Rotating Free Standing Mast Design

[Eunice Montjoy]

Hello,
Wooden Boathouse in Florida was building their 12', 14', and 16' wood-epoxy Prema dinghies, and they wanted to add rigs to each one. They all had to be of similar design style, and they also needed rudders and daggerboards. All they had to do was come up the road, and SYDI designed everything they needed--free-standing of course--in Cypress and Mahogany.

Thanks

[Chuck Losness]

Eric,
Thanks for your input. It is much appreciated. I just wish that Cat Ketches were more readily available on the used market with more to chose from then the older Freedom's. My opinions on why they didn't catch on are radically different from yours. I will share them with you in a private message if you'd like me to but don't want to do an open thread. Again thanks for all your input on cat ketches and free standing masts.
Chuck

[Eric Sponberg]

Chuck,

I've heard all sorts of reasons for the lack of cat ketches and free-standing rigs, and in fact, since I have been posting on this forum, cat ketches are much more readily accepted than before. And this is not due to me, really, but to the fact that readers have indeed studied them objectively, I think, sailed them, and have discovered that they have a lot to offer in the way of sailing ability and cruising performance. Most other people not in the know still feel they "look funny".

There are a number of other designs available on the used market, and the most common ones are the Herreshoff, Sparhawk, and Offshore cat ketches. Various sharpie designs also qualify.

Eric

[JimConlin]

Who might supply the bearings for one of the stub masts?
I think Harken quit the rudder bearing business.

[RHough]

Originally Posted by Eric Sponberg

Chuck,

I've heard all sorts of reasons for the lack of cat ketches and free-standing rigs, and in fact, since I have been posting on this forum, cat ketches are much more readily accepted than before. And this is not due to me, really, but to the fact that readers have indeed studied them objectively, I think, sailed them, and have discovered that they have a lot to offer in the way of sailing ability and cruising performance. Most other people not in the know still feel they "look funny".

There are a number of other designs available on the used market, and the most common ones are the Herreshoff, Sparhawk, and Offshore cat ketches. Various sharpie designs also qualify.

Eric

We saw this one whilst sailing the Whitsundays



Wylie 66

[troy2000]

Eric and Chuck, thanks for the answers on why one might prefer a stub mast -- even though it took me a few days to check back with this thread.

[Eric Sponberg]

Originally Posted by JimConlin

Who might supply the bearings for one of the stub masts?
I think Harken quit the rudder bearing business.

Hi Jim,

In a very few words, not too many people. For one of my current projects, the GT80 sloop, we approached two well-known bearing manufacturers in Europe, and one declined, the other never answered emails promptly or with any helpful information. We decided to design and build our own--"our" meaning I will design, and the builder will sub out to a mast builder/machine shop to build the bearings. The bodies will be machined out of 6082 aluminum ingots because the mast builder does that all the time--they are very good at it. We will have to hard-anodize the aluminum and over-wrap the carbon fiber in fiberglass to isolate the bearings from the carbon. The rollers will be stainless steel.

In researching that project, I came to the conclusion that cast silicon bronze bodies make a lot of sense--for strength and stiffness, for hardness, for corrosion resistance, and for galvanic resistance in relation to carbon. So I am advocating custom bronze bearings, again with stainless steel rolling elements (either balls or rollers) as the ideal way to make mast bearings. A good casting shop and machine shop could do a great job if they follow the plans properly. We are going to try to do this for the new Globetrotter 66.

Eric

[idkfa]

standing a mast over a stub, even on a small boat, requires a crane?

thks

[Eric Sponberg]

Originally Posted by idkfa

standing a mast over a stub, even on a small boat, requires a crane?

thks

Any kind of a boat over 28-30' is going to require a crane anyway to get a mast installed safely. On boats smaller than this, a stub mast may not make sense, and it just may be easier to make a one-piece mast with deck and heel bearings which one might be able to install with the equipment and people on board. You will likely not be going out in green water weather, or if you do, the amount of water that gets past the deck bearing my be easy enough to handle.

The first time I used the stub mast concept was on Wobegone Daze, a Freedom 38, and I have not designed any masts since smaller than this. And not for lack of inquiries, but most people who ask for a wingmast on a small boat come to realize that the design fee is more than they want to spend on the whole mast, and most don't have the skills, equipment, or budget to build the mast in carbon fiber on their own. Getting into the smaller sizes, it usually becomes apparent that aluminum sections or a wood-epoxy mast will work pretty well, they are relatively inexpensive, and could be built by experienced do-it-yourselfers.

Eric

[petereng]

Hi Eric,
Have you considered Orkot type materials? They have similiar properties to bronze (their claim) They are usually cloth reinforced phenolic resin bearings. I have also infused PET cloth with epoxy to make custom bearings and they have worked quite well. As masts are slow moving roller type bearings are not required? I usually design spherical bearings for free standing masts to accommodate the mast bending. P{lain bearings can jam up under load? Cheers Peter s

[Eric Sponberg]

Yes, I have used Orkot type materials for mast bearings, but usually in special situations where I know the turning power is pretty large--think balestron mast and boom. Generally, I prefer rolling elements and bodies all in hard metal so that friction is reduced to the minimum and so that there is no distortion of the rollers or balls. Masts really load up highly very quickly, and even when there is finger-touch smooth turning unloaded. When the load is on, it takes two really strong arms, or more, to turn the mast.

Eric

[Eunice Montjoy]

Hello,
Wooden Boathouse in Florida was building their 12', 14', and 16' wood-epoxy Prema dinghies, and they wanted to add rigs to each one. They all had to be of similar design style, and they also needed rudders and daggerboards. All they had to do was come up the road, and SYDI designed everything they needed--free-standing of course--in Cypress and Mahogany.

Thanks!
________________
steel replacement windows

[brian eiland]

Originally Posted by petereng

Hi Eric,
Have you considered Orkot type materials? They have similiar properties to bronze (their claim) They are usually cloth reinforced phenolic resin bearings. I have also infused PET cloth with epoxy to make custom bearings and they have worked quite well. As masts are slow moving roller type bearings are not required? I usually design spherical bearings for free standing masts to accommodate the mast bending. P{lain bearings can jam up under load? Cheers Peter s

How about a large diameter spherical bearing made of glass reinforced nylon?

[petereng]

Hi Brian,
Nylon is unsuitable for marine work due to its change in volume when it absorbs water (and dries out, gets wet etc). It can't be machined to the tolerance required for a bearing and then be expected to stay there. If it is machined dry then it will jam when it gets wet. The fibre reinforcing dosn't help either. Orcot is very good but pricy down here in Oz. Cheers Peter S