Cutting Bronze

[Capn_Tom]

I cut the holes for my new hawse pipes but i need to trim one side of the bronze casting (x6) to make them fit the depth of the bulwark. I of course would like to end up with a smooth intersection between the two pieces. Any advise on tools/ technique for cutting bronze would be appreciated.

[Zach]

You'll want to use a depth gauge, like the back half of a vernier caliper... or the sliding stick on a folding rule to measure the depth around the edge.

Install one side, and double check that you don't need to take off more on one side or the other. Mark the part indelibly, perhaps a number punch if you've got one so they become pairs... also so you can index it the same way every time and not goof. Make sure the hole is a darn tight fit, exactly where you want them to end up. Epoxy some wedges, or thread in some long screws and cut the heads off so you have sliding pins that locate the part.

Use your depth gauge to transfer from the edge of the bulwarks/toe rail to the back of the hawse pipes. Mark a line around if you are lucky and it is even. If the piece isn't to wickedly curved, use a hose clamp to carry the line, failing that lay it on a flat table, set a block on the table and set a sharpie on the block. Hold the part steady and mark around it's circumference. The height of the block+pen = whats on your depth gauge...

As far as cutting bronze, I'd just grind it. Cutting wheels are one better on than hack saws in their ability to go further off course the more you try to guide them. Use a silver sharpie to mark it... or a soap stone... so your mark doesn't burn off. Any old metal grinding wheel on a grinder will move things on at a quick pace. If its dead flat you can finish up with a big wide mill file running on 45 degree angle to the skinny side, or lay it on an upside down belt sander... or spray adhesive a sanding belt to a piece of glass and work the last smidge down. Put a sharpie line or some prussian blue, when it's all gone after a pass sanding you've got something thats flat.

If you are lucky, these things overlap and are two different size castings... if not you'll need to come up with a way to seal the joint so they don't leak water between the gap. If they are two different castings, you can use modeling clay or play dough on the fixed side and squish it together to see the gap that would otherwise be hidden. It'd be overkill, but if you really wanted to be able to seal two that but against each other you'd make a plug that fits the inside radius of each casting, with big wood washer on each side held in place by a piece of all thread. Fill all the screw holes and drill new ones while it is all aligned and pulled together. Machinest dye is how you'd get them perfect. Blue one side, put it together under tension with the screws, take it back apart and see where you don't have blue... sand everywhere but there. Personally I'd shoot for a 1/16th inch gap and fill it with a huge bead of polysulfide. One better would be to file a V in the gap and fill it with jb weld, but you'd have your work cut out for you if you ever wanted to take it back apart.

To tight of fit is almost as bad as to much slack, as there has to be enough thickness in the goop for it to reach full strength to accept the expansion and contraction of temperature, and the working of the boat. There is a point of good enough... get the bottom half tight, as it won't leak from the top unless you've got a breaking wave coming over...

Shew...

[Capn_Tom]

Wow! That was a detailed response. The 2 castings are round and the same diameter. The installation is through an open bulwark. The seal is acheived by caulking and installing a piece of thick walled hose around the outside of the casting. Are you refering to an angle grinder, a bench grinder or some other variation on the theme.

Your description of a small caulked gap between the 2 halves gives me comfort as the desire for a perfect 360 degree mating is what has been causing me the most stress. I only wish Sika made a bronze colored caulk that changed color at the same rate as the surrounding material!

[Rachel]

Tom,

I take it you are installing the hawse pipes on your W-32? I have often wondered if it wouldn't be better to 'glass a fiberglass tube in there (making a mini-version of a bow thruster hole) and then install the bronze hawse pipe into that.

Since the bulwark is hollow, and you just have a hole in each "wall" with a hollow space (open to the rest of the boat) in between, the manual's suggestion of two halves of bronze hawse pipe flush-butted and sealed with caulk and a hose always gave me pause (strangely, I was just reading it yesterday).

Rachel

[Capn_Tom]

Rachel - any hole in a boat gives me pause! When I rebuilt my deck scuppers I used the technique you describe and fabricated oval fiberglass tubes and glassed them in in place of the brass tubes. The original Westsails had spun brass hawse pipes the new ones are heavy bronze castings. The hose that covers the joint in the 2 castings is cut to fit the width of the bulwark so it can't slip off. As such, total failure is impossible. Worst case would be annoying leaks. The hose is heavy walled and I feel that caulked properly it should be leak free. Now if only I can get the courage to start grinding!

[Rachel]

Tom,

Yes, it was leaks I was thinking of (such as when pounding into a head sea).

Rachel

[BALANCE]

Tom,

Be aware that the pipe ends up on an angle, not straight through - meaning - the gap, say on the forward end of the cylindar will be narrower than the aft.

Rachel, that is a great idea. Absolutely brilliant. (Just reading the manual yesterday? Yikes.)

[Rachel]

Heh, well I'm not THAT nerdy. I just happened to be sitting around at a friend's house who has one, and it was lying out on the table. Of course I did eschew a half dozen magazines in favor of the manual...