HAVE YOU REBUILT YOUR HATCH? WHY?

[xe1ufo]

There is a nasty little secret circulating in the Teardrop underworld: a good many of you have had to rebuild your hatches, some several times.



So be nice to those of us who are just getting started:

1. If you were starting from scratch, what would you do and also not do?

2. What would you consider to be the weakest (or most problematic) part of your hatch?

3. Is it truely possible to have a water-tight hatch the first time around?

[john]

I had to rebuild mine due to spring back. The gap between the hatch and side walls increased at the top and bottom of the hatch after applying the skin (wood not metel) to the hatch frame. The skin straightened the curve of the frame.

My fix. As I built the second hatch I prebent the skin. I bent the skin into a U shape and kept it that way with some bagage ties for what turned into a month (I had other things to do). When I applied the pre bent skin I had to acctually flatten it to put it on. No spring back.

just my experience


john

[Roly Nelson]

Strange that you should ask that question today. I just got in from the little known, UITCCUSA ("Universal, International, Teardrop Construction Center of the United States of America"), which is just a portion of my little garage!

After fastening the 1/8" plywood to the hatch lid, installing the piano hinge, (cheaper than a huricane hinge, Sorry, Grant). and finding that there was a bit of spring-back, it didn't fit tightly against the pre-cut sides. I scribed a parallel line to match the new shape of the hatch, belt-sanded the side plywood to suit, and now it is ready for coating with epoxy glue and weatherstripping. This may be a backwards way of solving the problem, but it sure works great.

Roly.....glueing, screwing, epoxy-filling and getting ready to paint the little 1/4 Nelson Stacker, perhaps with a wild paint job, yet to be decided.

[mikeschn]

If you have enough ribs in your hatch you should never have to rebuild it due to springback!



Mike...

[IraRat]

"To all friends of Bill:

"My name is Ira, and one day, I am going to be a hatch rebuilder."

But not because of springback--my 1 1/4" side gussets (two pieces of 3/4" laminated ply) are rock solid, and no way a 1/4 sheet of ply is going to bend them. My problem is how those side gussets SIT as they relate to the side wall, and how they look.

The left side is fine, except I chipped up the skin there, and the right side sits higher than the side wall. Also, I had to use unsightly screws into the side gussets, because the brad heads kept pulling through the sheet of ply (red oak).

For now, I'm just waiting for my eBay fish netting to arrive to cosmetically repair the problem. If it DOES, I'm cool. But I just don't know.

I really don't want to have to redo it--I want to build one of those 1-sheet boats instead.

Now THAT looks a lot easier than a hatch.

[ALAN GEDDES]

I havr to build another hatch because of some dampness that caused some wood rot due to a small leak.

[Denny Unfried]

I would suggest using a good grade of hard plywood for the ribs. The cheaper soft ply has voids and can bend with little effort. I used birch ply for the ribs. It's also it's a good idea to restrain the frame while your skin adhesive cures.

Yup, it is possible to build a non-leaker first time around.

Denny

[john]

But not because of springback--my 1 1/4" side gussets (two pieces of 3/4" laminated ply) are rock solid, and no way a 1/4 sheet of ply is going to bend them. My problem is how those side gussets SIT as they relate to the side wall, and how they look.

The side gussets on my hatch that experienced springback were made with (3) 1/2" ribs on each side glued together with pl. I thought a total of 3" of ply would hold the hardboard in the shape i desired especially with an extra 1/2" bit of ply added on each gusset at the strongest part of the curve (the gaps that were left in the 4th ply were filled with a hatch prop), but the 1/4" hardboard I used for covering was much sronger than I had expected. At first there was no springback, but over a week it became an obvious issue. Hatch shape, of course, would cause different springback results. Not just how sharp the curve is, but also how long the curve is. Mine was curved along the whole hatch with a sharp bit about 2/3 down the hatch.

I hope the pics help with the words.

anyway
john


http://pg.photos.yahoo.com/ph/johngwalk ... pg&.src=ph


http://pg.photos.yahoo.com/ph/johngwalk ... pg&.src=ph


http://pg.photos.yahoo.com/ph/johngwalk ... pg&.src=ph

[IraRat]

John, there were probably two main reasons I didn't have a problem with this.

First, maybe two layers of 3/4 gusset is actually stronger than three layers of 1/2.

I know this defies conventional laminating strength "theory," but in the case of the hatch gussets, the stress isn't side to side, it's the OTHER way. So maybe 3/4 is stronger in this respect.

Next, my 1/4 skin (red oak ply heavily varnished) bended to my curve without a problem. Granted, this might not be the best MATERIAL to use for the hatch, but I went with it anyway.

Also, yours appears to be 5' wide, so maybe that extra pull of the extra skin contributed to the springback.

[Guest]

Dr Steve,
Not only have I heard folk say that they had to build their hatches over, but just about everyone, myself included talk about getting it right on the 2nd tear. (The whole project, not just the hatch)
Just about everyone that is except Gage...
I had the pleasure of meeting him at Redwoods Revisited and he stressed that he told everyone from day one, that he was only going to build one tear and let me tell you... he got it right the first time.
I wish I would have passed the cooking duties onto someone else, so I could have had more time to chat with him. Almost all of our talks were interupted because I had to go check on the cooking.
My best advice would be to talk with Gage before starting on your hatch.
I'm looking forward to meeting more people at gatherings, because I'm beginning to enjoy the conversation more than the destination.

[xe1ufo]

There is a lot of good information here. Thanks to all who are participating.

For those that experienced springback: Did you run your plywood vertically, or horizontally?

[Ken A Hood]

I think if you run your "curved ribs" north-south (top to bottom);like in Mike's photo there's less of a chance for warping/springback. If you just have 2 ribs (on the edges); and run the "straight ribs" east-west (side to side) there can be more warpage....

[emiller]

I'm redueing my first tear after the AzRoundUp. My secound tear I did out of metal as you can see in the hall of fame EMiller in Phoenix

[john]

John, there were probably two main reasons I didn't have a problem with this.

First, maybe two layers of 3/4 gusset is actually stronger than three layers of 1/2.

I know this defies conventional laminating strength "theory," but in the case of the hatch gussets, the stress isn't side to side, it's the OTHER way. So maybe 3/4 is stronger in this respect.

Next, my 1/4 skin (red oak ply heavily varnished) bended to my curve without a problem. Granted, this might not be the best MATERIAL to use for the hatch, but I went with it anyway.

Also, yours appears to be 5' wide, so maybe that extra pull of the extra skin contributed to the springback.

I forgot about the width. The extra foot would make a difference in the pull. I had to use the ugly screws in the side of the gussets too.

One of the changes I made that I forgot to mention was an increase in the depth of the gussets from 1 1/2" (approx the width of the ripped 2x4s I used for cross braceing) to 2".


john

[IraRat]

I have to measure my depth--don't remember. I just remember making it as wide as I could before it would hit the middle galley bulkhead wall/the cabinet top..