hatch spring back

[metoady]

ok build a hatch and then find it sprung over 2 inches past where it should
be .....

ok
1 do i try again

2 run over this one with my truck to bend it back

any ideas

when life gives you lemons.....

[doug hodder]

Yup!!!! I had the same problem when I installed the interior ply. It was 1/4"' and I didn't support the frame prior to attaching it. Wood grain was running lengthwise so it was pushing against the structure of the frame more than if I ran it laterally. I had to build up the low spots using 1/8 material and lots of shaping with the belt sander. I only had about 3/8" of a problem though. A lesson learned.............Doug Hodder

[Woody]

Mine sprungbach about 2" also. I took a bunch of racheting straps and applied presure the counter the spring back. It was a battle, I eventually won it. WHAT A PAIN IN THE A$$ IT WAS THOUGH.

[bdosborn]

Have you installed the inner skin? If you haven't, you can pull it back into shape with ratcheting straps, apply the inner skin and leave the straps on until it dries. I'd pull it under an 1" before I installed the inner skin. I clamped my hatch to my bench while the skin dried.


I had a little springback (~1") but I took it up with draw latches on the sides.
Bruce

[doug hodder]

And you guys should check out bdosborns woodwork on the galley, it's awesome!!!! Doug Hodder

[Marck]

I had the same springback problem.
Being the cheapskate that I am I tried to use 3/4 inch OXB for the spars, cutting 8 of them and gluing 2 together for each spar, the result after I glued the 1/4 ply to the exterior was nice, until I came out the next morning and found it had sprung back enough to break my OXB spars. Had to rebuild the hatch all over again.

It doesn't pay to be cheap..... you'd think I would have learned that by now.

[john]

My first hatch frame flatened by about 1/4" after applying the skin. It pulled away from the trailer at both the top and bottom of the hatch. It was also closer midway between top and bottom.

On my second hatch I used straps to "pre bow" the skin and thickened the spars. Due to upgrades at a duplex rental the skin remained under tension for well over a month. I had to flatten it some to apply it to the frame.

These changes worked for me.

john

[IraRat]

I wish I knew the problem you guys are describing. Can't visualize it.

BILLY!!! WHERE ARE THOSE DANG ALTERNATE HATCH PLANS!? I'M GETTING NERVOUS HERE!!!

[doug hodder]

Don't worry Ira, it'll happen to you soon enough if you haven't built your hatch, just reread this thread before you skin it.....Doug Hodder

[roger-c]

Do it the easy way. Build the hatch and make the tear fit the hatch!
Thats what I did and It worked fine. Even so when I skinded the hatch
I didn't notice any spring back. I used 4 bows and they are 31/4" deep.

rogerc

[madjack]

...haven't skinned hatch yet BUT I am using 4 vertical bows that taper from 2.5 to 3" wide....just seems like vertical is better than horizontal unless of course you are refiring to the "BOP"
madjack

[Denny Unfried]

Made my hatch frame from 3/4" cabinet grade birch ply which has no voids and resists spring back. It can be bought in half sheets.

Before installing the bottom bulkhead I clamped the framework to the tear from the inside and then glued and screwed the outside skin in place. When unclamped from the inside the radius held. I also restrained it when installing the inside 1/8" ply lengthwise and it fits perfectly.

Denny

[Gerdo]

I notice in the Kuffel Creek plans that I need to notch the sides for the hatch to inset into. Is this how everyone has done this? If so how deep of a notch?

[IraRat]

I notice in the Kuffel Creek plans that I need to notch the sides for the hatch to inset into. Is this how everyone has done this? If so how deep of a notch?

The Cubby plans have a 3/8 notch, starting at the hatch spar. So although I didn't get to my hatch yet, I'm assuming that's going to be the thickness of the hatch, so it sits flush with the side walls.

[TomS]

I notice in the Kuffel Creek plans that I need to notch the sides for the hatch to inset into. Is this how everyone has done this? If so how deep of a notch?

The Cubby plans have a 3/8 notch, starting at the hatch spar. So although I didn't get to my hatch yet, I'm assuming that's going to be the thickness of the hatch, so it sits flush with the side walls.

I plan to start framing my hatch this weekend. I think the 3/8 inch notch is supposed to accomodate the weatherstrip.