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 Post subject: Re: Urethane rails?
PostPosted: Mon Jun 28, 2010 2:42 am 
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Just ordered some from smooth on. The high density PU plastic and some silicone mold to make up fin molds. Thinking about trying PU twintip fins. Maybe with carbon tow mixed in.


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 Post subject: Re: Urethane rails?
PostPosted: Mon Jan 30, 2012 3:44 pm 
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Just a follow up on Urethane rails, looks like Lib-Tech is using them in their new surfboard line:

http://business.transworld.net/85257/features/lib-tech-cofounder-mike-olson-on-new-surf-line/

Not positive that's what they are using, but it would make sense, especially carrying it over from the snowboard tech.


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 Post subject: Re: Urethane rails?
PostPosted: Mon Jan 30, 2012 8:32 pm 
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Built one with the urethane rails last summer. Mix in small batches as it kicks fast. Also it would work better if you vacuum degas it. Nice and flexible continuous rail that shaped nice. Real itchy fibers so use care when sanding.


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 Post subject: Re: Urethane rails?
PostPosted: Thu Feb 02, 2012 4:29 am 
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gbleck, very cool, thanks for the feedback!
Got any pics?
How did the resin adhere to the urethane?

I snapped my homemade plywood board a few months ago, so I'm planning on building another one. I really want to try urethane rails on it, and there is very little info to be found.


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 Post subject: Re: Urethane rails?
PostPosted: Thu Feb 02, 2012 6:41 pm 
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I'll see if I can find the build pics at home tonight.


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 Post subject: Re: Urethane rails?
PostPosted: Thu Feb 02, 2012 7:07 pm 
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I have been casting kiteboard rails with PU for over 7 years and never had a board or rail fail yet.
I have kept my process real quiet so the big bully boy companies don't steal the ideas that I have built up but now I am I will share some of it with you :-)

The stuff I use rated Shore 90 and cures in 5 mins with a white cured finish.

Process.
I make up an outline router template, this needs to be13mm smaller that the finished outline + rail.
Turn the bottom of the board so that is facing downwards.
Lay the template onto the corecell and position, using 2 small felt rooming names through the foot strap position marking points to secure to the corecell.
Set up the router with a 12.5mm bit and set the depth to that of the finished rail, for me this is 4 mm ish.
Route around the template leaving one continuous trench.
Place wide masking tape on the board side of the rail, keep it real close to the rail, this is to catch any overspill and make it easier to clean off later.

Now make sure the corecell is on a 100% level surface with some weight on it to hold flat.
Pour the PU into the trench and make sure you overfill the trench as PU shrinks.

The good bit here is that the PU gets into the open cells created around the trench as it was cut into the slot, the PU gets into these and locks solid to the core.

Once the Pu has fully cured, about 10 mins for the stuff i use, take a new Stanley knife blade and using it as a scraper flatten the overfill/overspill PU until its flat with the surface and remove the protective tape.

Cut around the outside of the cured PU rail and remove the unneeded corecel and you are left with outlined core blank with rail attached.

Turn the board over and shape the top down to the rail and then the to the tips,
Now fit the inserts and route some holes for the fin blocks and using the same PU set them in place.

TOP TIP - before you laminate over the core, take some thin "pin striping" tape the same width as your rail thickness and put it around the outside of the PU rail.
TOP TIP - Make this tape as bright as you can horrid lumi green works a treat, the purpose is to make it much easier to locate the rail when you are cutting or grinding the flash of the finished board. The tape help you identify if you going too deep or are a long way off the rail :-)

Hope this help you guys out?

Unfortunately for me I can't build boards anymore or go Kitesurfing, the sports of Wakeboarding and Kitesurfing that I love so much has f00ked my knees, so why not share a little :-)

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 Post subject: Re: Urethane rails?
PostPosted: Thu Feb 02, 2012 10:39 pm 
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Location: Teahupo'o, Tahiti
With a shore hardness of 90 what could you compare it to in the real world. A roller skate wheel? Can you dig your finger nail into it? Did you de-gas your pots or would they go off to quickly?


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 Post subject: Re: Urethane rails?
PostPosted: Thu Feb 02, 2012 11:40 pm 
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JMF wrote:
With a shore hardness of 90 what could you compare it to in the real world. A roller skate wheel? Can you dig your finger nail into it? Did you de-gas your pots or would they go off to quickly?


I am not sure is roller skate wheels use the same scale.

Basically if you are going to give the PU system a go, you should be looking at a shore hardness of 90 ish, lesser the number softer the cured results.
FYI, I have never added any micro fibres to my mixes and as yet had no cracking or failures.

Give it a try, its a revolution for speeding up production.

Forgot to say Make sure you scuff the PU with 40 grit before laminating the skins on.

Degassing not really needed and I dont do it myself, my Pu is as thin a condensed milk and flows without any major bubble issues.

My PU starts to go off in 60 seconds so its a bloomin rush getting it poured but not too bad, no failures yet but with such a quick time you need not really mix in small batches.

Forgot to say, no you cant dig your nails into it, its hard but retain a little flexability over length especially in 4mm x 12.5mm thicknesses.


Last edited by XSwind on Sun Feb 05, 2012 10:56 am, edited 1 time in total.

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 Post subject: Re: Urethane rails?
PostPosted: Fri Feb 03, 2012 7:13 am 
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Joined: Mon Sep 02, 2002 1:00 am
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Location: Teahupo'o, Tahiti
XSwind wrote:
JMF wrote:
With a shore hardness of 90 what could you compare it to in the real world. A roller skate wheel? Can you dig your finger nail into it? Did you de-gas your pots or would they go off to quickly?


Yup roller skate wheels use the same scale.
Basically if you are going to give the PU system a go, you should be looking at a shore hardness of 90 ish, lesser the number softer the cured results.
FYI, I have never added any micro fibres to my mixes and as yet had no cracking or failures.

Give it a try, its a revolution for speeding up production.

Forgot to say Make sure you scuff the PU with 40 grit before laminating the skins on.

Degassing not really needed and I dont do it myself, my Pu is as thin a condensed milk and flows without any major bubble issues.

My PU starts to go off in 60 seconds so its a bloomin rush getting it poured but not too bad, no failures yet but with such a quick time you need not really mix in small batches.

Forgot to say, no you cant dig your nails into it, its hard but retain a little flexability over length especially in 4mm x 12.5mm thicknesses.


I also only used poured rail method couldn't be bothered with gluing ABS to much effort. I used plain old epoxy without fibers for my rails. I was always a bit wary of adding any type of chopped fiber to my pots, theory being that it would make rails to brittle.


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 Post subject: Re: Urethane rails?
PostPosted: Sat Feb 04, 2012 7:20 am 
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That looks awesome! Thanks for the details. I'm about to start my first board. Can you give more details about how you handled the inserts? Also, I was thinking about a balsa core. Any thoughts, do you prefer foam?

Thanks in advance

Dan


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