hey guys i have an idea! (I hope someone else has already thought of this so they can help)
So could you just make a set of wood rails and then sandwitch them between two pices of ply and then shape the rails?
would this be a good idea or will it be really weak and flexy?
thanks :)
I've been thinking the same thing, so I decided to try it out. I built my rails first
added plywood bottom
rough-shaped the rails and added plywood top
finished shaping the rails
painted and ready for glass (on order from foam e-z)
Just wanted to test how much inner structure is really needed, so I decided to build this one with no inner structure. I may go back and add a bit of support if I think its needed, but wanted to finish and ride it first. Skins are 5.2mm 3-ply from Home Depot, rails are 2x redwood and 1x cedar from same. Feels pretty solid, small amount of flex in the skins but not much, and should firm up a bit when glassed (4 oz.).
been wondering the same myself. about as simple a design as you can get, but with so much possibility. i hope the glass shows up soon…I can’t wait for a ride report!
just thinking out loud, but supposing this is strong enough, could you build the rails and put a skin on the bottom that is put in a mold and steam bent to allow for bottom contours? where I’m going with this is a new possibility for crazy flex patterns in boards.
for example, you create a mold of the bottom of the board with a single concave running into a double concave. Can you steam or vacuum bag the ply to the mold and the proper type of wood would hold the shape? Then when the board is glued up, it could be argued that with only the perimeter rails (or perimeter stringers) holding the skin in place, the bottom would be much more free to spring and flex as you move across a wave…things could get pretty funky.
any thoughts?
ps. Huck, is there a vent plug in that? i can’t see one
**If you’ve not taken a few minutes to look up monoquoque construction, it would be of benefit to do so.
**
Brian_CaB: thanks for the tip. So that is the technical name of what’s going on in this thread. What I gleaned from the wikipedia article is that monocoque structures are often stronger than a reinforced structure, and almost always lighter (obviously depending on materials used). What I’m wondering is if a wooden skin that is steamed into shape to mimic the contours of a foam shaped board (rather than a wood bottom in which contours are planed or carved out of the wood) will have “springier” characteristics that might make the board flex in a novel way. I’m thinking that if a wood skin has the attributes of strength (it wont snap) but is not too strong that any contours bent into the wood are stiff after glassing AND the contoured skin can move and flex a touch, then the board will pop and react differently when turning and moving up and down the board. Without internal bracing, the bottom is free to move as one naturally twisting body. Also, with no internal braces, the board would be a lot lighter and (like mat riding) you would feel connected to the water in a much more direct way.
just thoughts…im sure someone has already done it, so speak up if it’s you out there!
You guys are just a big wealth of knowledge.
First off, Huckleberry, is there any concave in the bottom or is it just all flat?
Second, Spudsrfr, I wish I had the tools and skills to do what you are saying because that sounds so cool.
I was kinda thinking of this because is sounds like less work and time than a normal style wood board.
Btw, wouldn’t length and width have an effect on the spring if there is no inner support? longer/wider = more flex V.s. shorter/narrower = less flex.
Huck what are the dems of that board?
Very cool! Thank you for looking that up.
Give a fish vs. give a fishing pole.
Okay, skin/structure is a satisfying method for construction but the flip side is cascade failure. Plan for complimentary failure where a single issue in the structure works against other potential problems to prevent catastrophic results.
However, if you’re able to get to a point where you’re engineering a solution on that level then you’re way ahead of me. I grasp this on an empirical level but cannot pretend to do the math to that extent.
Now, a buddy was at ASR this past year and ran across a board that was tuned by inflation pressure so think about everything that is going on in a “hollow” board. I have it on good authority that the Atlas missle relied on a pressurized aluminum skins that if lightly dinked, crumpled like toilet paper and the films were awesome to watch.
God I sound like an old man but I’m not. No. Really.
Anyway, don’t worry about steaming anything. Press the snot out of any plastic skin - and wood is plastic - while anticipating any reactive characteristics while thinking 3D which is the key for a body construction approach.
A satisfying approach to a hollow board will include skin variations that reinforce the structure. Have you looked at fractals? The skin would probably have smaller design features that would reinforce the overall structure.
This though has to be said;
Unless you can make a very real breakthrough, you’ll likely wind up with an interesting acedemic exercise and lousy board.
Enough. Good luck. Show us what comes of your exercise.
I’ve got to get back to work on installing the dust collector in my shaping table.
i am rooting for you guys. i spend time scheming up different ways to minimize or eliminate foam. whats wrong with trying other methods. the biggest question mark for me is with this is, spuds said natural twisting, that might be the double edged sword. lying on the beach, it torque into a cruel picassolike facsimile of yer former creation…lets hope not,though!
dpicton you’re probably right about a single twisting body (the bottom) probably being a double edged sword.
this is really peaking my interest though…
im having visions of my extra foam scraps glued up and shaped as a mold, and the vac bag in the woodshop I no longer work in sitting idle… so many possibilities…
and Brian_CaB: I like your fractal idea of layering wood skins for strength. i layed up a few fiberglass pannels with the weaves arranged in different angles relative to one another and some strange flex patterns presented themselves. Whose to say that wood won’t do the same thing while strengthening the whole? 1/8" skin -45 degrees offset; 1/8" balsa skin +90 degrees on top; 1/8" -90 degrees to cap it…
i’m trying to finish applications to grad school, go to work, move out of my house, and get ready to leave for three months to Indo in less than two weeks and all i can think about is a hollow surfboard…I think swaylock’s has left an indelible mark on me…
7'4" by 21" by 2 5/8", the bottom is flat - I decided to keep it simple for this one, since its a bit more experimental than my others. It has a hole drilled in the deck, but will get a vent screw when glassed.
bottom contours are possible without steam-bending - pics below show channels that were sanded into the bottom plywood (another board). and plywood can be bent in different directions, up to a point. Also itching to get started on my latest project off the drawing table, an older guy's 6-0 shortboard with stepped deck for volume.
my board was not built hollow for flex, that is a separate issue that I am not incorporating in this design - but there will be some (minimal amount of) flex, of course, since its hollow. I'll see if and how it affects the ride, then decide if and where I want to stiffen the skin. My goal in building a completely hollow board was to see just how much interior structure is necessary, and to arrive at a system that allows me to "shape" a hws, rather than 'plan-and-build', in other words, I determine the foil, deck dome and cross-section by the spring angles I shape into the rails, not by cut out ribs following a pre-determined design.
BTW, glass has arrived, those guys at foam e-z are fast! Hope to get glassing soon.
Theres a guy here Ipecfgh (sp?) who does molded boards and intricate internal bracing, hopefully he'll join in.
Idea 1.
Do you think guys that theres a way to make a 100% hollow board with a deck and rails as suggested above,
but with a totally flexible hull, like a mat..? So its hard on top and soft underneath ? Either totally sealed or open ended ?
Maybe inflation to keep it pumped or using Herbs induction ports ( with a gortex deck vent to pull air in or a vent underneath to stop water filling the void.)
Idea 2.
Boards are so thin these days anyway, maybe just make a separate deck and hull (see pic below or Google- snow skateboard)
This would have a deck and a hull section but totally detachable.
Then the hull section could be moulded for strength and the deck section would provide the bouyancy. Mix and match parts and materials and a broken deck doesnt mean the whole boards ruined.
Component specialisation... of sorts.
What I think would be wild is a custom fabbed innertube. Maybe do a couple of them running the length of the board. You’d only have to worry about losing air pressure if the tube got punctured. They use pneumatics for all kinds of support tasks, up to and including jacking up buildings.
Another idea I’ve been kicking around is the use of high density polyurethane or XPS foam “ribs”, like maybe a 1/2" thick and drilled to allow air to pass through. Build the rail frame, skin the deck. Glue the ribs in, shape them for the bottom contour, and bag the bottom skin on. Maybe lay them in a diagonal pattern to complement the grain of the wood (I really like this one). Or lay two layers of them at opposing 45* angles, like Roy does with his Pawlonia builds.
Or, chamber an EPS blank and build it out compsand style. Shape a stringerless 2# EPS blank, bag a 1/8" deck on like normal, rout out a bunch of holes to the deck to remove the material but leave a supporting structure, then bag the bottom on under low pressure and finish as usual. I would think the voids would allow for a little more flex while the overall shape would help maintain the structure and give you something to anchor the rails to when building them out.
Maybe a variation of the above using veneers. Shaped EPS blank with 3 layers of wood veneers on the deck, two at opposing 30* angles and the last at the 0-180. I’ll bet that a skin vacuum-built like that would practically hold it’s own shape. Then rout the chambers in. Maybe do slots instead of holes. Maybe do more chambering at both ends and less in the middle. Prefab a bottom skin (also 3 layers) and bag that to the bottom.
Here’s one: Two layers of veneer separated by a layer of 6oz innegra.
God thinking gdaddy ! So you think of doing it like a HWS with chambered ribs of XPS ?
Nice !
How about doing a hollow internal wood box with ply and vent, and then skin top and bottom with 1/2 in XPS sheet and rail / end blocks?
The strength/ bouyancy comes from the wood, and the XPS is thick enough to do bottom contours.
https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/BF.JPG
Maybe skip the XPS deck overlay. Gary Young says he seals his XPS/Bamboo veneer boards with a plastic film. Maybe something like a vinyl heat-shrink wrap.
That works. I can see it already with a contoured foam hull and a polished wooden deck, good idea about the heat shrink wrap !
The smaller internal wood frame would have less wood than a full HWS and with its reduced length and overall dims it should have more strength.
How about a hollow XPS like you said, but glass the internal surfaces as well as the outside ? More strength to compensate for the flimsy foam.
Danny Hess, from Hess Surfboards, uses only eps cross members as support for the skins. I think the purpose is to give the skins some shape, but not structural. Go to his site and look at the pics.
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been wondering the same myself. about as simple a design as you can get, but with so much possibility. i hope the glass shows up soon...I can't wait for a ride report!
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First ride report is in. Small beach break waves, 2-4' glassy, board rides great so far. Conditions were pretty good despite being a bit small, but it was definitely uncrowded, so I got a lot of waves. Duck dives easy, paddles easy enough (a bit more work than my 9' 6" I've been riding lately LOL), catches waves easy, stable for easy up, feels lively underfoot, turns and projects well, and mainly, doesn't feel any different really than any of my other surfboards as regards being "completely hollow" - just feels like a surfboard! Once the board was glassed it became real sturdy, you can hardly tell its hollow.
killer 
i like the green.
So know that its proven to work, can you explain how you made the rails. Did you cut them out and glue all the pieces together or just bend the wood with steam, and heat, and stuff?
