Brass mast step plate?

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Jimmylovescake
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Brass mast step plate?

Post by Jimmylovescake » Fri Jul 04, 2014 5:38 pm

It's been a while since having a chance to look through themail site, but progress is being made and I'm just getting together all the fixing and fittings in between varnish coats.

I have decided to go for brass / bronze fittings simply for as the tics (silly I know) and have most of what I need.

My question is, can I use sheet brass for the plate on a mast step. My mast foot is an old proctor mast foot which I think is cast alloy, but I'm no expert.

Any advice would be gratefully appreciated.

Jimmy

Ian Malcolm
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Re: Brass mast step plate?

Post by Ian Malcolm » Fri Jul 04, 2014 9:44 pm

Categorically *HELL* *NO*!!!!

Aluminium alloy +copper alloy + dirty water/damp = *massive* electrolytic corrosion problem unless they are electrically insulated from each other.
The problem is so bad that even painting an outboard, outdrive or saildrive leg with a copper oxide based antifouling usually voids your warranty due to traces of unoxidised copper in the paint having the potential to cause massive pitting of the aluminium alloy..

If usually wet, most brasses de-zinc on their own due to local electrolytic action between zinc rich and copper rich grains at the metal surface leaving behind a reddish brittle partially oxidised copper sponge. Ever tried to take out an old brass screw and the head simply popped off? That's why it broke. . .

I'd use aluminium alloy, stainless or Tufnol sheet, and if using aluminium, bed it on a 50/50 mix of Sikaflex and Duralac to avoid poltice corrosion.

You would get away with a good grade of bronze for a deck stepped mast step plate on a purely freshwater sailed boat that is stored with the mast down, but I'd want to apply a corrosion inhibiting coating to the mast foot fitting and keep an eye on it. I wouldn't care to use a bronze plate on a sea or estuary sailed boat, nor for a hog stepped mast where the joint could remain wet if you leave the mast up a few days.

An insulating gasket cut from something like the side of 2L fizzy soft drinks bottle would be a good idea if you are leaving the mast up for a week or two and decide to use a bronze plate.
Ian Malcolm. London, ENGLAND. (FORUM REPLY PREFERRED)
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phil58490
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Re: Brass mast step plate?

Post by phil58490 » Sat Jul 05, 2014 7:27 am

I have some off cut bits of aluminium sheet in the garage, 3mm thick (I think without going to measure it) how big a bit do you need?

If you can give us some better idea of what you are trying to do we may be able to offer a better solution, I might even have a mast foot fitting in my junk shop ( garage).
Last edited by phil58490 on Sat Jul 05, 2014 9:58 am, edited 1 time in total.
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cweed
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Re: Brass mast step plate?

Post by cweed » Sat Jul 05, 2014 9:42 am

Hi.

I haven't tracked what boat you're working on, but if it's 60's or 70's, an option could be tufnol.

Jimmylovescake
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Re: Brass mast step plate?

Post by Jimmylovescake » Sat Jul 05, 2014 9:59 am

The boat I'm working on is a 59 Enterprise.
I have an alloy plate from before I started, but as I'very special to hours tracking down as much brass or bronze hardware as I can, I really wanted to avoid the silver / grey look of stainless or aluminium.
Tufnol looks good. How does it hold up and any considerations I'don't need to think out when working with it?

As usual, thanks for the help folks.

Ian Malcolm
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Re: Brass mast step plate?

Post by Ian Malcolm » Sat Jul 05, 2014 4:07 pm

Actually, the Tufnol dingy fitting timeline goes right back to the early '50s. It was the high-tech composite of its day and a fair bit of the early supply would have been surplus ex-WWII aviation industry. It should fit right in with your boat's character.

Its strong and extremely durable so as long as you design the step with enough 'meat' at the front and sides of the slot, where the highest loads are, carefully radius the slot corners with a thin rat-tail file so there are no stress-raisers and make sure the mast foot tenon and the fixings aren't sloppy in the slot and holes it should last a lifetime. An occasional good scrubbing and wipe of linseed oil should keep it looking good.

I'd want to make the whole step out of solid tufnol rather than having a thin plate on top of a wood block, but you can glue two or three sheets together to get the thickness - scuff up both surfaces really well with 80 grit W&D, and glue with a *THIN* layer of a exterior construction adhesive or marine adhesive sealant or similar knifed over both faces to get total coverage. Epoxy also works but may be a little too brittle - microfibre additive would be essential. The screw or bolt through each corner (and maybe an extra one in the middle of each side) will stop the joint from ever moving. If well bedded in place with a drain hole at the bottom of the slot, you'll never have to worry about mast step rot again. Through bolt if possible as the lateral loads are very high. If you must use a plate, don't go under 1/4" thick and scuff up the bottom as described before screwing/bolting and gluing in place.

Ease of working it falls between metal and fine grained siliceous hardwoods. Use really sharp tooling suitable for aluminium alloys or hardwoods and support any edge you are cutting towards. Use a good dust mask or keep it wet while cutting/sanding as the phenolic dust is quite nasty.
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Jimmylovescake
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Re: Brass mast step plate?

Post by Jimmylovescake » Sat Jul 05, 2014 5:11 pm

Thanks Ian. That's my mind made up.
I'd planned to make a base out of sepele or iroka and then have a tufnol plate.
The current base is 23mm thick with a 3mm plate.
The sepele I have 22mm thick and I'don't thought 4 mm tufnol would do.

Would I be better off using thicker tufnol and routing a recess in the sepelee to allow for this?
Thanks again.
Jimmy

Ian Malcolm
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Re: Brass mast step plate?

Post by Ian Malcolm » Sat Jul 05, 2014 8:55 pm

You don't want any water traps so certainly don't want to let it in the top of a Sapele block. Sapele is quite difficult to work without grain tearout and may be only moderately durable against rot. A thin plate let in will flex and bruise the wood under it so water will get in. You will get dark stains in the end grain near the fastenings. Avoid!

Ideally you want a solid Tufnol base/step and to make it a little larger round the front and sides so it hides any marks from removing the old base.

You are trying for 26 mm.

3 layers of 8mm with two glue joints is going to come out pretty close to 25mm
2 layers of 12 or 12.7mm is going to come out at 24.5 or 26mm
25mm and 25.4mm sheets are available - absolute best choice

You *really* don't want to buy a whole sheet because its very expensive so you are looking for offcuts.

If the stack-up is too thick, you can take some off the bottom side by milling, grinding or belt sanding. You could even manage this safely with a router sled. Make sure the glue is fully set and the work is properly secured i.e. a ply plate screwed down to the pre-drilled final fixing holes using countersunk screws and expanding wallplugs or similar, then flipped and screwed or bolted down to the mill table or workbench round the exposed ply outside the block. If sanding/grinding beware of heat build up and either use a sled to control final thickness or if working freehand cut witness marks level with a hacksaw to approx 1/2mm under the desired depth to remove, sand/grind till nearly gone then sand very carefully checking the work is flat and level.

Do NOT attempt to plane it. It will almost certainly chip and split unevenly and may break electric planer knives.

Finish sand external cut sides and 'break' exposed corners and edges with a fine file or sanding block so they don't chafe lines or dig holes in people. You will probably want to file the slot to final size after glue-up to get clean sides to the hole. Through bolt the fixing holes while working on the sides and slot so you don't stress the glue line(s)

A drain hole can be left at the back of the slot bottom by routing or filing a 3 to 4 mm deep groove in the centre of the aft bottom surface, and preventing the bedding compound blocking it by packing it with a good length of smooth cord saturated with candle wax or grease then pulling it out after the sealant has set. Clean it out with a pipecleaner occasionally to prevent dirt buildup
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cweed
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Re: Brass mast step plate?

Post by cweed » Sun Jul 06, 2014 8:54 am

Tufnol sheet.........

I've got quite a bit of 1/8th sheets. If you want a few pieces of, say, 8'' x 3'' x 3 or 4 pieces, you can have gratis, let me know what (over) size you need. Please pay the postage unless you want to collect from junction 11 area of the M25, Surrey.

It cuts OK with a jigsaw, but I don't know if it's still available as I was told it contains formaldehyde.

Ian Malcolm
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Re: Brass mast step plate?

Post by Ian Malcolm » Sun Jul 06, 2014 4:31 pm

A generous offer, but unfortunately I believe 1/8" would be a bit on the thin side for the O.P's application. There's not a lot of margin for wear and gouges from stepping the mast + the step's top plate is exposed to static side loads of up to 70% of the kicker tension and dynamic loads of at least double that (think accidental crash gybe while dropping off a wave so marginal down force to keep everything in place) so it needs to thick enough to resist buckling.

Tufnol is still in production by the original manufacturer and to the original specs: http://www.tufnol.com/ There are clones from other manufacturers which may be just as good - or may not, so if you want the proven durability, get the genuine stuff. What you cant get any more is the grades made with Asbestos fibre - and a good thing too!

Here's a seller with 25mm Whale brand Tufnol part sheets:
http://www.bearingboys.co.uk/Tufnol_Wha ... m_-46859-p
Not used them, but the pricing looks to be fairly normal for the thick stuff.
Their 8mm sheet is a lot more reasonable:
http://www.bearingboys.co.uk/Tufnol_Wha ... m_-46830-p
but that will require faffing about gluing it up in layers.

It is also usually on EBAY in various forms and sizes, occasionally at much better prices if someone is ebaying scrap offcuts from work for beer tokens - as usual, buy carefully!

Caution: Tufnol make a whole bunch of composites. Make sure you are ordering a phenolic resin bonded cloth laminate, not a crappy Paxolin type bonded paper laminate. "Whale brand" is the commonest and most popular for this sort of application but here's the list of the others: http://www.tufnol.com/tufnol/default.asp?id=21
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Jimmylovescake
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Re: Brass mast step plate?

Post by Jimmylovescake » Sun Jul 06, 2014 8:03 pm

Had a look at the link, I didn't realise how expensive it was.
I guess I'love be scanning eBay for a while to see if I can get any bargains before I finish getting the deck on.

Thanks again for the advice; you could write a book with the quality of some of the advice on here.

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neil
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Re: Brass mast step plate?

Post by neil » Sun Jul 06, 2014 9:41 pm

Also Tufnol is used by other industries - when I needed some a few years ago I found an air craft supplier 10 miles away that had some sheets.

http://www.lasaero.com/site/products/ar ... =N00SSN31X

Think I was the smallest sale they had ever had.
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PeterV
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Re: Brass mast step plate?

Post by PeterV » Sun Jul 06, 2014 9:49 pm

Tufnol is also used for galvanic isolation in marine applications, it has some health warnings when machining but they are just to avoid breathing the dust.
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Ian Malcolm
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Re: Brass mast step plate?

Post by Ian Malcolm » Mon Jul 07, 2014 12:51 am

Actually, the sticker shock isn't that bad.

Lets compare the price of that 25 x 300 x 300 mm hunk of Whale brand Tufnol with the Pinnel & Bax High Density Mast Step for all Masts (ENTMS)
http://pinbax.com/index.asp?selection=d ... &uid=36467 which would be the modern day equivalent.

Hunk'a 60's composite: £73.89
There's free delivery on orders over £75 ex VAT so the order needs topping up.
A 13-20mm stainless Jubilee brand hose clip is £1.53 and might even be useful.
New cost £75.42 + VAT = £90.50

Fancy P&B "high density" mast step £43.28 + £4.95 p&p = £48.23

So the Tufnol is 88% more expensive.

But the maximum permitted Ent mast diameter is 73mm so it should be able to be cut up into nine 100mm squares to make nine steps. That brings the materials cost per step down to £10.06, 21% of the P&B price. If you have access to a CNC mill, you could make 'retro' high tech steps and under-cut P&B slightly!

Alternatively, start thinking about what *other* Tufnol adornments your boat deserves that you can sensibly make from the remainder of your sheet.
If you have access to a lathe, new mast and boom sheaves would be a very good use. A simple deep holesaw lets you cut bushes for centreboard or rudder pivot bolts. Cleats can easily be cut out and hand finished - just keep the original sheet surface normal to the fixing holes to avoid splitting under load. Need a chunky anchor warp cleat? a 25mm square bar of Tufnol through bolted with 6mm countersunk machine screws on two 25mm round pillars would be the bees knees. Basically the world is your oyster (or maybe Whale <VBG>)!

Caution: While reading the class rules I noted the maximum permitted mast step thickness AS FITTED is 26mm. Don't over-do the bedding compound. [;)]
Ian Malcolm. London, ENGLAND. (FORUM REPLY PREFERRED)
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Garry R
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Re: Brass mast step plate?

Post by Garry R » Mon Jul 07, 2014 12:02 pm

I actually went the other way on my mast and fitted a sheet of tufnol to the bottom of the wooden mast which was getting pretty chewed at he base/ I can see that alloy to wood might need a sliver of tufnol. Why not use a wooden step block and face the bearing surface with tufnol?

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