Searunner Build Time

[DreamBig]

Originally Posted by 8472

Has anyone here ever built one of the larger Searunner variants from scratch? If so, can you estimate the total man-hours required?

And while we're on the subject, what would be involved in scaling the 40 up to 50 feet? Would that be a fairly straightforward process for the designer?

Call John Marples with Marples Marine in Maine. Great guy, he will get you fixed up. :-)

[Kaimana]

Originally Posted by Pauls

Small changes in length can often be accomplished simply. Going from 40' to 50' is not a small change. This is a major change in all respects. The 50' will require heavier scantlings, meaning that the structural elements of the boat will need to be heavier. A larger rig and increased righting moment will mean significantly greater loads on the rig and the hull the rig attaches to. There is a fair amount of work here and you will need a pro to do this work for you as it is technical.

I want to also draw attention to Roverhi's very good point about handleability of a 50' tri. You are going to have large, powerful and heavy sails to deal with. I'd caution you to be really sure you want a boat this size before you build one.

One other point is that a boats weight goes up (generally speaking) as a cube of its increase in length. So you would expect a 50' to weigh 1.95X as much as a similar 40'. That means double the amount of material to buy and about double the amount of work to put it all together. Believe me, bigger boats take a lot more time and work to build.

I'm responding to this because I'm both a marine architect (no degree, I just designed my own boats for the last 45 years), and the last boat I designed, then built all by myself was Tropic Bird, my 56-foot sailing fishing boat. There's more details about Tropic Bird here on our website: (https://oceanpeople.org/tropic-bird-...hing-trimaran/), but basically, Tropic Bird was a SeaRunner 37 scaled up to 56 feet. (Yay Jim Brown! My mentor! The Godfather of the Modern Trimaran).

(Below) Tropic Bird trolling in the Trades, on her way to the fishing grounds.



She had a cutter rig; and she's about the biggest boat I would ever consider putting that rig on. It worked because she had a self-tending staysail on a boom, that tacked and gybed itself, so that when tacking or gybing I only had to contend with the foresail. Well, and the main boom taking out the mast at the gooseneck when gybing in 45-knot winds and 15-18 foot seas. Been there, done that, I didn't get no T-shirt; but I didn't lose the mast, either.

I singlehanded her quite a bit, because I always hated: A. Waiting for crew to show up before I could go, or B. Having to take on idiots that actually made the passage or trip more dangerous just so I could have "crew".

Had a good Furuno 36-mile radar, so I could radar-check the surrounding area, multiply and divide, and usually sleep deeply for 30 minutes before I had to wake up to the alarm and check the radar again. I learned how to get a full night's sleep in 30-minute packages, interrupted by 2 minutes of radar check.

BTW, the only reason I could sleep like that is that the boat had a BIG version of Jim Brown's Searunner self-steering installed, with the angle pieces on the tail end of the vane to make it more sensitive in light winds. Yay Jim again! It actually WAS a "tail vane"; my windvane on Tropic Bird was the tail of a Beechcraft twin-engine plane from the dump, with a shaft installed inside it by me!

Having said all this, let me qualify: I didn't just take a set of Brown 37 plans and make things 56 feet long. There were materials tests at the local university's stress testing machines, so I knew how strong the wood, plywood, and epoxy/glass I was putting into my calculations was. There were calculations. I won't even go into that here, but unless you model the stresses the boat will face in the real world, using structural engineering math and calculations, you're "just guessing" on any boat over about 25 feet long.

And when I launched her, there were some things that were still "a little light". I'd spent $500 getting recommendations on spar specifications for her 65-foot stick (IXX, IYY, section dimensions and wall thickness) from a "well-known West Coast spar designer", then put that mast on the boat. It wavered like a piece of spaghetti in any wind over 15 knots. Back to the drawing board, I ended up with a spar that was 13-1/2" in the fore-n-aft dimension, 8-1/2" in the athwartships dimension, with a 1/4-inch thick wall. No froblems after that! (The "no froblem" thing is a whole 'nother story).

Snapped the steering gear once when I got thrown backwards in a big sea during a missed tack, and put in the emergency tiller which was stowed under the cockpit seat the steering gear ran under (gee, who thought to weld such a big heavy socket for an emergency tiller on top of the stainless steel rudder top pintle?). Then back home I beefed that up; it never broke again in 17 years. I called her my "sailing ten-ton dump truck".

Other than those two minor things, the boat did fine, and lasted 34 years, until "the Kauai Coast Guard found her, upside down, after she got loose from her mooring and got capsized by a hurricane". That's a whole 'nother story.

How strong was Tropic Bird, really? I got a call after I'd sold her from a marine attorney whose client was a guy who'd gone on a charter on my ex-boat, and whose legs had gotten broken on the boat. I went "what!" .

Apparently the skipper was driving the charter boat "around the corner" on the Na Pali coast of Kauai, notorious for its steep, sharp wind chop, and neglected to throttle back when he hit the windline. This guy was standing on the foredeck, hanging onto the bow pulpit on both sides, facing forwards, when the boat came off a wave and fell. When Tropic Bird hit, it collapsed the guy to the deck, breaking both his legs.

There's more to the story, but the point is, this event broke this guy's legs, but DIDN'T break my boat! Wowser! If the boat doesn't break, at least you know you didn't under-build her.

And "time to build?". I built my SeaRunner 37 by myself in one year, and earned the money for her in the same time. What I found when I built and launched Tropic Bird, by myself, in one year also, is that "boats take me a year to build". I'd anticipated 3 years on Tropic Bird because of her size, and was pleasantly surprised when she was done in a year. I ascribe this to two things:

1. It's the number of pieces in a boat, more so than the area and size, that takes the time. Think of all the boats-in-a-bottle that have taken the builder years to build, painstakingly making all those little parts. My 56 took the same time as my 37.

2. I'm a South Pacific workboat builder. Although I fastened and glued my boats with the highest standards, faired them well, rounded edges, glassed scrupulously to waterproof and ding-proof them, I spent NO time on a yacht finish, on sanding and topcoating and sanding again. There is NO varnished woodwork on my boats. Most would describe my boats as "rough", but the fish don't care, and the passengers going from Nuku Hiva to Hiva Oa don't care. Do you?

Would you rather go sailing, or spend that time in the boatyard, sanding fiberglass?

With Warm Aloha, Tim

[Boatguy30]

Pauls

You are a bit off in your maths! Hull volume, displacement increases by the cube. Hull area increases by the square.

So generally, every piece of timber wouldn't need to be 1.xx bigger for a bigger boat so the boats weight should be far under the cube, but with somewhat larger scantling. IE 12mm mainhull sheathing, 12mm ama bottoms, etc. The weight increase can hopefully be kept not much more than the square especially if using Okoume.

I think scaling the SR 34 to around 42' or so would be the biggest reasonable owner builder. Do an aft cabin pilothouse similar to the Chris White designs, but hopefully with Jim's good Karma to keep them from flipping over!

[8472]

I've been otherwise engaged for some time now, but I want to thank you all once again for contributing, and assure you that your efforts have not been for naught. I'm learning a lot from you folks, and I greatly appreciate it.

Originally Posted by Sand crab

Do you have a place to build this right next to the water because renting commercial waterfront property ain't gonna be cheap. Also you'll need a covered space and possibly climate control. Freezing temps and boat building resins aren't the best of friends.


I don't know why you are focusing on Searunners especially when there aren't stock plans. Try Ed Horstmans designs. He's got plans for many big tris and cats. Ed Horstman Designs


There is also Kelsall plans but he's all cats. My advice is to build a cat or better yet just buy an older cat or tri and fix it up as you go.
Multihulls - Multihull boats come in three main types - Catamaran, Trimaran or Proa. Catamarans have two normally equal hulls while T

I wasn't even aware of Horstman's existence, thank you! I haven't yet got any waterfront property, but I'm confident that I'll be able to work something out on an inland waterway with sea access. As for the shipyard facilities, I'll have to look into that. I suppose it will come down to a function of the relative expenses of suitable HVAC systems and a fully enclosed and insulated shed versus more southerly properties and a simple Quonset structure, likely on the Mississipi or some navigable tributary thereof.

Your advice to buy an older cat or tri is probably the saner route for most people, but finding one of a size suited to carrying multiple years' provisions, along with extensive equipment and triple-redundant systems would in itself pose a significant challenge, to say nothing of the expense of any sufficiently large vessel, such craft likely being more luxury- and status-oriented. Additionally, my initial research indicated to me that trimarans tend to be more seaworthy than cats, which caused me to discard the latter as unsuitable for my intended use case.

I probably seem rather obstinate, but I really do appreciate your advice, and that of everyone in this thread; I simply have rather stringent requirements in certain aspects of this undertaking.

[Pauls]

Boatguy - My statement is correct. What you are missing is that length, breadth and depth all increase together. For that reason, all things being equal, weight will increase as the cube of length. That logic is of course based on using the same materials, okoume or whatever. The spars joining the hulls, for example, will be longer, deeper and wider to handle the increased displacement combined with the increased righting moment from the increased beam. Other things being equal, it's a cube function.

[Pauls]

8472 - I don't know what research led you to conclude that a tri is more seaworthy than a cat. Having spent quite a bit of time on cats I'll just point out that there have been many cats making trans ocean passages for the last 60 years or so.

If you are looking for a large multihull that is relatively quick to build I'd suggest you look at Wharram's cats. He has designs up to more than 50' and they're well proven boats.

Seaworthiness in any multi comes down to design details, construction details, and very much the ability of the skipper. Cat or tri, in and of itself, is not important.

I've designed and built several boats. And I'm a mechanical engineer. Unless you understand stresses and strength of structures you do not want to stretch a 37' design to 50'.