Top Mold question

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AndrewT
Posts: 17
Joined: Tue Jul 12, 2005 8:38 pm

Top Mold question

Post by AndrewT »

I know the top mold doesn't need to be exactly fitted because the bladder will compensate for it. How much difference can there be though? If I make a press I'll make an adjustable one and I'd rather not make a different top mold for every different size of ski.

Would a top mold made for say a 170 ski still work for a 165 or 175?
Go skiing
AndrewT
Posts: 17
Joined: Tue Jul 12, 2005 8:38 pm

Post by AndrewT »

ok and I would also like to ask another question. I'll just ask it here rather than starting a new thread. Does the fire hose need to be wider than the ski because 5" is the biggest I can find and that certainly isn't gonna be wide enough for some of the skis I want to make
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Buuk
Posts: 150
Joined: Wed Apr 26, 2006 2:49 am
Location: The Netherlands

Post by Buuk »

Why not use two firehoses as is done in the 'how to' section of this site.

Buuk
cliffhuckster
Posts: 3
Joined: Fri Jun 09, 2006 7:53 pm
Location: Bellingham, Washington

Post by cliffhuckster »

you could use two firehoses, but you shouldnt need to. i have yet to build my own skis, but i have talked to a guy that builds snowboards. he uses 2 fire hoses lade next to eachother. the only firehose i've seen is 5 inches when its fully inflated (the hose is a circle). the firehose lays 8-9 inches when flat. this snowboad friend of mine says he leaves enough room between the molds so that the firehose has about 1.5-2 inches of clearence before he inflates it. if you want to build a pair of skis at the same time, then 2 firehoses is the way to go i think. 1 firehose should be good enough if your pressing one ski at a time unless your making some sort of reverse sidecut mega-fat ski.
MLReed05
Posts: 82
Joined: Sat Jun 10, 2006 5:12 pm
Location: Western MA

Re: Top Mold question

Post by MLReed05 »

AndrewT wrote:I know the top mold doesn't need to be exactly fitted because the bladder will compensate for it. How much difference can there be though? If I make a press I'll make an adjustable one and I'd rather not make a different top mold for every different size of ski.

Would a top mold made for say a 170 ski still work for a 165 or 175?
Should be fine. The negative isn't critical.
team08
Posts: 55
Joined: Thu Nov 10, 2005 3:34 pm

Post by team08 »

Should be fine. The negative isn't critical.
This is only true if you are only using a hose that covers the entire ski (and you are POSITIVE that it is covering the whole ski). If you have a distribution layer (ie cat track) the negative is extremely critical for even pressure.
AndrewT
Posts: 17
Joined: Tue Jul 12, 2005 8:38 pm

Post by AndrewT »

so the top mold can be a little small but too big?
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MLReed05
Posts: 82
Joined: Sat Jun 10, 2006 5:12 pm
Location: Western MA

Post by MLReed05 »

team08 wrote:
Should be fine. The negative isn't critical.
This is only true if you are only using a hose that covers the entire ski (and you are POSITIVE that it is covering the whole ski). If you have a distribution layer (ie cat track) the negative is extremely critical for even pressure.
Yeah thats a good point. My ski was completely coverd with hose so my negative didnt matter too much. I did a rush job on it and the one ski I have done so far came out fine
Greg
Posts: 225
Joined: Thu May 26, 2005 11:41 am
Location: Sweden but home is NW Washington

Post by Greg »

I have used the same top mold for a pair of 180cm skis and 205 cm skis. For the longer skis I added extra filler on one end, but I haven't really seen any detrimental effects of not having a totally flat bladder. The only critical part is that the bladder completely contacts the ski's top surface.
AndrewT
Posts: 17
Joined: Tue Jul 12, 2005 8:38 pm

Post by AndrewT »

ok so it's 9 inches laid flat and 5 inches when it's filled. When it's in the press it's about 7 inches then?
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G-man
Posts: 600
Joined: Sat Mar 25, 2006 3:58 pm
Location: northern sierra nevada

Post by G-man »

Hi Andrew,

I'll chime in here. Yes, if you have about 2 inches of space between your top and bottom molds, an inflated 5 inch fire hose bladder has a surface contact area of about 6 1/2 to 7 inches. I also throw in two 8 inch wide layers of 1/8 inch masonite (smooth sides down) between the ski lay-up and the bladder. I used to use an HDPE pressing layer, but it didn't hold up to the heat very well... warped pretty badly. The masonite works well for me. The masonite also helps to insulate the fire hose from the heat of a heated press. My fire hose is only rated to 122F or 50C. A bladder pressure of 50 PSI is a lot of pressure (KA-BOOM), so, I think it's worth while to pay attention to those fire hose temperature limits. Hose-man, what's your take on it?

G-man
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