worth trying some boards if you can, I’ve recently been really surprised how different they all feel.

38 to 32L was felt more significant than I’d have guessed (~70kg/150lbs), feels great and only a 15% volume decrease

Rule of thumb? I like the idea, maybe half your Kg weight as an easy place to start (Quarter your Lbs weight), and then go down from there, towards 25L as seemingly the floor.

If you don’t surf then catching waves on a smaller board is going to be a hassle so consider that

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I also think volume makes a big difference in the type of waves you are foiling in. Initially, you can get away with more liters on a wave that has a softer takeoff. Boards with more volume in quicker punchier surf makes the drop way harder to handle.

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There’s really no need to go anywhere else. I mean eventually you could go down to the 32-35 liter range. But that length is pretty decent. You might go a bit narrower or thinner at some point. That board shouldn’t really hold you back though. Not for at least a year.

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I have been on the 4’7 for about a year. When I tried a 4’6 35L I felt like I lost a lot of wave catching ability for pretty modest performance gains. My 4’7 has been fine for as big and punchy as it gets, but the width has become an issue sometimes on backside carves.

I’ve been prone foiling 3-4 years , 73kg & currently on a 30L board…contemplating getting something longer & a bit more volume to hopefully help with paddling in earlier on punchy beach breaks.

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Are most people really riding similar volumes to the short boards when prone surf foiling? I am pretty fixed on my short boards between 32 and 33L. But with my foil boards I feel like I need a touch more. If its small and gutless it obviously helps to catch them, but also when its big, the board gets in early and I find it easier to make the drop. I am sure there are a million other variables such as rocker, bottom shape, width, so interested in some views on this. Thanks

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This is a great topic with LOTS of variables… Heavies (190lbs+) unite! I’m 6’1 220lbs/100Kg , prone the weakest of waves most of the time and make my own boards as well as try everything I can. Volume is key, can’t do with out it. Given that shorter and narrow feel better on foil here’s my thoughts on dim ranges:
Volume: 38L-46L 42L sweet spot… Agility vs catching small waves
Length: 4’4-10" - 4’6 sweet spot… Pump vs catching +waves
Width: 19-22" - 19.5 sweet spot… paddle speed vs planing speed
Thickness: 2.75"-4" - This is where I’ve been compromising… see construction
Layup: 5.5-10oz of carbon/S2-glass - 5.5oz of T300 or IM7 3K with 4ox of S2 fiberglass is stiff & durable.
Construction/Box: Forget pre made 5lb foam boxes… they’re v1 tech. Heavies should take a note from flying dutchman, Armie FG, and go with a build that runs vertical carbon i-beam stiffeners from just behind the foil box all the way to the front foot. They must also be bottom to deck.
Hope this helps

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Really depends on the surf for me. In smaller surf, our normal conditions, I love small boards. My daily drivers are about 24L and I’m 185lbs. I find that once you generate a bit of speed in paddling the foil is adding volume through lift. Downside is paddle speed getting back out if you dont make it out on the pump, which is always my goal. Been testing some bigger boards with a different shape to minimize touch points and add paddle speed and its going great. My next clips will be on a 35-36L board I’m calling the Transmedium. Went bigger not necessarily for the volume but for the added thickness in hull and what that lets you do for skipping on touchdowns and working in the foam. It might take over for me.

I’ve ridden 34 liter boards down to 28 liter. The smaller boards paddle back out to the lineup worse. They can catch waves just as well if they’re designed by a major surfboard label. So in my experiense, volume isn’t really what catches waves. Good shape is what catches waves.

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OK. thanks guys. Makes sense. In fact I have 2 boards, supposedly equal volume, and 1 paddles probably twice as good as the other, even if it has other aspects I don’t like so much. So I guess its just about finding the right design. Wish I lived in the US as seems to be more options available.

Thanks for the input! 4’6x19.5 @42L is about what I was thinking too. Its too bad I can’t think of any production models that are close to those specs. I’ll probably need to find someone who does a truly bulletproof board and order a custom.

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Very good discussion - this thread just convinced me to pull the trigger on a FFB 4’9 Fusion. I have been struggling with my Armstrong 4’5 SKT and at 200lbs I think a little more length and vol should make a noticeable difference for prone. The SKT volume is more towards the rear of the board as well so hopefully the newer design with more volume in the front and a pulled in tail will give me the best of both worlds.

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Great thread. Ive been attempting to downsize in board size but keep going back to my original. I’m 70kg and ride a 4’5”x 19.8 x 37L. This board allows me to paddle into most waves with ease and what I like best about it is the stability getting to my feet. I’ve tried downsizing to a 4’x4” x 18 x 32L and while the paddling is fine I lose that stability getting to my feet and blow more takeoffs. Is that a function of liters or width? Or just a matter of getting used to a new board?