Designing for ferrocement vs wood or steel

What brand of epoxies do you use and what solvents? Like I said, I'm not an industrial user like yourself, so you may have EU safe products we can't get here.

 

We don´t use off the shelve products, we get our stuff tailored by the industry.

There is no difference between the US and European products.

Solvents are strictly forbidden in marine epoxy.

The fact that we work in safe conditions, since ages, was caused by my own ignorance.
When I started the wood epoxy building 36 years ago, I thought we would have to deal with similar things as in polyester jobs, like Styrol. I thought Styrol would cause cancer and allergic reactions (and I still think so), and we prepared our labourers accordingly.
So, they worked for a dumb "Patron", but safe!

Regards
Richard

 

Safe is good. Thanks for the info. Cold molded wood always seems to make a wonderful boat if done with thought. Covey Island Boat Works has built that way for a long time over here and their WESTERNMAN and others by Nigel Irens and Ed Burnett make a great case for wood/epoxy boatbuilding.
In the long run, cold molding is probably best, even though it costs more to build. Plank on frame is very fast and efficient build, but only has a very long life if very expensive (bronze, teak, etc) materials are used. Pine/oak boats with iron fastenings last 30 years or so. A cold molded boat, properly cared for, could last a hundred years or more it seems.

 

The more I read about it the more I'm liking the cold molding idea. I'm a little fuzzy on how you get that first course on though. I understand making the mold, but what do you glue the first course to? Are you edge-gluing it to itself?

How do people feel about using staples and then pulling them out? I know this is a bit controversial on cedar strip kayaks which is a similar process.

Is 1/8th inch considered the way to go for thickness? Is it usually done with the cove and bead strips?

How does epoxy respond to constant agitation while in the pot?

When I was still working in lumber mills we used a product called nacan glue for finger-jointing and edge-gluing. It was a two-part something which used a pretty nasty caustic catalyst and stayed liquid as long as it was agitated. Once applied it completely dried in about 7 or 8 hours, and cleaned up with water. Once it dried it was pretty indestructible. Is there an epoxy with similar properties, except maybe the water cleanup?

 

Let us first know what design we are talking, before we comment on any material!

And make sure you refer to the right method! Cold moulded is done by laying thin veneers diagonally on each other.

Regards
Richard

 

I actually did a SOR in my kayak tender thread, but i'll repeat it since I think it flew under the radar.

OK, maybe you can clarify where multi-layer laminated strip planking ends and cold molding begins. I was under the impression that strip planking usually referred to one relatively thick layer of wood whereas coldmolding was using multiple layers in a cross laid pattern.

I'm looking to build a kayak tender (think destroyer tender rather than yacht tender) to live on while on trips to various places to go kayaking. Here's the SOR:

Must haves:

Comfortably sleep 4 people in 2 cabins for 7 days

Trailerable, with maximum dimensions of 40' long, 11' beam, and 15' total height.

Range of 1000 miles at 8-10 knots.

Pure displacement hull

Capable of being safely navigated in rough conditions (6'-8' seas) in an emergency.

A "real" pilothouse with a centerline wheel.

Space to carry kayaks on deck

A minimal galley and a head with shower.

Would like to have:

A design in which the pilothouse is not also used as a hallway

2 heads, 1 with shower

2 engines

Hull divided into watertight compartments

A larger than minimal galley.

Commentary

What I'm looking for is a boat that I can go out to someplace remote and use as a base for kayaking from; someplace comfortable to come back to at the end of the day.

The designs I've been looking at have tended to be the aft cabin trawlers such as the Little Island Trader, Power Cruiser 36 and Power Cruiser 39 from Chesapeake Marine Designs.

Based on the features I like from these and other designs I'm working on a composite design tailored to my application. In the end I will probably end up buying a commercial plan and making modifications as needed, but I want to go through the design process as a learning experience.

The design I'm currently working with is a 34' aft pilothouse. I'll try to post pics later tonight.

 

NZ method is over a mold of close together ribbands, covered with plastic. First layer of 1/8" x 3 or 4 inches is not glued at all, just carefully edge fitted and stapled to ribbands. Second layer's gluing and stapling glues the first layer's edges. Layers alternate at 45 degrees to w/l so are at 90 degrees to each other. Faired up when mold is stripped out. Also you can build interior with bulkheads, bunk flats etc with permanent stringers and lam over that.
Another method is strip plank first, then laminate over, and this is stronger, but much more work and material.
NZ shipwrights in the 1860s were building large laminated ships fastened with nails and trunnels, so it goes way back there.

 

CT:

Questions which might seem off topic...
-4 people..is this you and kids?
-are you planning on BC Coast or all the way to Alaska for sure or maybe??
-have you done this sort of longer term kayak sorties before?

Look up Jay Benford's site,the site is kinda screwy...he doesn't even show 20% of the boats he designed...look for the plans pricelist to get an idea.

Also Devlin may have something to suit.

 

Take a look at Glenn Ashmore's site for some ideas.

http://www.rutuonline.com/

Also note just how far his initial timeline blew out, but it seems that he did a really nice build job.

PDW

 

OK, that makes more sense. Do you take the staples out as you put down the next layer?

No, 4 adults. I'd keelhaul myself before I would spend a day on a boat with kids.

Mostly BC coast and Puget Sound. The 1000 mi is Bellingham to Ketchikan with a 15% reserve in case I ever decided to do that. Possibly install two tanks and only use one for long distance work. Also possibly near-coastal to California if I can find the courage.

I haven't done these kind of longer trips before. My 'yak is a 9'6" plastic boat and so not suitable for long open water paddling. On the other hand, it's perfect for exploring those small little places that you could never get a bigger 'yak into, and this is what it's all about for me. In addition to just going out boating with friends, this boat is intended to get me close enough to the places I want to be to use my little 'yak and give me a comfortable place to sleep at the end of the day.

I'll take a look at rutuonline and Jay Benford.

 

If plastic staples, don't bother. Same for monel. In repair I used to use monel and leave them in. Some use steel staples through a cardboard or plastic "washer" to be easily withdrawn. Don't leave any steel staple in. Find John Guzzwell's book "Modern Wooden Yacht Construction" (hope I got the title right) on Amazon or ABE books and he has his own take on the method, and uses I think a little thicker lam. I've met this 80 something circumnavigator and rabidly competitive ocean racer and seen his vessels and they are a real testament to epoxy/wood construction and very modern design. TREASURE, whose build is documented in the book, is still in excellent condition and regular use after more than 30 years.

 

Seems to me you're stuck..you want a skinny trailerable 40' max boat with 2 double cabins and 2 heads is a very tough nut to crack.
But an aft master-cabin coastal boat will give you tons of room.

I've been up and down the BC coast for 25 years since I was a kid and never had a full displacement power boat...been around Vancouver Island many times,around Queen Charlottes and most areas in between.

From October through March is the worst part,and you wouldn't want to be yakkin' anyways.

I've found the speed capabilities of a semi help with weather windows and fighting currents...and running down to trawler speeds I get better fuel economy than trawlers. And heaps more liveable space.

Just watch the weather,and besides if you never make it to AK or Cali you'll have spent a whole lot of money and time on scantlings/capabilities you'll never use.


I know you'll build but look what can be had for space in a aft,some cheaper ones

http://www.yachtworld.com/boats/2005/Meridian-368-Motor-Yacht-2250093/Miami/FL/United-States

40 Bayliner
http://www.yachtworld.com/boats/199...wo-Heads-2184210/Grasonville/MD/United-States

Silverton

http://www.yachtworld.com/boats/1998/Silverton-392-Motor-Yacht-2221728/Jacksonville/FL/United-States

 

Both cold molding and strip planking have several different and distinct versions of the method, each with advantages and disadvantages (I can think of at least a dozen different types). Then of course are the combinations, where a strip planked core is used and a set of veneers is molded over the exterior. Lets not forget the the old balls too, such as the Lord strip plank method (the lightest of all methods) or Ashcroft molding. These decisions are best left to the designer.

Cthippo you need a design and it appears most of your SOR would fit into many stock designs, though the 11' beam requirement may force a custom design or at least a semi custom (modified stock) if you found a 11' beam, 40' design to work with. Secondly, trailing a 40' yacht is, well, not something you'd want to do very often. This isn't the type of rig that you could use to drag this puppy out at the local boat ramp. You'd need a travel lift or crane to hoist your boat out, then place it on a waiting custom trailer. Is there some logic to this trailer requirement? Are you thinking about weekending a 40', twin engine, duel head yacht? Traveling up and down the west coast highways with a 50' rig dangling behind an F-350 Super Duty dually with the biggest engine available, struggling to drag it up mountain passes is a bit silly, if not impractical. Yachts of this class are "transported" not trailered.

In short, you need a design. If your search has brought you here, there are quite a few qualified to render a yacht of this class. If your search has had you through page after page of stock designs with no luck, then it's time to consider the obvious, your SOR has sufficient enough "uniqueness" that you need a designer. It's an interesting SOR and I'm sure there would be several interested in fulfilling you desires, but you need a pro to nurse you through the process.

 

Funny you should mention it, but I have a design, or at least a concept in mind (see attached).

Dimensions are 34' LOA minus davits, 10' beam, 4.5' draft and 14.5 feet keel to maximum height. Power will be a 60 hp diesel.

I'd like to go with a twin engine design, but the more I look at it the single looks adequate. I also didn't manage to make the pilothouse not a hallway, and in fact it evolved into more of a saloon, but without adding length I think I'll have to live with it.

I have looked at a lot of stock plans and have seen several that could work with a little modification, but as I said earlier, I want to go through the process as a learning experience.

Regarding trailering, I think you're right that it should be transporting. What I have in mind is building it somewhere that is not on the water and moving it for launch, then bringing it home at the end of the season.

@ WestVanHan, several of the designs I've looked at include aft cabins, I'll keep them in mind.

Thank you to everyone who has offered input in this thread, I appreciate you all sharing your knowledge.

 

cthippo have you done any of this before ?

Your design is the absolute last design I would pick for your intended use. How on earth are you planing on getting into and out of a less than 10' of plastic kayak in a rolly anchorage from that boat? I would have picked something like a semi displacement downeast or lobster boat with a big cockpit and big swim platform for that type of work.

I take it that you are not trailering this boat far or very often and know the clearances along the route as this design exceeds the height restrictions on the roads. It also requires permitting and quite possibly bonding or insurance.

Also the way that you have this boat drawn it would have a Cp of about 0.7 and would need to displace around 70k lbs to draw 4'6". 60hp and trailering won't do it.

A used production boat would be a good fit and far cheaper. Then think about custom if it does not do the trick. Find out the problems you face before jumping into a custom built boat. You will end up with a better design as a result.