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Author Topic: Deck or keel stepped?  (Read 2733 times)

g4yvm

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Deck or keel stepped?
« on: August 08, 2013, 05:59:20 PM »

In a model yacht is there any advantage to deck stepping?  Im making a 38" long, 1.3m masted, non-scale yacht.  I can see all sorts of advantages to keel stepping (one tube epoxied in, takes strain off shrouds / stays, always in right position etc etc ) and almost none for deck stepping.


Am I right?


David
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hmsantrim

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Re: Deck or keel stepped?
« Reply #1 on: August 08, 2013, 07:17:20 PM »

Hi David.
 Agree on most of what you have said. In MHO I feel it gives the best support to the mast having it stepped into the keel as it gets secondary support from passing through the mast hole.    You have one of these (they are called mast track here) mounted inside the hull.
  Make a slot in the mast base and mount it onto the track.  Keel stepped also allows flexibility off the mast.
  The deck stepped set up requires wire shrouds, crimps and turnbuckles.   
http://www.ebay.de/itm/Mastschiene-83-x-13-x-8-mm-Aeronaut-/300786922048?pt=RC_Modellbau&hash=item46084c3240
Goose necks
http://www.ebay.de/itm/Baumbeschlag-12mm-Mast-6mm-Baum-Segelboot-/300786559114?pt=RC_Modellbau&hash=item460846a88a
http://www.ebay.de/itm/Baumbeschlag-15mm-Mast-8mm-Baum-Segelboot-/400522966554?pt=RC_Modellbau&hash=item5d4107761a
 A plan more suitable to the build and yes it has the hull sheer I checked my 1978 plan hand book, a 2 sheet plan.
http://www.myhobbystore.co.uk/product/27854/mm266-racing-yacht-lancet
 Frank.
 
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g4yvm

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Re: Deck or keel stepped?
« Reply #2 on: August 08, 2013, 07:21:31 PM »

Frank
Thanks

That Lancet looks very much like mine. I think ill get the plan. Thank you
D
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mrpenguin

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Re: Deck or keel stepped?
« Reply #3 on: August 08, 2013, 11:54:38 PM »

@g4yvm:
I am assuming we are discussing a Bermuda rig sloop sail plan (jib and mainsail)
 
A keel stepped mast is more rigid but much less adjustable. You can still move the mast top fore and aft by changing the length of backstay and forestay/jib halyard, but that only rakes/bends the mast, it does not actually move the entire mast. Bending the mast also will change the curve of the mainsail leach when close hauled.
With a deck stepped mast you can move the foot of the mast fore and aft - this is one of the major adjustments in managing  weather helm. To get similar adjustment with a keel stepped mast you need multiple mast sockets; some boats have this arrangement.
 
I don't think it is practical to use the mast track that hmsantrim mentioned with a keel stepped mast; that is intended to be mounted on the deck, not inside the boat.
 
A keel stepped mast can be almost self supporting depending on materials used; still needs a backstay and jib halyard. A deck stepped mast needs to be supported by shrouds at the sides (I would suggest a minimum of two each side, one through spreaders) and a backstay, plus the jib halyard and an optional forestay.
 
Using a deck stepped mast with a fractional rig there is a vast range of adjustment available.
 
For a boat this size you could use 100lb dyneema or similar for the shrouds and stays. Attach the shrouds and stays to the chain plates with fishing snaps. Works great for me.
 
Using wire stays looks good and allows you to rig the boat pondside with everything going back in exactly the same spot. The downside for me with wire rigging is that it enormously strong and if the boat is blown over while on a stand it is likely to tear the chain plates loose. With dyneema and fishing clips, the clips will pop undone before anything more substantial breaks.. I have had damage a couple of times from the boat being blown off the stand while ashore, I now lay the boat on its side on the grass.... I have never had any damage to the rigging while sailing, apart from a cheap bowsie breaking during a gust. Most damage happens while handling the boat, particularly in gusty conditions.
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g4yvm

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Re: Deck or keel stepped?
« Reply #4 on: August 09, 2013, 12:34:23 AM »

Thanks Mr Penguin for a very full reply!


David
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tigertiger

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Re: Deck or keel stepped?
« Reply #5 on: August 09, 2013, 12:47:49 AM »

The other thing that springs to mind is the original design.


I always stick to the original on anything structural (not superstructure). There are fewer risks.


If the boat was designed with deck stepping, the keel may not be up the extra forces the mast would transfer.
If it was designed with keel stepping, the deck area may not be strong enough.


If she was designed with no-wire rigging in mind and you use wire, it may be possible to over tighten the shrouds, overstress the keel/deck and in the worst case punch the mast through the hull/deck.


My 2c.
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tiaki

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Re: Deck or keel stepped?
« Reply #6 on: August 16, 2013, 11:20:26 PM »

Keel stepped is quicker and easier to rig. You also get the same setting each time so that if you have set up the yacht correctly to start with it will replicate each sailing session. Setting the sails and back stay become the variables depending upon conditions each time. Also if you happen to break rigging while sailing there is still a good chance you can still sail back to the dock or indeed finish the race. With deck stepping forget those ideas.
Cheers
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hmsantrim

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Re: Deck or keel stepped?
« Reply #7 on: August 26, 2013, 01:42:11 AM »

quote :mrpenguin
 I don't think it is practical to use the mast track that hmsantrim mentioned with a keel stepped mast; that is intended to be mounted on the deck, not inside the boat.
 
 Hi  mr penguin having found my 1977 vic smeed yacht book he is showing exactly the same item as described for the keel stepped mast
 Frank
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mrpenguin

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Re: Deck or keel stepped?
« Reply #8 on: August 26, 2013, 06:03:01 AM »

quote :mrpenguin
 I don't think it is practical to use the mast track that hmsantrim mentioned with a keel stepped mast; that is intended to be mounted on the deck, not inside the boat.
 
 Hi  mr penguin having found my 1977 vic smeed yacht book he is showing exactly the same item as described for the keel stepped mast
 Frank

Thank you, I stand corrected!! That is clearly a keel stepped mast track, not a doubt of it...
I wonder how it is waterproofed where the mast passes through the deck...? There is a large slot in the picture, but I would assume this is covered somehow once the mast is positioned....
 
I also like the keel fin with a handle built into the top edge; very clever...
 
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hmsantrim

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Re: Deck or keel stepped?
« Reply #9 on: August 26, 2013, 07:17:36 AM »

the mast slide covers the hole and allows the mast to be moved to the desired position. The mast slide is a piece of metal sheet with a collar fixed to it for the mast to pass through. Fig 88 on book page One side of the slide has a row of small holes drilled in it. The slide is inserted into a thin metal tray which has the sides folded over which retains the slide. The tray has a slot in it to allow the mast to be adjusted. With the mast position decided  A wire pin usually a screwed eye is inserted in to one of the holes in the mast slide to lock it into place.
 Frank
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tiaki

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Re: Deck or keel stepped?
« Reply #10 on: August 26, 2013, 09:15:02 PM »

Simple and effective as long as the CLR and CE are setup correctly.
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