Did the 10” Box centered 10.8" behind the centre of buoyancy work out okay?
Attached were my original calculations showing the 10.9" behind CG (Center of Gravity) shown in GREEN. The CG is easier to measure than the Center of Buoyancy (CB) and ends up more relevant to balancing the teeter totter. The CG is just the balance point of the final board layup (no foil). I have added in YELLOW the distance to the Leading Edge of the Mast, which also corresponds to the center of the front Bolts on the Axis System.
After 99 sessions I am currently most comfortable running 5.3" behind the CG (Compare to YELLOW), which means I should have installed my tracks 1/2" further forward. This primarily with Axis Silly Short Advanced+ Fuse, 1401 and 40 skinny tail (but also have flown with 1201 and 1121). The 10" tracks, installed for light weight, give slightly more than 2" of travel and I am not quite all the way forward. So I am happy for now on the Advanced+ and Advanced (-40 mm) fuselages.
In simple form here is a picture of the bottom of the board.
Note: I now mark the CG on the bottom of all my boards and using a silver paint pen to note the distance from CG to the side of the base plate. A thin strip of clear packaging tape helps preserve the ink.
5.3" back from CG to Leading Edge of Mast / First Set of Bolts.
Be done with this Puh-hoooyeee of measuring the distance from the tail. There is no objective way to do that with boards ranging from 7’ to 10’. I have a pro-level rider in the neighborhood and we have standardized on this metric. He is running 5.5" behind CG with his Advanced+ fuselages.
The mass balance point of the board is not really the same as the center of buoyancy. It certainly is the easiest thing to find once you have a completed board. I would think the mass center is a bit behind the buoyancy center because of the track weight. But good enough for what we’re trying to do.
Thanks Beasho, that’s actually amazing. That’s got to be the most detailed response to a question I’ve ever received; much appreciated!
Jondrums point made me think I could measure the CG of the blank with the foil boxes resting on top, which would give a slightly more accurate measurement (except for the weight of the carbon reinforcement etc).
Beasho, my Insta is @espitaka if you’re keen to check out some of my board builds. I’ll use that same stringer/foil track system as it’s bombproof, but I think you’ll shudder at the weight of the stringers
I’ve said this on other threads but if you commit to a hard chined shape where you can make the mold out of sheet goods this is 100% doable. I made a hollow wood wing board and the shape is 100% fine - just a little heavy.
Hey Beasho, that’s a very good documentation, very nice to watch. I hope that you have found suppliers for big enough foam now, so that you don’t have to glue it all together. Most of us become allergic to epoxy if we don’t protect our lungs. I even know someone who has become hyperallergic. I never use epoxy indoors, and even outdoors i only use it if there is some wind and if the wind is from the right angle to take these nasty vapours away. After working with epoxy i allways rinse my nose (yes it hurts and is terrible) and brush my teeth and drink huge amounts of water, and if i get a drop on me then i never clean my skin with acetone because acetone dilutes epoxy and penetrates the skin and takes microscopic particles of epoxy it right into the bloodstream. But probably you are now using protection, i hope so. Anyhow, it is inspiring to see your process done so clean, i usually make a big mess with foam and dust everywhere. Keep up the good work!
Hey Lapaloude, yes that guy is doing a very very impressive job, and really nice to see, and so many details included in his videos. The only things in this video that might be open for improvement: when i see him glue it seems that he uses quite much of it, and i think the railfoam could have been trimmed down even more and then laminated from the inside. What do you think?
I dont have an opinion on the built. I haven’t really paid attention to all the hollow board building craze.
For me, I think its too much of complexity for a casual rider/builder like me. Shit…being a young father of 2, I barely have enough time to have other activity then riding. For now, I much prefer the method developed by Beasho here. The method is way cheaper than an hollowboard and you can end up with a board as light and in less time.
I’ve built a SUP and a parawing board and have probably 50 sessions on each. I should do a review of the method on a new thread!
With foiling on a calm ocean i don’t see people bashing on their decks, i don’t expect much delamination. In the old days (before vacuum) it was different, many people built XPS windsurf waveboards, most of us had delamination in the stresszones, for example under the feet (we all jumped a lot and landed hard). To prevent delamination i put in many wooden microstringers, usually 2.5mm wide and 20mm deep, of various lengths, they helped a lot, especially when they were only 70mm apart, and right under the footstraps only 25mm apart. I could keep my laminate thin and still have an unbreakable board. Delamination without the ministringers was usually after 2 years, but with my boards it was more like 6 years. With modern XPS foilboards for light conditions i think that delamination will not be a major problem, especially if the boards don’t heat up too much in the sun.
