To Thread or to Embed Nuts in Epoxy ?

[akio.kanemoto]

Howdy,

I'm just planning on installing a bow roller. Currently, the boat doesn't have one as it was a racing boat... I now have a brand spanking anchor and am about to have a bow roller fabricated.

Now the issue is that the boat has a very pointy bow - meaning that there is zero access below decks for the first foot from the bow.

The bow roller assembly itself is about 3.5 feet (1.2m) long and also incorporates the forestay attachment point. I plan on (ridiculously!) through bolting the 2 feet aft of the first foot and using backing plates etc, but for the first foot with no access below decks, the only things I can think of are:

1. drill oversize holes, ream out foam core, fill with epoxy thickened West System 403 (I don't have access to anything but 403 or 411 in Australia), redrill smaller hole and tap the hole for the bolt.

2. drill oversize holes, ream out foam core and embed a pair of nuts in there with the thickened 403, using a greased bolt threaded into the nuts to keep the nuts vertical.

I'm leaning towards option number 2 as it seems stronger (and easier!) to me - does anybody have handy hints on how to accomplish this a "better way" than I am planning on doing it?

Also since I've never had a bow roller before, I'm not sure about what bolts to use for this application - when drilling out the base plate of the roller - should I drill straight and use hex-head bolts or drill + countersink and use CSK machine screws (same diameter)?

I'm a big fan of hex-heads, but worried that the chain or anchor stock could get stuck on them... ?

Thank you very much in advance!

[daddle]

How did the forestay attach to the hull before? Can you use it's fittings?

[Sailorman Ed]

Could you drill a thru hole and install a longer bolt from the outside of the "pointy" hull? Counterbore the bottom of the hole so the bolt is not noticeable and have the nut on top of your new bow roller. This would be a lot stronger than trying to embed nuts to threading into epoxy. Or since you are having this custom fabricated AND you are attaching your forestay, wrap it around the very front and down the front of your bow. With the load of a forestay, you need something quite strong!!

[akio.kanemoto]

Originally Posted by daddle

How did the forestay attach to the hull before? Can you use it's fittings?

Howdy,

Thanks for the quick reply!

Forestay was attached about a foot back from the bow where there is some access... (as an aside - since the access below decks at this point is really horrible, they hadn't used backing plates here either and even the tie rod to the hull was effectively loose. So I would wager that for 25 years, the deck took the entire load and it's a miracle the bolts+washers didn't pull through as it was raced with a massive genoa!)

But in short, the first foot of the bow roller has to be fastened using one of the two options above as there is literally zero access below - I believe that in fact it might all be solid as the two sheer battens meet here as well.

So from the bottom you have both sides of the hull coming up, and from the sides, the two sheer battens (2" x 1" approx cross section on each side), and then the 1" thick deck from the top... and since they all meet at very shallow angles, you have a big solid chunk right at the bow.

[daddle]

Originally Posted by akio.kanemoto

Forestay was attached about a foot back from the bow where there is some access... (as an aside - since the access below decks at this point is really horrible, they hadn't used backing plates here either and even the tie rod to the hull was effectively loose.

Okay, that's the same as my very pointy boat. Her custom bow roller weldment wraps down around the hull topsides enough for a row of smallish (6mm / 1/4" maybe) screws to be bolted thru to backing strips. Maybe you could do something similar.

The imbedded nut idea sounds risky to me. But I wouldn't really know.

[akio.kanemoto]

Originally Posted by Sailorman Ed

Could you drill a thru hole and install a longer bolt from the outside of the "pointy" hull? Counterbore the bottom of the hole so the bolt is not noticeable and have the nut on top of your new bow roller. This would be a lot stronger than trying to embed nuts to threading into epoxy. Or since you are having this custom fabricated AND you are attaching your forestay, wrap it around the very front and down the front of your bow. With the load of a forestay, you need something quite strong!!

(love your avatar btw!)

... as for boring from underneath - the chainplate is laid into the hull at the stem - so wouldn't have much luck trying to accurately/reliably drill around there.

As for strength however - at the point that the forestay will attach - there will be two straps passing through the deck and there will be a tie rod back to the chainplate inside (although I can't tension it - which is another problem... as no 5/8" pin turnbuckle will fit in such a small space)... but tensioning aside, since there will be a direct transfer of pull from the forestay PLUS a metre of solidly fastened metal distributing the load, I'm quite confident that the forestay component will hopefully be fine as it will be lightyears ahead of what was there for 25 years

On the wraparound/shoe idea - I'd love to, but I'm in Australia and even getting simple geometrical shapes welded in flat bar is hideously expensive... a shoe, which would actually require more than straight weld beads would be extremely cost prohibitive..

[aclmck]

Originally Posted by akio.kanemoto

Howdy,

I'm just planning on installing a bow roller. Currently, the boat doesn't have one as it was a racing boat... I now have a brand spanking anchor and am about to have a bow roller fabricated.

Now the issue is that the boat has a very pointy bow - meaning that there is zero access below decks for the first foot from the bow.

The bow roller assembly itself is about 3.5 feet (1.2m) long and also incorporates the forestay attachment point. I plan on (ridiculously!) through bolting the 2 feet aft of the first foot and using backing plates etc, but for the first foot with no access below decks, the only things I can think of are:

1. drill oversize holes, ream out foam core, fill with epoxy thickened West System 403 (I don't have access to anything but 403 or 411 in Australia), redrill smaller hole and tap the hole for the bolt.

2. drill oversize holes, ream out foam core and embed a pair of nuts in there with the thickened 403, using a greased bolt threaded into the nuts to keep the nuts vertical.

I'm leaning towards option number 2 as it seems stronger (and easier!) to me - does anybody have handy hints on how to accomplish this a "better way" than I am planning on doing it?

Also since I've never had a bow roller before, I'm not sure about what bolts to use for this application - when drilling out the base plate of the roller - should I drill straight and use hex-head bolts or drill + countersink and use CSK machine screws (same diameter)?

I'm a big fan of hex-heads, but worried that the chain or anchor stock could get stuck on them... ?

Thank you very much in advance!

Hi , First thing If you choose to use epoxy to fill your cored holes check with ATL at the Gold Coast, last time i checked they had several "west System epoxies " all for various reasons ,they may be able to advise on compatability issues with your existing structure and the "foam" that will be used to form the mould.

I like hex bolts but i wouldn,t advise using them in the path of the chain or rope warp it will end up a drama unless you recess them, i would simply weld lugs on each side and bolt through them

I don't know whether you have aready started but i purchased a suitable bow roller from "Sarca" the anchor people and had a few bolting lugs added and polished for less than $100 aud but get a quote first before proceeding it will save you. incidently i needed my lugs to raise each side a little then set it on a bed of polyurethane to distribute the load over the entire area. from memory the bow roller was 4 or $500

[akio.kanemoto]

Originally Posted by aclmck

Hi , First thing If you choose to use epoxy to fill your cored holes check with ATL at the Gold Coast, last time i checked they had several "west System epoxies " all for various reasons ,they may be able to advise on compatability issues with your existing structure and the "foam" that will be used to form the mould.

I like hex bolts but i wouldn,t advise using them in the path of the chain or rope warp it will end up a drama unless you recess them, i would simply weld lugs on each side and bolt through them

I don't know whether you have aready started but i purchased a suitable bow roller from "Sarca" the anchor people and had a few bolting lugs added and polished for less than $100 aud but get a quote first before proceeding it will save you. incidently i needed my lugs to raise each side a little then set it on a bed of polyurethane to distribute the load over the entire area. from memory the bow roller was 4 or $500

G'day,

Yep, I buy the West products from ATL (indirectly through their agent in NSW) - but interestingly enough, they only bring in 403,411 and 410 into Australia.. perhaps they don't think there's a market for the other stuff here.

In any case, I've found 403 to be great for most structural work and I sometimes mix in 411 @ 50:50 for filleting etc.

As for the Sarca bow rollers, I checked these out as well and my bow is so pointy, I really can't find anything that will work with my angles.

Thanks for the idea about the lugs though - I'll look into trying to recess the hex heads. If I can't make the geometry work, I'll countersink.

[gulfstar37]

try emailing west system at www.westsystem.com ›. They may have a suggestiion for you. Anyway they are good at answering questions about their product.

[atoll]

better than using nut's get some stainless bar drilled out and threaded,about 5 cm long embed these in the oversized holes using greased bolts,cut slots in the bar for added adhesion to the epoxy.

works great did it on first boat for the forestay chainplate /bow roller mast still up after 25 years.

epoxy 403 is good but need to use collodial silica to thicken.

would use countersunk (csk) hex m8 0r m10 bolts for a nice flush finish

[roverhi]

The forces on the bow roller are primarily going to be straight down. You really only need to fasten the aft end of the roller assembly and somewhere between there and the bow with enough moment arm to keep the roller assembly in position. I'm assuming that there will be support at the bow for the roller. Bolting it at the bow would be better but probably not all that necessary. Use a rope pennant to take the strain of the chain/line to a cleat at the bow while at anchor.

[Mark Johnson]

The bow roller installation needs to be equally as strong on both directions, as the waves hitting the anchor from below are putting a tremendous upwards shockload on the mount. I learned this the hard way!

The below photo attachment was, first... a platform made of 3/8" ply with 1/4" of carbon and glass fiber on EACH side. Then I glued it down to the deck, off center in order to clear the forstay chainplate. This was followed by 5/16" through bolts in the back, and ONLY 3" machine screws forwarded of the chainplate, because this bow area, under the deck's 3/8" ply, is just foam!

So These machine screws go through over an inch of glass, carbon, and wood, before going into the foam area underneith, that I previously drilled large and filled with WEST resin... with High D, Silica, and glass fiber in the mix.

I just drilled the final holes for the machine screws small, tapped threads, and epoxy bonded the screws in place. It is STRONG! Stronger than nuts!

I later put LARGE carbon covered fillets under the platform, when I realized that I hadn't taken the severity of the UP load into account.

The number of fastenings are a bit over done, but 15 years and a dozen hurricanes later, it has held up well.

BTW... I have done a lot of experimentation compairing the relative strength of epoxy bonding, compaired to using nuts... With a 3" X 5/16" machine screw, threaded into a overdrilled 1" wide hole that's 3.5" deep, then filled with the above mix, threads tapped, and epoxy bonded in... You have VASTLY exceeded the strength of the head on the machine screw. I suspect that a similar experiment with a screw half as long would also be strong enough, but I KNOW that @ 3" long, it is stronger than a conventional nut and washer.

Hope that there is a useful tidbit in here,

Mark

[thendel]

G'day mate,
A couple of thoughts that might assist as well -
1) Use button head socket head cap screws instead of either hex heads or countersunk heads. The countersink in your bow roller assembly will only work properly if the plate thickness is enough to allow a countersink deep enough for the depth of the screw head without enlarging the clearance hole for the fastener.
2) If you are having things fabricated then get someone to turn up a flanged nut to embed in the epoxy. In effect this would be like an upside-down top hat - you can have whatever thread you like tapped into it and the flange (the 'brim' of the top hat) will assist in pull-out strength in the epoxy bedding.
3) Stainless fabrication is expensive, but there are some decent people around.

If you're in Sydney then drop me an email and I can recommend a guy who straightened a bent pulpit rail for me at a very reasonable charge, and also a fastener merchant who offers terrific service and will get almost anything (or recommend another source).

Good luck.

[North26West80]

You can drill and tap West System epoxy just like anything else but you need more threaded contact area than with metal fasteners. Look around their website for their advise on doing this.

[Mark Johnson]

If you can't go with, or don't like the glued down platform idea, covering 3" X 1" wide epoxy plugs into the foam, and then tap threads 3" down for the epoxy bonded machine screws.. Which is a LOT of hassle, but far exceeds the strength of the bolt...

The above captive barrel nut idea will work as well, if your glass deck has at least 3/8" thickness up there.

Up here, on the top side of the world, we have these SS barrel nuts with a washer sized flange and little spikes. They are meant to be driven into the backside of what you're mounting to, but can also be epoxy bedded to the deck. Just use a temporary nut to keep epoxy out of the threads while bonding it in well. I got these off of the shelf, and bet you guys have them too!
Mark