Today we pressed our first skis. We have run into a lot of problems along the way, but all of our layup went well....except the epoxy. We are using QCM EHV-0050 resin and QCM ECA-315 hardener. We heated the resin up by putting the whole container in some warm water (fresh off the stove, pretty hot.) We mixed up 500 grams of resin with 100 grams of hardener for each ski, but after approximately 5 minutes, the epoxy cured within seconds. One second it was totally liquid, the next it was completely hardened. It turned an orange/brown color and got so hot it melted our gloves, brushes, plastic containers and pretty much anything in its path. Interestingly enough, it didnt heat up once spread out (the skis didnt heat up). If anyone knows anything about this particular resin-hardener combo I would greatly appreciate your insight. I am pretty sure that we heated the resin up too much and mixed too large of a batch. I am also unclear about the mix ratio. QCM recomended this epoxy for ski/snowboard building because it is very stong and cures fast at room temperature. Unfortunatley QCM also told us to mix a 4:1ratio (and also sent us 1 gal. resin and 1 qt. hardener) but the product information sheets say to use a 5:1 ratio. What will varying the ratios change? Thanks for your help.
:: View topic - epoxy madness
A couple of things:
1.) I would heat the epoxy in a water bath with hot tap water. Water off the stove may be too hot.
2.) Your batches are too big. The epoxy reaction is exothermic, meaning it generates heat as it cures. Big batches in a container will generate a lot of heat and cause it to cure really fast, which generates more heat. Spreading it out does not allow the epoxy to build up as much heat. We are using a slower resin combo, but we only mix 200gms in one container. You may need to make even smaller batches if your epoxy is really fast to begin with.
QCMs website says 5:1 ratio, but I would call them and double check. Also, the harder/ resin amounts almost never match up, so you'll usually end up with more of one than the other. It's hard to predict what will happen if you vary the ratio. Most of the time, it just won't cure.
-kelvin
The first time is always the worst. But here is some help.
I use the same resin (ehv-0050) and hardener (eca-315) and I have found that it works great. I think your problem was that you warmed the epoxy and hardener up too much. I mix mine at room temperature (about 68 F) and I get about 15 to 20 minutes working time before it starts to gel. Then, it cures in about 3 hours with heat (about 100 F) in the press. Without heat, it takes around 6-8 hours at room temperature to cure to where it is workable.
The rapid heating you experienced is pretty common with epoxy. It hits critical mass, then like a nuclear reactor, kaboom. Once my dad was epoxying on a warm day and the epoxy started curing in about 1 minute, then it caught the plastic mixing container on fire and was solid within a couple minutes. With my setup, I use fiberglass as tip spacers, and this makes for a lot of epoxy at the tip and tail of the ski. When the epoxy squeezes out of the tips, it forms large pools that get really hot like you experienced.
I just finished up my third pair of skis using this epoxy setup and have had really good luck to date, so if you have any more questions about it, feel free to ask.
Whoa! Be careful there when epoxy overheats like that and starts eating itself it can generate some very toxic fumes.
Do _not_ heat your epoxy in the pot. The manufacturer of any epoxy will tell you what the pot life is at a certain room temperature and a certain volume. Usually about 77F and something around 100g. Mix your epoxy and hold the pot close to that temp. Dont artificially heat or cool it. Once you have your skis laid up, then press them, and _then_ apply heat. Adding heat to any epoxy will always make it cure faster, but of course you dont want it to cure until youve got it where you want it. I usually mix 600g of resin with 150g of hardener at a temp of around 68-70F. I keep it all in one pot and layup a snowboard and get it under pressure in about 25 min. I usually end up with about a half inch left in the bottom of my mixing cup (a 1qt cup) which finally hardens after about 40 min. This is for an epoxy with a pot life of 25 min, 105g @ 77F. If I left all 750g of mixed epoxy in the pot at 68-70F then Id expect it to catch on fire in under 20min. Your mileage will vary, of course, depending on the specific epoxy you use. The main point is to remember that cure rate is a function of volume, external heat, and epoxy formulation. You can prevent any epoxy from curing or make any epoxy cure amazingly fast (or catch on fire) by varying any of those enough. The key is to stay close to what the manufacturer recommends for your formulation so you achieve a final product with good physical properties.
Hi,
Do you know where I could find carbonfibre in Europe ?
Thanks a lot
Cheers
Hi Davide,
Thanks a lot for the info.
I am trying to build my first pair of skis.
A+
Hey, I found this site from another forum, and let me first say I'm most impressed with the skis you all build, especially the ultra-fat reverse sidecut/camber powder monsters. I've read the construction process over several times, and was wondering if anyone's considered any radically different construction techniques. I know this process is pretty much down to a science among hobbyists and niche ski producers, but what other ways can skis be built?
This page was of particular interest to me. The skis are sort of a throwback to the early days of wooden skis, except with shape of modern skis. According to the text, all the skis listed are crafted out of solid wood, no laminate construction at all. They seem to have a regular plastic base and either regular edges or lignostone edges. It's an interesting idea, but would they actually ski? Assuming that a solid core didn't warp or do anything strange during the construction, would it hold up? Could a completley exposed wood surface like that stand any chance of surviving even one outing of real skiing?
Onto my next question, has anyone actually made skis using just a clamp press? I'd really like to try my hand at making skis sometime, and have access to all the necesarry tools, but don't have the space or equipment to build a pneumatic press. I understand that setting up the skis and creating a quality product would be much more different, but is it possible? I figure that a top mold held down with threaded bolts tightened to a uniform pressure would have a decent chance of being able to apply uniform pressure.
A quick design question going along with the press question, would a zero camber ski make working with a clamp press easier? I would want to build some sort of powder ski, and I noticed that several of your fatties are built with no camber. I would think that this would make it much easier to build a clamp press, because aside from the variations in thickness from the core profile the only curve you'd have to worry about would be the tip. Is there some truth to my assumptions or am I completley clueless here?
Sorry for making you read through all this, and I appreciate any insights you may have.
If just space is the problem making you think about clamp presses and zero camber i would recommend to think about vaccum bagging. I pressed my ski in the kitchen with about 2,5m *1,5 workspace using a mold for just one ski and a vaccum bag.
I think a solid wood skis could be quite nice to ski. This company (www.skis-bois-tardy.com) is making skis only with laminated wood, and I read they work quite nicely (just unstable at very high speed, in piste).
I have in mind to make wood skis also.
In my opinion, the only problem is that a narrow wood ski has to be thicker (up to 20/25mm in the center) than a composite one, to have the same stiffness, so it gets more fragile when it is bent.
But if you make a wide ski, then you can decrease the thickness (maybe down to 18/20mm) and have the same stiffness than a composite one.
A friend of mine made two pairs of skis with a clamp press: it can work. There is somebody else on the forum that is doing the same. If you look around you can found some pictures. Maybe ask him for advice on the press design.
Heres a new one for you. Think comp-sand. Have a look at this link. This is a very long thread on this site, but worth the read just for the simple ideas/tech you can develop. Look for the stuff by Bert_Burger. Hes the one putting the ideas out here.
It is surfboard related, but think about the possibility of making the cores using this tech. It would be possible to build the core with the camber built in. It may seem a bit more complex, but if done right has some really possibilities. The only big tools you really need would be the vacuum press and a way to cut out the final ski. Bert starts this out with some very low tech ideas/tools i.e. a vacuum cleaner, plastic sheeting and masking tape. Also substitute wood veneer and ABS/UHMWPE for divynacell(sp?) for our use.
I plan to try this with some skateboards and snowboards first. If I like the result its on to skis.
Hafte
check out grafsnowboards.com, they designed a pretty decent clamp press to start out. They created some simple molds, which can probably be used later if you upgrade to a pneumatic press. They clamped their molds together with allthread.
I would like to point out that I designed a clamp press to laminate my cores and its a little tricky beacause the high pressure spots near the threads pull the washers through the wood, and when threre is uneven pressure the wood will crack...
all in all, i think this is a good and cheap way to start, then once you get the technique and the time, upgrade to a vacuum or pneumatic press.
i think the effort and time to make a clamp press would be much more than a vacuum press. and with a vacuum press it's more likely to get better results.
vacuum presses don't have to be very expensive either. i just a vacuum pump for $30 on ebay.
Most of the reason I'd like to try a zero camber ski is ease of construction. Without any camber creating the bottom mold would be a breeze, as it would only be necesarry to cut curves for the tip and tail. It is true that creating a clamp press might be rather difficult for making multiple pairs of skis with different cambers, I think it would be pretty easy for a no camber ski, and could be a good starting point without getting too commited to making skis.
Vacuum presses do look pretty easy to build, and I think a vacuum press would be a logical progression from a simple clamp press.
I think that if your heart is set on a clamp press, then your going to have to try a clamp press. The number one thing with any of this stuff is to do what you want. That is why we all read these forums, because we want to do our own thing.
How about combining the fire hose concept with the clamp press? Instead of using a super accurate top mold, why not replace the top mold with inflated fire hose, with a solid surface above the hose? Put a pressure gage on the hose and clamp down the surface above the hose until you are reading the pressure that you want. The fire hose may allow for even pressure on the part.
Going on your idea, I don't understand how you would be able to inflate the firehose. After all, it wouldn't do any good just sitting there.
I think what he is getting at is to seal off a fire hose, i inflate it first, to any pressure, and then clamp it down, this way you will have more even pressure than with a simple solid top mold. For the time and effort, I think your best bet is to go with your instinct and do what is easiest for you and best suits your financial situation....I planned on investing $600 into a pneumatic press and am in over $2000 already, so keep it simple at first, and follow the progression