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Urethane rails

Posted: Mon Jan 26, 2015 1:39 am
by TheJoe
Can anyone help me with which type to use and where to get it from in the USA?

Re: Urethane rails

Posted: Mon Jan 26, 2015 3:12 am
by downunder
www.Smooth-on.com

Smooth Cast 300 series (ie 310 white, or 326,327 with pigment).

But really, a pre cast PU rails is a go.

Re: Urethane rails

Posted: Tue Jan 27, 2015 3:50 pm
by wood1
Hello,
I had great succsess with" Smooth On cristal clear" that i cast into a groove in the wooden core ,
no problems with bubles and very strong bond' I attached two photos of boards in the making ,
good winds

Itai.

Re: Urethane rails

Posted: Tue Jan 27, 2015 4:38 pm
by BWD
Did you have to vacuum and heat cure the cristal clear?
I used a 300 series product and chose to live with the "tiny bubbles", creating the "champagne of rails," after my testing showed it was strong enough despite the bubbles. Bubbles may even improve flex, which might be desirable in some builds....
Just curious about others' experiences...

Re: Urethane rails

Posted: Tue Jan 27, 2015 4:55 pm
by sijandy
I use Polycraft SG2000. I find I get less (almost zero) bubbles with the fast cure stuff (2min pot life) than I do with the slow cure (8mins) but as you can imagine 2mins is not a lot of time to do anything. I'm intrigued by downunder's pre-cast rails but have yet to see any advantage (for myself) yet. No vac or heat cure required...just a big ass mess where I havn't established a decent way of pouring the rails yet.

Re: Urethane rails

Posted: Mon Jun 08, 2015 3:23 pm
by Danydan
Does the smooth cast 300 series works well with corecell as well?

Re: Urethane rails

Posted: Tue Jun 09, 2015 3:27 am
by downunder
Yes :)

How I would do it (applicable to any core):



Joining:



If thinking of pouring a PU, this is what you need to do first, full vacuum in a glass pot:




Why would I do a pre-cast rails:

From Smooth-on

http://www.smooth-on.com/tb/files/Smoot ... 1,_322.pdf

"For Best Results . . . Best results are obtained using a pressure casting technique.
After pouring the mixed compound, the entire casting assembly (mold, dam
structure, etc.) is placed in a pressure chamber and subjected to 60 PSI (4.2 kg/
cm2) air pressure for the full cure time of the material.

Post Cure - Castings will reach “full cure” faster and achieve maximum physical
properties if post cured. Allow material to cure for recommended cure time at
room temperature followed by 4 - 6 hours at 150°F/65°C. Allow casting to
come to room temperature before handling."

I've done lots of experimenting. A lot is described here, even some destructive PU testing :

http://boardbuilders-forum.1077691.n5.n ... 34i40.html

The idea of using a PU pre-cast rails is to make as many rails as possible in the shortest period of time. If not, the PU in a container will go off very soon hence waisted...

1.8kg (part A+B) of PU can make 16 boards (1/4 inches rails width).

I would never ever go back to poured rails which is a disaster for the most 1st time DIY builders (even with epoxy)...

Re: Urethane rails

Posted: Wed Jun 10, 2015 9:27 pm
by Danydan
Lots lf good info, thanks downunder... I will have to look at your links in more details before taking a decision on the best (and most cost effective) way to proceed. Cheers, Dany

Re: Urethane rails

Posted: Fri Jun 12, 2015 9:40 pm
by KerryBara
@ downunder

The channel that you routed into the bamboo isnt all the way through right? Once you have insert your precast rails, do you flip it over and shave a mm off?

Do you use epoxy to bond the rail in place? Do you do it in a bag?

I used epoxy rails on mine, dont like the look and dont think its the right material for the job

Re: Urethane rails

Posted: Mon Jun 15, 2015 1:12 pm
by downunder
KerryBara wrote:@ downunder

The channel that you routed into the bamboo isnt all the way through right?

Right.
Once you have insert your precast rails, do you flip it over and shave a mm off?

No, 5-10mins job with small router bit with bearings and Dremel.

Do you use epoxy to bond the rail in place? Do you do it in a bag?

Now using a PU glue. Yes, a quick vac bag.

I used epoxy rails on mine, dont like the look and dont think its the right material for the job.
As seen from above, a PU is a go.