How to Install Brass Trim Between Hull and Deck??

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Centurion
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How to Install Brass Trim Between Hull and Deck??

Post by Centurion » Sat May 04, 2019 6:30 am

I have a 20 year old 23' Elliott Bay Hull and want to dress it up with brass trim where the hull joins the deck. I guess it might even be called a rub rail since that location is the outermost profile of the hull.

It appears that the best option might be half round oval brass that comes in coils. If that's true, I have questions on how to install it
  • Brass seems to be available in 3/8, 1/2 and 5/8. What should I use?
  • It appears that the brass only comes with a flat (solid) back making it difficult to install on a rounded surface. Are there other brass trim profiles I should use?
  • If not, the joint between the hull and the deck is not flat. Do have to sand or grind a flat spot the width of the brass in the fiberglass prior to installing the brass?
  • I assume I would use brass screws to install it. What should be the screw spacing?
  • How do I make joints. Just cut at 90 degrees? Any need to solder joints?
  • Do I need sealant behind the brass? If yes, what kind?


I'm excited about dressing my vessel up for the upcoming season. Any advice from the experts would sure be appreciaed.
Last edited by Centurion on Sat May 04, 2019 2:51 pm, edited 1 time in total.
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Re: How toInstall Brass Trim Between Hull and Deck??

Post by RGSP » Sat May 04, 2019 9:29 am

Most brass sold as household decorative trim is straight apha phase material, and not very well suited to salt water use. You'd be better using what we know as bronze in the UK, and I think you know as Red brass in the US. Otherwise "Naval Brass" which has 2% Molybdenum in it is good if you can get it. Otherwise, don't dismiss a marine grade of aluminium alloy - it works very well, and looks fine too, and needs no cleaning.

Most people seem to go for about 1/2" strip for a boat of that length, and if you can get it in straight lengths of around 12' long, so much the better: it will make putting it on neatly easier.

No need for any fancy joints: just cut it off nice and cleanly and square, and make sure the joins don't come anywhere likely to take a lot of knocks like right at the bow or stern.

Screws need to be quite big: I would suggest a minimum of 0.75" long, and Number 8 gauge in UK terms, which is just over 4 mm shank diameter. The length does depend on the structure you're screwing into: you don't want to go right through the hull or deck material.
Screw spacing isn't critical, and there's something to be said for making them a bit closer at bow and stern, and wider elsewhere, but around 4" or 5" should be fine.

Most people use ordinary countersunk head screws, which will stick out a bit at the sides. A file can be the answer here, or if you can get domed (not round) head screws, so much the better. On my boat, a previous owner used ordinary countersunk brass screws, but skimmed the corners off the heads in a lathe. You may well think this is excessive, but if you have a lathe available, it doesn't take long to do a batch.

You MUST pre-drill the holes into the hull fairly accurately, and put in a steel screw of the same thread first, before inserting the brass one. Brass screws normally seem quite tough, but Sod's Law predicts you'll break one or two off if you don't put steel ones in first. Given that there will be a hundred or more to do, a cordless drill/driver with a variable torque limiter is very highly desirable. Sod's law also predicts that you'll strip the threads in the hull material for one or two screws: in that case I'd suggest cleaning out the hole and then pushing some epoxy putty into it. You can of course just put a larger screw in, but when the strip needs to come off temporarily in a few years time for painting or repairs, you'll curse having different sized screws!

Soldering the joints is not needed, and indeed may be worse than useless.

The hull surface behind the strip doesn't need to be completely flat, but you might like to go along with a file before starting to take any little lumps down. If you can get proper marine rubbing strip, it does have a somewhat concave back surface, and so will fit reasonably flush to gentle curves, but I wouldn't worry if your's is flat.

I wouldn't use any sealant or filler behind the strips unless the hull was very rough (cleaning it up is a pain), but if the deck gets varnished, a bit will trickle down into the crack behind the strip, and will do no harm
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Re: How to Install Brass Trim Between Hull and Deck??

Post by Lopez Mike » Sun May 05, 2019 3:16 am

Questions, questions.

Many of us have bits and sometimes more than bits of shiny metal about our boats that we polish up and call brass. Is this what you call Alpha Phase? When you say that it's not that good for a marine environment is it because the zinc 'leaches out' leaving weak and pourous copper? I've been warned off of having such brass below the waterline but except for needing to polish it regularly I haven't had any problems above the water line.

Below the waterline I've stayed with bronze (tin instead of zinc) but up where it shows it is like copper. Not that great to look at.
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Re: How to Install Brass Trim Between Hull and Deck??

Post by RGSP » Sun May 05, 2019 7:26 am

"Alpha" brass is a metallurgists term, but I don't know a more common name for it. Ordinary brass has a classic binary phase diagram, with a high copper alpha phase which is ductile and fairly soft suitable for rolling into strip; that changes rapidly with increasing zinc to the beta phase which is harder, not very ductile, but casts well, and indeed machines nicely.

Mike is right that ordinary alpha brass will be fine in low-stress applications well above the waterline, and would be fine as a rubbing strip in fresh water. I suppose it would be OK for that in salt water as well for some years, but I'd prefer bronze myself (copper-tin alloy). Brass degradation is often not very visible on the outside, but "dezincification" (horrible word) can go quite deep, making it weak and certainly totally unsuitable for rigging components, but maybe OK for a decorative rubbing strip.

I don't know in detail how the 2% molybdenum in naval brass works: there was a firm belief by dockyard workers that it was there only to identify scrap brass as being stolen from the dockyard!
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Re: How to Install Brass Trim Between Hull and Deck??

Post by Lopez Mike » Sun May 05, 2019 10:16 am

The bottom rudder bearing on my 36' sailboat was cast out of ordinary brass. It lasted for years mostly due to the low stresses. Two trips across the Pacific ocean and then, one day as I had the boat out in the marina yard, I gave the bearing a whack to dislodge some barnacles and it fell into several bits.

I suppose the statute of limitations has long passed since the boat left the builder's yard in 1971 but I sat there imagining what the consequences would be if that had happened half way to the the Marquesas! Criminal on the part of the builder. I was able to break the remaining bits up with pliers.

My understanding, though, is that the zinc is removed from the copper by electrolytic action thus the brass would need to be immersed in the salt water for it to happen. I could be misunderstanding this though.

I wish that bronze would take a decent polish. Ah, vanity.
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Re: How to Install Brass Trim Between Hull and Deck??

Post by steamdon-jr » Tue May 07, 2019 11:30 pm

The others are correct you do not want to use brass, definitely naval bronze which will be hard to find. When my father purchased our Elliot Bay he bought 1" and 3/4" directly from Pat Spurlock and it came home from Portland in the bilge, having it shipped will not be cheap and neither will the material. The best way to install it is to lather it up on the backside with some marine bedding compound and screw to the hull, the bedding compound will help fill any voids and also keep water out of the holes you pieced in the hull. if you have any questions and want to see pics of what we did email me.

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Re: How to Install Brass Trim Between Hull and Deck??

Post by Lopez Mike » Tue May 07, 2019 11:56 pm

Can you tell me the makeup of "Naval Bronze"? I can only find Naval Brass on the web which is 59% copper, 40% zinc and 1% tin.

Mike
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Re: How to Install Brass Trim Between Hull and Deck??

Post by cyberbadger » Wed May 08, 2019 10:37 pm

Mike,
The addition of tin also gives the alloy an inherent resistance to dezincification, thereby further inhibiting the impingement by seawater at higher than normal temperatures. Copper Alloy 464 has uses for decorative fittings, turnbuckles, shafting, and as a universal non-corrosive marine alloy.
The addition of Tin also gives Naval Brass a high resistance to dezincification. Dezincification is a type of dealloying in which one of the constitutes of an alloy is removed by corrosion. Dezincification was first recognized as a serious problem in brass tubes used for ship condensers around 1920. At the time this problem was referred to as “Condenseritis”. Since then various alloys have been formulated to stop this process, one of which being Naval Brass.
http://www.nationalbronze.com/News/what-is-naval-brass/
http://www.farmerscopper.com/naval-bras ... 46400.html

I used cartidge brass 260 for a 6"x6" sheetmetal plaque for my boiler and sprayed painted it with a good gloss enamel. It looks excellent and hasn't changed in a few years. It sees mild heat, but not direct boiler temperatures, it's on the outside of the lagging.

-CB
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Re: How to Install Brass Trim Between Hull and Deck??

Post by marinesteam » Thu May 09, 2019 5:45 pm

Be careful, Naval Brass and Bronze are not the same thing. Brass is copper primarily alloyed with zinc and bronze is primarily alloyed with tin.
Navy M Leaded Bronze C92200 Bronze is an alloy of copper, further classified as a bronze (copper-tin- alloy). Is used for a variety of steam pressure applications involving temperatures up to 550 F.
Seawater’s corrosive behavior effects the material used to transport it. Many metals alloys cannot handle the destructive nature, so specific material must be used to provide greater resistance. Selecting the appropriate material can drastically extend the life of the component. Naval Bronze (C83600) is an excellent material choice when handling seawater as the medium.

Naval Bronze is a copper alloy comprised of 85% copper, 5% Tin, 5% Lead, 5% Zinc (85-5-5-5) and a trace of other alloys. The thermal conductivity is very high, which makes it a great option for contact cooling at low temperatures. Copper itself can be very porous, so Tin, Lead, and Zinc all aid in eliminating unwanted porosity issues. In addition, Tin gives the alloy a high resistance to corrosion and weakness. The higher tensile strength and resistance to cavitation make it an appropriate selection for seawater applications.
Navy G bronze:
A proven alloy in a wide number of uses, C90300 (SAE 620) Tin Bronze is most often used in high load, low speed applications. The alloy is hard, strong and can be counted on to withstand wear and corrosion. C90300 can be used for welding, brazing and soldering. Final components made of this alloy require good alignment and lubrication of mated parts.

Cheers

Ken
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