Converting keel stepped mast to deck stepped

[Northman]

I am currently looking at a 38 ft steel sailboat that I like very much. What I don't like at all is the keel stepped mast running through the deck. Attached are some pictures from the deck, mast step below and the monstrous mast inside the main cabin.
The original builder asked for a mast "that can take everything" and it looks like it does. What would it take to convert this to a deck stepped mast?
I thought of shortening the mast and putting it in a tabernacle with a mast support to the keel. Would that make a more substantial standing rigg necessary?
Any opinions appreciated!
Regards
Walter

[Landlubber]

Well yes you can convert, but the mast still needs support to the keel, so you can have a compression post installed, directly under the mast base, or create a ring frame/bulkhead arrangement to support such. Either way, forget it....as it will be totally out of style with the interior arrangement to install bulkheads, and the compression post if the bulkhead idea is not used would not be all that less intrusive than the current arrangement. A steel compression post would be about half the size of the mast, so really it does not do much for you, just accept that she is well set up as it is, the mast floors look well made and strong.

[BATAAN]

I believe I see running backstays in the picture.
Does the boat have a permanent backstay?
Some keel-stepped boats don't and get a longer boom and big roach that way.
For a deck-stepped rig, a permanent backstay is necessary.
I agree with Landlubber in just leave it as-is and go sailing.
If you don't like a mast in the cabin, get an apartment.

[PAR]

You don't need fixed back stays for a deck stepped rig, though they do make it a fair bit strong. You could make this conversion, but the compression post in the cabin will divide it up about as much as the mast does now. Lastly, you'll want the conversion preformed by or checked by a designer or NA. It's very probably you'll need to make considerable adjustments to the rig with the new arrangement, particularly if you elect to split the backs or do away with them entirely for more mainsail roach. Simply put, it's not as simple as just cutting the stick and making a deck step over a compression post.

[Northman]

Thank you all! The rigging is rock-solid. Bataan: if you define running backstays by using a fractional rigg, this boat has permanent stays - see http://en.wikipedia.org/wiki/Backstay. If you count only a single backstay as permanent, it has running backstays. Attached a screenshot from the boats "behind".
Lubber: I thought of a compression post, not a ringframe. The reason is as much to get rid of part of the volume of the huge stick through the cabin as to have a watertight deck. That is one reason why I want a steel boat.
PAR: You are right, of course. I will have checked this by a NA, but wanted to get some input first. As I said, everything on this boat is solid, including the rigging. The boat handles great, even if a little on the tender side. More mainsail and/or roach is not needed. Another thing I want to do if I decide to go with this boat is to put a low pilothouse on it. That will need some calculations, too, but I will save this for another thread.
Thanks for the input, please feel free to comment more!
Walter

[PAR]

Northman, you have splits backstays, which is a common cruiser setup. These aren't running backs, as they aren't on tackle, which have to be released on each tack or jibe. These are fixed, split backs. Now, it looks like you also have "runners", likely at the height of the headstay tang, which I'm assuming is the purpose of the whip tackles located abreast the forward end of the cockpit.

[michael pierzga]

Northman, it looks like you have "inline " rigging...no fore and aft lowers..no baby stay. Without fore and aft lowers, or aft lowers and a babystay, how will you keep the heel of a deck stepped mast on it step ? I say your rigging configuration will make conversion to a deck stepped mast complicated.

[PAR]

I can clearly see a port lower, an upper, a cap, a runner (possably) and split backs, so once again Michael . . .

[Northman]

Originally Posted by PAR

I can clearly see a port lower, an upper, a cap, a runner (possably) and split backs, so once again Michael . . .

I don't know what you mean with a "cap", but for the rest you are correct. Thanks for the input.
Walter

[michael pierzga]

Be extremely careful with observations and advice passed on by PAR....He calls himself a naval architect but cannot understand the term INLINE rigging. Mr Par...the boat in question has a single set of chainplates..SINGLE SET.....hence INLINE rigging. Split backstays or whatever jibberish you talk has nothing to do with it.

Fore and aft lowers require 3 sets of widely placed chainplates per side. The boat pictured uses the standard rigging plan for a deck stepped mast.

[Paul B]

Originally Posted by michael pierzga

Northman, it looks like you have "inline " rigging...no fore and aft lowers..no baby stay. Without fore and aft lowers, or aft lowers and a babystay, how will you keep the heel of a deck stepped mast on it step ?

Why would you need fore/aft lowere, or aft lowers/babystay to keep the mast on the step?

There are countless deck stepped boats out there with in line uppers and lowers, with no aft lowers, forward lowers, or babystays. They have been sailing for many years with no issues.

From a geometric perspective, I don't see any reason staying as you suggest would have any impact on keeping the heel on a step.

[michael pierzga]

For and aft lower shrouds are used To Reduce the compression load on mast section and hull by increasing the angle of the shroud base and control mast PUMP..inertia..to keep the heel of the mast in its step

[Paul B]

Originally Posted by michael pierzga

For and aft lower shrouds are used To Reduce the compression load on mast section and hull by increasing the angle of the shroud base and control mast PUMP..inertia..to keep the heel of the mast in its step

Nope. Fwd/Aft lowers of aft lowers/babystay are not part of the equation for calculation the total compression of the mast.

If your mast is engineered and set up properly it will not pump. Even if a mast did pump it could not lift the heel off of a properly designed step, or come loose from a tabernacle.

[michael pierzga]

Some reading for you

[michael pierzga]

And to the original poster....consider the thin stick analogy contained in this article when pondering compression loading on a deck step compared to keel step mast section.

http://www.classicmarine.co.uk/Articles/masts.htm