Need help with new HWS project

General Discussion
1

Hello to all. I’m in the proccess of building my fifth HWS. This time I wanted to try something different and decided to build a bisected board (look at the attached pictures 1 and 2). The final measurements for the board will be: 7’ long, 22’’ wide, 18’’ nose and 15.5’’ tail, low rocker (haven’t measure it yet but looks like 3’’ nose 2.5’’ or so in tail). Now, the next stage is building the mechanism that will hold the two halves together. My first idea was to use something similar to the original bisect board, but now I’m thinking in using 3 stainless steel allen screws, 1 in the middle, and one on each side, runing lenghtwise and through 3 T-nuts installed on the opossite half of the board. The stress over the screws will be redirected in some way to the top and bottom skins and to the laminated rails, but I still don’t know how. In picture #3 you can see in yellow the 4 chambers available to build this “mechanism” and in red the location of the 3 screws. I want to hear your ideas and opinions about this board, and how you think this 2 parts will be held together in the best way.

Any info and help will be apreciated, thanks in advance.

Jack

2

Hey Jack

Those little yellow clamps will never hold!!!

I like the idea, my thoughts would be to extend the braces to the two cross ribs above and below the main join, that would distribute the stress acoss a wider span.

Stainless steel tubing will probably do the job…

Good luck…

3

Hi Jack,

I used to row sectional 8 man rowing shells back in high school. They weren’t as stiff or fast as the one piece deals, but much easier for teams with small boat trailers to get around. I’ve attached a couple pics of the middle connection that I stole off the web. As you can see, it’s basicly two extra thick layered ribs with a bunch of heavy bolts going through. If I remember right, there was also a 12" steel rod that went into a hole at the bottom of the boat near the keel. It would be hard to fasten the bolts like this on a surfboard because both decks are closed. Have you thought about access for the attachments? If you had a removable deck pannel too that would take care of the access issue.

If those pics don’t load, I got them off of this site:

http://sta.umbc.edu/orgs/umbccrew/forsale/schoenbrod/index.php

It’s images 5 and 7 that show the connection.

I also found this on a patent website: whatever “intelectual property” is. :wink:

http://www.patentstorm.us/patents/5476403-fulltext.html

It doesn’t have any pics that I could find, but maybe you could dig them up.

Hope this helps. Let us know what you end up with.

Pat

4

Thanks! I never thought on metal to solve this problem. I’m a wood lover and my metal skills are almost unexistant. I’ll search someone to build me the pieces today, and keep you informed of the progress.

Jack

5

Uhmmm - a few things,

Like Hicksey said, you want to extend your attachment mechanism to more frames than just the two at the join. I’d advise maybe even some sort of box girder that went well up the nose and tail sections to spread out the stress.

See, what’d give you problems with just that two-frame thing is that you’d have to make them awfully heavy and thick to basicly take all the stresses of the whole board, right there on a few small fasteners. And beef the bejeebers out of the wood close by those fasteners, so they don’t tear out of the wood either.

Now, on a rowing 8, you don’t have those kinds of stresses. The boat is basicly a channel shaped girder to begin with, and the load is distributed pretty evenly across the length of it, as is the support. Besides which, they are not meant to take impact loads from above or below amounting to several times the normal, in use load. For instance, the rowing 8 is happy with nine guys on it, and 8 of them great big guys at that, but if you had them all jump onto the thing in the middle, at once, from six feet up, with the biggest guy carrying the coxwain ( who would be screaming all the way down, coxwains are like that )…well, the 8 would bust like a bread stick. Indeed, some of the more lightweight and lightly built eights have folded up in bumpy water

What’s more, a surfboard on a six foot wave can be subject to the shock load/impact load I described above for the rowing shell - board in the trough and a fair size wave hits it, blammo.

So, how would I play it? Maybe make four pieces: nose section, tail section ( both with some rugged box girders built in) and a couple of well-reinforced inserts to take the main strains and distribute them. You could go with wood and carbon fiber and do very nicely I think, for both the box girders and inserts. Then, all you’d have to do is use a few screws to keep the pieces from moving apart - kinda like this -

It ties into the frames nicely, several of them. The screws can go into solid wood parts of the inserts, through built-up parts of the structure, all should stay fairly watertight. Skin structure can be tied in nicely…you could even make it all a little flexible at the ends.

hope that’s of use

doc…

6

“Now, on a rowing 8, you don’t have those kinds of stresses. The boat is basicly a channel shaped girder to begin with, and the load is distributed pretty evenly across the length of it, as is the support. Besides which, they are not meant to take impact loads from above or below amounting to several times the normal, in use load. For instance, the rowing 8 is happy with nine guys on it, and 8 of them great big guys at that, but if you had them all jump onto the thing in the middle, at once, from six feet up, with the biggest guy carrying the coxwain ( who would be screaming all the way down, coxwains are like that )…well, the 8 would bust like a bread stick. Indeed, some of the more lightweight and lightly built eights have folded up in bumpy water”

I haven’t laughed so hard since an hour ago. Right you are Doc. The coxwain would be screaming. I think doc has some extremely valid points here. Rowing shells are pretty much just that…thin shells.

Doc, even with som reinforcement going nose to tail, how would you solve the problem of how to fasten everything down? Are removable deck pannels really the way to go? That would seem pretty hard to do with an HWS and still have it water tight. This board is looking more and more like a kayak in my mind’s eye.

Pat

7

Heh- yeah, Pat, lets say I have met up with some coxwains in my time…

What I was thinking is that if you had a couple of insert tubes, say, that ran from a couple frames forward of the join-up to a couple frames back of it, then that takes care of the main strength neds of the board. Keeping the two halves from drifting apart, well - that doesn’t take much strength, just a screw down through the deck in each half would pretty much do it - kinda like this Really Bad Sketch

The main strength needs to be to keep the board from folding like a cheap jackknife - just holding 'em together really isn’t a big deal, so something easy would do it. Don’t need any removable panels or anything like that. maybe a little spacer-type stuff between reinforcement tubes and the deck where the screws would be, but that’s about it.

Dunno, what do ya think?

doc…

8

Doc, I agree. There needs to be some sort of joiner that spans a good portion into each half of the board. When I make 2 piece airplane wings I use a aluminum tube which fits into a fiberglass channel in each wing half. The fiberglass channel is made by waxing the aluminum tube and glassing it, then sliding the glassed portion out. The glass tube is nested between the top and bottom wing spars and the whole thing is wrapped with kevlar tow to make it one unit. There are tremendous shearing forces where the tube goes through the wing so the whole thing needs to be firmly held together from top to bottom. Here are some pics of a 2 piece wing. By the way, Ive been putting some hours on my HWS and it is amazing. I just finished tearing up Huricane Alberto!!

9

3’-4’ long 1"-1.5" radius hollow carbonfiber tubes they sell at ACP or Fiberglass Hawaii might work

Kind of pricey but light and strong.

Hollow aluminum tubes would work too but it’s heavy.

You might be able to vacuum bag with epoxy some ACP honeycomb between sheets of ACP carbonfiber glass over some PVC pipe coated with mold release to create your own large diameter carbon tubes if the premade ones are too expensive.

You could even try four 1.5"-2" diameter bamboo poles that run pretty much the length.

You’ll need some reinforced baffles to pass them through.

Its just like how Pope Bisects slide togethor.

But you might end up violating one of their patents if you do this.

10

I know nothing about surfboards [hence the lurking and first post] but if you go the carbon tube route and want to make your own solarcomposites.com [not affiliated] sells braided carbon sleeves for pretty cheap, $2-$4/ft in the sizes I think you’d want. Cool thing about the sleeve is that they cover maybe 75% to 125% of the stated diameter. I think they mostly supply people building paddle shafts. They say you can use high quality heat shrink tubing to compress the sleeve around a mold, easy if you don’t have a vac setup. And from what I’ve heard they’re super helpful, and probly could tell you what the trick is to making two tight fitting tubes.

Best of luck.

[as for the pope patent, as long as you’re not selling the board it doesn’t matter. but I’m not a lawyer.]

11

lpcdefg - exactly! The two-piece airplane wing is maybe the closest thing to a two piece surfboard, though I’d use more than one joiner ( twisting loads which the fuselage takes up on the airplane but a surfboard would have to deal with by itself) . Tied in to the framing with kevlar tow ( or for that matter, fin rope would work in this application) and there you have it.

In fact, your wing gave me an idea for an alternative way to hold the pieces together - those two aluminum pins sticking out of the leading edge there - I dunno if you’d use some sort of elastic to pull the two sections together, but something similar could be used as well…or elastomer, or a couple of screws as I described above.

oneula and collin - hey, I didn’t even know they made hollow tubes or better yet sleeves of fabrics that you could laminate. The thing is, with mebbe a little balsa , some harder wood at the ends, a lathe and what have you, you could make a very nice spar or something of that sort, laminate the bejeebers out of it and then form the hollow ‘receivers’ over that, equally strong and maybe glass on some wood bits to make it fit the framing nicely. The harder wood at the ends could accept some sort of fastener to hold it together, and then, in turn, the very close fits would act to do a good deal of the work of holding the two pieces together under short-term loads, kinda like how a couple of five gallon plastic buckets can get stuck together and need a good deal of effort to pull 'em apart - less strain on the through-deck fasteners in use, their main work would be to hold the board together when paddling and maybe act as vents when you do want to disassemble it.

Gents, I have to say I’m impressed -

doc…

12

Thanks everybody for the advice, but I decided for the metal reinforcenment option. Have no camera now, but in the pic you can see in black the position of the metal pieces. I don’t care about weight right now, since this board is more like a prototype. I went cheap, and if it works maybe I’ll build something nicer and lighter. The purpose of the L shape pieces is to transfer the stress to the rails of the board, since they are one of the strongest parts of a hws structure.

Jack

13

Hey, Jack -

Don’t worry about weight. Not really all that big an issue versus strength. The main thing is to think about what will deform under stress. The angle stuff may actually help, as when it does twist a little when pushed hard it will ( via friction) tend to lock things in nicely. The rails are indeed one of the more solid ( not to say the main ultimate strength ) parts of the structure, so that for tying things togther it’s a good place to start with.

hope that’s of use

doc…