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 Post subject: Why bother with ABS rails?
PostPosted: Fri Jun 11, 2010 6:33 pm 
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HI,

This forum has been a great resource for building my firs plywood board. Now I poked around and try to learn what more sophisticated board building technology I should use for my next project.

Way back, I have build a windsurf board with glass and polyester. I have repaired windsurf boards with glass and epoxy. Never done vacuum bagging.

I looked at many topics and most (if not all) seem to use ABS or some other form of edges. Why? What makes this needed for a kite board but not for surf or windsurf boards? Why not just overlap the sides with multiple layers of glass?

Thank you for any input.

Dan


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 Post subject: Re: Why bother with ABS rails?
PostPosted: Fri Jun 11, 2010 7:39 pm 
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Location: rhode island
you should not bother with ABS rails

unless you dont know how to wrap glass rails.
or
haven't decide what rail profile to use and would like to alter it later.
or
you find it convenient or cost effective to pop top, bottom and rails in the bag/mold all at once for a quick build.

they may be a bit more durable, but i'm not really a fan.
-bill


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 Post subject: Re: Why bother with ABS rails?
PostPosted: Fri Jun 11, 2010 7:47 pm 
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Thank you! So to make sure I understand, people use the rails and laminate up on to the rails but not around them?


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 Post subject: Re: Why bother with ABS rails?
PostPosted: Fri Jun 11, 2010 9:03 pm 
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correct


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 Post subject: Re: Why bother with ABS rails?
PostPosted: Sat Jun 12, 2010 8:10 pm 
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umm, not so sure about what he says.

boards that have abs rails have way more flex. Its the same idea as a pipe of fiber will be way more stiff then two flat pieces put one above the other

i tried both and the boards with abs are:1 easier to glass both sides at the same time , more flex, better feeling and more durable.


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 Post subject: Re: Why bother with ABS rails?
PostPosted: Sun Jun 13, 2010 2:40 pm 
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swim82 wrote:
umm, not so sure about what he says.

boards that have abs rails have way more flex. Its the same idea as a pipe of fiber will be way more stiff then two flat pieces put one above the other

i tried both and the boards with abs are:1 easier to glass both sides at the same time , more flex, better feeling and more durable.



swim,
we are mostly in agreement.
if everything else is equal....
abs w/o the wrap will allow for more flex than a wrapped glass rail.

thats because the Modulus (E) of ABS is much less than fiberglass.
however, i believe you would find it easier to taylor flex by altering the glass content in the top/bottom lams or changing the overall thickness distribution of the board.
The largest contributers to strucural stiffness are E and I.
(modulus and area moment of inertia)
these values are greatest and most easily controlled at the top and bottom lams of any cross-section.

i do think ABS is more durable than glass.
but the bond to ABS is always so crappy that it easily delams, which makes repairs difficult for the non-builder.

oh well, we agreee on 2 out of 3.
no worries,
-bill


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 Post subject: Re: Why bother with ABS rails?
PostPosted: Thu Jun 17, 2010 6:29 pm 
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So now that this was explained, how would I go about with hand layup? If I want to put in a bit of rocker, I think I should do the top layer first?

How would I go about overlapping the layers around the edge? What procedure works best for a kiteboard?


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 Post subject: Re: Why bother with ABS rails?
PostPosted: Thu Jun 17, 2010 9:38 pm 
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With abs rails you don't overlap at the edges. You bond the glass to the top on bottom of the abs rail and then round off the abs after glassing. The abs is on the outside at the edge. If your going to do an overlaped fiberglass rail you can just use epoxy with some kind of filler, shape the edge then wrap it.


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 Post subject: Re: Why bother with ABS rails?
PostPosted: Thu Jun 17, 2010 10:39 pm 
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My guess is ABS was used to streamline the production process. They want to be able to make boards in the least amount of steps possible and by putting ABS rails they can do the top/bottom layers in one hit on the press (they use huge hydraulic presses not vacuum bags for production boards). So it's not so much for performance or flex as it is for ease of manufacture.

It's nice to have the extra edge protection though. Most of the heavily used boards I've seen all have nicks or dents in the rails and the ABS keeps those from become a problem with either a foam or wood core.

If you just wrap your glass around the rail, you will only have 2 layers of glass protecting the core from any impacts.

I've used fiberglass strand and resin to make solid rails on my 2 plywood boards and it's a messy pain-in-the-ass. ABS or poured thickened resin and/or urethane would be much easier and less overall work.

This years Liquid Force boards are using urethane for the rails instead of ABS:
"The new addition of Liquid Rails (poured urethane rather than ABS) has increased the durability and adds to the overall smooth ride that you get with the 2010 Liquid Force Influence. "
reference: http://www.realkiteboarding.com/index.cfm?page=newsitem&id=1671


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 Post subject: Re: Why bother with ABS rails?
PostPosted: Fri Jun 18, 2010 4:43 pm 
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daspi wrote:
How would I go about overlapping the layers around the edge? What procedure works best for a kiteboard?


it not really that big of a deal.....assuming this is not a production job and you are not trying to bag it in on shot.

one of many ways would go like this:
a rocker table will help.
otherwise a flat table with a couple of bricks to prop up the ends and some clamps to hold down the center section.
some smooth plastic sheet to act as a 'release cloth' between your board and the table and the clamps.

cut a piece of glass for the top with 1" of overlap on to the bottom.
cut darts in the corners where necessary
use masking tape to hold glass in place on bottom of board
once all is smooth, laminate with resin of choice ( epoxy or polyE)
it will be fine if you impregnate glass down to the bottom edge of board and not the bottom.
clamp board to rocker table
once "green", remove clamp, trim back all the 'nasties' with a razor then clamp until full cure.
once the top is cured, clean up lap area again.
repeat above for bottom lam.
tape off a smooth line to cut lap to once green (if you want)
cut bottom cloth to overlap top lam by approx 1 inch ( anything over 1/2" is fine)
clamp in table to reset rocker( dont forget plastic sheet this time)
let it cure (2 days) before unclamping, trim, and sand.
check some left over resin in the mixing pot to see if its suitable for sanding ( or even cured)

use good laminating procedures
prepare/plan for all the steps in advance of doing any of them.

clean surfaces
remove grease/dirt /contaminants etc with isopropyl alcohol
blow off all dust with clean air ( no oil)
weigh parts before mixing (glass/resin/ hardener)
with epoxy you should be able to lam with equal parts of resin and glass
(for epoxy ,if you are wrong you can add more later)
(for poly mix more than you need)
a small test piece is always a good place to start to iron out all the details
yes/no ?


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