G&M's 'Drop

[tony.latham]

You sure did a great job cutting the hatch ends off the walls.



Tony

[GarthB]

You sure did a great job cutting the hatch ends off the walls.



Tony

Thanks Tony! I'm glad that deed is history.

[GarthB]

Finished framing out the hatch tonight by using two pieces of 7/8" thick oak as the bottom spar of the hatch. I beveled them to match the profile of the hatch with the table saw. Once cut, I installed them individually, joining their faces with glue and screws. The pocket hole screws were tough to send home since the spar above it was so close.




While installing the bottom spar, I decided it would be a good idea to reinforce the top spar of the hatch with an additional oak spar mated right up against it. The flexural strength of the poplar is plenty strong in the strong axis direction, however it's weak axis strength isn't all that great without continuous sheathing on both sides. With this being the hinge attachment point, I think the rigidity of the oak will be beneficial.



Once the spars were complete, I decided to add a temporary piece of 1/8" birch to the outside of the frame in order to prevent any movement prior to the interior birch ply getting installed. Joe's hatch nightmare has been at the forefront of my mind and I believe I saw Tom & Shelly do this in their build for similar reasons. I considered using two pieces but I think one with multiple screws in each spar should suffice.



Last, I got the blocking installed on both hatch sides. This task was pretty straight forward. Just a bunch of gluing and screwing.

[tony.latham]

I decided to add a temporary piece of 1/8" birch to the outside of the frame...

I think that's a good idea. I too stressed over what Joe went through.

Tony

p.s. I woke up to this book review this morning:



I wish Ken would educate me on what's the latest way to build... Maybe he's just talking about your temporary 'gusset' piece.

[Tom&Shelly]

Once the spars were complete, I decided to add a temporary piece of 1/8" birch to the outside of the frame in order to prevent any movement prior to the interior birch ply getting installed. Joe's hatch nightmare has been at the forefront of my mind and I believe I saw Tom & Shelly do this in their build for similar reasons.

Worked very well for us. I don't recall any problems with movement.

(Not our original idea, of course. It was before Tony's book, but Steve Fredrick did it also.)

Tom

[Tom&Shelly]

p.s. I woke up to this book review this morning:



I wish Ken would educate me on what's the latest way to build... Maybe he's just talking about your temporary 'gusset' piece.

Wonder how many he's built?

Tom

[western traveler]

p.s. I woke up to this book review this morning:



I wish Ken would educate me on what's the latest way to build... Maybe he's just talking about your temporary 'gusset' piece.

[/quote]

Oh, crap. But I’m so far along! Do I need to start over?

[tony.latham]

Oh, crap. But I’m so far along! Do I need to start over?

Maybe a layer of carbon fiber...

Tony

[GarthB]

Got the strut brackets mounted and the hurricane hinge temporarily mounted today in order to do a test run of the hatch. It was pretty pleasing to see it function properly.




Overall, it works as it should. Remembering another lesson from Joe, one of the first things I inspected were the hatch brackets. Sure enough, same issue.



Having the opportunity to see it in person gave my mind enough of a visual to determine the issue. The bracket is failing because it is buckling. The 90 lbs of compression force from the springs far exceed the lateral stability of the bracket in this direction. Comparing it to the lower brackets, it may be a bit more clear. They will never fail because the strut is pushing [img]away[/img] from the bracket's mounting screws rather than towards them, thus the plate is in tension rather than compression:



I'm not sure if there is a factory made bracket that would suffice here due to the location of the mounting ball on the hatch gusset. I'm considering drilling out the back side of the mounting ball on the bracket, tapping it, and threading a screw/washer into it from the opposing side of the hatch gusset. This would brace it from buckling and the washer should distribute the load enough to not tear out the gusset.

I also noticed that Joe came up with a solution and posted it today as well. A stiffer bracket plate like he made should work as well.

The only other strut related issue I noticed was that it is pushing the upper part of my hatch away from the upper edges of the walls, creating a gap. I only had half the screws in the hinge for the test, so doubling them may clear up the solution. If not, lighter weight struts may be necessary.

[swoody126]

¿ PONDERMENT ?

¿ is it possible to mount the ball in the geometric center of the plate ?

¿ and the mounting screws on all 3 corners ?

i had similar issues w/ the struts on the rear hatch of my Jeep Cherokee

found a strut w/ a thru bolted heim joint supported from both sides rather than just one and the mounting plate was in line w/ the force instead of beside the force

this would require some metal fab for the bracket and a block for it to mount to instead of along side of

maybe mounted against a spar that is reinforced w/ blocking behind(actually in front of) it to the next spar

just an old man trying to wrap his mind around the issue

sw

[tony.latham]

I've been scratching my head on this issue.





I've got a sliver of distortion in mine after nearly three years and lots of lid lifts... 90-pound struts. The tipping point must be 100-pounders.



Tony

[cjlangellier]

This may be a silly question, since I don't have the same struts but, can you flip the top bracket 180 degrees so that when the hatch is open the forces on the bracket are pushing away from the mounting point and not towards them? If you were to flip that bracket are there clearance issues that aren't apparent in the pictures?

[GarthB]

Thanks for all the insight everybody. The ideas are much appreciated!

Swoody, that idea is a good option. I would need to cut the stud off since it appears to be press fit through the plate (or some form of a rivet). If my drilling and tapping idea doesn't work, I'll give it a shot.

Tony, your plate (from your photos at least) actually does look slightly thicker. It could just be the way the photos make them look though. Maybe different vendors have different thicknesses?

CJ, flipping it around would work. The minor change in the stud location likely wouldn't be enough to change the hatch opening geometry. I'd just like to avoid drilling additional holes in my hatch gusset if possible.

[tony.latham]

This may be a silly question, since I don't have the same struts but, can you flip the top bracket 180 degrees so that when the hatch is open the forces on the bracket are pushing away from the mounting point and not towards them? If you were to flip that bracket are there clearance issues that aren't apparent in the pictures?

It’s not a silly question. But those brackets are held with bolts and T-nuts. It’s not a viable option at this point.

He’s following the instructions from my book. I think tomorrow — after some cogitation— I’ll add your suggestion to the manuscript and upload it to make the change.

My brain’s cranking. Thanks.

Tony

[GarthB]

Maybe different vendors have different thicknesses?

There are in fact different thicknesses. The ones from McMaster, like I ordered have a plate thickness of 0.08". The ones linked below, from Amazon, have a plate thickness of 0.121". They are slightly different dimensions so I'm still going to try the drilling/tapping first in case the bracket below's holes aren't in the exact same spots. Not sure whether the additional thickness would be enough.

https://www.amazon.com/Spring-Strut-Bracket-Mounting-Support/dp/B08MXM22Z3/ref=asc_df_B08MXM22Z3/?tag=hyprod-20&linkCode=df0&hvadid=494939685805&hvpos=&hvnetw=g&hvrand=15439607414602143554&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9052016&hvtargid=pla-1164727434638&psc=1