Bomar Hatch Strut - stripped threads

[keneasley]

Seeking ideas for how to fix this.
The Bomar hatch over the main cabin is held up with a strut.
The bottom of the strut is attached to the hatch frame with a bolt.
When I acquired the boat the threads in the frame were stripped.
I put an undersized bolt in it for purposes of this picture:

Bomar_Hatch_Strut.jpg (82.7 KiB) Viewed 632 times

I think the bolt should be a 5/16" coarse thread or an M8 size.
Not sure which.

Any ideas on how to renew the threads?
Drill and tap to larger size?
Epoxy it in?

Thanks for any ideas.

[jbenagh]

I faced a similar or worse dilemma last year. I had a broken stainless bolt in the casting. A part of the casting prevented me from drilling the bolt. I also needed new "glass", one new strut and would have to remove the hatch and bring to a machine shop who quoted about $200-300 to machine off the casting, remove the bolt and helicoil.
If you are at aluminum of the casting and have good access for drilling oversize, I think you have 2 good options. Oversize bolt is easiest; not much stress here but it will be a little weaker than the original design. Second is to get a heli coil kit and use the original size bolt.
Jeff

[wikakaru]

If you are going to the trouble to remove the hatch and have a machine shop do something, you may as well just install a new hatch.

A different and much simpler option is to remove the support arm altogether and use a wooden prop to hold the hatch open. It's not sexy but it gets the job done.

Smooth sailing,

Jim

Hatch Prop.jpg (103.05 KiB) Viewed 618 times

[tjr818]

If the hole is too worn to drill for an oversized bolt, perhaps you could move the strut to the other side of the hatch.

[jbenagh]

Jim,
I ended up replacing the hatch rather than gong the machine shop path. Be careful with other vendors; the interior radius can be different, causing leaks. So I went with the same Bomar but paid $$$ due to supply chain problems in Jan 2021. Also, Bomar changed the bolt pattern which meant filling all the holes and redrilling
Also, the original Bomar had two struts so I used the backup for about 5-7 years but then got nervous about that side also breaking. In warm, calm weather, we often try to leave the v-berth hatch open and with any seas the stick doesn't quite work since it bounces out.
Jeff

[John Stone]

Hi Ken
I would consider two options. Best solution is to install a helicoil. Not difficult. It's the strongest solution and really the right way to do it. This would be my first choice. Here is a simple video to depict how it works.

https://youtu.be/u08XLjy6_Kc

If for some reason I could not do that then I would clean the hole with acetone, aggressively sand inside, vacuum, acetone wipe down, and use gFlex epoxy. Coat the bolt with wax. Fill the hole with the gFlex and insert. Get good squeeze out. Make sure bolt is vertical. Let it cure hard. Unscrew the bolt. You are done.

The hatch riser bolt is in sheer so the epoxy solution should be strong enough.

Again, I'd consider helicoil first then go to epoxy second.

[keneasley]

Thank you everyone for the insights and ideas.
I'll try the heli-coil tomorrow and report back.
The brand that I found locally is called "Fix-a-Thread"

[John Stone]

Ken
Make sure the helicoil is for aluminum. Interested to hear how it goes.

[keneasley]

Yesterday I got down to the boat.
Drilled out the 5/16" hole to be 21/16", tapped it, and installed the Fix-a-Thread.
I used a bit of red loctite on the threaded insert. I waited a couple of hours for the loctite to set.

As you can see -part of the problem with the hatch is that the part of the frame into which the bolt goes has a piece broken off.

Hatch_Stut_1.jpg (59.21 KiB) Viewed 542 times

Then I fastened the strut to the frame with a spacer and a 5/16 - 18 bolt.

Hatch_Stut_2.jpg (1.76 MiB) Viewed 542 times

When I tightened the bolt and then tested out I found that the bolt would tend to move.
So I took out the bolt and applied some Loctite and tightened it down. Then I left it alone to set.

I'll test it again in a few days. In the mean time I ordered some fasteners from McMasters that might lead to a better repair: a short piece of threaded rod and a binding barrel.

If the Loctite has not made the bolt hold fast then I'll use the new fasteners and send another picture.

Thanks again for everyone's help with this.

[keneasley]

Oh - that should say - "...drilled out the hole to 21/64"..."

[John Stone]

Ken
Looks like you did a good job. I don't tighten the bolts. I coat them with Tef-Gel and hand tighten them. When I open the hatch, which is almost daily out cruising, I like to give them a turn one way and then the other. If left alone, over time they will suffer galvanic corrosion and become seized. That's what happened to mine and I had to drill them out during the rebuild. Major PITA which you know all about.

By the way, during the rebuild I removed my hatches, drilled out the snapped off bolts, had them sand blasted and painted them with Awlgrip. Then I sent them off to "Hatch Masters" for new acrylic glass. It was expensive but not near as much as new ones. They came back like new.

[keneasley]

Thanks for that input John.
I tried it with the bolt hand tight but I wasn't satisfied with it because the bolt rotated with the movement of the hatch strut and whobbled a bit.
The problem is that the part of the hatch lid into which the bolt goes is partially broken off so the bolt has only about 1/2" of hatch frame to screw into.
So I went with Plan B and incorporated a Binding Barrel into the set up so that the bolt would not rotate with the movement of the hatch strut :
I tried drilled out hatch strut to 3/8"
and used a Stainless Steel Binding Barrel, 5/16"-18 Thread that was 3/4" Long
and a 1" long piece of Stainless Steel Threaded Rod
and a home made oak washer at hatch frame as a spacer.
So far it works. Nice to have s a small but annoying problem fixed.