Re-Bedding Fixtures and an Apology

To drill through gel coat without causing cracks I saw the folks at NMI start the hole with a countersink bit and then followed by a drill bit of the needed size. I watched them do it, and it really works.
 
Hi Tom,
Yes I've done it before but it was yrs ago. I wonder though how deep? I'm assuming only the depth of the Gelcoat as I believe it isn't the fiberglass that is potentially cracking but rather just the gelcoat???


Tom Hruby":sf27xsw2 said:
To drill through gel coat without causing cracks I saw the folks at NMI start the hole with a countersink bit and then followed by a drill bit of the needed size. I watched them do it, and it really works.
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Tom Hruby":qai25bwl said:
To drill through gel coat without causing cracks I saw the folks at NMI start the hole with a countersink bit and then followed by a drill bit of the needed size. I watched them do it, and it really works.
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You run the drill in reverse to get through the gelcoat to prevent chips. Cracks are a different issue.
 
Well that'll be a first. I. never did that but I do drill in forward but gently...

You run the drill in reverse to get through the gelcoat to prevent chips. Cracks are a different issue.[/quote]
 
Don Yes they used the countersink only to drill through the gel coat. To drill through the fiberglass however it is best to use the hardest bit you have. The glass is abrasive and can easily dull a standard bit.
 
The bed-it tape is 1/2" Wide. Many of my fittings are one inch or more in width, case in point the bimini mount I'm about to mount is over 1" wide. How do you handle the tape? Do you double up, stretch it or what? My thoughts are to double it up.
 
I think either could work. The idea is to have enough of the tape in place to seal the area, but the only area that is critical to seal is the hole thru the boat! My experience with it resulted in lots of tape material being pushed out from under the fitting that had to be removed. As you slowly tighten the fastener, the tape material will be pushed out, at which time you can remove it. You want to achieve a mate to the exterior with full seal around the penetration, so you tighten slowly to allow the 'ooze'.
 
mstrpo":mldz4ma0 said:
I think either could work. The idea is to have enough of the tape in place to seal the area, but the only area that is critical to seal is the hole thru the boat! My experience with it resulted in lots of tape material being pushed out from under the fitting that had to be removed. As you slowly tighten the fastener, the tape material will be pushed out, at which time you can remove it. You want to achieve a mate to the exterior with full seal around the penetration, so you tighten slowly to allow the 'ooze'.
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Depending on the temperature, you should allow about 24 hours after you think you're done to tighen again.
 
okay. Now I know. Sounds like it is just what I need.

Depending on the temperature, you should allow about 24 hours after you think you're done to tighen again.[/quote]
 
I did more online research and realized I should not use 3M 5200 for Items that need to be fastened and removed regularly. The Tape is somewhere in btwn in its fast removability. 3M 4000 UV and 4200 fast cure seems to be the easiest to
remove.

The Job at hand is the mounting of a bimini that is, if it's like any other Bimini's
I've had, to be removed for cleaning or replacement every couple of yrs. If I use 5200 it will take an act of congress to remove the fixtures later...and as of recently we know how long it take congress to act. The tape would be doable but for almost thirty dollars I'd use less than 10" and it will sit on the shelf a couple yrs until I rebed everything else on the boat. I can buy the 4000UV in a 3oz tube which would be much more than needed for the Bimini Install. And the shelf life for the left-over is a year. So, for the bimini, I'll be using the 4000UV. In a year, two or three I will be using the tape for stations, cleats, and windlass fittings.

This posting, along with everyone's input, has evolved and has caused me to do due diligence to develop my preferences. I really appreciate everyone's contributions.

Don




Depending on the temperature, you should allow about 24 hours after you think you're done to tighen again.
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[/quote][/quote]
 
I have used a number of Bimini tops on boats for over 60 years. I never had to remove the deck fittings (SS). There should be pins or bolts holding the frame to the deck fittings. Those should be unloosed if you need to take the frame off. The Bimini should have zippers on the part you use on the bows--they zip on and off.

My experience with Butyl take is mostly on RV's and I had yet to see one instance where there was not some dirt and water trapped under the fitting and the fiberglass or metal that it is attached to. That experience is also over a period of 60 years. I would use 4000 or 4200.
 
Well there ya have it...60yrs is a long time as I'm only 66. I like 5200 and 4200 but I'm going to use (amazon just dropped it off) 4000 Fast cure UV. I had some experience on my Skiff that casued me to remove the mounts, I forget what and why, It was so easy as there was no bedding used on the outside open gunnels.

thataway":3nf5uzel said:
I have used a number of Bimini tops on boats for over 60 years. I never had to remove the deck fittings (SS). There should be pins or bolts holding the frame to the deck fittings. Those should be unloosed if you need to take the frame off. The Bimini should have zippers on the part you use on the bows--they zip on and off.

My experience with Butyl take is mostly on RV's and I had yet to see one instance where there was not some dirt and water trapped under the fitting and the fiberglass or metal that it is attached to. That experience is also over a period of 60 years. I would use 4000 or 4200.
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I first came across over drilling and creating a epoxy plug around bolt holes through a balsa cored deck and cabin tops while helping a friend commission a new boat about 35 years ago. The rigger who showed us how to do this also had us countersink the new bolt holes to form a small v-groove around the bolt when the fitting was replaced. This v-groove filled with caulk when the fitting was rebedded— sort of an additional o-ring of caulk. We redid all of then deck fittings including the lifeline stanchions. All these years latter non of the fittings have ever leaked and are still our original job. The balsa core is dry unlike her sister ships that were not redone. I don’t remember what caulk was used, probably 4200 or similar.
 
I take it you did not overdrill, fill with epoxy and redial before you bedded?

30and again 35 years ago I used Lifecaulk, a polysulfide. It had idiosyncrasies and I was poor at accommodating them. Took forever to cure. I always made a mess of it though thankfully it was effective in waterproofing.

olsurfdog":1ptzf1zf said:
I first came across over drilling and creating a epoxy plug around bolt holes through a balsa cored deck and cabin tops while helping a friend commission a new boat about 35 years ago. The rigger who showed us how to do this also had us countersink the new bolt holes to form a small v-groove around the bolt when the fitting was replaced. This v-groove filled with caulk when the fitting was rebedded— sort of an additional o-ring of caulk. We redid all of then deck fittings including the lifeline stanchions. All these years latter non of the fittings have ever leaked and are still our original job. The balsa core is dry unlike her sister ships that were not redone. I don’t remember what caulk was used, probably 4200 or similar.
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The Bimini product I'm using did not come with backing plates and only roundhead wood screws came with it. Furthermore when I drilled the holes guess what? Yup, wood fiber came out. I thought for sure that this area had no core. But it did.
Now I will over drill and fill with epoxy and then redial tomorrow. Bummer. nice to have a long weekend to do this unexpected extra work.
For backing plates I am thinking to use fiberglass. I recently cut up a 15' 1972 tri-hull ski boat. I have lots of pieces of it to use however I need and I think that with large washers these trimmed pieces of 3/8" fiberglass will make nice backing plates for the few pieces of Bimini hardware.
 
Donald, sorry, I guess I wasn’t very clear. We did over drill the holes (using a small Allen wrench chucked up in a drill), filled the cavity with thickened epoxy and then re-drilled the bolt hole and lastly added the counter sink. Thickened the epoxy with fiberglass saw dust. We also added quite a few stainless backing plates. Too bad the manufacturer didn’t do all this in the first place. I guess understandable from a cost point of view but it still needed to be done! Cost a lot more to repair rotten spongy decks.
 
Too bad the manufacturer didn’t do all this in the first place.
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Some manufacturers do put in solid glass or even tapped plates during the initial process. Unfortunately C Dory never did this. One place where there is solid glass is the very outside of the top, including the sides and eyebrow. Many owner add handles there for safety when going forward, until the person can reach the cabin top rails. Unfortunately those cabin top rails are not installed in solid core, and I have had to over drill and epoxy plug them.
 
Drill, undercut, fill, drill pilot hole.
 
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