Need help with the hatch design

[DesertApprentice]

I think I have cornered myself by cutting the side walls first, then work on the hatch design
I got feedback my hatch design is prone to water leak, and bending the aluminum will also be a serious challenge with the angles. As much as I hate it, I may consider redoing the design if it's not workable. But I have to do that before I screw and glue the walls. I have put my build on hold. Any feedback is greatly appreciated. I would like to know if my design is workable or salvageable.

I bought a hurricane hinge with 1/4" offset and 040 aluminum sheets. I see a possible way to add the hatch (shown in the drawing): bend the roof edge 2" on the back, place the hinge at the red circle position (about 5'8" or 68" from the ground). I want to make sure two things: 1) the design is not inherently flawed that will lead to water leak 2) the gate can be lifted high enough, a 5'8" or 5'9" guy can stand under the open lid.

Since I don't have a curved back, can I even use a hurricane hinge like shown? Any other way to place the hinge?
If the design is flawed, any way to reshape the already cut plywood? e.g. rounding off the corners.

I'm already considering rounding off the top roof corner above the hinge, and also the big angle on the lower part of the hatch. But I don't know if that fundamentally changes anything.

hatch-design-small.png (278.17 KiB) Viewed 414 times

[MickinOz]

As drawn, that design doesn't look particularly flawed to me. Assuming you put the correct half of the hinge on the upper side, let it protrude a half inch to an inch past the side walls, seal it properly where it screws down, I can't see it being any more flawed than any other design.
I had an issue with water getting under my hinge. $5 worth of Sikaflex 252 properly applied fixed it.
viewtopic.php?f=50&t=71977&start=261

A suggestion that may or may not improve your sleep:
If you have not yet cut that 24.6 x 59.2 roof panel, consider making it 25.6 x 59.2. An inch of overhang on a slight downward slope would direct a lot of run-off away from your hinge.

[MickinOz]

For the side seal, can I suggest you do something like I did?
I cut a couple of pieces of plywood to the same profile of my side wall, then inset one piece 5mm when I glued and screwed them on. This resulted in a reinforced rear profile with a 5mm rebate that a) gave me somewhere to lay in a 12mm d-seal, and b) channels anything that gets past the d-seal down, and out.
It was simpler to do than it is t describe.
I hope this post explains what I mean.
viewtopic.php?f=50&t=71977&start=133

[DesertApprentice]

MickinOz , thank you very much for your reply!

I haven't cut the aluminum yet. I have 5x10' sheets. My roof is 5x8'. I plan to have one sheet to cover the entire roof and with the extra overhang for the back side.

For the hatch seals, with your method, do you still use aluminum T-moldings on the sides of the hatch? I found a discussion by Wayne and Tony here viewtopic.php?t=69135? Looks like that method will also have the groove. I don't think it even uses T-moldings.

I also browsed your other photos. I love the supporting poles on the hatch. I'll do the same. You can cut and mount them precisely as you need. Using struts (shocks) seems to involve a formula of weight, height, and position. If not done correctly, it can cause problems. Your poles do not involve complicated mechanism. I don't see they can ever break.

[MickinOz]

I didn't use T-mouldings mate.
To be honest, by the time I got to the hatch I was getting a bit tired of searching the whole country for stuff that was practically off the shelf in the US.
A lot of stuff can be found, but is expensive and the freight can be a killer.
So the edge of my hatch is simply painted plywood.

It does look like Tony used the same approach I did for his sister's 4 x 8. I'm sure it works well.

I would have used gas struts, but for a couple of reasons:

1) I assumed they'd be expensive and hard to find, so I didn't design for them. Consequently by the time I discovered Bunnings (our version of Home Depot, I reckon) had a large selection on the shelf, there was no room for them.
2) I had no machinery for sizing timber. Still don't, though the barmaid at the pub today said I can borrow her DeWalt planer/thicknesser any time I need it. Yep, that's the world I live in the - the chick behind the bar at the local eatery has better timber working tools than I have.
So, I put in a fairly modest timber to take the hinge. It is a little bigger than what is called for in the generic Benroy plans but its only pine. I didn't trust the timber to hinge screw connection to hold up to the extra stresses of gas strut operation.

One salient point about my strut setup I expect you will have noticed - the actual point of support is around about centre of the hatch, the aim being to balance it with neither excessive down forces nor excessive up forces acting on the hatch. All bets off if you leave it up in a windstorm.

I have now located, after nearly finishing the basic structure of #2, some lovely 70mm x 30mm planed all round hardwood being sold for fancy fences.
It's lovely stuff, arrow straight, roughly equates to 2.75 x 1.25 inches. It's only $5.54 per foot.

[tony.latham]

It does look like Tony used the same approach I did for his sister's 4 x 8. I'm sure it works well.

It does work fine. It was an effort to reduce the weight from what Steve Fredrick suggested in his PDF. But it was kind of a pain when it came to installing drawer slides since I had to add 1/2" ply where they needed to be mounted so the drawers would clear.

That's the reason I changed the inner wall to a thinner 1/4" when I built the teardrop that I wrote the book for. Instead of Fredrick's 1/2". (Or the partial inner wall like I did for my sis.)





It works really well and is a lot lighter than using Fredrick's 1/2" lip. (I'm not dissing Steve, I think he moved the ball forward on hatch design about two miles.)

I cheated on my first teardrop. I bought it. It was built by Hunter and more-or-less had the T-moulding system for sealing. It really didn't seal very well. We always had dust in the galley after cruising on a dirt road. I'd be curious to hear candidly from builders with the T-trim style hatches how dustproof they really are.



Tony

[MickinOz]

So, I was up at 'ol mate Reg's place helping him turn over his trailer chassis.
Mission accomplished the conversation turned to TD building in general.
We were looking at his first build, a square drop. The galley hatch is a flat panel on the back wall.
He used 4 butt hinges for that hatch. He showed me how the hurricane hinge he bought for the next build will not open far enough.
It only opens a touch past 90 degrees, and that isn't enough!
I never thought of that.

Squaredrop hatch.JPG (24.24 KiB) Viewed 302 times

[tony.latham]

It only opens a touch past 90 degrees...

Good catch, Mick. I was wondering how well they would seal when installed vertically.

Tony

[gudmund]

I'm wondering if it maybe the difference between "hurricane hinge" manufacturers, as too how far the different brands can be opened ?? - this picture here shows my trailer and it's galley door when open - which can be seen here to be 'open' further than 90 degrees..... I do not know what the brand of it is? being I bought the trailer this way 4 years ago.......But when putting a 'protractor' against this picture today, it scaled out to be open about 110 degrees........today this door is at 94 degrees when open, I ended up lowering it a few years ago being it have gotten to be 'just too' much of a reach when opening/closing.

[MickinOz]

Reg's 1st trailer is a full on squareback. So the hatch when closed is exactly perpendicular to mother earth.
The hinge he has for the second build I estimated at maybe 100 degrees fully open. It might be the same 110 degrees you measured, I was just guessing. In any case, his hatch would be 10 or 20 degrees degrees above horizontal at maximum opening. Not enough to provide the headroom he wants if he uses the same squareback design he used for the 1st trailer.
He's going to fix it like this on the next build:

hinge position.JPG (14.23 KiB) Viewed 268 times

[MickinOz]

It only opens a touch past 90 degrees...

Good catch, Mick. I was wondering how well they would seal when installed vertically.

Tony

I reckon they'd be no different than when laid on the curve or flat on the roof, except for one thing.
With a square back, the hatch is flat, not curved. If opened above horizontal, it's not like a curved hatch where some still runs off the back. All rain water runs toward the hinge, and in a decent downpour this might overwhelm the hinge's ability to channel it out the sides, some might overflow through the hinge mechanism.
Even so I think it'd have to be fairly heavy rain, you'd probably be inside with the hatches closed.

[tony.latham]

some might overflow through the hinge mechanism.

Grant Whipp came up with a fix for that issue. You attach a D-shaped seal on the rear portion of the hinge. It channels the water off to the side.

Tony