idea: foilboxes set with carbon stringer + bonus foilSUP design images

[jondrums]

I'm thinking about a construction for a foilboard where the boxes are set in at the same time as building in a dual carbon stringer.  The idea would be to route out slots for the foilboxes (without any PVC foam), then hotwire the shaped board into three pieces the long way.  Then layup the stringers and install the foilboxes at the same time.     I would vacuum bag the blank+stringerlayup+foilboxes to get a good adhesion to put the three pieces back together.  The point of all this is to be able to use 1lb foam (divinycell sandwich deck).  What do you guys think?




Or, I am also thinking of possibly splaying out the hotwire cut to give the board some stiffness underfoot while paddling


images of the shape I'm thinking about - pretty much a hybrid between Dwight and Kalama designs with what I think is a little more fair lines.  Blue coloring is just an idea for paint scheme I'm playing with.

[exiled]

Tim Carroll out here in Hawaii is building his boards using double pvc stringer blanks. Makes for a cheap and easy-ish build that still gets the job down durability wise. I think he's still using 1.5 foam though.

[surfcowboy]

I like it. I did boxes glued and glassed to 1 1/4 x 1/4” wood stringers routed into the bottom for my latest prone board. KT on Maui does carbon stringers too.

Only thing I’ll say is that cut will be a challenge once the board is shaped but you know that. I chickened out and just routed mine and went straight. lol. But I want to do a high density and carbon stringer too.

Also I wonder if you might make this cut simpler too by just putting the boxes next to the stringer and glassing them to them. But this way looks bomber for sure.
 
The stringers really just need to be beneath your feet, to me. So that might simplify the cut too. Foiling your not going to get to put heavy pressure that far out to the sides so I’m not sure how much to worry about torsional stiffness. Dual stringers will be awesome underfoot though. Solid as a rock for pumping. I need to post all the stuff I did for this prone board. It’s over on foilfeed but I need to post here too.

[PonoBill]

I like the design, but it looks like it will be a fairly difficult build. Once the stringers are in place it will be a challenge to do any sanding, and I would be nervous about vacuum bagging it--the carbon won't compress at all while foam still might. It looks like a construction method that would be great to perfect, but probably would be a challenge as a one-off.

I doubt you'd need to splay the stringers to gain stiffness. With any reasonable glassing schedule the board should be very stiff. My old Kenny Tilton longboard was a double stringer with a very light layup. I weighed about 245 when I was surfing that, and I was always amazed at how well the board behaved when I shuffled to the front.

I'm fiddling with an I-beam design inspired by the Gong inflatable--or perhaps by what I thought the Gong design might be. I'm using a carbon mounting plate from the Foilmount folks. The structural elements would be the plate, a PVC/carbon box that links the foilmount to a carbon/PVC deck plate that incorporates the standing area of the board. The rest of the board is minimally structural--just enough to hold everything in place and resist dings. Preferably closed-cell foam.

I might ditch all that and just build a board that adds enough reinforcement under the plate to ensure it doesn't delaminate the skin under the torque of the foil. The new carbon plate is beautiful and comes with foil mounting hardware. At 169 bucks it's a pretty cheap way to mount a foil, my only reservation about using it with a conventional board is the delam issue, which I can deal with fairly easily. I think two rectangular blocks the lenght of the foil mount X2"X2" with a layer or two of carbon bagged on to the face the Foilmount contacts and a full width carbon, innegra, or glass patch a little longer than the Foilmount will suffice. The Foilmount itself is extremely stiff. I clamped 1/3 of it to my bench and put 125 pounds on the remaining 2/3 and couldn't measure the deflection.

Your design could be modified to work very well with this approach. I like the design a lot. Would you be willing to share your design file so I could get it mowed here locally? I suspect I'd need to modify the dimensions, as I recall you are not in the Clydesdale class.

[jondrums]

sure, I can send you the design.  I'm not going into the foilboard building business anytime soon, just doing this so I can get onto equipment that is exactly the way I want it.  I'm not using shape3d, its in Solidworks - so I have a variety of file export options but I haven't figured out while file type is best for the cnc shaper guys

I really like the foilmount  and I-beam idea.  I might work up some sketches of this - I think it would be a lot easier to chop the blank in two pieces rather than 3 and it would still be incredibly stiff.

I had the same thinking to put the structure into the boxes, stringers, and deck and the rest of the board is as light as it possibly can be without falling apart.

[PonoBill]

Actually, the way I came up with for doing it while I was installing a dryer vent in my shop (had to think of something creative while I was doing messy, mindless shit) you wouldn't have to chop the board at all.

I was trying to think of the simplest and cheapest way to do this. Take the semi-finished blank and saw a block from the center of it that is the width of the foilmount, and long enough to reach from the back of the foilmount to the front footstrap mount. Sand the top and bottom of the block a bit to make the block slightly recessed from the rest of the board. Bag it with several layers of carbon to turn it into a box, glue it back into the hole you cut it from, sand the blank flush, add strap mounts, handles and a vented leash plug--all of which go in the carbon box. Glass with a silly light schedule. Stick on the foil mount. Done.

[clay]

Cool idea.

One of the things I've seen on some boards is the stringers start to pull through the bottom of the board.  My guess is this happens after breaching or coming off the foil and landing full weight on the nose of the board.  So feet are pushing stringers down and water is pushing foam or the nose of the board up or in the opposing direction.  I think in these cases the stringers didn't run full length and or top to bottom also.

[PonoBill]

The problem with any idea like this is that established methods already have the kinks worked out, so it's hard to replace them unless there is an overwhelming advantage to the new approach. A piston and crankshaft internal combustion engine is the stupidest way to generate rotary motion imaginable. But 100 years of engineering have turned a dumb idea into the standard. Nothing has ever offered a big enough advantage to overcome the refinement and the inertia. Even something as obvious as electric cars has a huge infrastructure problem to overcome.

Foil boards of any flavor have to resemble surfboards for only a very short time--when you're first getting to your feet and onto the foil. But only the people with alien balance, reflexes, and skills can get past the surfboard requirements, The rest of us need float and stability. Once you're on the foil what you really want is something like the most minimal kite foil board.

Fortunately, we folks screwing around with making a better foilboard don't have to worry about changing the world. Just keeping the cobwebs swept out of our heads and building something we can have some fun with.

[jrandy]

sure, I can send you the design.  I'm not going into the foilboard building business anytime soon, just doing this so I can get onto equipment that is exactly the way I want it.  I'm not using shape3d, its in Solidworks - so I have a variety of file export options but I haven't figured out while file type is best for the cnc shaper guys

I really like the foilmount  and I-beam idea.  I might work up some sketches of this - I think it would be a lot easier to chop the blank in two pieces rather than 3 and it would still be incredibly stiff.

I had the same thinking to put the structure into the boxes, stringers, and deck and the rest of the board is as light as it possibly can be without falling apart.

Jondrums,
I like the design and pictures. 
Even though I have a small CNC and have access to a larger one, I generally just use the CNC for templates and do the majority of the work with hot wire and planers in 1.5# foam, for me it is easier to shape and a little less easier to damage while shaping. Shaping machine softwares do have some nice efficiencies built in for chasing a surfboard shape, but to do the deck inlay and foil boxes could be problematic unless you have the modules for 3D extras. I have used the STL file format to get surf shapes out of BoardCAD, Inventor,  and Fusion360 to go into the front end of my CNC software.  You might be able to give them STEP files too. If you  can get information about their machine (english/metric, size of cutter, origin, file format) you might be able to use a CAM postprocessor out of Solidworks like HMSWorks. If you discover a good path for this and are willing to share I am sure that myself and others here would appreciate hearing ways that work.

[surfcowboy]

I like the box a lot. And honestly, you could make your own without the foilmount I bet and it’d work pretty great.

Clay, I’m pretty sure this stringer idea will eventually go but I wanted to see what a simple version would do. The board was cheap and fast to make. But I suspect the right way is to go deck to bottom.

The stringer setup, in my mind, just spreads the load about 42” down the bottom in my case so I’m hoping at my weight it works til I’m ready to retire the board.

I agree that us home hackers will surely come up with some fun stuff.