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Flex paipo construction techniques?

 
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PaipoJim
Director of CTU


Joined: 31 May 2004
Posts:
Location: Oregon

PostPosted: Sun Jun 13, 2004 10:55 pm    Post subject: Flex paipo construction techniques? Reply with quote

I have really been enjoying my new HPD SR board especially the "snap" it provides on bottom turns etc... and I want to start experimenting with flex designs in my garage. I remember a Greenough flex spoon type kneeboard I bought at a surf shop across the highway (on the lagoon side) of Cardiff reef in 1969. It had the foam scooped out from the top so that most of the board was just fiberglass and resin and was translucent, especially at the tail where even the last section of rail had no foam. You can see examples of this kneeboard build style at Ron Romanosky's web site where he still can be coaxed into spending the large amount of time making one for a hefty fee. http://www.romanoskykneeboards.com/html/flex_spoons.html

As I recall the foam is shaped for the bottom contour and rails and then glassed on that side. Then the top is scooped out and that side glassed. The trick that was explained to me about my board was that there are multiple additional layers of glass each one starting at the nose and ending succesively shorter from the tail so that as you go down the board it gets thinner and so the board has more flex at the tail.

I have two or three questions and if anybody on the board knows about this or could point me in the right direction I would greatly appreciate it.

1) In what order do you build up the glass layers on a flex spoon? Romo implies that they are added to the top but I thought the guy who sold me my board said that they are added to the bottom - short layers first.

2) How do you lap/finish off the edge of the layers of glass at the tail where there is no foam? Do you somehow bead in a thin strand of glass rope or what? This is where the board would experience maximum flex and it needs to be robust and durable to prevent immediate delamination problems.

Is fiberglass and polyester resin still the material of choice for this sort of design or do more modern materials have a place in this? Carbon/aramid is supposed to snap back to original position quicker isn't it?
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kage
Dolphin Glider


Joined: 12 Jan 2004
Posts: 286
Location: Santa Cruz

PostPosted: Mon Jun 14, 2004 3:58 pm    Post subject: Reply with quote

This is exactly what I have been mulling over in my mind for the last two months. I was just in a meeting where I was doodling the flex tail paipo I want to build. I also have an HPD and I keep thinking of that design with two small fins to hold the edge when I ride kneelo. With no fins I slip down the face too much. I have also spent a lot of time studying the photos at the Romo site. The amount of hours he (and others) claim it takes to build a flex spoon like that are pretty scary. Well, the wife and kids are leaving for a week and I'll have a three day weekend to build something start to finish.
Anyway. I don't know but I suspect that the fiberglass doesn't actually taper that much once it's free of the foam. I think its't the length that allows it to bend. A more sustantial lip at the edge could be built up by lapping first one side then the other, maybe wtih some roving in at the early stage. From searching around on swaylocks I get the impression that it is a minimum of 8 layers probably more like 12 to 16. If some of those layers are tapered and then the final layers do the lapping...
I am thinking of starting with a 1/2" x 24 x 48 sheet from fiberglass hawaii, shaping and tapering the top, temporarily gluing some curved struts to the top ( for side to side rocker), flipping it over and glassing the bottom. I hope that will hold it's shape once it's dry, flip it back over and start adding the layers. I'll see if I can find a couple of small fish type fins -- mounted straight straight and near the back. One question is how much foam to scrape/sand out.
Doc, Beeline, any advice? I know it's probably nuts, but I'll keep thinking about it until I do it. PaipoJim, let me know how you are progressing.
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Poobah
Dolphin Glider


Joined: 09 Jan 2004
Posts: 696
Location: California, San Diego

PostPosted: Mon Jun 14, 2004 10:05 pm    Post subject: Reply with quote

Solo mentioned in another thread:

http://rodndtube.com/paipo/forum/viewtopic.php?t=22
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PaipoJim
Director of CTU


Joined: 31 May 2004
Posts:
Location: Oregon

PostPosted: Tue Jun 15, 2004 2:24 am    Post subject: Reply with quote

kage wrote:

I am thinking of starting with a 1/2" x 24 x 48 sheet from fiberglass hawaii, shaping and tapering the top, temporarily gluing some curved struts to the top ( for side to side rocker), flipping it over and glassing the bottom. I hope that will hold it's shape once it's dry, flip it back over and start adding the layers. I'll see if I can find a couple of small fish type fins -- mounted straight straight and near the back. One question is how much foam to scrape/sand out.


The problem of holding its shape seems to imply that you need to add all the layers of glass to the bottom before you start removing foam from the top. A single layer of glass could easily twist along the longitudinal axis of the board once you start removing foam (or even if the foam is not thick enough to begin with.)

I was originally thinking along similar lines: Use something like double-scored Balsa or Divinycell http://www.fiberglasssupply.com/pdf/core/GSGUIDELINES.pdf stretched over a male plug or some sort of lofting jig with some longitudinal plywood stringers cut to the correct curves. The downside to this approach is that there is a scant amount of foam left if you start removing it and I want this puppy to float! Plus, the scored material doesn't really get properly infused with resin unless you vacuum bag it and some of these materials need to cure at higher temperatures in order to retain their shape.

So that's why I to want to start with a fish or kneeboard foam blank. A beginning foil that contains no tail rocker. Shape the nose and rails and then glass multiple layers on the bottom. Correct selection and orientaion of the cloth weave has to be done so as to invest the end product with the right sort of flex in the proper direction.
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baidarka
Matt Master


Joined: 15 Jan 2004
Posts: 44
Location: Washington State

PostPosted: Tue Jun 15, 2004 10:11 am    Post subject: Reply with quote

http://swaylocks.com/forum/gforum.cgi?post=160028;sb=post_latest_reply;so=ASC;forum_view=forum_view_collapsed;guest=395640[url][/url]
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kage
Dolphin Glider


Joined: 12 Jan 2004
Posts: 286
Location: Santa Cruz

PostPosted: Tue Jun 15, 2004 11:03 pm    Post subject: Reply with quote

A lot of information to consider. I am probably thinking less flex than you guys. Smaller board -- 48" max, probably a little more float. I could see the front 24" having some foam though feathering out. I am also thinking several layers 3 or four on the bottom before turning it over an sanding out foam. I would like to see Solo's board I wonder if it is somewhere on Swaylocks. I will look around. I am also in love with that yellow Romanovsky paipo. I wonder how it would work with squared corners Very Happy?
I would never think about attempting something like this without the support and info from this forum and swaylocks.
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