galley hatch out of alignment

[Diemjoe]

Hi,
I getting close to road worthy but have a situation that could be troublesome in the future. Plus it just doesn't lol very good.
My galley hatch was built in the standard way. The plywood ribs were cut to match the wall curve. It fit nicely before I skinned and attached it. I notched the wall to make room for the trim and weather stripping.
But now that everything is attached, I find that the bottom foot if the hatch on both sides is about a half inch from meeting the weather stripping.
I shaved off a bit if the hatch footer piece but there was no change.

Any ideas on how to fix this? Or will I need to just source some extra thick weather stripping?

Starting at the hinge, alignment is good

WP_20160308_001a.jpg (64.32 KiB) Viewed 1539 times

the bottom is out though

WP_20160308_003a.jpg (64.67 KiB) Viewed 1539 times

Thanks

[halfdome, Danny]

I don't know the type of plywood you used for your ribs but it sounds like they have absorbed some moisture.
I use Baltic Birch from Crosscut Lumber which is on 1st Ave in Seattle.
From your tiny pictures it appears the hatch is right next to a garage door in Seattle.
Our garage has eave ventilation since the ceiling has never been enclosed and I'm assuming that's where the moisture is coming from.
Our hatch, which is fully covered and sealed, can absorb a tiny amount of moisture if left open in the garage during the winter.
It's 13' away from the door & it can make the part that goes to the threshold a little difficult to close with the side clamps.
I just adjust the side clamps out a bit & leave it closed for a few days, it then returns to the original shape.
If you have your original rib as a jig, maybe you could clamp the lid with 2 x 4's & 2 or 3 ratcheting tow straps to the original shape.
I'd put it in a room with less moisture.
You could also try clamping it to the teardrop in the same manner as described above.
If you just ignore the deflection and cover it with thick seals you're inviting water intrusion while traveling in the rain.
Danny

[Diemjoe]

Wow, I had not thought about the wood shifting, I just thought the hurricane hinge edge was not attached correctly. Your idea does make sense as the tail end of the trailer has been up against the garage door since I started this a year ago. I may have to rebuild the hatch now. I don't have the template anymore though.

[Diemjoe]

Hi Danny,
Reading through your reply again (was in a meeting the first time I read it

Sadly, My only parking/storage place is the garage. I am not sure but my ribs are either 1/2 or 3/4 Baltic birch. I think they are 1/2 since I glued ribs together for extra strength too. At least 2" wide.

I wonder if Clamping would work. Would it just bounce back over time?

I am planning to use it for my US roadtrip this summer starting June 1, Hence my hesitation to rebuild the hatch with that goal looming. I definitely have other projects to keep me busy while I wait to see if the straps work.

Don

[Diemjoe]

Was wondering if this is a common issue. I thought I bought good lumber. I stopped by Lowes tonight to get a piece of 3/4 plywood since it wasn't raining but wanted to get more info on if the thickness matters, type. Lowes had oak and maple but no birch. Maybe I'll get a weather break on Saturday for a crosscut or compton visit.

An engineering friend of mine thought that maybe steel cable tighteners might help it to keep shape. Seem like overkill and probably not doable with the curve.

Don

[halfdome, Danny]

Don, do you have a larger picture of just the hatch?
What did you skin it with and did you skin one or both sides?
Any time you have unequal sealed/skinned surfaces one side is going to absorb more ambient moisture and you'll get some deflection.
If the outside covering is under great stress it will try to pull the lid back to it's original flat shape.
It's best to use a plywood skin like Baltic Birch and apply it in the direction of least resistance.

Back in the 1970's I was working for a cabinet shop that we had to replace all the cabinet doors in a multi story hospital.
It took us quite some time to make the replacements.
The front of them was covered in plam (plastic laminate) and the back in vinyl, from the panel factory (unequal materials).
They all warped about 1/2" and this was in a building.
We ended up making new doors with plam on both sides (equal materials) and the problem was solved.
Danny

[Nobody]

Springback??

[Gunguy05]

Springback??

This is what my initial thoughts were. Seems like you need a gusset of some type, to resist the forces of the skin (the luan I am presuming) and the aluminum from bowing outward and pulling the curve out of the hatch.

Alternatively, I have seen a piece of thick (1/8) aluminum used on the end of the last spar on each side of the hatch, to reinforce it and help to eliminate the springback.

Not saying I'm right here, just thinking out loud.

[tony.latham]

Your ribs are 2" wide laminated plywood. But how deep are they? That's where the strength is.

T

[bobhenry]

I cut my ribs out of 12" deep 1 3/4" thick Timberstrand engineered lumber . Here is a pic of two of the four ribs.




WE laugh at spring back.

[halfdome, Danny]

Don, here I'm clamping the galley lid while the adhesives cure.

I use my original template rib to gauge how much tension I need on the strap clamps.
Danny

[KCStudly]

Did you build the hatch in place and it changed, or did you skin off the camper and it didn't fit once you put it back on?

I am in the same school of thought as Tony, I made my hatch ribs 3 inches deep (or was it 3-1/2? ), from 1x (3/4 thk) miter joined Red Grandis boards skinned with 5mm Okoume ply.

I have seen a little movement over time during the build but that seems to be the cantilevered edge of the ply skin more so than the structure, and only a scant 1/16 inch or so, depending on the weather (mostly dry work shop, humidity ranging between 30's in the winter and high 90's in the summer).

Are you sure it is an issue of warping and not trying to over compress the seal? If you did not allow enough gap for the seal I could see that holding the hatch up. Rule of thumb is to plan for 2/3 to 1/2 of the seals free height when compressed. In other words if your seal is 3/4 inch thick, its compressed height should be from 1/2 to 3/8 inch thick.

[Nobody]

When I built my TD I wasn't too worried about keeping weight down. I figured I'd end up with 1K# plus & my 'ready for travel/camping' weight is about 1150# give or take a few. I cut my 'ribs' from 3/4" cabinet grade (11 plies) Birch plywood. There are 6 ribs, 3/4" wide, 2" deep (actually finished depth was closer to 1 7/8"). I used a 1x3" oak 'header' at upper side (where the 'Better than Hurricane' hinge fastened), rabbeted into the ribs, & 1x2" spruce 'butted' into the ribs at bottom, & a single course of 1/2" soacers between the ribs, midway down, pocket holes & glued. Buttressed the 2 middle ribs at location of 'T' handle, & where the license plate bracket/light would be located. Clamped it in place for a 'dry fit', then assembled it on the bench with glue & screws. Assembled the doors at same time. After the glue dried I clamped it back in place on the TD & stapled/glued the 1/8" Luan to the ribs before adding the 0.040" aluminum outer skin & trim. We've towed the TD more'n 25K miles over the past 9+ years & never had a problem with 'warping/springback'. After a couple of years I did 'skin' the inner side of the hatch with 1/8" pre-finished beadboard. My hatch is kinda heavy, swing weight is probably 30-35#, & I use hinged 3/4"x 1 1/2" oak strips as props. It has worked great for us for more'n 9yrs. Actually I'm pretty sure I 'dry' assembled it while clamped to the TD, & merely re-assembled it with screws'n glue on the bench...