How to correct bow back in hatch on a finished trailer ?

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How to correct bow back in hatch on a finished trailer ?

Postby RootsandShoots » Fri Nov 16, 2018 2:17 pm

Just got my first teardrop! Somebody else did a lot of great and hard work on this DIY build but there are some areas that need attention to make it rain worthy.
I believe the hatch is suffering from "bow back" where the seams meshing it and the side walls don't meet evenly and it leaks. I have some thoughts on how I can fix this but would love to hear anybody's experience, thoughts, or experiments.

Main Issue: Hatch Leaks at seam from bow-back

Suspicions:
I'm sure there's a lot of ways to describe "bow back" but what I'm referring to is the hatch not staying true to it's original shape after the plywood skin is affixed to the ribs. I suppose the ribs were not strong enough to resist the pressure of the plywood wanting to straighten back out out and it deformed from the the intended radius to one that's slightly larger. The result is... If it's hinged at the top, like I am, the seals along the sides become looser and looser as I follow them towards the ground. In my case the the seals are not touching by about an inch by the time I get to the bottom. Somebody has already attempted to correct the leak by doubling up the gasket at the bottom and sticking small wooden stubs under the gasket at the top. Neither of these things are working.

I imagine correcting this by adding eyelets to the top and bottom of the hatch and then connecting them with wire and a turnbuckle. I can then tighten the turnbuckle until the hatch bends back to the tighter shape I want. At this point I can affix additional, external ribs to the inside of the hatch to make it more rigid OR ??? Anybody's experience, thoughts, or experiments appreciated!

I also need to address the hinge itself. I feel like it doesn't extend far enough to the edge of the trailer so when it diverts water from the roof, it dumps it all directly at the seam. I have to research this next but if anybody wants to drop some experience here it would be much appreciated. Do hinges typically extend out further?

I made a quick web page to show the images of the trailer and the problems I'm working on:
http://www.rootsandshootsnursery.com/teardrop.html
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Re: How to correct bow back in hatch on a finished trailer ?

Postby KTM_Guy » Fri Nov 16, 2018 8:30 pm

Something like an Adjustable-Grip Draw Latch would help. Can you pull or push on the hatch and get it to go back to normal? Two of these on each side might do the trick.
Image
https://www.mcmaster.com/1864a25

Another idea is if you know a metal worker or a local place that would have a roller you could get some say 3/16 X 1.5" angle rolled into a radius tighter than what the hatch should be. You could thru bolt to the hatch. That should work to hold the hatch and shouldn't pull back. Downside, could be pricy and would add some weight so might have to get stronger gas struts if that is what holds open the hatch.

On the hinge, I think it should hang over the edge. I used a 3" aluminum piano hinge and covered it with EPDM rubber roofing. One change on each side is 1.5". See Bob's post in this thread.
http://www.tnttt.com/viewtopic.php?f=21&t=70648

Todd
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Re: How to correct bow back in hatch on a finished trailer ?

Postby halfdome, Danny » Fri Nov 16, 2018 10:13 pm

Can you provide a picture of the interior of the hatch?
If the inside is open framing that may be the reason for the spring back but moisture may also be the culprit as it appears the flooring seams have had moisture issues.
The Adjustable-Grip Draw Latch that was suggested won't work in your situation since you need something to attach the catch to like the insert molding on my teardrop.

I use them and they work great but you mentioned an inch gap at the bottom, they only have a 1/2" range.
Image
Here's what insert molding and the adjustable-grip draw latches look like on my TD.

Maybe you could remove all the seals and see how the hatch lays on the teardrop profile and go from there.
Another thing is that unusual looking hatch hinge, if possible it should be replaced with a hurricane hinge available from Vintage Technologies.
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You also mentioned hinge overlay, here's how I do mine.
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We store our teardrop in the garage year round.
In the winter if I don't close the lid and latch it, in a couple months time it won't fully close because of ambient moisture from us coming and going through the garage door.
I'll have to back off the Adjustable-Grip Draw Latches a little in the spring time to gently coheres the lid back to the intended shape.
Our lid is insulated and covered (contact cement) with plastic laminate on the interior and aluminum on the exterior to fight off moisture and spring back.
:D Danny
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Re: How to correct bow back in hatch on a finished trailer ?

Postby RootsandShoots » Sat Nov 17, 2018 3:29 pm

I've added a few more pictures of the hatch inside but unfortunately it's trimmed out so I'm not sure what the skeleton looks like.
If I push on the hatch when closed, I can complete the seal though it does take an awfully firm push to do so. I'll remove the side gaskets and see exactly how the two parts align as soon as I can get the trailer under a canopy. I'm in the coastal plain of South Carolina and it's basically 100 percent humidity, 100 percent of the time so if humidity has anything to do with it, that adjustable latch will work wonders.

I inspected the hinge set up a bit closer and it's a plastic hinge, I'm guessing like another item for sale by vintage technologies. https://www.teardroptrailerparts.com/hinges---aluminum-trim.html
This can't be very rigid at the top and I imagine it affects the way the whole thing sits on the trailer. I'd prefer not to see how many times it can bend back and forth before breaking at the joint so I'll place an order for a hurricane hinge.
Once installed, maybe the hatch will sit a little tighter and if not I'll work out how to bend the radius tighter.

...I'll order the hinge long enough so it extends beyond the walls.
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Re: How to correct bow back in hatch on a finished trailer ?

Postby halfdome, Danny » Sat Nov 17, 2018 7:11 pm

Sounds like your on the right track to fixing the problem. :thumbsup:
You could use a stud sensor to determine the ribbing in your hatch.
It may be the victim of poor sealing and the moisture got to it.
Can you get a copy of the original profile from the builder to determine what needs to be corrected?
The last teardrop I built I used web band clamps to keep the lid shape while everything cured.
Image
They were a lot heavier duty than these but maybe a few would do if the lid was put indoors for a period of time.
Maybe use a 2" x 4" the length of the lid width, top and bottom to help the web clamps.
Measure corner to corner to make sure it stays square.
:D Danny
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Re: How to correct bow back in hatch on a finished trailer ?

Postby UK-Corlett » Tue Nov 20, 2018 11:42 am

Hi rootsandshoots

I didn't have enough stiffness in the hatch, so when I put the skin on it flexed like you are reporting.

I Put a wire from the edge of the door back to the hinge. I made a feature of it with stainless steel boat fittings and a rigging bottle screw.
I can add tension and tune the contact point where the edge of the hatch meets the kitchen.

Image

It is a handy place to hang a towel or light.

Clive
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Re: How to correct bow back in hatch on a finished trailer ?

Postby RootsandShoots » Thu Apr 04, 2019 9:10 pm

Uk-Corlett, I attempted to do something similar to your solution but unfortunately the galley kitchen was built so the kitchen counter obstructed the tensioned lines. Otherwise, testing that method with the hatch off the trailer showed a ton of potential to really change the curve of the hatch. The more I dissected the original hatch, the more problems we found so I rebuilt the hatch completely. It works!
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