Kampai Custom

gav wa · Post by **gav wa** » Thu Jun 05, 2014 4:49 am

A 16 inch bladder, now that would be cool, and probably makes life a bit easier too eh.

I was actually toying with the idea today of making a large bladder myself. some fiberglass and maybe silicone or something tougher. Would obviously need to hydrostatic test it after its finished but that is easy. Oh well, back of the list for now - behind some more boards, fixing the girlfriends car, finishing the cubby house for her daughter, building the electric scooter esky etc etc.

back to the sandboard,
I built this mainly so I had something I could test over here and therefore see if what I was putting together was actually working right or was unreliable.
I didn't want to make a few boards only to find out in a couple of months time when I actually get to put them on snow that they all fall apart.
To be able to test all parts of a build I therefore had to make it more like a small snowboard than a proper sandboard.
You can ride a real snowboard on sand dunes so it will still work, but normally it wouldn't have steel edges and although Ptex can and has been used as a base, normally the base is just Formica or hardwood. Most sandboards look very much like an over sized skateboard deck.

I will post some pics later today. I had some issues but these were good lessons learnt and you learn more from mistakes than you do from things going perfect.

chrismp · Post by **chrismp** » Thu Jun 05, 2014 5:46 am

@knightsofnii: where did you get that 16" bladder?

@gav wa: how did you plan on constructing the seam in a dyi bladder?

gav wa · Post by **gav wa** » Thu Jun 05, 2014 6:42 am

Chrismp - I hadn't actually planned on much at all, it was just some day dreaming while I was at work.
Maybe when laying out whatever resin is used a few inches along each side of the glass could be left free of resin. Then when the main part has set, overlap the two edges and pour resin into this section.

Does a bladder that big even need a top mold?
If not your seem could be clamped together along the top inside your press, that way you could use any material you could find that will take the pressure.

Hydro testing at such low pressure is easy, your garden hose will be between 650-1000 kpa so you have a pressurized water supply ready.

chrismp · Post by **chrismp** » Thu Jun 05, 2014 11:45 am

I've been thinking about this quite a lot recently. Clamping the seam came to my mind as well, but how do you close the ends if you clamp the whole seam?

I'm currently looking into adhesives for nylon as I think cordura would be the best fabric to build a bladder. I might just build a sample bladder with the Adiprene resin I have if the silicone hose (see: http://www.skibuilders.com/phpBB2/viewtopic.php?t=4686) doesn't work out.

gav wa · Post by **gav wa** » Thu Jun 05, 2014 2:42 pm

Ii have a couple of ideas for the three seems (the top and the two ends) but they are hard to discribe. I have some sheets of 1.6mm rubber at work, I might try a test bladder too. If I can get it to work without a top mold that would save heaps of time retooling the press for different shapes. No more pulling it all out to change top mold.

gav wa · Post by **gav wa** » Thu Jun 05, 2014 3:43 pm

I think your idea of using vinyl is a good one. Can get a poly vinyl sheet cheap as that is very flexible but also pretty tough.
Another job for the weekend

SleepingAwake · Post by **SleepingAwake** » Thu Jun 05, 2014 11:24 pm

I have been thinking about a DIY bladder as well.

What if you take a heavy duty pond foil and roll it up to have a double layer. then you glue that together with silicon or even better, weld it together like they do for the biotopes.

It just has to be air tight, and once it gets inflated and the foil presses against the mold and top mold friction should prevent it from blowing up

chrismp · Post by **chrismp** » Thu Jun 05, 2014 11:30 pm

I've done a sample bladder with PVC fabric. I welded the seam with a hot air gun and a roller about 50mm wide. Burst open at the seam at very little pressure. My skills with PVC welding could be better though. I might give it another try with some Tetrahydrofurane and make wider seam.

Dtrain · Post by **Dtrain** » Fri Jun 06, 2014 7:23 am

So....I work as a firefighter, and was flipping through catalogues at work and found a Canadian company that makes 12 inch double polyester jacket firehose. When laying flat it is 19.5 inches wide. Rated to 400 psi. I'm about to create and account with them and get the prices.

There may be a 50ft minimum

If the price is right , I would be looking for 4-5 people to buy a length.

The silicone stuff sounds rad Chris, but your like a million miles away from me. Keep us posted though

vinman · Post by **vinman** » Fri Jun 06, 2014 8:54 am

No idea on price but I found this

http://www.hosecraftusa.com/model/UD4_T ... ingLayflat

Up to 12" diameter. 200 psi and 170 deg F tolerance.

The 170 would be fine for me with a wooden cat track, could be close for some with aluminum cat and cassettes.

knightsofnii · Post by **knightsofnii** » Fri Jun 06, 2014 10:11 am

chrismp wrote:@knightsofnii: where did you get that 16" bladder?

@gav wa: how did you plan on constructing the seam in a dyi bladder?

i just posted where i think it can be obtained elsewhere on the site.

skidesmond · Post by **skidesmond** » Fri Jun 06, 2014 3:19 pm

vinman wrote:No idea on price but I found this

http://www.hosecraftusa.com/model/UD4_T ... ingLayflat

Up to 12" diameter. 200 psi and 170 deg F tolerance.

The 170 would be fine for me with a wooden cat track, could be close for some with aluminum cat and cassettes.

I think that's where I bought my hose from. Min order is 50ft now. I bought 25ft a few years ago. Prices must have gone up a lot, 50ft of 8inch PD2 PVC HEAVY DUTY LAFLAT DISCHARGE HOSE is $950 US!! I thought I paid around $300 for 25ft.

gav wa · Post by **gav wa** » Fri Jun 06, 2014 4:34 pm

Im going to try for a 14 inch bladder without a top mold or cat track. Without a cat track I can shorten the tip sections of the bottom mold so the rise and lower that the bladder has to conform to is not too much. This way I can use two strips of steel to clamp the top of the bladder as a seal. 25 x 3mm steel will allow it to flex at the ends so the end is still easy to clamp.
Off to the steel merchant now. Ill be back later

vinman · Post by **vinman** » Fri Jun 06, 2014 5:39 pm

Capital rubber has 8" reinforced discharge hose. Back a few years ago I bought 10 ft for like $60 plus shipping I think.

chrismp · Post by **chrismp** » Sat Jun 07, 2014 12:35 am

I know a supplier that has 14" TPU hose, but thats still too small the way i planned it. I want the hose to press at 45cm width and make up for the space of the topmold (about 10cm). For this I need a 16" hose.

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