Hatch Revamp

[RRRLBASS]

I am revamping my hatch. The struts were stressing the latch and wrecking the wood where they attached. Took those off along with the plywood on the inside. Going to go with poles to hold the hatch up.

The hatch fits much better on the body but now I am getting quite a bit of flex from the hatch. I reinforced the corners with metal angles. I also revealed the builder used 2 pieces of plywood to shape the skin and there is a seam down the middle of the hatch. The formica covers the seam but....

I thought I would cut and glue the old plywood back into the cross beam sections of the hatch to reinforce the seam and the hatch as a whole. Hopefully that will lessen the flex too. I do want to leave the cross beams exposed.

Thoughts or other solutions?

RRRL

Hatch seam.jpg (30.08 KiB) Viewed 1465 times

Hatch .jpg (46.79 KiB) Viewed 1465 times

Hatch Seam 2 .jpg (31.24 KiB) Viewed 1465 times

[MickinOz]

I do have a couple of suggestions, one I have done myself, one I have not.

My hatch is single skinned, with exposed framework too, I just tolerate the flex.
My outer skin is 7mm structural plywood commonly used for bracing house frames, so its reasonably strong and not super flexible.

The L brackets you added will strengthen the hatch frame, but given their location and orientation, there is only so much they can do with regard to reducing flex.

If I did want to make mine more rigid, I would add plywood gussets. In a way, I guess I am talking about putting back just a bit of the inner skin, just where the frame members join.
I drew what I mean in paint. ( One day I'll dedicate the time to learning cad. )

Gussets.JPG (19.09 KiB) Viewed 1425 times

There are pictures of what I mean right here:
http://railroad-line.com/forum/topic.as ... hichpage=3

Its a modelling forum, and there are some serious skills there.
In particular, the eighth and ninth pictures match what I see in my head.

[MickinOz]

That's the one I haven't tried.
Here's the one I have.
I didn't plan far enough ahead, and came to the conclusion my hinge area was underbuilt for the rigours of gas struts on the hatch, so I did this:

http://tnttt.com/viewtopic.php?f=50&t=71977&start=163

The struts fold. In the open position, I have used draw latches to lock them straight.
Because they are attached by hinges top and bottom, they also restrain the hatch from being lifted by the wind. Naturally, in strong wind conditions, one wouldn't leave the hatch up, but on a breezy day these work a treat.

[RRRLBASS]

Great idea. That should do the trick. I will try it. I know there will still be SOME flex. Just trying to minimize it without putting the inside skin back on.

Also....What about the reinforcement for the seam idea? I suppose I do not need to go the width of the hatch but definitely 4 to 6 inches either way..

I do have a couple of suggestions, one I have done myself, one I have not.

My hatch is single skinned, with exposed framework too, I just tolerate the flex.
My outer skin is 7mm structural plywood commonly used for bracing house frames, so its reasonably strong and not super flexible.

The L brackets you added will strengthen the hatch frame, but given their location and orientation, there is only so much they can do with regard to reducing flex.

If I did want to make mine more rigid, I would add plywood gussets. In a way, I guess I am talking about putting back just a bit of the inner skin, just where the frame members join.
I drew what I mean in paint. ( One day I'll dedicate the time to learning cad. )

Gussets.JPG

There are pictures of what I mean right here:
http://railroad-line.com/forum/topic.as ... hichpage=3

Its a modelling forum, and there are some serious skills there.
In particular, the eighth and ninth pictures match what I see in my head.

[tony.latham]

Took those off along with the plywood on the inside.

I keep looking at the dark brown lines on the cross members. What kinda glue was that? How easy was it to pop the plywood off?

I'm liking Mick's gusset solution.

Tony

[TimC]

As far as seam reinforcement I think I would go with some 1/8" plywood (or other easily bendy ply) and glue a nice wide patch over the seam. Maybe 6" inches on each side of the seam patch. Lauan comes to mind as it is very flexible. Use what ever size there is room for. Spread glue on the entire surfaces, old ply to new patch, not just a squiggly line. Start with one thickness all the way along the seam. Let them dry well. Put another 1/8" layer on top of that. Maybe slightly smaller. I wouldn't go more than two layers as that section of hatch may cause problems if it is stiff and the rest has some flex. One layer may be all you need.

If you have stiffer plywood for patch material and you are getting initial spring back while the patches are still wet let them partially dry, or start out with contact cement which will grab and hold as soon as it touches the other surface.

I covered the inside of my hatch with canvas rather than plywood. Much lighter and easy to remove if problems develop. Good luck.

Tim

[RRRLBASS]

No idea on the glue...didnt stick very well either. The deeper I get into the construction, the realization of how shoddy it was made gets more and more apparent.

I have Aluminum gussets going in this week. will update!!

Took those off along with the plywood on the inside.

I keep looking at the dark brown lines on the cross members. What kinda glue was that? How easy was it to pop the plywood off?

I'm liking Mick's gusset solution.

Tony

[RRRLBASS]

I ended up doing 4 " wide patches of 1/8" hardwood plywood with good amounts of wood glue. Seems OK so far! I am with you on the amount of glue...no time for the zig zags!

As far as seam reinforcement I think I would go with some 1/8" plywood (or other easily bendy ply) and glue a nice wide patch over the seam. Maybe 6" inches on each side of the seam patch. Lauan comes to mind as it is very flexible. Use what ever size there is room for. Spread glue on the entire surfaces, old ply to new patch, not just a squiggly line. Start with one thickness all the way along the seam. Let them dry well. Put another 1/8" layer on top of that. Maybe slightly smaller. I wouldn't go more than two layers as that section of hatch may cause problems if it is stiff and the rest has some flex. One layer may be all you need.

If you have stiffer plywood for patch material and you are getting initial spring back while the patches are still wet let them partially dry, or start out with contact cement which will grab and hold as soon as it touches the other surface.

I covered the inside of my hatch with canvas rather than plywood. Much lighter and easy to remove if problems develop. Good luck.

Tim