HWS planning, questions

Got the bug to build an HWS, say 6’ long 22" wide, 2" EPS rails, door skin “perimeter stringers”, 1/8" mahogany center stringer. Exterior glassing 4 or 6 ounce E bottom, 2x6 oz E deck, epoxy lam with PE hot coat and finish. Bottom skin only sealed on the inside. Deck skin open to discussion.

I made a test box section of 1/8 and thinner mahogany ply, 15" x 11" x 2.75". There is a 1/8 thick “stringer” along the long edge and four 1/8 ribs 5 inches apart, with the thinner ply as deck and bottom. None of the wood is drilled out. It appears quite stiff but I haven’t jumped on it yet since it was only glued up yesterday and is not glassed.

Sways general opinion seems to be that skins need glass on the inside. Trouble is, Fiberglass Hawaii no longer sells 1.8 oz kevlar (which I would have used). They have 5 oz kevlar and 4.8 oz carbon and cost $25 and $32 per square yard respectively. Though I don’t expect to use much, both of these are too heavy for their material.

I want to use 1.8 oz kevlar or similar on the bottom of the deck skin, rather than E glass, thinking the kevlar or carbon will be very stiff, thus providing the deck skin I need.

Questions:

What should the internal rib spacing be for me at 240 pounds? Hmmmm I could use two longitudinal stringers spaced 6" apart rather than a single center stringer. Based on the test box I don’t think longitudinal stiffness is an issue the exterior glassing will address that. Hmmm the stringers could be close at the nose, wider apart toward the tail.

Will the deck skin using 1/8" mahogany ply be adequate with a layer of 1.8 oz kevlar inside and 2 layers 6 oz E outside, epoxy glassed?

Who has some light kevlar or carbon cloth, preferably near Honolulu?

FWIW from someone who has only built a single HWS, I would drop the interior glass or carbon on a door skin as mine came out heavy and the door skins themselves are plenty strong to support my weight. I’d seal the interior with epoxy tho in case of a leak or forgotten vent plug. If I’d do it again I’d make a test piece like a box slightly bigger than my foot (ie. space out the ribs so your foot will fit in between) and try to put my foot through it just to make sure. If you can put your foot through it, then add some glass/carbon/kevlar/whatever and try again. On the outside I’d use 2 oz on the bottom and 4 on the top, but I weight 40 pounds less than you… One last note, the quality of door skins wary enormously, some have a center filler ply that is more air than wood while others are rock hard.

Good luck

Haavard: what was the rib spacing, deck skin thickness and glass schedule you used?

I have cut up a sheets of this stuff to make fins and other things. Even found in the scrap pile, the internal quality seems better than the fir plywood that has lots of interior voids and surface defects. Internal quality is not much a concern, but thanks for that note.

I will stomp test my trial box after I glass it with poly resin. The “real thing” is planned to be laminated with epoxy for its perceived better bond to wood, and flexibility which I hope will prevent delaminating. Internals will be all sealed.

Quote:

Haavard: what was the rib spacing, deck skin thickness and glass schedule you used?

The rib spacing was according to the free (at the time) plans by paul jensen, A rib every foot if the images at the paul jensen site don’t lie… Glassing was pretty much as you describe only with carbon on the inside, honestly cannot remember the weight of it tho… WAG 5oz. Skins where 3mm + .7mm veener. It’s paddles good, surfs good, but it’s heavy so I don’t like to take it into a crowd as I’m worried I might kill someone.

If you are really brutal on your boards, I’d consider using the double stringer as you suggested, one under heel, one under toes.

Charlie

check out:

http://www.grainsurf.com/forum/viewforum.php?f=11&sid=e380c71d6302f8ebef431f16ca524f22

all the HWS guys hang out there including Roy

most of all the stuff you need to know can be found there and I’m sure they can answer a question or two.

I can email you a couple of skeletons if you are interested just cut and glue and built out your skins and rails…

normally they go no thinner than 1/4" on the skeleton. I have several sets of 1/4" cedar “fish bones” and "mal bones"cut out already I just haven’t found the time yet to start assembling them you’re welcome to a set if you want to save time and just work on the skins and rails which are difficult enough. …

couple majors is ther need for a cheapo vaiable rocker table as a clamping jig for all the pieces and a hundred spring clamps or cut PVC tubes as clamps… They explain it all on the site.

-b

I feel like I have reached the limits of thinness for skins. I did strips of 3/32" pine and Spanish cedar for the deck and the bottom. The bottom has only 4oz glass on the outside and would never hold my weight. The deck is 4oz under and 2 x 4oz with a 4oz deck patch and it can handle someone 180lbs i wouldn’t think it would handle your weight for the long run.

Here is a pic of the frame so you can see the spacing of the internals.

Finished board

The finish weight is 19lbs. I don’t think I could make it any lighter and if I did it again I would put glass

under the bottom skin. The board is kind of fragile for an HWS.

Hey Honolulu I have built 5 boards with 1/8" ply. No glass inside and 1 layer of 4 oz

bottom and deck. Ribs are 12" on center. So far no problems. These boards are tough.

The only time I glass the inside is

if I use wood ( not ply ) and I want to make sure the glue lines dont open. Weight is hard

to control on these things so do everything you can to keep it down. On a 6’6" I built I

used 1/2" divinacell for my frame 1/8" cherry ply for the skins and divinacell for the rails.

With fins it came out at 8.5 lbs.

All glue is epoxy. The next one I will use lighter foam. Good luck and have a ball.

                                                                                                                     Mike

Okay guys thanks for the advice. I’ll look over the grain site tomorrow (little late just now).

Home Depot has 3’x7’ mahogany door skin sheet for 7 bucks and 1/8 sheet 4’x8’ for 13… total twenty bucks for enough wood to make all the frames and skins, with left over for fins. I have poly resin from another local Sways member at $25/gallon though I think epoxy for the deck and bottom lam, then poly hot coat and finish. Futures boxes. Got most of a roll of 6 oz E glass in the garage. This one should be pretty inexpensive.

There are a couple other things I’m thinking like high density foams for the rails… but I only need foam rails to shape and wrap glass on, so 1 pcf EPS will likely be the result. The “crazy hollow carbon fish” thread used foam rails as a mold for hollow kevlar-epoxy rails, but he had better materials access than I.

High density foam ribs? I don’t think that after drilling the ribs out, then waterproofing them with resin, there would be much savings on a shortboard. Six drilled ribs of 1/8 lauan can’t weigh so much that there’s a savings there. Better to reduce weight in the upper skin by whatever means, but all searches to date for kevlar or carbon cloth all lead to the mainland.

I should avail myself of an accurate scale and track material weights start to finish.

I’m getting to thinking of orienting the ribs in different angles, and variable spacing, to address foot stress. More I think about double stringers, more I like it. Just the sort of thing to keep an engineer up at night. Like all engineering assignments it’s an exercise in maxi/minimization. Dilbert would be right at home with this. Hmm a Dilbert lam would characterize this board…

Up the street someone has thrown out a bookshelf with nice cherry-looking veneer. Wonder if I can strip just the veneer… probably (worthless) particle board or MDF underneath.

Oneula thanks for your generous offer, I will think it over.

well as soon as we figure a way to one day to catch up…

-2 blueboo2 compoopoos and 2 bluerailed rebuilds

-16’ lb homedepot EPS styro canoe SDP (sit down paddle)

-12’ stewart peepee (parallel-profile)

we can start constructing all our HWS which have been also sitting around for a year or two…

I even bought a 100 or so extra large spring steel paper clips from fisher and t-bar brackets to glue up with 5min epoxy to make little t-bar clamps to hold all the 1/4" skeleton frames togethor.

With our plastic peg board surfaced (to hold the rails in) adjustable rocker table we should be able to layup the HWS skeletons pretty easily.

meanwhile back at the skunkworks the ewa beach maddening heat has the backyard bozos doing even sillier things…

We bought a 2" thick 4’x8’ bluedow panel($35) from lowes cut it in half and ripped one half into a 2’x8’x1" slab.

We then bought a 1mmx4’x8’ sheet of the woven bamboo ($30) and cut it into two 2’x8’ sheets.

Then we vacuum bagged at max pressure a sheet of the woven bamboo on each side of the roughed up bluedow with 2oz and epoxy

From these homemade SIP panels we’ll cut our fishbones which at 1" thick and vertically oriented bamboo skins would provide more than adequate support for the top and bottom cedar shells at about 1/3 the weight of a 1/4" solid wood version.

No drilling of holes, no coating or sealing of the wood skeleton that adds nore weight and a 100% waterproof skeleton that even floats better than wood.

anyway it’s just another crazy idea we’re playing around with before we retire.

We can probably get 3-4 sets(maybe more) of “bones” from the 2’x8’ bamblueD SIP panel.

not core but who gives a rip when you’re doing it for fun…

The one thing I don’t understand about all the HWS kits being sold is this idea (hint) that came to mind as I was looking all my newly bandsaw cut cedar ribs that now need assembling…

Since these kits are being CNC pattern cut anyway, why couldn’t they also cut what I see as “connectors”?

just like any other model kit, why couldn’t there also be little wood connectors that would have four interlock fingers from the top and bottom with little round table tops sitting flush against the top and bottom.

These connectors would lock in the spine and rib components while providing additional structural vertical support along the seams and little support post platforms that provide a larger support surface area for the deck and bottom skins to bond to.

This one additional component could allow the HWS kit builder to assemble the ribs with out the need for any additional complex clamping network.

This came to mind as I saw how all the HWS guys glue in these little bracing pieces here and there within their structures to provide either more joint support or greater glueing surface area… Keith mentioned it to me as well when he was out here talking about what the balsa model airlplane folks do this to provide support surface areas.

anyway just another crazy idea but it could take the HWS home kit market to the next level if you could build one just with what’s in the box…

sorry for the diatribe…

dilbert sounds appropriate

or maybe how about this slogan…

“so easy a surfer can make one!”…