Hatches - Mounting, Hinging and skinning

[Toytaco2]

Its time! I can avoid it no longer. I must cut my hatch notch, mount the Hurricane Hinge and skin my Hatch. I think I have everything figured out except for one thing and would appreciate some expertise from the group:

I have 2 layers of 1/8" ply on the TD roof and am thinking I will have only a single layer on the hatch (for wieght savings). Would I then only need to notch the side walls by 1/4 inch instead of the 3/8" called for in the Generic Benroy Plans? Thus I would have an "effective notch depth" of 3/8 inches made up of an extra layer of 18" ply on the roof plus the 1/4" notch cut in the side wall.

OR: am I creating some unforeseen alignment problems due to mismatched layering and should really put 2 layers of 1/8" on the hatch just as I did with the TD roof and notch the sidewalls by the standard 3/8"?

Maybe I'm just making too big a deal out of 1/8"!


Thanks,
Mike

[Miriam C.]

It is easier to remove more than to add it. I would cut it less and remove more if needed.

[2bits]

I think your logic is sound, remember the notch is only cut to make room for the seal, so less would just mean a tad less compression on the seal and more would mean more pressure needed to latch the hatch down. I would trust your numbers. Miriam has a good idea too so it you have a belt sander handy, you've always got the ability to scribe a line and remove a little, but I think you are fine with your original idea. Not that I have any experience or anything, I just can see that you have thought it through correctly.

[looped]

:thumbsup: It is easier to remove more than to add it. I would cut it less and remove more if needed.

So true on that! when i made my hatch spars i didnt take into account a slight change to the curve and now i am finding myself adding material to the walls 1/8th inch at a time so yeah she is soo right!

[Hoosier Greg]

What does it matter one layer or two. It's the first layer what will come in contact with the Galleys walls..
I think we are talking about two different issues here when the question is applicable to one. The hatches top skin kept at the same angle,flush with the builds main roof line. .No?
Greg.

[Miriam C.]

What does it matter one layer or two. It's the first layer what will come in contact with the Galleys walls..
I think we are talking about two different issues here when the question is applicable to one. The hatches top skin kept at the same angle,flush with the builds main roof line. .No?
Greg.

Greg the question I addressed was "to cut the seal gap the same despite the thinner hatch skin?"

And it can get confusing for sure! The top hatch skin will meet the roof at the hinge. It will not necessarily meet the hatch wall as intended if the roof is less thick. With a 1/8" difference you can compensate with a thicker seal.[/quote] It won't fit all the way around the same I think as the seal will compress different at the hinge than the bottom.

[Toytaco2]

Greg the question I addressed was "to cut the seal gap the same despite the thinner hatch skin?"

And it can get confusing for sure! The top hatch skin will meet the roof at the hinge. It will not necessarily meet the hatch wall as intended if the roof is less thick. With a 1/8" difference you can compensate with a thicker seal. It won't fit all the way around the same I think as the seal will compress different at the hinge than the bottom.

Miriam, you are getting to the heart of my real question - is there some critical alignment problem being created? My hatch profile matches the sidewalls currently. Once the hinge and hatch are mounted, the hatch (single 1/8" skin layer) frame will protrude the 1/8" above the side walls.

Am I understanding your answer to be that the rubber hatch seal should absorb the difference and not be noticable? On the other hand, it's a simple matter to just put the 2nd skin layer on the hatch to match the TD roof. I'm just trying to save a little weight here and maybe its not worth the trouble. Again, am I making too big a deal out of 1/8 inch?

[Miriam C.]

This is what I found with mine. You are lined up perfectly to meet the roof with two layers of 1/8" and you take one layer away. This will bring the hatch up 1/8th" which is not a big deal, mostly because you do not have a big sweeping curve on the bottom. I had an extra 1/8th" gap as a result of the single layer of ply. I also had a bottom curve to fix and needed to sand some of the side wall away.


If it worries you you should be able to add a trim of 1/8" to the top skin at the hinge or bottom of the hatch to compensate but I doubt it will really matter that much. If anyone gets out a ruler just start laughing hysterically .

You might do a dry fit and see what I mean at the bottom. Easy fix right now. The seal can be any thickness you want also.

[Mauleskinner]

Another simple option might be an 1/8" doubler under the hinge on the hatch, either cut off flush with the edge of the hinge or beveled to feather into the hatch skin.

David