The Dreaded Hatch-idea

[GPW]

M... Lets talk !!! You know I built my TD and hatch like all the rest and I love it ... but I'm not gonna' build another one like that ... It's so much more space/build effective and easier on the "aged" like me, not to have to lift a hatch , but just open a door ... we're good at that!!! ... Please check out my new project ... the "Airliner" ... after 40 + years of assorted design work .... this was the simplest and most effective trailer I could come up with ...I know it doesn't have that Desi & Lucy retro effect ...or "the TD LOOK .... I understand!!!

never too late to change your mind ... ????

[GPW]

Sorry , just being "devils advocate" .... too much "agreement" going on here ... that's Un -American ....

[Miriam C.]

GPW
If I could put a door in I might. Mike got to Bernice and saw the usefulness of a full hatch. Imagine a 6foot wide hatch. Need a crane to lift it. He is buying the lifts. Next build, WW/escape hatch. I am sure it is easier.

Jim,
I'm not sure I should tell how I did mine. I had a 11degree angle to get the vertical framing to line up with the curve. When I did the hatch spar I glued two regular spars together, wide sides together, then put the hatch spar through the saw on both sides with the angle making a paralellagram. I messed with this on some 2x short pieces till it worked. Never doing that again.

The spar is plumb with the ground and fits the curve of the tear too.

The hatch ends I am making flat, straight up and down.
Good luck.

[GPW]

M ... I've got a 6'wide hatch ..light as I could build (simple but strong) ... still weighs a ton .... needs 1" Emt stick to hold it up .... hahahahaha

Parallelogram ???? wow !!! That's pretty exotic ... great you were able to do that "advanced " kind of woodworking/structural design ....

[PaulC]

Paralello-WHAT!!!!!!!! Squares, rectangles, even circles Miriam Fancy stuff like that --------Girl you're starting to freak me out a little



Cheers
Paul

[Miriam C.]

Paralello-WHAT!!!!!!!! Squares, rectangles, even circles Miriam Fancy stuff like that --------Girl you're starting to freak me out a little



Cheers
Paul

Ok an elongated, cubed, paralellagram. Really I don't know what to call it, just paralla. looking from the end. Not fancy, its a pain. Just lucky I remembered where I set the saw the first time.

We need "hatch hall of fame pictures" of all the ways to do it. Got pictures on a real camera, The digital isn't liking the close ups and cloudy weather. Chilly here.

GPW--UH HUH. I can just imagine. Getting lifts or not doing it.

[PaulC]

Don't know where I've been, but it's good to be back

Cheers
Paul

[kayakrguy]

Jim, my personal take is to use vertical spars...lessens springback issues...we used 3/4 ply to cut ours out of and they are tapered from 2.25"s at the top to 3"s at the bottom...we used 4 of them on a 4"er...the angle...on the last roof spar, we cut it so that the back side came straight down(plumb to the horizontal axis). So, when we cut the face of the hatch spars, it was also cut straight down (same plumb line)...remember that there will be a gap of 1/8th to 3/8th between the last roof spar and the top edge of the hatch depending on the type of hinge used.......
madjack

MJ,

We are isomg 3/4"ply for the vertical spars/gussets/ribs. Thinking of doubling them us--do you do that?

Second, do I understand you to mean that you cut the roof hatch spar so that the 'face' of the spar is plumb vertical as it meets the hatch spar, which is also plumb vertical? My head tells me that if that is right, then the roof spar would be wider at the bottom and the hatch spar wider at the top--is that right?

We got the ribs/gussets/vertical spars cut today....have to 'fine tune' them to the top and bottom spars. Cut 6--thinking of doing 3 double 3/4" ribs across a 5' wide hatch...

Jim

[GPW]

Wouldn't it be easier to make the hatch spar perpendicular to the radius of the side , then the hatch would be also .... easy to make ... not a lot of angle cutting except tying in the firewall sheeting ...

[Nobody]

GPW wrote

Wouldn't it be easier to make the hatch spar perpendicular to the radius of the side , then the hatch would be also .... easy to make ... not a lot of angle cutting except tying in the firewall sheeting ...

My thoughts exactly. That's what I did & it sure made it easier (for me anyway) than trying to figure out all that 'angle' stuff. 'Sides, I probably couldn't do the math anyway, I failed 1st year algebra about 50yrs ago & only learned enough 'trig & geometry' to get along in some work I did .

[madjack]

...due to an ongoing case of CRS, I went back and checked...the bulkhead comes up to the front(cabin side) of the last roof spar, which is doubled...this means that the cabin side is cut plumb for attachment of that bulkhead...the hatch side is perpendicular to the angle of the roof and the hatch spars are parallel to that...sorry about any confusion....
madjack

[kayakrguy]

Thanks, guys,

Ok, got the idea of perpendicular to the curve...that does make sense.

Jack, did you say in oine of your posts that you use bendy birch for your hatch? Is that less likely to cause springback? I mean, intuitively it sees that it would.

And a last question for everyone, does doubling the ribs e.g gluing two 3/4 ply ribs together help stop springback?

Best to all,

Jim

[madjack]

Jim, springback is induced by the ply trying to return to it's natural position, so the bendy eliminates that.....doubling your spars can't hurt...I believe Grant Whipp cuts a spar profile out of sheet AL and bonds it to two different spars to eliminate springback
madjack

[bledsoe3]

I think if you use enough vertical spars you won't have any spring back.

I used 7 spars.

[GPW]

See what a PIA the hatch really is!!!!!!!!!!!??????????? .... and after all that ,it's ridiculously expensive hinge time ....
Springback is the result of dirstortion of the ribs/spars original shape ... as we learned with airplanes, a rib that in fatter in the middle will distort less than one with a uniform width since stresses are concentrating in the middle ... Do we need a picture....
draw an Arc ... connect the two ends with a straight line ... OK !!! See ..

A door solves all these problems very simply ... want a "look " ... buy some new clothes .... get a haircut .... hahahahahahahaha