Wooden Ski Press? Am I building a bomb?

[UPSki]

Hello Everyone,

I wanted to know if I should expect this construction method to work, or if I should duck and cover. I'm having difficulty finding strength specs of the engineered joists that we plan on using.

We are planning on building a pneumatic press, similar to all of your steel presses, that will run between 40 and 50 psi, but we want to use 5 2x12 engineered Joists as the spanning pieces (5 for the top and 5 for the bottom), supported by solid untreated 4x6 posts. We'd run some threaded rods through the 4x6 posts and the engineered joists to hold it in place. We also planned on using some climbing webbing wrapped around the press to add a little extra flex resistance over the 7' span.

Thoughts? I dont' have details on the build specs yet, I just wondered if people have tried this method, and if there are any huge red flags that I'm missing.

Mike and the UPSki Crew

[originskis]

I built a press like you describe by making alternating 2x4s and 2x3 to make an i-beam of sorts. But mine is a cloth press, so the whole thing is wrapped with cordura. that sounds a little precarious.

[Jekul]

Do you have any sort of a sketch to acompany this? I know you will be dealing with ~100,000 lbs of force. With my steel press I've calculated (using finite element analysis) that I have approximately 0.010" of deflection and the stresses exerted on the steel give me a lowly safety factor of 1.3. I'd make sure to run all of the calculations for the yield and tensile strength of your wood before applying the full 50 psi. I know people have built them, so good luck, and have fun!

[UPSki]

After doing a little research, we are going to compliment the press with a cordura wrap. Once I know the details I'll add the info.

[KevyWevy]

skidesmond recently built a wood press similar to what you're talking about, but used steel on the ends and in the middle (if i remember correctly) to help with deflection. I'd say wood is fine as long as you put a few steel supports (detachable) around the middle.

i'd give you a link, but i don't have time to search for it right now, PM him about it.

[skidesmond]

Yes, I built mine out of wood and steel. The beams are wood just as you are describing. I did not use engineered beams (LVL or laminated beams) but I would have if I knew where to buy them at the time. It would have been a huge time saver. I use 3/4 in sheets of OSB plywood and cut them 8 inches wide. Then bolted them all together w/ 1/2in steel threaded rod every 12in. It took 7 sheets of OSB to make the 2 beams. IT IS HEAVY! I'm guessing the entire press, with forms, etc is in the neighborhood of 600-700 lbs. It's worth buying a long drill bit to bolt the beams together.

I press at 40-45psi. I get about 1/8in flex. More than I expected but acceptable. If you are using 2x12 I think you'd get less flex. I'm contemplating of adding more support around the middle.

Hard to say if the 4x6 beams will be adequate to hold it together. I used 4in U channel steel a friend of mine had. He did the welding. Here's some pics of mine:





Feel free to PM me or ask questions. Let the fun begin!

[jono]

I built a wood press that is reinforced with metal. It does not
noticeably deform when I press at 50psi. Based on the specs for threaded rods in terms of stretching and shearing I could go up to 80-90 psi if I wanted to. It has been through over 20 cycles and shows no signs of fatigue.

I used two 4"x4" doug fir boards on the outside with a 2"x4" sandwiched between two lengths of 5/8 plywood on the inside for my wood beams. This gives enough width for a single ski. The beams are 84" long and are routed on top (to keep the top flat) to accept a 72" piece of 1/8", 1.5" angle iron. The beams have five 3/4" threaded rods going through them that connect to ten 3/16"x3"x18" flat metal pieces (these connect the upper and lower beams). Additionally, I have eight 1/8", 2" angle iron pieces, bolted in pairs with a 2"x4" in between, mounted transversely. These are tied together with 16 3/16 threaded rods. All metal components are bolted to each other and to the wooden beams with lag screws. I think this press weighs less than 200lbs but I have not weighed it. It is easy to roll around.

The hardest part of making this press was drilling the holes in the metal. The metal does most of the work in my press while the wood acts like a reinforced core.

Good luck!! Make sure your calculations are correct and that you press at pressures well below the maximums allowed in your calculations.

[skidesmond]

Nice design. I wish I would have used more metal like yours and less wood. Mine is very heavy and even though it's on HD caster wheels, it still takes some muscle to move around.

How do you load the skis into it? Through the end or do you unbolt part of the press and load through the side?

[jono]

My press loads from the end. This can be a pain but over time I've removed protruding bolts from my molds to avoid catching on anything. The skateboard wheels make it so I can load a mold/laid up ski/hose/top mold apparatus with one arm.

[H-man]

edit:

i noticed now you made a comment about beefing it up with cordura, how did that work out?