Help please - gas shock sizing???

[mvweebles]

Pinging the TF Bigger Brain for recommendation in sizing gas lift shock for my engine room butterfly hatches, and an access hatch. New install so no prior shock to copy. I can provide dimensions and weight estimate and need someone knowledgeable to make a recommendation. The online calculators I've found thus far do not inspire confidence I got it right. Also need mounting brackets (all in Stainless Steel).

Thanks in advance -

Peter

 

[O C Diver]

Do you want to add some lift and hold it up or basically eliminate most of the effort? Part of the issue has to do with the angle of gas lift shock relative to the hatch in the closed position.

If the shock is parallel to the hatch in the closed position, the shock offers no lift advantage when closed. If the shock is perpendicular in the closed position, 100% of the lift is in play when you start to open it.

Also understand that in the perpendicular position, if the shock is mounted closest to the end that is opening, 100% of the lift is in play. But if you mount the shock half way down the side, it takes twice the force and so you will have only have half the benefit when trying to lift the hatch.

I helped a friend with this and it ended up being no gain in effort until the hatch was up 20 degrees and then held it solidly open at 100 degrees.

Ted

 

[ranger58sb]

Pinging the TF Bigger Brain for recommendation in sizing gas lift shock for my engine room butterfly hatches, and an access hatch. New install so no prior shock to copy.

I don't know much about the calculations, but if it helps...

We have a good size hatch at the top of our flybridge stairs; essentially the width and almost the full length of the "stairway." Don't know how much it weighs, though...

The gas springs are from Ameritool, 60 psi, 26" x16", newly replacing the originals of same pressure/dimensions. The hatch raises itself. And we have to push down on the hatch to get it near closed so we can then turn the latch to lock it down.

Our brackets were custom made for the boat, but I think Ameritool offers various brackets that might work for you situation.

-Chris

 

[smitty477]

Years back we used a fish scale type of weighing device to measure the loads at various %'s of opening and at various distances from the hinge end.
We then bought SS gas springs and brackets from "Strutwise" who was easy to use at the time.

 

[jungpeter]

Pinging the TF Bigger Brain for recommendation in sizing gas lift shock for my engine room butterfly hatches, and an access hatch. New install so no prior shock to copy. I can provide dimensions and weight estimate and need someone knowledgeable to make a recommendation. The online calculators I've found thus far do not inspire confidence I got it right. Also need mounting brackets (all in Stainless Steel).

Thanks in advance -

Peter

Hi Peter,

Unfortunately, there is no easy answer to your issue. Gas strut sizing is all wrapped up in geometry and weight issues of the hatches, linkages, and mounting geometries, as well as more subjective issues regarding how much assist you desire in opening and closing the hatches. You will likely require the services of an (ideally) licensed professional mechanical engineer to provide your answers.

If you've made detailed measurements and drawings of your desired installation(s), including weights of the various hatches in question, perhaps there's a willing PE on this site that would take on the challenge, if you'd post more detailed information.

Regards,

Pete

 

[KnotYet]

This kind of project can be fun as long as you aren't under a time constraint.
Also, I assume you are in Mexico which adds a complication unless you have
a local supplier.
I have bought gas springs from McMaster-Carr in the past.
They have mounts, too.

 

[JuJu]

Associated Spring RAYMOND was the OEM for the gas struts on my engine hatch
(2000 Mainship Pilot 30). You will find a wealth of info on their website "ASRaymond.com" and you can purchase struts, brackets and mounting hardware from them as well. My engine hatch is roughly 5'x3' and weighs well over 100lbs and requires 2 struts rated at 100#.

 

[mvweebles]

Thanks to all who responded. What seemed fairly easy and straightforward is, as several noted, much more complex: a physics problem replete with Newton force calculations coupled with calculus and geometry. Not my strong suits in school, and passage of time hasn't helped the brain cells......

A good friend recommended liftsupportsdepot.com. Probably have the best prices but for the life of me, I could not figure out what I needed and sort in stainless steel.

I spent some time on Gasspringshop.com which has a decent interface for sizing and design. I will likely go with them.

I did check McMaster Carr. I like their stuff - 316 SS (vs 304). I tried taking size from GasSpringShop.com, but only got close.

Someday I'll have a simple boat project where I can go to a store, find what I need, and install it 30-minutes later without duress. Yea....right.

Peter

 

[RT Firefly]

Greetings,
Mr. mv. How about an appropriately sized stick?