Fitting to a steel deck

Discussion in 'Metal Boat Building' started by Nick.K, Dec 9, 2013.

  1. Nick.K
    Joined: May 2011
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    Nick.K Senior Member

    How would you fit aluminium genoa track (and other fittings) to a steel deck?

    Drilling and tapping is the obvious option, but any leaks will work havoc under the insulation. Is there a better way? :confused:

    Nick.
     
  2. gonzo
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    gonzo Senior Member

    You can weld a stainless flat spacer with tapped (threaded) holes. Alternatively, you can bolt the spacer.
     
  3. TANSL
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    TANSL Senior Member

    Gonzo, why complicate things by adding a new metal?. The solution you give, in steel, is very good. It was the solution that was used before the bimetallic plate was invented.
     
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  4. pdwiley
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    pdwiley Senior Member

    How much trouble do you want to go to?

    Generally I weld every fitting possible to my steel deck. Why create holes?

    In this case, if you drill & bolt, you're compromising the integrity of your deck, true. I don't like that idea either. However, every alternative I can think of is going to raise the height of the track to a greater or lesser extent and increase it's tripping hazard & toe breaking ability.

    To raise the track height I'd make spacers from A36 steel and weld them down. Drill & tap first, then make sure you seal the screws well with a thread sealing compound. You could use 316 spacers/standoffs but you'd better be certain to use an antiseize compound on the screws because 316 screws into 316 steel are notorious for galling and becoming impossible to remove without drilling them out if you don't. This is why I wouldn't make the standoff spacers from 316 in the first place - I'd want the screws set in Loctite and a CSK screw might not want to come back out.....

    Shape & size of track and exact location on deck would also influence how I'd attach stuff.

    So what's your feeling for the tradeoffs? It's your choice.

    I would probably custom make the genoa track out of 316 and weld it to the deck. But I am a nutcase with a machine shop.

    PDW
     
  5. gonzo
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    gonzo Senior Member

    With welded stainless spacers the holes can be blind which will prevent water intrusion. There are flat tracks that are made to be installed over a toe-rail or a spacer which won't increase the height more than necessary.
     
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  6. Nick.K
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    Nick.K Senior Member

    Thanks for the replies all

    I already have all my deck gear which came from a wreck that I bought for salvage. The tracks are Harken and too good to pass up on.

    I had not thought of doing the spacer in mild steel, but thinking about it, there are advantages.

    PDW.. sounds like you have a nice set up there, mine is a bit more basic!

    Nick.
     
  7. tazmann
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    tazmann Senior Member

    To keep them flush and not use through bolts that leak I would look at welding in acorn nuts or make your own out of solid shaft with threaded blind hole , drill deck holes to same OD as the shaft or acorn nuts slip them in flush on top side and weld them up
     
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  8. Nick.K
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    Nick.K Senior Member

    I like the shaft idea with the method for fitting it. Will also simplify the fitting of the track since I will be able to drill and tap them after blasting and painting; thanks Tazmann.

    Flat bar would work...but there is the height issue and also I'm a bit concerned as it is about the weight of the deck and am reluctant to add more! The shafting will also allow a slightly deeper threaded hole than flat bar without the weight penalty.
    I had thought about using welded nuts, but rejected the idea because I think I'd probably distort them so much that I'd have to drill them out and re-tap them also, I imagine it would be tough to get the exact positions...but with the shafting I can use the track as a drilling template, if the holes are off-centre, so what?
    Nick.
     
  9. pdwiley
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    pdwiley Senior Member

    Umm, yeah, they *can* be.

    Now I don't know about you, but for me drilling 5mm dia holes 5.5mm deep into 6mm 316 FB and then tapping those blind holes out to M6 x1 is going to be...... interesting. Good luck even getting a taper tap to start in a hole that shallow, then you need to use an intermediate tap & a bottoming tap. Thicker section, easier, but increases tripping hazard. How many do you need to make?

    Acorn nuts work, I've done that. See my comments WRT stainless on stainless galling because it still applies.

    As for drilling & tapping round shafting to make your own, see first comment if you use stainless. I'd go the acorn nut road long, long, long before I'd do this unless I had a turret lathe to punch the things out in bulk. I'll bet nobody here has one of those - even I don't (though I have a friend with 3).

    Problem is I don't know what equipment you have available to you and that makes a big difference. I like the acorn nuts personally. If I was worried about getting the hole spacing right, I'd lay out the track and drill through the screw holes with a drill bit the size of the minor diameter of the threads, enough to make a dimple. Come back & drill to size for the nuts then weld in with your favourite technique, as long as it's TIG or MIG. Put a bolt in each nut as you weld it, something to hang onto and also a heat sink and prevention of weld spatter sticking to the threads.

    The other way is to drill all the holes *slightly* oversize, put screws through the track into the acorn nuts, lay the whole thing down on the deck in position and tack from the underside. Assumes you can get at the underside of course. Then remove track & finish weld from above.

    I've done this sort of thing with M12 acorn nuts quite successfully - there's a grid of them in the transom of my boat in case I want to bolt stuff there one day. I'm assuming you won't need anything bigger than M6 which doesn't actually make it easier due to heat distortion, but it's do-able. Just depends on how much aggravation you want to go through and how high you can live with the track above deck.

    PDW
     
  10. Nick.K
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    Nick.K Senior Member

    Thanks PDW..

    Equipment? That's easy to list... inverter welder, big grinder, little grinder and a bunch of hammers! A MIG and TIG setup would be nice, but I don't have them...

    I have about five meters of straight track (in different lengths), I was planning to use about two meters on each side butt joining the lengths (which I'm told will work fine). Off my head I don't remember the bolt spacing, I suppose about 100mm so about twenty bolts per side.

    Iv'e experienced the stainless galling problem on rigging screws. Can be a real pain. I have tacked in place a few stainless nuts around the boat and find it quite tough to do by stick without pulling the nut out of shape so I would go for the mild steel nuts anyhow.

    I would much prefer not to have flat-bar on the deck so I'll do some experiments with the dome nuts and see if I can get it to work with what I have. If they don't work then I'll go for the shafting.


    Small change of subject...
    While reading up on two part foams, it occurred that this could be a good way to protect the interior of steel tube. The volume of liquid required could be calculated and pumped in to the tube at one end, the hole being closed by a plug. As the liquid expands it would be forced down the tube to a bleed hole at the other end. The foam would also stiffen the walls of light wall tubing.

    Nick
     
  11. pdwiley
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    pdwiley Senior Member

    Depending on your inverter welder you may be able to add a TIG torch to it. I can on mine. DC only but that's what you need for stainless anyway.

    I wouldn't stick weld M6 acorn nuts, too much chance of bad distortion even with 1.6mm electrodes.

    If I had to do this and couldn't use acorn nuts I'd turn up a pile of spacers like a flange nut then weld them into the deck using the smallest stick electrode I had. Say a 20mm dia by 3mm thick flange with a 12mm body tapped M6. Drill 12mm hole, drop them in and weld around the flange periphery. But you need access to someone with a metal lathe. Perfect job for a small capstan or turret lathe actually, they were designed to make stuff like this. I do know one man in England who could do it, not sure if he would or the cost though. Given you need 40+ it might be worth getting a quote from an engineering shop.

    PDW
     
  12. pdwiley
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    pdwiley Senior Member

    Afterthought...

    Consider how much your 'free' track is actually going to cost you in time, materials and aggravation to fit to the boat.

    Considering a Plan B and flogging the track on Ebay might be a lot better alternative. Sometimes 'free' ends up being very expensive in other ways.

    Guess how I know that......

    PDW
     
  13. Nick.K
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    Nick.K Senior Member

    Thanks again PDW
    I've a feeling that the bolts that came out were M8.
    My inverter has the scratch TIG option, I was going to get the torch, bottler, gauges etc for the stainless rails but a friend offered me use of his in his workshop..

    The track wasn't 'free'! I bought a half-tide wrecked boat expressly for the purpose of fitting out this one. It took two long and very wet and cold weeks to separate all the gear from the boat and clean up the mess. But you are right...that free (or cheap) stuff often turns out to be the most expensive option..

    I'll do some experiments (in the new year) and let you know how they work.

    Nick.
     
  14. waikikin
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    waikikin Senior Member

    This would represent a change of t(r)ack, when my Dad built his last steel yacht, he used staino flat bar 1&1/4" 32mm drilled off to suit the matching Ronstan cars, to space off the deck he used nuts.... "on edge".... maybe 3/8 or whatever suited first welded to the staino & then to the deck all round, no leaks, neat & strong, one end was bent through 90 degrees to meet the deck also & welded.
    Jeff.
     

  15. Nick.K
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    Nick.K Senior Member

    Problem solved.
    I did some trial welds today of the dome nuts on scrap 3mm plate. I drilled the plate with a 16mm hole saw, tacked the nuts from the under surface and welded the nuts flush with the top surface. I started with 6013 rods but had a bit of slag trapment, doing it with the 7018 got rid of the slag...just have to keep it moving! No problems with distortion of the nuts.
    Thanks a lot
    Nick.
     
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