H170 and the dreaded rotten wood in the motor mount area, my findings to date.

Apr 16, 2017
841
Federation NCC-1701 Riverside
The point you are at now leaves me thinking that maybe you might want to consider doing exactly what I did with the motor mount. Carve out the top 1/2" of foam & lay in glass, one sheet at a time, rather than buying the prefab G10. You can carve out the foam up under the existing Luran & pick up a large area to distribute the load. If you want to get fancy, you can taper the thickness of the glass towards the ends & only have full thickness in the area where the screws grab. The selfish part of me would like to see you do something different so that I can compare those results to mine & learn more, but the practical part of me doesn't want to see you pop any more holes in that boat to get the backing plate in.
If i dont use a bilge backer, then putting the G10 deep into the foam AND undercutting the luran with FRP might be the ticket.

What i should have done is placed barrel nuts under and through the G10, put the bolts in, epoxied the board to the bilge FRP, then foam to the top.
IMG_20190610_225535.jpg

The foam being 1-2 inches undercutting the luran. Nothing would pull that out..Could probably lift the boat up and not fail. Then FRP with luran undercut. Remove bolts, set the mount, and put bolts back in with butyl or other sealer.
 
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Sep 22, 2018
1,869
Hunter 216 Kingston
If i dont use a bilge backer, then putting the G10 deep into the foam AND undercutting the luran with FRP might be the ticket.

What i should have done is placed barrel nuts under and through the G10, put the bolts in, epoxied the board to the bilge FRP, then foam to the top.
View attachment 165856
The foam being 1-2 inches undercutting the luran. Nothing would pull that out..Could probably lift the boat up and not fail. Then FRP with luran undercut. Remove bolts, set the mount, and put bolts back in with butyl or other sealer.
I think you are on to something there. Do the barrel nuts have “teeth” on the flange to ensure they don’t rotate when you tighten the bolt? I guess they might just stick in the epoxy or you could add a lock washer to be sure
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
I think you are on to something there. Do the barrel nuts have “teeth” on the flange to ensure they don’t rotate when you tighten the bolt? I guess they might just stick in the epoxy or you could add a lock washer to be sure
Doh! Excellent point. The ones for wood do.

So close. back to the bean bag for me for solve this "limit" problem to another decimal point.
 
Aug 22, 2017
1,608
Hunter 26.5 West Palm Beach
I think you are on to something there. Do the barrel nuts have “teeth” on the flange to ensure they don’t rotate when you tighten the bolt? I guess they might just stick in the epoxy or you could add a lock washer to be sure
You can drill a couple of holes in the flange area & put small screws in the holes to prevent spinning the nut.
 
Sep 22, 2018
1,869
Hunter 216 Kingston
You can drill a couple of holes in the flange area & put small screws in the holes to prevent spinning the nut.
Jim
Nice MacGuiver thinking!
I’m not sure how “firm” G10 is, will something actually bite into it or is too hard??
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
You can drill a couple of holes in the flange area & put small screws in the holes to prevent spinning the nut.
These might work if they can handle larger bolts.
IMG_20190611_140827.jpg


Epoxy would fill the gaps and make locking colums between the FRP and the G10.
 
Sep 22, 2018
1,869
Hunter 216 Kingston
So G10 VERY firm!!

I was thinking you were going to use the holes in motor mount as template for where to drill holes through the G10 big enough for the outside diameter of the “ barrel” of the nut. Insert the nuts from the “underside” of the G10 and then stick the G10 to the existing FRP. With that approach and these “ nuts” you could add three screws to hold the nuts in place while you placed it onto the FRP bedding you would lay down as the “glue” layer. Once the G10 is sitting on the new bedding while it’s still wet you could again use the motor mount with temp bolts as a guide to ensure everything is lined up and level for the G10 to cure to the bottom FRP.
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
Should i use biaxial sewed cloth or can i use the cloth every store sells next to the bondo supplies. I really dont want to order more stuff or drive to West Marine.

Ready for this project to end. Its so magically windy out right now.

Any other places sell that kinda stuff
 
Sep 22, 2018
1,869
Hunter 216 Kingston
Should i use biaxial sewed cloth or can i use the cloth every store sells next to the bondo supplies. I really dont want to order more stuff or drive to West Marine.

Ready for this project to end. Its so magically windy out right now.

Any other places sell that kinda stuff
I get that you want it to end and get sailing. I apologize for repairing vicariously through your journey. Probably infected you with my overthinking stuff!!!

I would think it wouldn’t make a difference what cloth you used for this part of the project as it’s hidden from site and would logically be just as strong. The woven stuff might be nice for final outside layer as it would finish nicer but that’s your call.
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
The new foam was scooped out and I storyboarded an installation as if using barrel nuts and dont see this being practical. Each nut is at a different level (plus or minus 5/8 in). It will be sketchy trying to get the nuts lined up and the backer level so thst the bolts line up.

This leads me to the next proposal, which is to just use 1/4in bolts and epoxy them to the FRP, going up. They can be set up quickly, and the mount can be used for the support, kinda like how bolts for street lamps are placed in concrete, or deck foundations are cast.

Then washers can be added until the G10 is resting flat.

The foam is poured in two batches. The first batch is for under the G10, the next is for over the G10.

Cloth is layered then smoothed out, working around the protruding bolts.

I dont like the buried bolts and thinking maybe the bolt should be encased in a plastic tube or something so it is not touching the top luran/FRP.

Cutting 4 inch hole and adding a access panel is looking more attractive. Then use bilge backer and bed the bolt holes.

IMG_20190612_131807.jpg
 
Sep 22, 2018
1,869
Hunter 216 Kingston
The new foam was scooped out and I storyboarded an installation as if using barrel nuts and dont see this being practical. Each nut is at a different level (plus or minus 5/8 in). It will be sketchy trying to get the nuts lined up and the backer level so thst the bolts line up.

This leads me to the next proposal, which is to just use 1/4in bolts and epoxy them to the FRP, going up. They can be set up quickly, and the mount can be used for the support, kinda like how bolts for street lamps are placed in concrete, or deck foundations are cast.

Then washers can be added until the G10 is resting flat.

The foam is poured in two batches. The first batch is for under the G10, the next is for over the G10.

Cloth is layered then smoothed out, working around the protruding bolts.

I dont like the buried bolts and thinking maybe the bolt should be encased in a plastic tube or something so it is not touching the top luran/FRP.

Cutting 4 inch hole and adding a access panel is looking more attractive. Then use bilge backer and bed the bolt holes.

View attachment 165904
It’s sort of clear why they just screwed the mounting plate on in the first place, just build the boat and then add the piece from the top, easy peasy lemon squeezey as my grandson says.

Your right to think getting the bolts standing in the right alignment and glassing around them could be challenging.

Through bolt with backing plate is obviously common approach. I just don’t know about access panel on the floor of the boat where someone is likely to step on it, crack, leak flood hull etc.

Oops there I go “thinking” again. Sorry!
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
I have just sold my soul.... What have done :)

20190612_184006.jpg


This G10 stuff is alien technology for DIY. Its crispy and feels like solid glass, melts like plastic and dulls tools like its titanium. Its not really supposed to be screwed into like wood.

It will hold threads. For a test i drilled a hole just smaller than the screw threads in the backer designed for the rudder. The screw is one of the long ones used for the rudder, but the diameter is the same as the shorter screws used for the motor mount.

Its a very tight grip and i had to back out a couple times and finally put a little chain oil on the threads for lubrication to go through.

There is no way those are going to pull out. The test included grabbing the screw with pliers and when it held i rested the piece on the ground with the screw digging down and bounced with all my weight on the backer hoping to push the screw out or twist it.

The only weakness is if the screw was moved side-to-side. This seemed to crush the material. The screw was very long, so it was pretty easy to start enlarging the drilled hole.

I then backed out the screw and then combined the actual mount with the backer with the screw. I was able to torque the screw such that the two pieces were locked together without movement. This was after the hole had been enlarged.

Its looking like the four factory wood screws will be just fine with 1/4 in G10.

If in 10 years the mount starts to loosen up, the solution will be easy...Drill 1/4in holes, open an acces point, and use backers with bolts.

The final plan is to epoxy the G10 right to the inner FRP, overflow with foam, add more FRP to undercut the luran, glue the luran back on, MMA the Luran back to the boat, one more FRP, then fair and paint.

To add the mount drill 4 holes using the mount as a template.

The G10 is a little bit bigger than the luran cut out and it is covered with at least an inch of foam that extends about an inch beyond the cut out panel. By placing the FRP over the foam its never going to give it a chance to crack and pull out.
 
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Sep 22, 2018
1,869
Hunter 216 Kingston
Well it looks like you have driven a screw into a solid looking substrate, or sat in your chair long enough WISHING you were sailing and decided on a way forward.:beer::beer::beer:

Looking forward to seeing what you cooked up!
 
Sep 22, 2018
1,869
Hunter 216 Kingston
The final plan is to epoxy the G10 right to the inner FRP, overflow with foam, add more FRP to undercut the luran, glue the luran back on, MMA the Luran back to the boat, one more FRP, then fair and paint.
I'm not sure what happened but my response above was based on the fact that most of the txt of your post was missing , all I saw was your comment above the photo and the photo.

The plan sounds like a really good solution to the dilemma you faced trying to get a backer plate in the small gap between the hull and deck. The screws will be well anchored in the G10 (effectively a really good "backer plate" and you will have a full sandwich layup to support the motor mount so I can't see it failing. You have gotten rid of the wood so even if water does get in I can't see how it could hurt anything (unless of course it was wet and froze)

As usual impressive work!!
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
Rudder mount is completed, well, mostly.
20190618_202842.jpg

I just need to drill a 7/32in hole all the way through the four existing starter holes. That should allow the embedded G10 plate to take on the threads of the factory screws. The stater holes are 1/4 inch (bigger) and counter sunk. The screw threads wont touch the luran.

There were no big issues. I'll give another update after the mount is attached and field tested.

The foam used was 4lb 2 part urethane. Total boat 5:1 epoxy with glass cloth was placed over the foam extending under the luran.

The luran panel was stuck onto the unset epoxy. When the epoxy cured, it was cleaned around rhe edges and Plastic bonder was placed in the gap.

That was ground down and a layer of cloth was placed over the luran out to about an inch.

Fared with west 407 as a filler, sealed, then painted.

There was some minor fish eye issues with my 407 sealer, and i think i contaminated it with plastic dust.
 

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