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Old 20-07-2016, 12:49   #1
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Cabosil, or ???

Cabosil, or ???

So, I have the Lewmar V3 windlass disassembled. It takes 4 M8 studs under the deck plate, through the deck (~1/4" fiberglass), a substantial (~1.5") wood core, another fiberglass layer, and my 1/4" aluminum backing plate, with washers and nuts to hold up the motor and gear case.

Whether a matter of poor installation at the time (try drilling exactly placed holes exactly vertically, which is what's needed to be able to drop the deck-plate-mounted studs down the holes) which then required wallowing the hole(s), or the reason for our disassembly, that being that the deck plate had crept forward enough to cause a misalignment in the shaft, resulting in a squeak as it turned. The backing plate holes are pretty much round and of the right size, so didn't require attention.

I will be completely servicing the windlass, including new studs (at least one of them was not perfectly vertical any more), so they will be perfectly vertical to the windlass base.

To remedy the now-sloppy deck holes, and to avoid a repetition of the creep and resultant shaft misalignment, I'm thinking along the lines of drilling (Forstner bit, nice clean edged hole) a 1" hole down to the backing plate (removing all the material in a 1" column directly over that backing plate hole). I'd coat the fiberglass and wood core with epoxy to start, and then use it as a form, while the epoxy hadn't yet cured. Think of a concrete piling made from a bored hole and filled with concrete to get the effect.

After filling and hardening/curing, I'd drill down, using a tool I don't have (I need recommendations on that, please), perfectly vertically on the centers of the stud pattern. I'd rely on the strength of whatever I used in that hole to withstand potential shear loadings if the base tried to creep forward under load in the future.

And thus to the topic. Bearing in mind that I'd have to drill down close to 2" to get to the backing plate, is epoxy (say West Systems) with Cabosil sufficient to achieve that hardness? My original thought had been to get a cutoff from a prop shaft and machine out the center (drill chuck to lathe turn) to the appropriate size to fit into my Forstner-bored hole. Except that would require even more precision, during the boring process, in order to guarantee that the milled holes were exactly in the right place and exactly vertical, to boot.

Is there anything I can put in these bores which will be very strong but not brittle, and reasonably drilled after they've cured? Cabosil makes several different products, so I'm somewhat uncertain if what I have in stock is appropriately a "structural adhesive" as it seems to be called in the trade. If Cabosil's the answer, which of their products do I use?

I've used Belzona to good effect previously, but it was a courtesy couple of spoonfuls I got from a machine shop; otherwise it's only available in commercial quantities. JBWeld or similars may be other options.

So, two questions:

Have you used something for a similar purpose, or know of how to determine specs as to shatter/deformation resistance in such an application? If you were doing it, what would you use (no offense, but I'd prefer not to have guesses, please; I donít want to do this again)?

And, how do you make absolutely vertical bores (drilling for the studs)? Is there a tool that will do that? It's not like I can take the deck to a machine shop to mount in a jig

Well, maybe a third. If you understand my challenge, is there something you'd do differently to get to the same end - exactly fitted holes which have sufficient strength to resist, perhaps, a 500# or greater side pull at the shear line?




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Old 20-07-2016, 13:37   #2
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Re: Cabosil, or ???

Hey Skip

There are things called 'Drill Guides'. I have one. Haven't used it yet. Dunno how accurate they are but likely better than 'eyeball' plumb!

Now as for the epoxy fill. I'm guessing you're going to want to torque down on this pretty hard. Cabosil won't do much if anything for strength. It'll help keeping your epoxy glue mix from running. I would think that chopped strands & micro spheres (both of which West sell) would be a better combination where strength is an issue. I use wood flour, cabosil & microspheres for making structural glue.

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Old 20-07-2016, 13:49   #3
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Re: Cabosil, or ???

Here's how I've done basically the same, and in general what WEST says in their very detailed guide.

1. Drill out holes to 2x fastener size.
2. Seal hole edges/core with neat epoxy
3. Fill holes with epoxy thickened with their 404 high density filler.

If the studs are long enough to mount the motor, are they long enough to get through the backing plate when the windlass is ~1cm above the deck (without actually mounting the motor)? Then drill oversize holes. Prepare studs with release agent (if they are threaded all the way this is more difficult, but possible) - sometimes wax to fill all the threads is easiest, maybe followed by a single-layer very thin film (Mylar, parchment paper,...). Mount windlass to backing plate with windlass held ~1cm above deck. Fill annular space with thickened epoxy. When hardened, heat studs just slightly to soften wax, pull out windlass and clean up studs. Remount permanently. If you use a very thin film over the studs you don't actually have to get it out of the hole, leaving a tighter fit. You just want it there to keep the epoxy from sticking to the studs, so that future removal is possible.

If you've never tried this before, it is worth it to grab a stray pipe/tube of about the same size, and a stray bolt of about the same size, prep the bolt for release, fill the thing with the same epoxy you will be using, and test the removal. That will help you in working out your system. It can also be easier to put some tape over the hole in the backing plate, fill the holes in the deck with the thickened epoxy, then push the windlass down through the holes. That means you have to get the backing plate to stay in place by magic.
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Old 20-07-2016, 13:51   #4

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Re: Cabosil, or ???

Used flox (cotton fibers) or chopped strand. Don't use micro spheres, They're for saving weight. If you use chopped strand you might add some cabosil to make it work better.
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Old 20-07-2016, 13:59   #5
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Re: Cabosil, or ???

Yeah, strengthen that epoxy with fiber - Bondo is close to what you want, but why not insert the bolts through the epoxy while its still wet, getting your alignment right?
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Old 20-07-2016, 14:39   #6
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Re: Cabosil, or ???

If you have access to a drill press you can make a jig by inserting "drill bushings" into a piece of thick plywood. That's how people used to drill repeatable holes precisely back in the day before things like CNC machines. See photo below and use the google to find them.

Regarding filler, Gougeon Brothers recommends high density filler for bedding hardware as above. It's basically finely ground marble dust and imparts high compressive strength to the epoxy which is what you want for this application.
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Old 20-07-2016, 16:19   #7
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Re: Cabosil, or ???

Originally Posted by Delancey View Post
If you have access to a drill press you can make a jig by inserting "drill bushings" into a piece of thick plywood. That's how people used to drill repeatable holes precisely back in the day before things like CNC machines. See photo below and use the google to find them.

Regarding filler, Gougeon Brothers recommends high density filler for bedding hardware as above. It's basically finely ground marble dust and imparts high compressive strength to the epoxy which is what you want for this application.
This is an excellent suggestion... a practice that can be used in many applications on boats where lots of surfaces are curved, angles not 90 degrees and the "work place" may be rolling about randomly.

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Old 20-07-2016, 17:36   #8
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Re: Cabosil, or ???

I usually just drill a hole in a thickish piece of wood offcut on the drill press to use as a guide for drilling perpendicular holes. Works fine for casual use. I've recently played with some 8uM ground glass thickened epoxy and that stuff is hard. Might be too brittle by itself though, but I just had to jackhammer out some half inch diameter tubes of the stuff from rotten wood and it was surprisingly tenacious.
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Old 20-07-2016, 17:54   #9
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Re: Cabosil, or ???

You can oversize the holes & use a thickened epoxy mixture (bog) to bed the bolts in, so that your holes don't need to be perfectly drilled. But keep in mind that with such deep holes, you'll have to keep the epoxy annulus fairly small, as in an epoxy pour of size, the epoxy will want to go exothermic on you if you use a lot of resin to make your bog.
To some degree you can avoid this by going with a super slow curing blend. But check the spec's on the resin first.

As to what to thicken it with. Since it's a structural, high load area, you can use milled or chopped (glass) fibers to make your bog. Such mixtures see service as the bedding for keels on all sizes of yachts, up to some Maxi's, so it's pretty solid stuff. And it's one of my fav's, well, unless I have to sand it much

When you're bedding stuff, in addition to mold release, packing tape or duct tape works well to coat parts in so that they don't get bonded in place. I've used both on a whole variety of items without issue.

Also, there are definitely times where it's worth buying some over-length bolts or rod stock to use when bedding things. As with their extra length, it's often a lot easier to line things up for a bog pour, particularly when you snip the heads off of them to allow parts or nuts to be slipped onto them from above or below, freely.

You can also use things like plastic pipe instead of bolts or rod, for alignment guides, & during your bog pour. Just make sure that they're well coated with mold release. And worst case, if they get bonded in place, plastic pipe pieces are disposable, & easy to remove destructively, without much marring to the surrounding material.

And I've yet to try this trick. But I'm told that you can cut a very thin kerf into pieces of pvc pipe, & cover the kerf with packing tape. So that when it's time to pull them out of a cured pour, the kerf compresses, to make them slightly undersized, & thus easier to withdraw. Which makes sense, I'd just test it out prior to doing it on an important project.

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Old 20-07-2016, 19:12   #10
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Re: Cabosil, or ???

1) At drill press clamp windlass to plywood jig, drill holes at location of holes in windlass using same size bit.

2) Unclamp windlass from plwood jig, enlarge holes in plywood jig with appropriate sized bits for a press-fit of drill bushings.

3) Use mallet to place drill bushings into plywood jig. Can get them hardened, but still.

4) Back on the boat shim plywood jig to deck, fasten in place with screws that will be covered by windlass later, drill holes through deck.

4) Remove screws and putty holes.

5) Install windlass.

Ain't rocket surgery. Can achieve .00" preciscion which should be plenty good enough. Easy peasy. Drill bushings are pretty cheap, available in different styles and different tolerences for different purposes.

Depending on bit size and length can transfer windlass holes with a center finder then back to the drill press if you don't have clearance.

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