# Masts - deck or keel stepped?



## Cwhit767 (Jul 20, 2014)

I've seen several boats with deck stepped masts instead of keel stepped. The keel stepped ones look sturdier, but hard to tell if that's the case. Aside from not having the "stripper pole" in the middle of the cabin, is there any other advantage or disadvantage of deck stepped masts?
Thanks!


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## bobperry (Apr 29, 2011)

Both masts can be engineered for their application.
A deck stepped mast has "two pin ends".
A keel stepped mast has "one pin end and one fixed end"
Measured in moments of inertia the deck stepped mast will have to have a "stouter" section than the keel stepped mast. Reality is that with the available alu mast sections and the good practice of rounding up in mast calculations both applications will end up with the same section. In that case, the keel stepped mast will be "stronger" due to one fixed end, i.e. mast partners and mast step.

For me it comes down to:
If I wanted an offshore boat I'd like a keel stepped mast. That way if I am ever dismasted I will have a stump sticking up that I can use to rig a jury mast to get me home. A deck stepped mast will leave you nothing.

But this is an extreme way of looking at it.
The boat I owned for the last 15 years had a deck stepped mast. I was very happy with it. There was no water in the bilge from the mast.


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## B.J. Porter (Aug 1, 2013)

Deck stepped masts also tend make for a drier boat, as you don't have this huge hole in the middle of the deck that you have to keep sealed.

We've had a deck stepped boat for the last 7 years, so far so good.


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## Bill-Rangatira (Dec 17, 2006)

deck stepped are strong if they have a support post under them
and don't leak


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## Minnewaska (Feb 21, 2010)

Cwhit767 said:


> .....Aside from not having the "stripper pole" in the middle of the cabin......


Well, there are a few pros and cons for each, as mention above already. However, if you ever found yourself in a position to need a stripper pole down below, it would be pretty disappointing not to have one.


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## Cwhit767 (Jul 20, 2014)

Thanks. I've been researching Catalina 310's, but have not been on one yet. From the photos, it looks like it is deck stepped, unless the pole is enclosed within the forward birth bulkhead. In any case, we will be coastal cruisers and weekend/day sailors, so not too worried about being caught out on the "big blue" dismasted, but it is a valid consideration. 

I didn't consider the leaking potential of the cutout. I did however, consider the potential need of the "stripper pole", but my wife just rolled her eyes!


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## flandria (Jul 31, 2012)

Guess what? When I saw this thread, I said to myself, "I don't know the answer, but a guy like Bob Perry would". And he was first to respond. Give me a gold star!


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## JonEisberg (Dec 3, 2010)

flandria said:


> Guess what? When I saw this thread, I said to myself, "I don't know the answer, but a guy like Bob Perry would". And he was first to respond. Give me a gold star!


Yet another issue/question Bob has already addressed in detail in his book...

In a perfect world, more folks out there would read it...

)


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## ccriders (Jul 8, 2006)

Not all manufacturers provided an adequate deck structure and deck to keel support for a deck stepped mast, so look carefully at any boat you are considering for deck compression and deck deflection. Especially if the boat has been aggressively raced.
John


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## capttb (Dec 13, 2003)

Most Catalina 310's I've seen have in mast furling which are all deck stepped aren't they? I really don't know, just assumed there are no keel stepped furling masts ? 
Good news is that deck stepped boats have a compression post in the cabin so stripper pole is included.


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## bobperry (Apr 29, 2011)

Thanks a lot Jon but let me adjust that:
In a perfect world more people would *BUY* it.
I am still about $450 of making back the advance on royalties!
I'm hoping to sell the movie rights for BIG money.


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## MikeOReilly (Apr 12, 2010)

Each have their advantages and disadvantages, much like most boat choices it seems. Get a well designed, well built boat and either would be fine. 

BTW, ours is deck stepped, but alas, no stripper pole. Our compression post is a solid timber of teak. Try as I might, I can't convince my beautiful partner to give it a try :-(


Why go fast, when you can go slow


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## Faster (Sep 13, 2005)

The issue of 'leakage' with keel stepped mast is not so much leakage around the deck/mast partners - there are many ways to seal that; the more difficult and unavoidable water is what gets into the inside of the mast through all the halyard exit/entry points and runs into the boat that way. Depending on mast design and configuration this water ingress can be considerable.

I'm leaning towards deck stepped should there be a 'next boat'...


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## JonEisberg (Dec 3, 2010)

capttb said:


> Most Catalina 310's I've seen have in mast furling which are all deck stepped aren't they? I really don't know, just assumed there are no keel stepped furling masts ?


I'm pretty sure the GMT in-mast furling spar on this Hylas 70 was keel stepped...

Saw ARCHANGEL in Newport a couple of weeks ago, she's looking as good as new...

From a distance, at least... 










Panbo: The Marine Electronics Hub: Summer bummer, please don't blame charts or electronics


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## bobperry (Apr 29, 2011)

Nice Hylas.
Is that jiffy reefing? Looks like it was quick.


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## SVAuspicious (Oct 31, 2006)

Cwhit767 said:


> I've seen several boats with deck stepped masts instead of keel stepped. The keel stepped ones look sturdier, but hard to tell if that's the case. Aside from not having the "stripper pole" in the middle of the cabin, is there any other advantage or disadvantage of deck stepped masts?


As a practical matter there is no particular structural advantage or disadvantage. I think stowing your spinnaker pole on deck instead of on the mast (where mine is *grin*) would have a greater positive effect on survivability and self-sufficiency after a casualty.

As Bob Perry notes, keel-stepped masts are modeled as having a fixed end while deck-stepped masts are modeled as pinned. On larger offshore boats the reality is that the keel-stepped boats have more flexibility at the coach roof than a true fixed end would indicate, and deck-stepped masts have more resistance to rotation at the step than a pinned end would indicate. As a practical matter, Mr. Perry is spot on that naval architects will always round up to the next standard available production section, and if the rounding is "too close" (a judgment call) will round up another step. On top of that you may go bigger yet to keep roller furling straight in a pre-bent mast and have room for conduit for all the goodies aloft. Ultimately, a finite element analysis provides better assessments than the simpler pinned/fixed calculations. Given the other considerations it just isn't worth the effort for a few more decimal points of accuracy.



bobperry said:


> Thanks a lot Jon but let me adjust that:
> In a perfect world more people would *BUY* it.
> I am still about $450 of making back the advance on royalties!
> I'm hoping to sell the movie rights for BIG money.


As a degreed naval architect (Webb '82) I looked forward to Mr. Perry's book with eagerness. I pre-ordered (from Amazon I think) and read it carefully. I enjoyed it. I didn't necessarily agree with all his design decisions (I have sailed a lot of Perry boats on delivery) but reasonable and competent people can look at the same information and come to different conclusions based on priorities and experience. I never lose sight of the fact that there are a lot more Perry-designed boats on the water than Skolnick-designed ships, or that boats and ships are quite different beasts.

I highly recommend Mr. Perry's book to anyone interested in what leads to the boats we choose to purchase and sail. You don't need to be particularly technical to gain a lot of knowledge from it.

The coffee table format does make storage on the boat a tad awkward. I keep my copy in the bottom of an odd-shaped locker instead of a book shelf.

On behalf of my alma mater, I also appreciate Mr. Perry's support to the Webb winter work program. Is it too late for me to gofer in your office?


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## knuterikt (Aug 7, 2006)

bobperry said:


> Thanks a lot Jon but let me adjust that:
> In a perfect world more people would *BUY* it.
> I am still about $450 of making back the advance on royalties!
> I'm hoping to sell the movie rights for BIG money.


How can I get a signed copy?


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## bobperry (Apr 29, 2011)

knut:
There are two ways you can get a signed copy of my book.

The preferred way is for you to bring a copy of the book up to my beach shack in a brand new, red, Jaguar convertible. You leave the Jag and I sign the book. Easy squeazy.

Or you can mail me a copy of the book with return postage included. I'll sign and personalize the book and send it back to you.


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## bobperry (Apr 29, 2011)

Auspicious:
Come on up. I have some organizing of archives you can do. Not sure they taught you that at Webb but we can figure it out together.

My files are a mess since I moved the office. Can you file? I don't file. I pile.

Many thanks for the kind words.


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## outbound (Dec 3, 2012)

Have had deck stepped and currently keel stepped boats. Just wondering if the hydraulic backstay effects them differently. Would think with a fixed end and a longer section for the deck stepped even though there will be little or no movement at deck level the keel stepped will bend more with less force. 
Agree that keel stepped means more water in bilge. Note that sailing or on anchor/mooring this is less of an issue. The sail track is aft so out of the wind/weather and the halyard exits on the sides are some what parallel to wind direction usually. It is a more significant when in a slip unless wind right off your bow.
Have seen folks fill the section just above deck with foam and place a drainage hole above the foamed section. Having a small amount of fresh water in your bilge seems no reason to be concerned to me. I like having the light for the low level bilge go off every once in awhile. Nice to know it works even though I turn the high and low bilge pumps on manually before leaving my port to check them that's different then knowing the float switches work.


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## SVAuspicious (Oct 31, 2006)

bobperry said:


> Auspicious:
> Come on up. I have some organizing of archives you can do. Not sure they taught you that at Webb but we can figure it out together.
> 
> My files are a mess since I moved the office. Can you file? I don't file. I pile.


I'm intimately familiar with the pile method. *grin* I'll keep my eye on flights and let you know. Staying organized was necessary at Webb, and certainly in the real world.

We could work together to get you another current Webbie to work on your archives.



outbound said:


> Have had deck stepped and currently keel stepped boats. Just wondering if the hydraulic backstay effects them differently.


Too many variables. Rigging and section will have a greater impact than where the step is.

Everyone should have a backstay adjuster.


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## ccriders (Jul 8, 2006)

SVAuspicious said:


> Everyone should have a backstay adjuster.


Really? Even for a 1976 Pearson 28? When and how would you use it?
John


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## Minnewaska (Feb 21, 2010)

capttb said:


> .....just assumed there are no keel stepped furling masts ? ....


Nope. Ours is both keel stepped and a furling mast.


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## SVAuspicious (Oct 31, 2006)

ccriders said:


> Really? Even for a 1976 Pearson 28? When and how would you use it?


Tighten upwind, ease downwind. Tighten in heavy air, ease in light air.

You'll point higher upwind and keep more speed in light air. You can carry more sail as wind speed increases before you have to reef.


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## bobperry (Apr 29, 2011)

Auspicious:
Honestly, now that my office is in my remote beach shack having "interns" at all is a bit logistically awkward. I don't mind a kid or two living here for a week or two but it has to be the right kid. I'm not well set up for interns anymore. I feel bad when I turn them down.


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## Alex W (Nov 1, 2012)

ccriders said:


> Really? Even for a 1976 Pearson 28? When and how would you use it?


I added one to my 1986 Pearson 28.

I leave it off when winds are light and put it on when the wind speed builds, especially if we are going upwind. On my version of the Pearson 28 adding backstay tension will tension the forestay (flattening the jib and moving the draft a little forward) and add a little curve to the mast which will flatten the main. I've measured the change in mast bend at about 1" (normally there is 1" of mast bend, with the backstay on it is 2").

It isn't as noticeable as the skinny little stick on a boat with a fractional rig, but the effects are immediately noticeable and the boat does heel less and point a little higher in high winds with the backstay on. Likewise with the backstay off in low winds the sails have a little more power and the boat accelerates better.


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## blt2ski (May 5, 2005)

My Jeanneau is similar in specs, ratings etc to Alex's Person, my boat came stock with a back stay adjuster in 85. Great to have in the different winds here in Puget Sound, would imagine elsewhere too!

As far as which mast is better. Probably at the end of the day, both work, just depends upon the application you have. An awful lot of dingys are for the most part deck stepped with out stripper poles......my boat has a stripper pole, wife says it will not support her.......will not go there. 

Marty


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## bobperry (Apr 29, 2011)

I have given the deck stepped/keel stepped question a lot of thought. I have come to this conclusion. If you accept the engineering that each application can be as "strong" as the other, the choice may boil down to this.

If you are considering going offshore you might contemplate how you would jury rig your boat in the case you were dismasted. A good number of years back I think there were five boats dismasted in the TransPac Race. Two had deck stepped masts and three had keel stepped masts.

The keel stepped masts broke leaving a "stump" sticking out of the deck. Keel; stepped masts generally break just below the lower spreaders. leaving a "stump". This stump was helpful in jury rigging a mast with spin pole or boom so they could limp into port. The deck stepped mast boats were left with a clean deck when their mast went over the side. Their jury rig had to be built from the deck up and the result was a shorter and far less efficient jury rig.

So, for me, given the option I'd always go with a keel stepped mast. That said, my beloved PERRYWINKLE, the "mighty" PERRYWINKLE, had a deck stepped mast and I appreciated my bone dry bilge.


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## miatapaul (Dec 15, 2006)

bobperry said:


> Thanks a lot Jon but let me adjust that:
> In a perfect world more people would *BUY* it.
> I am still about $450 of making back the advance on royalties!
> I'm hoping to sell the movie rights for BIG money.


Well I just picked up a copy so you are a few bucks closer! I can tell I will not be sleeping for a few days. Now just to play fair I am looking for a copy of Brent's book but don't seem to see it anywhere. Does it actually exist? I see lots of mentions for it but no place to actually buy it. Heck it is not even on Amazon, and you can buy anything there.


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## bobperry (Apr 29, 2011)

Boy Miata, you sure know how to hurt a guy. On Amazon check under "BS". Even if you find the BS book I am willing to bet mine is a lot more fun to read.


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## miatapaul (Dec 15, 2006)

bobperry said:


> Boy Miata, you sure know how to hurt a guy. On Amazon check under "BS". Even if you find the BS book I am willing to bet mine is a lot more fun to read.


Oh I have no doubt yours will be better, but I was a Philosophy major so I just like to get both sides of the story so to speak. I have had a hard time at work not just sitting down in some hidden corner and start reading your book. I really like the size of the pages because the drawing show up nicely. Often a book will have typical novel size pages and the drawings are big enough to be clear. I have no doubt I will loose the next several nights going over it.

When I search Amazon for BS I get this:

Amazon.com: BS Button: Appstore for [email protected]@[email protected]@http://ecx.images-amazon.com/images/I/[email protected]@[email protected]@71iZAl78x-L

Not quite what I am looking for, but might be appropriate.


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## bobperry (Apr 29, 2011)

Miata:
Somehow that button seems perversely appropriate.


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## blt2ski (May 5, 2005)

Lets have a little PHUN here........

Assuming it would not matter in the end if I choose to have a deck or keel stepped mast on my new BS POS slower than slug boat, or my fancy smanshy BP coastal racer............

Which is more expensive to literally build into the boat? or is it close enough to a wash, that cost should not matter? I would surmise that the size of the boat may benefit one over the other at some point too......where might this be?

As noted before, not sure personally it would matter a hell of a lot for myself, as long as the boat functions........I'm sure there are some where it will mean a hill of beans......

so with that, will head to walk mr winston, maybe then put the fuels lines on my poor deezal back on to see if I have fixed my air leaks etc...........nice night for a walk here, sunny, reasonably cool, but not too hot........

Marty


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## capttb (Dec 13, 2003)

I've been wondering about the use of "sleeved" masts on a lot of boats lately, there's a Hunter next to me and the mast is joined about 8 feet above the cabin top, it's a conventional main, not furling. Last time I went to a boat show seemed like a lot of new boats had them?


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## miatapaul (Dec 15, 2006)

capttb said:


> I've been wondering about the use of "sleeved" masts on a lot of boats lately, there's a Hunter next to me and the mast is joined about 8 feet above the cabin top, it's a conventional main, not furling. Last time I went to a boat show seemed like a lot of new boats had them?


Well could be a repair but I was recently reading an article about Selden (think that was the brand) masts are available in 40 foot sections due to the size of containers and anodizing tanks. They say the slave is the strongest portion of the mast. So I think it is a cost saving thing.

Sent from my DROID RAZR using Tapatalk


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## Faster (Sep 13, 2005)

Our 30 yr old Selden stick is sleeved and riveted above the spreaders in similar fashion. I'm quite sure it's original, not a repair, and have also noticed the new Hunters doing the same lately.


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## mr_f (Oct 29, 2011)

Our seldon stick is also sleeved. It is about 10 years old. It seems to hold the sails up. 

Side note: Did anyone else looking at Bob's book on amazon notice that his namesake is making a killing selling books on shrubbery that are apparently worth 3 to 5 times as much as a book on boat design? Bob, have you considered becoming a landscape architect?


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## bobperry (Apr 29, 2011)

You do a sleeve to join spar sections not because sleeves are cool.

I think its probably a wash in terms of the cost difference between a deck stepped and a keel stepped mast.

However, look at how many modern production boats have deck stepped mats. Lost of them! That would make me think that deck stepped is cheaper. Hunter is deck stepping the mast because it is cheaper. Of that I am certain.


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## outbound (Dec 3, 2012)

Agree now a days longer masts are not uncommonly sleeved. Think if you are going to use back stay or are a race/cruise boat may want to be aware it's likely the sleeved portion which is stiffer will not bend like the rest of the mast. Many boats end up with 64' airdrafts to allow some ICW travel so if keel stepped well in excess of shipping container dimensions Would note some foreign manufactured boats( my own) and some quality local builders use U.S. made masts. I think this is to avoid sleeves. From what I see given most race boats have cf masts so a non issue.


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## paikea (Aug 3, 2014)

bobperry said:


> Thanks a lot Jon but let me adjust that:
> In a perfect world more people would *BUY* it.
> I am still about $450 of making back the advance on royalties!
> I'm hoping to sell the movie rights for BIG money.


I did buy it! Well I can't say I read it cover to cover yet! Thats a slow process and not done frugally. But I already see that for my sailing goals this book especially is going to help me a lot. Perfect investment.


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## casey1999 (Oct 18, 2010)

Agree with Mr. Perry, stepped mast if designed correctly will work. Note Jon Sanders broke records by sailing twice around the world non-stop and then three times around the world non-stop. Both boats had deck stepped mast, the S&S34 and the custom 47 footer:





"Jon Sanders was the first man to circumnavigate Antarctica, circling the continent twice in 1981 - 1982. For this accomplishment, Gate 17 of the new Antarctica Cup Racetrack has been named after him, with sector 17 named after the S&S 34 monohull Perie Banou, the yacht he had used during the circumnavigation.[2] Sanders Gate is positioned mid-way round the Indian Ocean zone; the gate is close to where Sanders suffered a 180-degree knockdown. During the voyage, he passed south of the three great capes: Horn, Good Hope and Leeuwin, before rounding Cape Horn a second time. He turned north to Plymouth, UK and returning south around Good Hope and returning to Fremantle.[3]

This voyage was recognised in the Guinness Book of Records through the following records:
The first single-handed sailor to remain continuously at sea twice around the world
First single-handed sailor to round the five southern most Capes twice on one voyage
First single-handed sailor to round the five southern most Capes twice
Longest distance continuously sailed by any yacht: 48,510 miles (78,070 km).
Longest period alone at sea during a continuous voyage: 419 days: 22 hours: 10 minutes

In 1986 Sanders set out again from Fremantle, and this time completed three solo non-stop circumnavigations aboard his 47-foot (14 m) yacht Parry Endeavour, rounding Saint Peter and Saint Paul Archipelago just north of the Equator each time to ensure that his course covered both hemispheres."

Concerning the 47 footer:

About Project Endeavour: Refitting the Parry Endeavour

"A heavier section mast (250mm x 175mm) some 2m shorter than the original rig was chosen from the Rolly Tasker Spars range. The mast is deck stepped, unusual for an ocean voyaging yacht: this is a characteristic of almost all Perth based yachts as they must 'shoot' the Fremantle bridges to reach the Indian Ocean. Consequently the local spar manufacturers are expert at deck stepped tabernacle systems."


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## bobperry (Apr 29, 2011)

Thank you Paikea. The Perry's will eat tonight.


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## dorymate1 (Dec 6, 2011)

On a new or newer boat I have no issue with a deck step vs. keel.
It does seem that the size and weigh of masts on boats over 45ft tend with a few exception go for a keel step.
However on boat 15yrs or older some water intrusion into the deck under a deck step may make a vessel less seaworthy due to deterioration under the mast. 
I have seen even on one of my own boats this happen. Evident by a depression from the mast at the step. 
If you notice this depression or that when you tune your rig the and the turnbuckles bottom out or your rig gets loose during the season.
Inspect very closely and make repairs.


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