refitting to a free-standing mast

Hi everyone, after many months of lurking I've finally decided to come forward with the plans I've been working on for a few years (what's the point in reinventing the wheel when you guys [and gals] have probably been there 10 fold more than myself) .

I graduate from college (university) in just under a year and before I start work I plan on doing some sailing. Being that I love working with my hands (why buy when you can invent, reinvent, improve, improvise, and ultimately build?) I hope to aquire a 28-34' boat and fix her up to sea worthy+ condition. Lately my plans have taken quite a change when I saw a junk rigged vessel and reading Annie Hill's book. Needless to say I've been bitten by the junk bug and there is only one thing holding me back, the mast. How can I safely refit a stayed vessel to an unstayed one? Will a GRP boat be able to deal with supporting the mast with a retrofitted deck tabernacle? There are a thousand variable that keep going through my head and all of them have a problem with the word "retrofitted". Luckily I can weld, work in glass/carbon, and wood so once I've worked out a possible plan building is just a matter of time and elbow grease. So these are my basic questions.

1) the possibility / difficulty in refitting a freestanding mast to an existing hull.

2) Possible mast material

2) a good basic (and ex-college student cheap) hull to use as a base.

Thanks in advance, I'm looking forward to quieting the design pundits in my head.

 

It's perhaps worth noting before getting too starry eyed about Annie Hill's Badger, that she did subsequently jump ship and go off on a very nice catamaran. It has been suggested (unkindly perhaps) that they are called 'junk' rigged for a reason.

Again not exactly the answer to your question, but having been in a similar position to you, I would caution against buying too much of a project. You might be better off looking for a 'fixer up' boat that is complete in everyway. You can buy complete boats for less than the replacement cost of their engines or even mast and rigging. It will still cost time, money and effort before they are ready again to cruise, but at least all the basics are all there. If you can find an ex real cruising b oat with plentiful anchors and kit, you often get all this stuff for pennies in the pound. Just check very carefully it is all in servicable condition.

But if you are set on going down the junk rigged route, you have loads of research to do. Very few people have ever managed to extract all the performance from a junk rigged boat that seems possible when observed on boats in the far east. Despite 'Jesters' undoubted place in yachting history, I don't think anyone would rate her performance as much better than dismal.

If you keel step the mast, your work will be far less than trying to use a tabernacle. The amount of work needed to beef up the bulkhead and partners is suprisingly little on a well found and built cruising boat. Just imagine the mast is a huge lever that can be used to pull the boat over onto its beam ends. If you imagine this would damage your boat, it needs reinforcing.

As for the mast itself search on 'bird's mouth masts' and even utility pole masts.

 

Thanks!

Thanks for the reply. I was kind of hoping for more ideas but it's a start. I talked to Robin Blain from Sunbird Marine and he's sending me some info. I also tried to get in touch with Eric Sponberg but I think my email has been acting up. I've been trying to locate aluminum tubing for a mast. The problem is that most sch 40 or 80 tubing is not only very expensive in Al but it only comes in lengths of 25ft at the most. I looked at Dwyer Masts but they don't carry anything round much less tapered. Handbuilding sound good to me as I love a project but the idea of wood makes me nervous (I know this is unfounded but I still think of wood as perishable and Al as permanent). I like Sponberg's carbon fiber masts and since mine wouldn't need to rotate it would be simpler but I've never worked in carbon and it seems much more expensive than GRP or wood. Any thoughts?

 

Get intouch with Rob Denney (member here) He is building and provides plans for carbon rotating masts. He is a practical builder, so low cost is always one of his goals.

 

I would! Perhaps dismal when compared to a 60' Orma tri.

See this thread for details. http://http://boatdesign.net/forums/showthread.php?t=5703


Tad

 

No-one "jumped ship".
Having spent more time in close proximity than any average land-based couple would normally do in a lifetime, Pete and Annie simply went their separate ways.

It was Pete who built the catamaran, and knowing absolutely nothing about boats and their rigging, he opted *yet again* for junk rig - can you believe it ? After so many thousand miles, and numerous ocean crossings, you'd have thought that he'd have figured out just how awful junk rigs are. And with this new junk-rigged boat, Pete just keeps on crossing oceans - safely and uneventfully.

And what of Annie ? Well, she married a guy called Trevor Robertson and joined him on his gaff-rigged Wylo II, although she misses junk rig and is talking about converting in the future. 'Iron Bark' is currently en route to Oz, afaik.


CabinBoy - checkout http://groups.yahoo.com/group/junkrig
and if you can source a copy, I'd heartily recommend the reading of Hasler and Mcleod's 'Practical Junk Rig'.

Colin

 

Cabin Boy,

Sorry you were not able to get through to me. You can write through the Contacts page on my website, or go direct to ewsponberg@sponbergyachtdesign.com.

Refits of free-standing masts to an existing boat are not easy. In my nearly 30 years of designing free-standing masts, only one project was for a mast refit. You can see it on my website on free-standing masts, the story about Copernicus.

The biggest problem with a refit is that the mast usually goes in a different location than the original mast. That means that the interior usually has to be rearranged and rebuilt--a bit of a job that costs lots of money.

The other problem is that there usually aren't any good plans for the vessel at hand (we had some good plan for Copernicus) so that we have to do a lot of guessing as to where to put the mast to balance for weight and keel area/sail area for proper lead. To get around the lack of plans means that you have to take lots of measurements on board the boat, and that means paying for the designer to visit the boat and take the proper measurements. That runs into some more money.

For a boat that you are contemplating, some aluminum tubes and pipes might work. You have to have some engineering done to estimate what the righting moment of the boat is so that you can pick the proper diameter and wall thickness for the mast. You don't want to go too heavy as it will make the boat much less stable, and you don't want to go too light because you need the strength and stiffness. You should also consider that the upper end of the mast(s) should be tapered, and you can probably buy tapered aluminum tubes that would be suitable, although you'll pay a premium for them. Then you have to weld them together (or bolt or rivet with an internal sleeve), and after welding, you should have the mast re-annealed to restore the virgine material strength in way of the weld. Not expensive to do, just awkward.

For a carbon fiber mast, I recommend going to Composite Engineering in Corncord, MA, and talk to Ted Van Dusen about the cost to fabricate a mast. He does most of my mast designs and produces good quality at a good price. His number is 978-371-3132, ext. 27.

Finally, I have never been a fan of junk rigs, and I am glad to see there are some other skeptics on this forum. They just do not sail well, and I have never heard anyone ever say that they do.

I hope that helps.

Eric

 

Well, here's one for a start ...

And I don't know of one single person who, once having sailed Junk Rig for an extended period - *and having learned how to sail the rig* - would ever consider returning to a Bermudan rig out of choice.

After some years experience, the only rigs I would now consider sailing are Gaff Cutter and Junk - both of which (interestingly ?) have their historical roots in working rigs.

In contrast the Bermudan sail has never been a working rig, and although a good rig for racing, it is not the ideal rig for short-handed cruising, sailing downwind for extended periods, or when it's cloth gets old and stretched. It also relies heavily upon highly stressed standing rigging, the failure of any part of which may prove catastrophic.

When comparing rigs it is important to consider *all* aspects of sailing, not just windward pointing ability.

I currently own three boats - one is junk rigged, one is a bare hull awaiting conversion to junk - the third is a classic British bermudan-rigged boat. Guess which one is about to be sold-off to make space ?



Concerning conversion: PJR gives all the information required to effect a junk conversion. The services of a designer or naval architect is not necessary in practice (although if you ask they will undoubtedly say otherwise - bit like going into a barber-shop and asking if you need a haircut !) - the worst-case situation is that you may have to beef-up the area around the partners.
Likewise, there is no need to taper the mast when using tube. Neither of my *hinged* (get your heads around that one ...) free-standing masts are tapered.

The only valid criticism being made is the inconvenient intrusion into the cabin of a keel-stepped mast, which is true for all keel-stepped masts, regardless of what type of sailplan they fly.

Regarding the re-location of the mast - this will undoubtedly be necessary, but there are several techniques available to ease this procedure if the new mast position happens to coincide with a bulkhead (for example): opting for multiple masts; canting the mast; selecting a more favourable sail aspect ratio. All covered in the book - which is hellishly expensive, but comprehensive - known in Junk circles as 'The Bible'.


Hands-on experience with sailing Junk Rig - and the conversion process - tells a far different story to that of heresay and prejudice, and to the cautionary words of those with understandable financial interests.

Colin

 

food for thought

So much new information and from so many different perspectives!
Weighing the pros and cons is going to take some time, thats for sure.
The pro's for me boil down to three things, ease of short handed sailing, the complete removal of standing rigging, and ultra simple sailplan (no spinaker for downwind, sail changes, no need for reefing in the traditional sense) The removal of standing rigging for me is a huge one. I personally do not like the thought of my rig held in place by wire and I don't like the sound of the wind in the wire during a blow.
The cons I guess would be supposed poor windward performance, complicated initial rigging, and a heavy rig.
My only problem here is that I've never actually sailed on a junk rigged boat! I've joined the junk rig yahoo group and I'm going to put up a "take me along for a sail" plea to someone in the New York, NJ , CT, area. There's nothing like a test ride to see if you like it I hope.
Regardless of the rig though, I still would like to convert my boat to a freestanding rig. the 2 or 2.5" of diameter gain in the mast won't be too intrusive down below and I would really like to get rid of that mess of cabling. I've looked into mast extrusions, utility poles, and flag poles. each has a wall thickness of about .1 - .125" (the mast being some where in the middle!) This was way less than I originally thought, thinking along the scale of sch 40. (5"@ 0.25 wall). Even the sch 40 is only something like 5 lbs per foot makeing a 35' mast only 175 lbs. When I think of the weight of some of the home made wood masts, this is much lighter. So far my problem has been finding 5" sch40 in lengths longer than 20' (might have to scarf it after all...)
Colin, thanks for the low-tech info, I most certainly don't have the finances to hire people to build my boat, and the truth is that I planed on doing all the work from the begining. Part of the reason behind this boat project is to BUILD the boat the way I wanted. I'm not looing for something lightning fast with a built in cappuchino machine, just something doable for a guy with woodworking and welding skills.
I don't mean to snub you Eric, I really appreciated your the advice from the other side of the coin. Though it might be safest and most professional to go through the proper channels, I simply won't be able to afford it (I'd much rather be out sailing than building my "dream boat" for a few years). I'm hoping that while I endure this last semester at school, I will gain enough boat design knowledge through books and frequenting this forum to do a halfway passable job of calculating my rig.
So I guess I should edit the title of my post .... "Economically refitting a full keeled 60's boat to a free-standing mast and hassle free rig". Any more takers?

 

Cabin Boy,

A 5" sch 40 pipe isn't going to be anywhere near what you will need for a free-standing mast. I did a quick check with the following assumptions. I have to guess and boat design parameters because I don't know what boat you have in mind to buy. But let's start with the following typical values:

Loa = 32'
SA = 520 sq.ft.
Displ. = 10,000 lbs.
Righting moment at 1 deg = 720 ft-lbs per deg.
Max. righting moment = 21,700 ft-lbs.
Mast material, 6061-T6 aluminum, yield strength = 35,000 psi.
Factor of safety over yield = 3.0

The required section modulus for a free-standing mast would be about 22.3 inches^3 [ 3 x (21,700 ft-lbs x 12"/ft)/35,000 psi ]. At that requirement, a free-standing mast made of schedule 40 pipe would have to be between 8" and 10" diameter:

8" sch 40:
OD = 8.625"
ID = 7.981"
Weight = 9.88 lbs/ft.
Moment of Inertia, I = 72.49 inches^4
Section Modulus = 16.81 inches^3 (too small)

10" sch 40:
OD = 10.75"
ID = 10.02"
Weight = 14.0 lbs/ft.
I = 160.73 inches^4
S.M. = 29.90 inches ^3 (too big)

So you are somewhere in between. At 10" sch. 40, the mast weight for 35' tall is 490 lbs.

The engineering numbers will tell you what you need and you can adjust your expectations and design parameters accordingly. All masts, stayed and free-standing, are designed to the boat's righting moment. If you get a slightly smaller and/or lighter weight boat, you might be able to get down to the 8" size. In general, it is more structurally efficient (strength/weight) to go with the larger diameter tube and thinner wall than to go with a small diameter tube and a thick wall. This guideline has its limits--you don't want to go so thin that the mast wall buckles prematurely.

I hope that helps.

Eric