Thru-mast Or Mounted On The Coachroof?

[carstenb]

So here is a question for the experienced blue water cruisers. What are your opinions on coachroof mounted masts, as they are in most production boats today. Versus a thru-roof mast that is stepped in the keel?

My boat has a thru-mast. I will be circumnavigating so I feel this is a necessity.

Other opinions? For coastal cruising, I feel rooftop masts are fine. Different story when blue water.

[Mike OReilly]

Well ... my Rafiki-37 is deck stepped. It is a proven circumnavigator, and true "blue water" boat. And it was built in 1977.

I think each (deck stepped vs keel stepped) have its strengths and weaknesses. Like so many other choices (Ex: keel design, hull shape, size, volume, rig, anchor choice, fridge, watermaker, etc...) there is rarely one right answer.

As long as the mast is stepped properly and soundly, I think both are fine. Just understand the trade-offs of your design.

[jeremiason]

Our Catalina 470 has a deck stepped mast. The mast is a little over 58 feet long and has both upper and lower shrouds. We have a five inch metal compression post under the mast which transfers the load to the hull.

The nice thing is there is no water intrusion. The only hole in the deck is the PVC pipe for electrical connections, which is off set from the race in the mast to keep the water from entering the cabin.

I had some reservations about a deck stepped mast, but now beileve it is better than a keel stepped mast for cruising.

[Wotname]

Originally Posted by Mike OReilly

Well ... my Rafiki-37 is deck stepped. It is a proven circumnavigator, and true "blue water" boat. And it was built in 1977.

I think each (deck stepped vs keel stepped) have its strengths and weaknesses. Like so many other choices (Ex: keel design, hull shape, size, volume, rig, anchor choice, fridge, watermaker, etc...) there is rarely one right answer.

As long as the mast is stepped properly and soundly, I think both are fine. Just understand the trade-offs of your design.

Exactly.

Both are bad when badly designed or maintained; both are good when properly designed and maintained.

I have had both, the deck mounted ones never leaked, the keel mounted one aways leaked a bit.

[sailorboy1]

I've had both and prefer the deck stepped for the drier boat inside. I don't think either makes a difference as far as strength.

Regardless of which I prefer if a boat choice really came down between the 2 I would go with your heart! Too many try to make buying a boat a head choice instead of a heart choice.

[zeehag]

i love my inferior hollow box wood keel stepped masts. they are short enough fo icw, and dont take up a lot of room below decks. they hold the sails nicely and i can use below decks sections for affixing items i dont wish to have roll around below decks...and they have these sexy new skirts(mast boots) that keep out ALL the rain water.......
my ericson with a deck stepped mast is wetter inside than my nice n dry keel stepped boat......LOL..deck stepped masts have a dish under mast base--the dish expands with corrosion causing cracking in house top--i love keel stepped masts--easier to maintain a dry boat.

best use of a deck stepped mast is the tabernackle device for lowering masts while canal cruising and for under low bridges.....

[denverd0n]

Originally Posted by Wotname

Both are bad when badly designed or maintained; both are good when properly designed and maintained.

There ya go. I think way too much thought/debate/angst goes into which one is better, and not nearly enough into whether or not it was done correctly--whichever way it's done.

[Sailmonkey]

We've got two deck stepped masts......they've been there for 35 years. I've personally sailed the boat in 12'-14' beam seas with winds of 30kt with gusts to 40+kt.......the masts are still there. The Schnauzer was not happy

[Vasco]

Lots of cats out there circumnavigating. How many of them have keel stepped masts? Keel stepped or deck stepped, it's a non-issue. Personally I prefer keel stepped because I have to remove the mast every fall and I feel safer with a mast that stands up without stays or shrouds. Less crane time and safer for diy. A minor factor.

[propellanttech]

The preference should be decided by where the pressure of the rig will go, and how you feel about it.

On a keel stepped mast, the mast transfers some of the load to the cabin roof laterally. The chain plates will take the other portion of the load, along with the forward stay, and back stay.

A mast/deck stepped mast will transfer it's load vertically to a compression post or other compression prevention with the chain plates taking the remainder along with the forward stay, as well as the back stay.

The main point to consider is the possibility of what happens if the boat were to capsize.

In just about any capsize with a mast stepped mast,the mast will be lost. But the cabin usually stays intact, although no better from the event.

In a severe capsize, a keel stepped mast can destroy the cabin, if the mast is lost. In a minor capsize (is there such a thing.....maybe a knock down) the mast may survive, and remain attached to the boat, but may still damage the cabin. It is possible to have a knockdown which doesn't damage the cabin, but a keel stepped mast does have a higher chance of damaging the cabin.

This is all academic of course, but should be a minor consideration when looking at the different types of mast attachment.

I'm a very careful person, and will try to avoid severe weather at all costs, but mother nature is not always compliant. Still, I'm looking at boats with a keel stepped mast.

Also, many keel stepped masted boats can be sealed pretty well from water intrusion.

Just items to ponder when looking at different boats,

James L

[Jim Cate]

G'Day all

The bugaboo about keel stepped masts somehow destroying the deck/coachroof/interior joinery is often heard,,, but seldom demonstrated. In our many years of cruising we've encountered a few dismastings, including one on our own previous boat (keel stepped), and have yet to see such a disaster. I suppose that it is possible, but I reckon there are better things to worry about.

There are advantages to both methods. To me, the mast standing sans rigging is useful, as in being able to remove all forward stays when being lifted by a small travel lift (as we must) or while replacing standing rigging (although I haven't ever removed all of them at once for that purpose!). The converse of that is we've seen a cat that lost a shroud just as they left Noumea. Their deck stepped mast simply fell off the other side of the boat and suffered little damage. We helped them get it secured, mostly out of the water and they returned to harbour where they were able to get a new shroud, restep the somewhat gouged mast and depart once more. Had it been keel stepped (obviously not gonna happen on a cat, but just for arguments sake) it might have stayed erect, but had it not, it would have surely been broken or kinked. Finally, if I remember correctly, one can specify a somewhat lighter section for a keel stepped spar, and that will reduce weight aloft.

So, as in so many factors in yachting, there are tradeoffs in mast design. As someone else has said, it is more important that it be well designed and executed and maintained than whether it be deck or keel stepped.

Cheers,

Jim

[Andrew Troup]

I personally think most naval architects overstate the benefits of keel stepping - the lighter sections they specify as a result would, I think, be viable deck stepped, provided a decent tabernacle, well tied into the deck beams and compression post, went some distance up the mast, and had the gooseneck mounted directly to it for good measure. This saves quite a deal of lateral load on the lowest panel of the spar.

If a mast is to derive benefit from being keel stepped, the mast collar at deck level must IMO be really well designed and installed. It also helps if the mast is sleeved locally to feed the support into the section without the risk of crumpling, especially if the section is lighter in consideration of the 'built in end' effect.

I have an abiding dislike of entry points for water, and while it's possible to keep water from running down inside a keel stepped mast, very few boats I've sailed on have managed it in practice. Some even struggle to stop it coming down between collar and spar.

[osirissail]

One thing that is probably driving the use of deck stepped masts versus keel-stepped is the ability to route the running rigging from the mast to the cockpit. It is quite easy and economical to do with deck stepped masts. However. with keel stepped masts, there needs to be serious modifications made to the cabin top/mast interface to allow the running rigging to be routed to the cockpit.

[rebel heart]

Originally Posted by carstenb

My boat has a thru-mast. I will be circumnavigating so I feel this is a necessity.

Can't really agree with you on that one. A well tuned rig is fine, either way. It's not like a snapped shroud on either in a big blow is going to stay up for more than a few seconds.

My vote would be for spare cable clamps, knowing how to use them, and some amsteel. Tie a quick trucker's hitch and you can fashion a temporary stay pretty quick.

I find it better to realize that the mast holds the wires up, rather than the other way around. It provides the vertical support. All other forces are on the wires.

[Rakuflames]

Originally Posted by rebel heart

Can't really agree with you on that one. A well tuned rig is fine, either way. It's not like a snapped shroud on either in a big blow is going to stay up for more than a few seconds.

My vote would be for spare cable clamps, knowing how to use them, and some amsteel. Tie a quick trucker's hitch and you can fashion a temporary stay pretty quick.

I find it better to realize that the mast holds the wires up, rather than the other way around. It provides the vertical support. All other forces are on the wires.

I have a question for you -- purely academic as my rigging is in good condition (not my opinion -- it's been checked).

I have a Hunter with swept-back spreaders, so I have a lot of rigging (it does have a split backstay). I get how easily the mast could come down if the forestay or back stay snapped, but there are three shrouds on each side. I do have line on board to replace one if it pops, but ... with three shrouds (assuming I'm not in adverse conditions at the time) ... would the mast be at risk of coming down immediately if one of those six shrouds gave? I hope I never find out from real experience but ... such discusions make us newer sailors curios, to say the least ...