Need Help Figuring Out Struts

[Jwh92020]

My hatch door is 55.5" long x 41.5" wide & weighs 37 lbs. I used the calculator and it says I need 24.9" struts @ 450 newtons (?) and the placement diagram has me baffled. I also looked at a couple of other calculators online and they said basically the same thing. I couldn't find struts rated at 450 newtons. Any ideas?

 

[gearsoup]

450 newton is only 101 lbs. McMaster should have something, no?
37 pounds for a hatch, that's quite light!

 

[Jwh92020]

450 newton is only 101 lbs. McMaster should have something, no?
37 pounds for a hatch, that's quite light!

Thank you for explaining the newton/# conversion. The hatch is a 1x3 frame with 1/4" on the outside, 3/4" foam board and 1/5" ply on the back. My goal was to make it strong but light.

 

[Tony Latham]

So.... I ran your dope, and it says you need two 65-pounders 37" long.

That's an awful light hatch. Are you confident it's 37 pounds?

"and the placement diagram has me baffled."

How so?

From some book about building teardrops:

Note that in my diagram, the strut points below the hinge when the hatch is closed. Without that design element, the strut pushes up on the hinge and causes issues.

Tony

 

[Jwh92020]

So.... I ran your dope, and it says you need two 65-pounders 37" long.

That's an awful light hatch. Are you confident it's 37 pounds?

"and the placement diagram has me baffled."

How so?

View attachment 1341352


From some book about building teardrops:

View attachment 1341353

Note that in my diagram, the strut points below the hinge when the hatch is closed. Without that design element, the strut pushes up on the hinge and causes issues.

Tony

The 37 lbs is correct. I kind of understand your diagram, but applying it to my hatch is where it gets foggy. My hatch is a flat panel hanging straight down.

 

[Tony Latham]

but applying it to my hatch is where it gets foggy.

Hey, gas struts cause brain fog. Been there.

I would do a life-size layout of the hatch in both the open and closed positions on a big piece of cardboard, or plywood, or some other flat surface. Use the results that the Excel file gave you as far as distance from the hinge.

McMaster-Carr has PDFs of their struts showing both closed and open dimensions. You don't want the strut to close fully. Close but not to its full stop.

Tony

 

[Jwh92020]

Hey, gas struts cause brain fog. Been there.

I would do a life-size layout of the hatch in both the open and closed positions on a big piece of cardboard, or plywood, or some other flat surface. Use the results that the Excel file gave you as far as distance from the hinge.

McMaster-Carr has PDFs of their struts showing both closed and open dimensions. You don't want the strut to close fully. Close but not to its full stop.

Tony

Thanks for the advice. I'll do that.

 

[Diego Pascoalino]

Hey everyone, I need some help with something I’ve been trying to figure out for the last 3 days.

I followed all the instructions from the chart someone provided, and it was amazing. However, I still can’t figure out the lower point fix. Whenever I try it, it doesn’t work because of the size and angles I’m dealing with.

Please see the attached image.

Many thanks in advance!

 

[tomhawk]

That's an awful light hatch. Are you confident it's 37 pounds?

On my build, the full sized hatch is pmf canvas covered 1" foam with a minimal 1/4" plywood skeleton and weighs 22 lb. I used two 40 lb struts.

While it is not very stiff, it has not been fragile. I have towed the trailer at 75 mph without issue (with the hatch closed of course). After 5 years I am happy with it.