Top Mold question

[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?

[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

[Buuk]

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

Buuk

[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]

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]

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]

so the top mold can be a little small but too big?

[MLReed05]

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]

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]

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?

[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