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First (wake)board build

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downunder
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Re: First (wake)board build

Postby downunder » Wed Dec 21, 2016 1:25 pm

No worries. The oven will work, just be careful.

If you like, here is my silicone blanket build:

http://boardbuilders-forum.1077691.n5.n ... d1064.html

Take a note of calculation since I've made a stupid but not fatal error...

Thinking to build a small piece for my HF build.

D.

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Re: First (wake)board build

Postby skriever » Sat Dec 31, 2016 3:04 pm

Pretty cool downunder :)

I glassed the top of my board. I'm letting it sit for a while even though the epoxy is cured 24 hours. I'm gonna take it out next year ;)
The oven was set to 25 degrees Celsius with a bandwidth of approximately 2 degrees. The vacuum gauge pressure was 96 kPa and as low as 90 kPa during off times of the pump (15 minutes, for cooling down the pump).

Image

I am very sceptical of having a good result since I think I will have some dry spots :(. I think that the bag was not able to pull an even vacuum. Using a bleeder+breather (to get an even vacuum) was not an option for me since I got poor results with it during the test phase.

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Re: First (wake)board build

Postby downunder » Sat Dec 31, 2016 3:58 pm

Thanks skri

huh, this might produce epoxy wrinkles on every wrinkled bag spot, unfortunately (I think).
See, the vac bag wrinkles are not a problem at all, in fact, we need to use heaps of excess vac bag for the bridging (ie step down in a board, like rails, etc). BUT, for that you need to use ble+bre+peel ply and the board will end up perfect. A bag with no wrinkles is not a good vac baging technique, btw.

Testing on a small pieces are nothing comparing to the real thing. So, this is your test. Not to worry, what you can do is take a scalpel knife and cut (scrape) the wrinkles off, like totally. Sand lightly your board, wet sand only. 300 grits and up.
Than 'hot coat' the board with thinned epoxy using a PX ( xylene). Mix PX 10% with hardener only, not with a resin. I use a disposable foam brush.
Thinned epoxy will fill all voids after sanding and scraping, and might be perfect. In a real life, you need a lot of elbow grease and experience, so take with a bit of salt.
Also, it is imperative to glass the bottom asap after taking it out from a bag. Trust me on that.

Good luck and happy New Year!

D.

PS
Now I see how you've clamped your board. This will imprint on the board as well. Use the same technique from the above to fix.

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Re: First (wake)board build

Postby max » Sun Jan 01, 2017 4:14 am

downunder wrote:Thanks skri

Than 'hot coat' the board with thinned epoxy using a PX ( xylene). Mix PX 10% with hardener only, not with a resin. I use a disposable foam brush.


Also, it is imperative to glass the bottom asap after taking it out from a bag. Trust me on that.

hey Downunder . . .

can I ask a couple of questions:

Do you mix the 10% xylene with the hardener first and then mix up the batch of resin/hardener in the ratio that is normally required if the xylene was not getting used?

What consequences were there for not glassing the bottom right away . . . does the board lose rocker? does it twist?

Cheers

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Re: First (wake)board build

Postby downunder » Sun Jan 01, 2017 7:16 am

Hey

Up to 10% (or more, test your epoxy, I do 15-20%), for a total amount of mixed resin and hardener ( ie. the amount with no PX), thinning the hardener first. Than mix everything as you would. And work fast. Do not overwork with a brush. This is almost an art.

It might twist and distort or completely loose the concave (or make it heaps bigger). It all depends on humidity/temp.

Hope this helps.

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Re: First (wake)board build

Postby max » Sun Jan 01, 2017 10:18 am

downunder wrote:Hey

Up to 10% (or more, test your epoxy, I do 15-20%), for a total amount of mixed resin and hardener ( ie. the amount with no PX), thinning the hardener first. Than mix everything as you would. And work fast. Do not overwork with a brush. This is almost an art.

It might twist and distort or completely loose the concave (or make it heaps bigger). It all depends on humidity/temp.

Hope this helps.

Cool thanks.

I use West System epoxy so will do a few tests tomorrow.

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Re: First (wake)board build

Postby skriever » Wed Jan 04, 2017 5:05 pm

downunder wrote: huh, this might produce epoxy wrinkles on every wrinkled bag spot, unfortunately (I think).
See, the vac bag wrinkles are not a problem at all, in fact, we need to use heaps of excess vac bag for the bridging (ie step down in a board, like rails, etc). BUT, for that you need to use ble+bre+peel ply and the board will end up perfect. A bag with no wrinkles is not a good vac baging technique, btw.
The epoxy wrinkels, casued by wrinkled vacuumbag, are removed when pulling of the peel ply.

Image

Good news:
- I ended up with a rocker of 6.2 cm.

Bad News:
- It seems as if the glass fabric buckled locally in the regions around the inserts (hard to see on photo's). Probably because I first applied vacuum and then applied a pre-rocker of 13.0 cm putting the fiber yarns under compression :( .
- I have some dry spots. (did not used bleeder+breather)
- The edges look a little bit messy at some spots.

I do my best finishing the board and get the best result as possible. Because there is no way that I am not gonna ride this board at least once ;)
downunder wrote: Than 'hot coat' the board with thinned epoxy using a PX ( xylene). Mix PX 10% with hardener only, not with a resin. I use a disposable foam brush.
Great tip on hot coating the top using PX. I also have a nylon topsheet laying around, but this might be a bit excessive for this build.

PS. I did not see any elegant way of using bleeder+breather for this build because I would have needed to add a huge amount of resin. A resin infusion approach would have been a possible solution.
PPS. A press would have been a good choise as well I think. However, I do not understand how air pockets in the layup would have had the chance to escape when using a press.

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Re: First (wake)board build

Postby downunder » Thu Jan 05, 2017 2:50 am

Ah,

ok, got it. I did not see a peel ply. Either way, the buckled FG you might fix with the same method. Wrinkled FG has no strength, removed or not it is the same. Hot coat not only the top.

There is a general view that a vac is used to remove the epoxy excess. I my opinion, not all true. We need to build a significant epoxy layer on top of vacuumed FG to protect it from abrasion. Or we can use a topsheet (not easy to obtain and apply). Hence, I 'hot coat' my boards multiple times and getting better and better each time. If I do not do that, the sand will abrade a FG in no time, leaving the door open for moisture.

Not sure about the PS1 :) I use extremely small amount of epoxy (comparing to a foam build), very rarely got any dry spots. Your build is even more 'elegant' for that coz there are no bridging (like I did with 2 wood layers boards). Epoxy infusion yes, but than glassing both sides at once. Not a fan. Too many things can go wrong. For a foam yes, for a wood, not the best.

PS2 Easy. They don't. Well, not all of them.

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Re: First (wake)board build

Postby skriever » Sat Jan 14, 2017 11:06 am

Oke, the ptex base is now added to the board. First, I put the ptex+glass+peelply in the vacuum bag. I then peeled of the peelply to get a rough surface. I then added the ptex+glass to the bottom of the board, using a decent amount of epoxy, and put the whole board in the bag again to apply some pressure.

I think I messed up a little bit. The idea was to let the ptex+glass+peelply cure but not fully harden. That way I could get a nice bond to the bottom of the board by applying some more epoxy and firmly press the ptex+glass to the core using a roller tool. However, I feel like I waited to long since the ptex+glass layer way allready fully cured. The base now feels a bit bumpy locally. Not sure, if that is the reason. I applied some heat as well which might caused the ptex to build up some stresses, not sure.

The bumpiness is not my biggest consern, it will wear flat eventually. I can clearly see some air trapped underneath the ptex layer which is pretty shitty. Not much I can do about that I guess. I will post a picture once I cleaned up the edges. Also, I still need to add a top layer. Maybe I will just go for a clear coat of epoxy since I don't want to invest more money in this build since it is not perfect anyway ;).

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Re: First (wake)board build

Postby skriever » Tue Apr 04, 2017 3:43 pm

Whoops. I promised some final pictures/info. Here they are.

Image

Image

Image

The board has an average bending stiffness per unit width of 1860 Nm which is in the neigherhood of the anticipated 1919 Nm. Or in terms of "flex"; the board deflects under my own weight (92.7 kg, he look at that I didn't gain any weight since then :D ) by:

Spanlength (deflection) *Bending stiffness per unit width*
80 cm (11 mm) *2151 Nm*
90 cm (20 mm) *1743 Nm*
100 cm (26.5 mm) *1684 Nm*

The board weights 4500 grams (without the bindings) which is 500 grams more than anticipated. I didn't account for the extra layers of resin which I used for bonding the p-tex layer and the top coat in my calculations.

My mistake was perhaps the usage of a 830 g/m² glass layup which didn't impregnate as good as I hoped. I intend to improve the quality of my boards by doing more testing and upgrading my gear in the future. But first I am gonna travel for a while and (hopefully) do lots of kiteboarding.

I'll be back 8)


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