build your own ski in your garage

[mack]

what happened to this thread? Did it die or ??????????

[oldjeep]

http://www.ballofspray.com/forum#/discussion/12147/the-how-to-build-a-water-ski-at-home-thread

[mack]

I guess with a new baby an all he has not had much time to work on it. Smiling....... i can remember how that was.

[MattP]

@mack‌ I brought that thread back to the top. Hopefully Adam will chime in. I'm sure the snow up his way is not too motivating right now either.

[Horton]

yeah yeah talked to adam the other day he's just busy.

[mack]

well...........he's got me motivated.............. i built a plug and a vacuum pump so far. getting ready to start work on a mold.

[AdamCord]

@mack that's awesome!! I promise I'm getting back to work! I moved everything into my heated basement so I can get this project finished.

[mack]

@AdamCord that's the same problem i have garage isn't heated and as my basement is completley finished i don't think my better half is gonna let me work on it there. i have hung a space heater and next spring i will insulate and run the gas line to heater. Do you think i can build the mold and use a hot box similar to yours in the cold temps . of southeast mich.?

[AdamCord]

@mack it can be done, it's just more tricky. You want to bring your resins inside overnight so they are room temp when you go to mix them. Also I would recommend putting the plug and your fabrics in the hot box before you start the layup. That way at least all your materials are warm when you start. Then you can put the plug/mold back into the hot box to cure. The important thing is that you can mix the resin and spread it out well. When it's cold the viscosity is too high.

[mack]

@ AdamCord Thanks Adam. I think i can get at least the Gel Coat on. I been thinking about how one might be able to do this in one infusion where both the bottom and top skins and core are infused in one operation. Also been thinking of using pre- preg. i'm perty sure that one would be able to do both top and bottom in one vacuum operation but i'm not sure if you'd get a strong bond between the inner surface of the composite and the foam core. Gheese............. then i would have to build an oven!

[AdamCord]

@mack I plan to build the ski I'm working on using resin infusion, all in one shot. When I was at Obrien we did the Elite skis that way. The difference was that was an RTM operation which means we used pressure to drive the resin into the part, so it's a bit different. That being said, lots of sandwich parts are made every day using resin infusion so I'm optimistic that this will work.

 

There are a few problems with using prepreg:

1. It's tough to get in really small quantities. It's usually sold on 50-60" wide rolls so you need a freezer that is at least that big.

2. Prepreg only carries enough resin to wet itself out, and not enough to bond to a core. So you need a prepreg adhesive layer to put between the fiber and foam. The only problem is that stuff is even harder to find in small quantities than the prepreg carbon is.

3. In order to end up with a good part using only vacuum (no autoclave or press) you need really good temperature control. Epoxy resins used in prepreg are just like any other epoxy resin except they have an extreeeemely slow cure time at low temperatures, and have extremely high viscosity at room temperature. When the epoxy is put on the fiber at the prepreg factory it doesn't saturate the fiber, it basically just sits on the surface. So you need to get the part up to a temperature where it's viscosity is low enough that it can fully saturate the fiber, but not so high that it cures before it is done flowing out. That is called "dwell", and it's where you ramp the temperature up, then hold it at a certain point (the dwell point), then ramp it up further to cure. Any hot spots and that area will cure before it saturates the fibers, any cold spots and that area won't cure or the epoxy could wick away leaving a dry spot.

 

So to recap: If you have a big freezer, a good source for prepregs, and a very big and highly controlled convection oven, then by all means use prepreg, because it's awesome to work with and you can make incredibly consistent parts. If not I'd say you're better off with an infusion type method.

 

Hope that helps!

[eleeski]

@mack‌ Prepreg isn't that hard to use. I used heater strips, a poorly insulated metal box and a Grainger thermostat to build a cheap effective oven. I bought a deep freezer (actually two - don't cut the walls out of a freezer) at the thrift shop. I found slightly out of date laminating prepreg really cheap. The adhesive prepreg was pricey and special order. I built some excellent honeycomb core skis with that setup.

 

When my adhesive prepreg got old (or I ran out), I switched to a wet adhesive (gorilla snot?) and got good results with that.

 

When I ran out of honeycomb, I switched to foam cores which did not like the heat of my oven and favored a completely wet layup (Applied Poleramic resins rock!).

 

When carbon got affordable, I switched to a carefully spot reinforced wet layup which made good use of unitdirectional stringers. A squeegee can be surprisingly effective at getting a dry layup - but it can be a bit messy.

 

My mold is an air pressure bladder squeezing the layup together at fairly low pressure with the bottom molded and the top a bit uneven to assure conformity with my desired water contact shape.

 

I end up doing a fair amount of secondary op finish work but most of the critical stuff gets molded in (until I experiment with my grinder - "insert evil laugh sound").

 

Fancy stainless steel molds in a controlled clean room might be nice. But completely unnecessary. Build something that gets by and enjoy the process. Lots to learn. Go fancy when you want to go in business (how do you make a small fortune in waterskiing? Start with a large... you've heard that before.).

 

Eric

[The_MS]

@eleeski I want to here the story about cutting the freezer walls out.

[mack]

@‌ AdamCord I am excited to see your process. A question about the construction of your foam core. You first tried lining the mold with visqueen and that process failed. then you were successful using packing tape. what kind of packing tape? How widewas the tape? i've tried to locate some real wide tape [8"] without success. Did u take like say,2" tape and butt joint within the mold then wax it? or????

 

@Eleeski my motivation is not to go into manufacturing water skis. building a slalom ski is something that has interested me for many years but never had the time to try. Being recently retired, i now have ...the time to try some of the things I am passionate about. Water skiing being one of those. I've always been somewhat of a DIY sort of person so this project lends itself to my personality perfectly. I think the learning process of doing this has the potential to improve my skiing which in itself will be rewarding. Also the process of creating something useful out of nothing [parts] has got to be,at least for me, one of the most rewarding things a person can experience.

[mack]

@Eleeski I expect to enjoy each and every step of this process. Laughing,I understand that evil grin that a grinder can bring to a person. An old freezer sounds like a relatively cheap and easy way to make an oven.

[AdamCord]

@mack I just used cheap 2" packing tape. It still wrinkled a little but by the time you sand the surface of the core to prep it for bonding the wrinkles are gone. I didn't use any wax because the foam doesn't stick to it.

 

If you want to use prepreg the best thing to do might be to build the ski in parts. That way you can get a better bond to the core and not have to worry about what the foam will do when heated. You can basically vacuum bag and cure the bottom skin and top skin separately and then use standard epoxy to glue them to the core.

 

There are lots of ways to build a ski!

[eleeski]

@MS‌ Can't the mistakes of decades ago quietly fade? At least used freezers were cheap. And we didn't have to pay a disposal fee then. I did destroy some ozone. Grinder abuse started a long time ago.

Eric

[The_MS]

Sometime I need to fly out and buy some of those good San Diego IPAs, get to your place and watch you make skis for awhile.

[eleeski]

IPAs make the building more fun. Might not improve the end result. Texture is an art requiring skill and concentration.

Absolutely come visit! 60 water, 80 air and great skiing at the desert lake last weekend. I wonder if we will have a winter this year.

Eric

[The_MS]

The IPAs may make it easier to ride one of those skis also. I wont see water til March but If I can get out west I will be @Snowbird.

[mack]

@AdamCord Ok, Got my plug mounted to parting board, all painted polished and waxed. built a hot box,8 ft. long 12" high 18" wide open ends. used two little [cheap] space heater on each end. with 20 degrees in my garage and the hot box fired up I was able to maintain 110 degrees inside the box with both heaters running. With one running , I got 85 on one end and and a hair over 90 on the other. i thought that was good nuff to place the gel coat on the plug. It's curing as i type. hopefully it'll work out. let you know in a while. Got my fingers crossed. I used clay to fill any gaps between the plug and the parting board. seems like sanding all that bondo would be a PITA. I hope the clay works as advertised.

 

[AdamCord]

@mack nice work!