Project: JetSki Shop Stand

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Ashby

New User
Ashby
Hello NCWW community,
I wanted to seek your advice in regards to material choice for a project I am working on. I have designed these interlocking stands that can be routed out so they can be assembled without tools. My question is in regards to strength and choosing the correct material. These stands will support a 300lb jetski you know the ones you see at the boat ramp and you ask yourself “do they still make those things?”. Yes they still make the 1 person standup jetskis but we don’t have a good way to store them in the winter without a trailer taking up a lot of valuable garage space, thus the reason behind the stands design. I would like the stands to be built from a material that can support +600lbs to add a nice safety ratio. So my question to the community is what would be a cost effective material for a project of this scope.


My first (inexperienced) though was to use 1/2” plywood but not sure if I would be better off using a hard wood plywood such as birch which add’s cost or if I’m better off bumping up to a thicker ply from a cheaper material such as pine. Or should I go a completely different route?

All input welcome, I take criticism well :slap:
-Ashby

Assembly.JPG
Outside.JPG

Inside.JPG
Runners.JPG
 

CDPeters

Master of None
Chris
Hi Ashby and welcome to NCWW!

Please take a moment to post to the "Who we Are" forum with a little about yourself.

To your question: Without doing all the engineering math, my gut tells me that 3/4" plywood would be your best choice. I think 1/2" is not quite enough. I would also consider placing hardwood cleats glued and screwed under the vertical half-lap joints to spread the load a bit more.

I should think that AC plywood or Sturdi-Floor underlayment plywood should be sufficient. The hardwood veneer on hardwood plywood adds no strength to hardwood plywood, it's just way too thin.

HTH,
Chris
 

ScottM

Scott
Staff member
Corporate Member
I agree with Chris in using 3/4" plywood vs 1/2". I would not use MDF or OBS sheathing. I would recommend using exterior grade plywood. Exterior grade plywood is made with glues that resist moisture. Garages tend to be damp and the glues used in interior plywood will not hold up well to dampness.
 

chris_goris

Chris
Senior User
Welcome Ashby! Thats a pretty neat concept! I would definitely make it out of 3/4 plywood if I were building it. A 2x safety factory to me seems insufficient for a consumer product though. Im thinking at least 3x and probably 4x. I would try to locate high grade plywood, as many plies as you can find for this as well. The only thing I might change from an engineering standpoint would be to cant the green supports inboard (not make them completely vertical) This to me seems like the entire assembly will be more stable. Im also wondering, how does someone get their jetski up on this once its setup?
 

Bas

Recovering tool addict
Bas
Corporate Member
+1 on 3/4" plywood. Since you are going to have interlocking pieces, I recommend a high quality plywood that is _flat_. Cheaper plywood tends to bow a lot, and really is meant to be nailed down along all edges. The extra $25 you spend on materials will save you many, many hours of aggravation.

Exterior plywood is a good idea, since you don't have to worry about water dripping from the Jet skis. But...most of the exterior plywood I've seen was pretty bowed, so you may want to go back to my previous suggestion. Since you have individual pieces anyway, a coat of paint is easy enough to apply.
 

DaveD

New User
Dave
You need a new hobby and more tools.
Some things just beg to be made out of steel.
A simple steel cart with locking casters would work just fine

BTW I like all those dimensions to 1/1000 of an inch
 

kooshball

David
Corporate Member
Another thought...if they are only 300lbs could you hang them from your ceiling? I've seen porch swings loaded heavier than that with no issues.
 

Pop Golden

Pop
Corporate Member
Kooshball's idea is good. And, just HOW are you going to get a jet ski up on to that stand? My suggestion is more bubbas.

Pop
 

Ashby

New User
Ashby
Thanks guys for all the suggestions; I was not expecting so much feedback. This seems like a great community. I not sure if it’s how I worded my original question which after rereading it’s biased towards going to a thicker ply? Nearly everyone is saying 1/2” won’t be strong enough but 3/4” would be. Any reason why 3/4" and not 1” My first hunch is to make it out of 1/2" and load test it. I feel like that it should hold 800-1000lbs before collapsing but this is a static test. After researching shipping cost going 3/4" is going to add to much for shipping making the project less feasible. Does anyone have or know of anyone with CAD simulation software to static test? I would gladly provide the 3D assembly and $ for your time. It’s a very basic set-up for simulation however, I have changed jobs and no longer have access to the software I use to do test similar to this on.

To answer the questions about loading them onto the stands. The skis are only 250 to 300 lbs not the heavy 800-1200 3 seater sit down jetskis you are use to seeing at the lake. It’s not hard at all to slide the stand up skis from the back of a trailer onto a shop stand like this.
 

smallboat

smallboat
Corporate Member
can't help you with the testing but I'll jump on board with the 3/4" vote.
1/2" ply is much less stiff than 3/4" ( and less flat in my experience) and I believe stiffness is your friend with this design.
If the arms of the green "x" frames flex allowing the crossing to bow in or out you'll lose all your carrying capacity.
Can't tell you how much load it would take to do that but can't imagine you have much margin with 1/2" ply.

Guess adding an additional cross piece tying the two green panels together at the center would help prevent bowing either way, but I'd still play it safe with the thickness.
If its a static piece and weight isn't an issue, why go light?

You should be able to pick up the ply locally without having to ship it. Unless I'm missing something.

For the record I'm a fan of this style of slot together structure, usually use it in KD stuff rather than fixed applications however.
 

chris_goris

Chris
Senior User
Looking back over your concept in my head, while (conceivably, this may be a struggle) it is possible to assemble the bottom 4 pieces together, the upper "bunks" can not be dropped into place since the slots are tapered away from each other........
 

Jeff

Jeff
Corporate Member
1 person standup jetskis but we don’t have a good way to store them in the winter without a trailer taking up a lot of valuable garage space, thus the reason behind the stands design.
Am I missing something about the story? So where will the jet skis be stored out of the weather to free up that garage space?

Also +1 to 3/4" t quality plywood for better strength and performance. It should be readily available in your area but steer clear of the junk at Lowe's and HD. You may want to consider Marine Grade Plywood for this application, but the cost is much higher.

http://www.mcilvain.com/do-you-really-need-marine-grade-plywood/
 

Henry W

HenryW
Senior User
I'd use a 'crate' made of 2x4s

Ahh the power of suggestion. ... Many have made good suggestions that would improve the design you showed.

However if you asked me how to build a cheap stand to winter Jet-skis, I would have suggested a knockdown design out of 2x4s. It would be cheaper and easy enough to fabricate. If you wanted to stick with knockdown, no tools required design, that can be done with 2x4s as well.

I haven't estimated the materials list for what you showed, but I bet a simple design using 2x4s would be stronger, easy enough to build with a Skilsaw and screwdriver, and likely at less than 1/2 the cost. It's just a cradle shaped for the bottom of these Jetskis, right?

Design? Lots of possibilities - that's the fun part for me.

Henry
 
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