Creating FG pads to install no-penetration stanchions ?

Trawler_traveler · Dec 6, 2019

For safety I'd really like to put some lifelines or even a solid rail on the dinghy deck up top (pilot house trawler). However, I do NOT want to screw into the cored dinghy-deck.

What I'm thinking about trying is to grind down to the FG in areas where the stanchions would go and build up solid FG thick enough to screw stanchions into without piercing the deck.

I'm looking for ideas about how one would do this most effectively as I assume we're not the first to try something like this ?

Thanks,

-Sven

wkearney99 · Dec 6, 2019

Don't know that you could do this effectively without it looking hideous. The most common practice I've seen (on other boats) is to bury a backing plate on the underside. This to avoid something large having to be created on the topside in order to gain a secure attachment. Not just for the sake of looks but also to avoid changing how things drain.

It's one thing to raise up a small circular area under a stanchion post to help encourage water to avoid pooling around it. It's another to have a large enough 'plate' glassed onto the existing deck. That then also becomes a potential tripping hazard, right where you're trying to increase safety.

Comodave · Dec 6, 2019

Well the fiberglass pad would have to be fairly thick in order to get enough bite with a screw, probably an 1” or more. Maybe get some G10 fiberglass and epoxy it down and then drill and tap the G10. You can get it from Jamestown Distributors in 1/2” and could always laminate 2 pieces together to get the depth you need. If you drilled and tapped it then when you put the screw in add some epoxy on the screw threads to lock it in.

boathealer · Dec 6, 2019

Might be easier and better looking to cut through the top skin of the deck at each position and hollow out an area of the core that you could back fill with an appropriate material and/or glass/epoxy.

Sailor of Fortune · Dec 7, 2019

Comodave said:
Well the fiberglass pad would have to be fairly thick in order to get enough bite with a screw, probably an 1” or more. Maybe get some G10 fiberglass and epoxy it down and then drill and tap the G10. You can get it from Jamestown Distributors in 1/2” and could always laminate 2 pieces together to get the depth you need. If you drilled and tapped it then when you put the screw in add some epoxy on the screw threads to lock it in.

I second the G10 suggestion. Cut and stack whatever thickness you think you need. 45 degree champher the edges and epoxy down. When painted or gelcoated, it won't be visible or unsightly.

FF · Dec 7, 2019

A raised pad is great for fewer deck leaks , but thru bolts are far better for a stanchion base.

Thick GRP is available on line , but a battery jig saw with a boat in a dumpster is fine too.

Just build so you can get to bolts to service the bedding compound.

Remember dock helpers will use the stanchions to catch or move the boat.

Trawler_traveler · Dec 7, 2019

Thanks for the suggestions. I'll definitely look into the G10 option !

Since these stanchions are on the dinghy-deck they are out of the reach of too-helpful dock hands and the lifelines will only be used for life saving

Thanks.

-Sven

Solly · Dec 7, 2019

" and the lifelines will only be used for life saving

"
That's the rub. Screwed stanchions might not save your life. Far better to thru bolt them.

Make a raised platform, drill oversize holes for the bolts. Fill them with epoxy and re-drill to size. Seal the base good and check for leaks once in awhile. That way the core should be sealed and no danger of water getting in it.

Comodave · Dec 7, 2019

Another way would be to make the blocks out of G10 and put bolts up through them from the bottom and have them stick out the top of the G10 blocks like studs and put nuts on top of the stanchion base. Alignment would be more critical but they would be through bolted. You would have to recess the head of the bolt in the G10. Maybe also tap the bolt holes and screw the bolts into the G10 from the bottom. Bed the G10 in thickened epoxy and make a filet around the G10 blocks to soften the look and also increase the strength.

healhustler · Dec 7, 2019

I’ve been wanting to raise my stanchion bases since I saw several examples On a KK39. I looked at the G-10 but I’d need to cut to size, shape, then grind off the usual gelcoat to laminate anyway, so I just had an extra thick center console made, cut the top off to make a new helm area in my pilothouse, and now I’ll be using the flat areas (probably about 30 sq. ft.) of skirt material to form the stanchion bases. I’ll likely stay with through bolting though, even after doing the drill, fill and re-drill routine.

The glass below my stanchions is cracked from decades of torquing. The new pads should spread the load, but there’s no guarantee that thicker bases won’t crack around the perimeter.

Comodave · Dec 7, 2019

healhustler said:
I’ve been wanting to raise my stanchion bases since I saw several examples On a KK39. I looked at the G-10 but I’d need to cut to size, shape, then grind off the usual gelcoat to laminate anyway, so I just had an extra thick center console made, cut the top off to make a new helm area in my pilothouse, and now I’ll be using the flat areas (probably about 30 sq. ft.) of skirt material to form the stanchion bases. I’ll likely stay with through bolting though, even after doing the drill, fill and re-drill routine.

The glass below my stanchions is cracked from decades of torquing. The new pads should spread the load, but there’s no guarantee that thicker bases won’t crack around the perimeter.

What kind of backing plate is there?

FF · Dec 8, 2019

"The glass below my stanchions is cracked from decades of torquing. The new pads should spread the load, but there’s no guarantee that thicker bases won’t crack around the perimeter."

The usual problem is GRP is never flat but a metal backing plate is.

A piece of 1/8 rubber between backing plate and deck underside usually solves this problem .

Russell Clifton · Dec 8, 2019

Here is a link to the West System Epoxy Repair Manual. Looks like chapter 7 would help out.
http://https://www.westsystem.com/wp-content/uploads/Fiberglass-Manual-2015.pdf

Comodave · Dec 8, 2019

FF said:
"The glass below my stanchions is cracked from decades of torquing. The new pads should spread the load, but there’s no guarantee that thicker bases won’t crack around the perimeter."

The usual problem is GRP is never flat but a metal backing plate is.

A piece of 1/8 rubber between backing plate and deck underside usually solves this problem .

I butter the side of the backing plate that touches the underside of the deck with thickened epoxy so that the backing plate is in good contact with the bottom of the deck. That way the backing plate isn’t just contacting a few high spots. I prop up the backing plate until the epoxy goes off and then drill my bolt holes. One benefit of the epoxy is that the backing plate will stay in place by itself while you are working on the fitting.

healhustler · Dec 8, 2019

Comodave said:
What kind of backing plate is there?

Original backing was a combo of SS plate, oversized washers and teak blocks. The majority would require custom fits such as the one pictured below which has four bolts, two inboard and two hidden under the teak cap board, easy to remove. I’m tempted to go with larger 1/2” starboard plates which would be easy to grind and form into tight areas.

healhustler · Dec 8, 2019

Here’s two good examples of raised areas on the KK39. No puddling, no water collection.

Lepke · Dec 8, 2019

The way to drill and screw into a cored deck w/o leaks is to mix some epoxy and use a syringe to squirt epoxy down the hole before screwing. The wet epoxy lubes the threads while turning, giving a stronger hold, and the screw is encased in epoxy so it can't leak. The drawback is it's difficult to later remove the screw. I use a small impact wrench to remove epoxied screws.

Comodave · Dec 8, 2019

healhustler said:
Original backing was a combo of SS plate, oversized washers and teak blocks. The majority would require custom fits such as the one pictured below which has four bolts, two inboard and two hidden under the teak cap board, easy to remove. I’m tempted to go with larger 1/2” starboard plates which would be easy to grind and form into tight areas.

The problem with Starboard as a backing plate is that it will compress some. I like a more solid backing plate. From the photo it looks like the backing plate is going to be visible which is too bad, now you also have to make it look nice. Maybe if you use Starboard then put the S/S backing plate on top of the starboard. When I am using metal, usually aluminum, I butter the side that goes next to the fiberglass with thickened epoxy so it will fill the gaps and have 100% contact with the fiberglass. Also looking at the photo that backing plate is too small, maybe why you are having problems. I would try for a bigger plate if possible.

psneeld · Dec 8, 2019

Lepke said:
The way to drill and screw into a cored deck w/o leaks is to mix some epoxy and use a syringe to squirt epoxy down the hole before screwing. The wet epoxy lubes the threads while turning, giving a stronger hold, and the screw is encased in epoxy so it can't leak. The drawback is it's difficult to later remove the screw. I use a small impact wrench to remove epoxied screws.

Another good method to remove is a powerful soldering iron to the head of the screw.

Most epoxies start to fail in the 300 deg F range.

Brooksie · Dec 20, 2019

Drill a 1/2-5/8 hole through the the top layer of fiberglass and to but not through the lower layer (easily done with a hole saw by removing the centering bit after it is started). Clear out the core around each hole using an Allen wrench chucked in your drill. Set a hex bolt into each hole head down. Pour in thickened epoxy using jigs to hold the bolts in exact position for the bases. I would insist on 316 bolts for such a permanent installation. No finishing work necessary if done neatly.

Creating FG pads to install no-penetration stanchions ?

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