Wooden Catamaran design limitations

[ProjectFiji.com]

Hello and be gentle. I'm new to the boat building world. Alright. So maybe I'm just a big dreamer.

I've started to study boat building in the last few months, reading all kinds of articles and books on the topic. After all my reading, I'm back to where I started. Buehler. I want to build a carvel planked wooden sailboat. WOOD. Real wooden planks. Of course, most people you talk to tell you "build a steel boat, build a fiberglass boat, build it out of anything but WOOD".

I'm gonna build in WOOD. Probably milled from trees I already own. The question I have is what to build? The only carvel planked sailboats that I've seen were traditional mono's. I guess my question is this: Why?

Could you safely build a blue water capable multi using carvel plank on frame methods? Mesh the old with the new, so to speak. 30-40' in length, 16-20' beam.

ProjectFiji

[Woxbox]

To work well, multis have to be built light. That's probably the main issue -- plus the designs out there all call for other types of construction both to keep the weight down and for maximum integrity of the structure.

I suppose if you could find a designer willing to draw up such a boat you could do it, but I'm not sure you'd find any inherent advantage in going that route.

[chrisk]

Don't know about Carvel Planking. Most I've seen use plywood for the skins.

But, these sites have some wooden catamarans:
James Wharram Designs:

http://wharram.com

Woods Design
http://www.sailingcatamarans.com

[rbgarr]

Twisting stresses on a multihull are more than you'd expect and monococque construction (panels, webframes, beams, glues, etc.) have generally been shown to be a safer and stronger way to build them, pound for pound.

[GregW]

As already mentioned, weight is a huge issue with catamarans. Since you are interested in milling your own wood, you might want to consider strip planking?

[ProjectFiji.com]

To work well, multis have to be built light. That's probably the main issue -- plus the designs out there all call for other types of construction both to keep the weight down and for maximum integrity of the structure.

I suppose if you could find a designer willing to draw up such a boat you could do it, but I'm not sure you'd find any inherent advantage in going that route.

This was my guess number one. Guess number two was the twisting and torque, I can't see how the caulked seams would hold up to the multi-directional live loads.

Oh well, guess it's time to come up with a mono design that I like.

Thanks for the responses.

[BarnacleGrim]

Another issue with catamarans is the fact that they are just as stable, if not more so when capsized. Their wide beam makes self-righting impossible. And sometimes difficult to store in marinas.

From a building point of view, you are essentially building something with the complexity of two boats, but with the capability of one. (Unless speed is important to you). I don't know about you, but I still haven't finished my first project, a small plywood skiff, so carvel planking with spiling seems pretty far off for me, at least for the time being.

[Jay Greer]

I once built a 50' wooden cat for wild life photographer Jim Dutcher. It was a Choy/Siemans design. I have also raced many smaller cats, Tornados, P Cats and Hobies. If I were to advise a customer as to building a wooden cat for crusing, I would first advise that one would choose a proven design by a reputable NA and build the boat by the epoxy saturation method. The wieght of carvel planked hulls is a negative factor to performance and strength in a multi hull boat.
Jay

[Uncle Duke]

Since you are interested in milling your own wood, you might want to consider strip planking?

Well, yeah... as with other comments here...
Carvel is a fairly heavy building method. Multi-hulls benefit from light construction, which would indicate cold-modling or strip planked. If you're really focused on a multi-hull you need to think "light".
Get Chris White's "The Cruising Multihull" book, look into the options, etc.
But carvel is not the right thing for multihulls....if you can't keep it as light as possible then you're defeating the purpose.
What does this add up to? Think about different ways to mill your wood, such that you can build a stiff, light boat - sadly, by definition, not a carvel boat.
Or: investigate this site:
http://www.chriswhitedesigns.com/
for thoughts...

[Daniel Noyes]

http://www.herreshoff.org/docs/Chronicle_1980_Sp.pdf


There is such thing as a traditional built wooden catamaran. Amarillis is lapstrake planked.
These traditional built cats were built by the most highly skilled yacht yards of the time and they are not beginner boat building projects.
catamarans were invented to race and they do that best, for cruising multihull look at trimarans.
Dan
http://dansdories.googlepages.com

[Woxbox]

catamarans were invented to race and they do that best, for cruising multihull look at trimarans.

That's an odd generalization. Crusing cats are manufactured by the thousands today. Cruising tris? Hardly any. Visit the warmer climes and about all you see now are people cruising in catamarans. (And I'll be flying south to board mine this weekend.)

[Paul Pless]

lots of polynesian outriggers around well before the invention of plywood...




http://www.woodenboat.com/forum/showthread.php?t=73455

http://atomvoyages.com/articles/hansklaar.htm

[Woxbox]

Paul -- Now you've hit on something. Fell those trees, shape them into a pair of log canoes, build up the sides and away you go. (Just braid some coconut fiber for lashings.)

Yep -- the Polynesian catamarans are pretty heavily built.

[JimConlin]

To realize the benefit of multihulls, they need to be light. Of wood construction methods, only cold-molding, strip composite, tortured plywood or hard-chine plywood have a hope of achieving that. A carvel or lapstrake multihull will either be unacceptably heavy or unacceptably fragile.

I know i'm farting in church, but if you want a multihull with performance better than monohulls, foam sandwich construction is the way to go. It does not necessarily require skills or tooling beyond wooden boat methods and it can include as much hand-crafting as a wood boat.

You'll get lots of religious arguments here about what God intended for boats to be made of, but i'd suggest that you do some rational engineering studies of the scantlings, weights and performance of alternative construction methods.

[Woxbox]

Jim -- Well said. But if a bloke doesn't want a fast boat, just a big, roomy, comfortable boat, then a heavy cat might do the job. But I do agree, if I had a stand of trees to use, I'd probably do a stripper.

[JimConlin]

Jim -- Well said. But if a bloke doesn't want a fast boat, just a big, roomy, comfortable boat, then a heavy cat might do the job. But I do agree, if I had a stand of trees to use, I'd probably do a stripper.

If he can get cedar (or other light) strips or veneer from his trees, or spruce or fir spars, or the interior finish stock, that's fine, but carvel planking or other traditional construction methods are downright dumb.
Let's introduce him to Mr. Wharram. He'll get a good boat and get sailing a lot easier and cheaper.

[Cuyahoga Chuck]

I only skimmed the above but didn't see any mention of the time requirement for drying lumber. If your trees aren't bucked, roughsawn and stacked to dry already you may be behind the curve. Your lumber has to be dried and fairly stable before you put it into a boat hull.

[DGentry]

The late Thomas Firth Jones had a lot of worthwhile things to say on the subject of wooden cats and tris (though not much about carvel construction of them).

These books of his are quick and fun to read and very informative:


and
*

Some of his designs can still be found at : http://jonesboats.com

Also, one poster mentions the old "multihulls can capsize and don't self right" argument. Not mentioned was the old "monohulls sink" counterargument. Take your pick!

Good luck! Dave Gentry

*TFJ was a good friend of Philip Bolger and, in New Plywood Boats, Mr. Jones wrote a great biography/dedication about him. Not to be missed if you're a fan of Phil Bolger!

[ProjectFiji.com]

I only skimmed the above but didn't see any mention of the time requirement for drying lumber. If your trees aren't bucked, roughsawn and stacked to dry already you may be behind the curve. Your lumber has to be dried and fairly stable before you put it into a boat hull.

I'm in no big rush. Trees are coming down first of March. I don't anticipate starting the build process until next winter at the earliest.

[ProjectFiji.com]

If he can get cedar (or other light) strips or veneer from his trees, or spruce or fir spars, or the interior finish stock, that's fine, but carvel planking or other traditional construction methods are downright dumb.
Let's introduce him to Mr. Wharram. He'll get a good boat and get sailing a lot easier and cheaper.

Cedar is what I have. Lots and lots of Cedar.

[slidercat]

Just to add to the chorus-- if you have cedar and don't want to build with plywood, then strip-planking is the best way to go.

Also, I'll point out that speed is not the only advantage multihulls have over ballasted monohull cruising yachts, or even the most important one. To me, comfort is the big one, especially with cats. Until you've experienced it, you can't really understand how nice it is to have wide stable decks to work on. Cats are a lot less likely to cause sea-sickness and severe bruising on a passage, because they don't roll rhythmically. You can put down a mug of soup, go tend to something, come back, and expect your mug to be where you left it, even in a seaway. Shallow draft is another thing multis have almost as a given, and then there's the ability to take the ground nice and level. Small light multis can save you money in faraway places. With my old Wharram Tane, I just hauled her up on a beach for bottom painting-- no lift needed.

As to the capsize issue, there's a lot less here than meets the eye, I think. Capsize is extremely rare for cruising multis. I'd guess sinking ballasted monohulls are a lot more common, and at least, if your cat flips, it won't leave you floating all by yourself in the middle of the ocean. Hitting a reef is a more likely disaster than sinking out in the blue water, and if you hit a reef in a cat, the reef may eat the bottoms out of your hulls, but the remains are a lot likelier to float to shore with the crew unharmed than if you're in a keelboat.

My Tane was our first cruising boat, and after I sold her I owned several ballasted monohulls. None of them gave me same feeling of safety and comfort as that beat-up old Wharram, though they all cost a lot more. Now I'm back to sailing a cat again (though a very small cat), and I'll never go back.

Multis have disadvantages, too, like the cost of dockage for a wide boat, of course. But safety is not one of those disadvantages. It's my firm belief that multis are less likely to kill you than ballasted monohulls, given boats that are in good repair, and that are well-sailed.

[imagine2frolic]

I have a 46ft. X 23ft wooden cat. It's a Roger Simpson design that has been altered a bit. A cat is a great crusing boat. Of course it has it's plus & minuses just like anything in life. I will tell you this. After cruising my mono & my cat. I would never go back to mono unless I was doing the Southern Ocean.I don't have any pictures small enough to load. PM me if you want some pics.....i2f

[Woxbox]

Well, like Ray says, cruising cats are nothing if not comfy. Here's mine at anchor in the Bahamas about 6 weeks ago. Flying back down this weekend.

So yes, you put stuff on the counter, which has no rails or anything else, and it just sits there in most any weather. And you can stand up in the cockpit with your hands in your pockets in -- well -- any weather I've ever been in, up to something around 30+ knots and 10-foot seas. And with two hulls, when there's company you don't feel like you're sleeping in the same bedroom.
And in the saloon, you can look around and see what's going on up ahead -- left and right, too.

Disadvantages? Unless the wind really picks up, it's like sailing a barge. 10 knots feels like about 6 in a mono. They don't fit in finger slips, but I've never been charged extra for the width. I suppose for the interior space, docking is therefore cheaper. Our (I'm in a joint ownership) 35' boat has the accomodations of about a 45' monohull.

And there is a lot of surface on the outside to keep clean. But then again, she's anchored in about 6' of water in the shot below, with room to spare when the tide goes out.

Anyhow, this boat is cored glass, but you could make the type as a stripper. I do beleive that's how they at least sometimes make the plugs for these boats. Stripper construction takes away the need for single-radius curves and really opens up the design possibilities, whether you want a modern or very traditional shape. Not, after all is said and done, a bad thing to consider.

[rgranger]

Losttrades.com has some really nice cats all wooden. But these were plywood on frame not planked. But he does talk pros and cons on wood vs. other material.

[john welsford]

While the perception is that multihulls need to be light, and ever lighter as new materials and technology make that possible, its not out of the question to build from solid wood. Moderately light is well within the possiblity of riveted cold moulded construction, PT boats, MTBs and such were three layers with rivets, and in New Zealand Logan and others were building beautifyl yachts, many of which still survive, using that method. The boats were laid up over temporary moulds with a keelson, bilge keel and gunwale as the only permanent internal framing, had a light fabric impregnated with read or white lead between each layer of wood and were riveted at the intersections of the planks.
For a 30 footer it would be well within the realms of possibility to build hulls at about 600 kg each including all the framing neccessary to carry the crossbeams and rig, an allowance for accommodation and motor mounts as well as centerboard casings. That would give a bridge deck cabin cat of about 2500 kg which would work fine.
If you did not mind using a whole lot of marine glue then strip plank is the way to go, while its a pain in the very low back to build a fat monohull the technique is brilliant for skinny multihulls and there have been many very successful cats and tris built that way.
Good luck with the project,

JohnWelsford

Hello and be gentle. I'm new to the boat building world. Alright. So maybe I'm just a big dreamer.

I've started to study boat building in the last few months, reading all kinds of articles and books on the topic. After all my reading, I'm back to where I started. Buehler. I want to build a carvel planked wooden sailboat. WOOD. Real wooden planks. Of course, most people you talk to tell you "build a steel boat, build a fiberglass boat, build it out of anything but WOOD".

I'm gonna build in WOOD. Probably milled from trees I already own. The question I have is what to build? The only carvel planked sailboats that I've seen were traditional mono's. I guess my question is this: Why?

Could you safely build a blue water capable multi using carvel plank on frame methods? Mesh the old with the new, so to speak. 30-40' in length, 16-20' beam.

ProjectFiji

[seedy]

Also, I'll point out that speed is not the only advantage multihulls have over ballasted monohull cruising yachts, or even the most important one. To me, comfort is the big one, especially with cats. Until you've experienced it, you can't really understand how nice it is to have wide stable decks to work on. Cats are a lot less likely to cause sea-sickness and severe bruising on a passage, because they don't roll rhythmically. You can put down a mug of soup, go tend to something, come back, and expect your mug to be where you left it, even in a seaway. Shallow draft is another thing multis have almost as a given, and then there's the ability to take the ground nice and level. Small light multis can save you money in faraway places. With my old Wharram Tane, I just hauled her up on a beach for bottom painting-- no lift needed.

As to the capsize issue, there's a lot less here than meets the eye, I think. Capsize is extremely rare for cruising multis. I'd guess sinking ballasted monohulls are a lot more common, and at least, if your cat flips, it won't leave you floating all by yourself in the middle of the ocean. Hitting a reef is a more likely disaster than sinking out in the blue water, and if you hit a reef in a cat, the reef may eat the bottoms out of your hulls, but the remains are a lot likelier to float to shore with the crew unharmed than if you're in a keelboat.

My Tane was our first cruising boat, and after I sold her I owned several ballasted monohulls. None of them gave me same feeling of safety and comfort as that beat-up old Wharram, though they all cost a lot more. Now I'm back to sailing a cat again (though a very small cat), and I'll never go back.

Multis have disadvantages, too, like the cost of dockage for a wide boat, of course. But safety is not one of those disadvantages. It's my firm belief that multis are less likely to kill you than ballasted monohulls, given boats that are in good repair, and that are well-sailed.

Ray,

Thanks for writing that. I just bought an old Wharram and am planning to go places, if gradually. Your words were encouraging. Only part of your recipe I don't have yet is well-sailed, but I'll be working on that.

[katiedobe]

Go to this website. Very enlightening. He says he has 60 acres of white cedar to use. I think he should look into talking to Wharram and see how best to use these trees to build his dream boat. He and his family want to circumnavigate the world, on a budget. starting with building his own boat first, from scratch. With no boatbuilding experience. IMHO I think he would be better spent marketing that cedar and using the money to buy a used multihull. My two cents. I think that IF he is still married by the time he builds his cruising boat they will be in a different position than they are now and may never take off on that cruise.

[weedeater64]

I once built a 50' wooden cat for wild life photographer Jim Dutcher. It was a Choy/Siemans design. I have also raced many smaller cats, Tornados, P Cats and Hobies. If I were to advise a customer as to building a wooden cat for crusing, I would first advise that one would choose a proven design by a reputable NA and build the boat by the epoxy saturation method. The wieght of carvel planked hulls is a negative factor to performance and strength in a multi hull boat.
Jay

By "epoxy saturation" do you mean without fiberglass? Just epoxy painted inside and out ?

[weedeater64]

While the perception is that multihulls need to be light, and ever lighter as new materials and technology make that possible, its not out of the question to build from solid wood. Moderately light is well within the possiblity of riveted cold moulded construction, PT boats, MTBs and such were three layers with rivets, and in New Zealand Logan and others were building beautifyl yachts, many of which still survive, using that method. The boats were laid up over temporary moulds with a keelson, bilge keel and gunwale as the only permanent internal framing, had a light fabric impregnated with read or white lead between each layer of wood and were riveted at the intersections of the planks.
For a 30 footer it would be well within the realms of possibility to build hulls at about 600 kg each including all the framing neccessary to carry the crossbeams and rig, an allowance for accommodation and motor mounts as well as centerboard casings. That would give a bridge deck cabin cat of about 2500 kg which would work fine.
If you did not mind using a whole lot of marine glue then strip plank is the way to go, while its a pain in the very low back to build a fat monohull the technique is brilliant for skinny multihulls and there have been many very successful cats and tris built that way.
Good luck with the project,

JohnWelsford

What sort of fabric would be good? And are not the lead products now unavailable?
Could you use water lesser glues on the inner layers and Resorcinol only on the outer layer?

[Jim Mathieson]

A 30-40 ft Cat in strip plank could easily be one of Richard Woods designs ,from the Eclipse /Romany /Flicka.
I strip planked the Eclipse hulls in CC Foam with glass/epoxy.
http://www.sailingcatamarans.com/

[bwd]

Another FYI, Morelli & Melvin designed a wood strip version of the hull used for the Gunboat 60, a foam/cabon cruising catamaran that hits 30kts and makes 300 mile days easily. So with the right shape, and composite skins, and weight discipline, wood can be plenty fast.

[JimConlin]

Another FYI, Morelli & Melvin designed a wood strip version of the hull used for the Gunboat 60, a foam/cabon cruising catamaran that hits 30kts and makes 300 mile days easily. So with the right shape, and composite skins, and weight discipline, wood can be plenty fast.

Was it built and if not, why not? How did the weight and cost estimates compare?

[paladin]

Cruising multihulls are not significantly faster except in larger versions.....the weight carrying capacity is relatively low if you want the machine to perform. Low weight carrying ability limits the range....
Depending on the wood....I would strip plank, cut veneers and cold mold over, laminate the primary bulkheads, stem etc to keep it light. Epoxy will be required.

[bwd]

Don't know, but I think it may have been.
For someone in the US northwest I think.
Try asking them, or ask some west coast barnacles.

M+M have redone their website and it is less transparent than past versions.
There were some hints of contention between MM and gunboat regarding certain design elements applied to designs for other clients.
Perhaps this is relevant, perhaps not.
Suffice it to say they have multiple designs for fast cats over 40 feet and scantlings for several materials. I once was on one, at a show. It was quite nice.
I think even the cheap versions of their designs, would not be too affordable to build. Even if you skip the foam, a lot of carbon might be needed.

[62816inBerlin]

>>>Cedar is what I have. Lots and lots of Cedar.<<<<

Then I agree with the diagonal-strip planking idea, rather than a carvel-planked boat.

The earlier Prout Shearwaters catamarans had wooden diagonal-strip hulls and I suspect that the cruisng cats of the period were built the same way. Although the method seems complicated, some friends of mine successfully built a Flying Fifteen that way although they had never built a round-bilged boat before (but I believe they had built one or two hard-chined plywood hulls).

The weight discussion seems a bit weird to me, after all, most single-hullers carry great amounts of iron or lead around simply to keep their craft upright!

Gernot H.