50ft strip plank sailer - producing the strips for planking

[TOALL]

50ft strip plank sailer

Having considered many building methods I decided on a sheathed strip plank hull. Not having built a boat before I looked at the different methods but ultimately was scared away from using a foam core because people were reporting delamination after even small knocks and collisions. Top end manufactures are using end grain balsa.
I work with wood everyday so stripping seemed the logical choice. I'm building a cruising boat so ultra lightweight was not really a requirement.
Its based on the current boat design and is like the current Hanse 56 and the Beneteau sense range.
The Boat has been professionally designed.

Does any one think I should be building it differently?

 

[PAR]

If this is your first build, you should consider (strongly) building the dinghy to it first, preferably with the building method your mother ship is. The odds of completion on a 50' yacht as your first build are extremely low. I don't think you know how much work a project like this entails.

As far as build methods, I'd look at molded plywood as a faster way to apply planking, though to be frank, the hull shell is the least of your worries, as it'll account to less than 10% of the time, funds and effort to complete this project.

Which design have you selected?

 

[waikikin]

Fair enough, that's why I posted it, so others can check the calculations. I am not the biggest math head. I spotted 2 serious errors in my calculations already so I will work it out again, using some realistic figures, because I want to seriously consider the option.

Say the hull is 8.5 meters long, and 4.5 meters in circumference
Lets make the gaps something realistic at say 6mm wide , (.006 meters width )
Say the planks are .019 deep (that's a usual thickness when glass is going on both sides)

So each "gap" is 8.5m x .006 m x .019 m = .00097 cubic meters per "gap".
.............................................................................................................

The circumference around the widest part of the hull is 4.5 meters, when divided by a wood strip of .025 = 180 strips, so 180 "gaps"
........................................................................................................


180 "gaps" at .00097 = .174 cubic meters of resin
Resin is 1.2 Kilos per Liter, so 1200 kilos per cubic meter
So a pure resin fill would = 210 kilos of resin if you were building a barrel.

But, reduce the number of gaps to allow for bow and some stern taper , say x 2/3, and reduce the resin mix by 1/3 to allow for the lighter filler, and it would come to

less "gaps"
120 "gaps" at .00097 = .13 cubic meters of resin

less resin with filler
.13 cubic meters x 2/3 = .098 cubic meters of resin (99 litres)

would weigh around 117 kilos.

But then take off the timber you save,
.1164 cubic meters of a light timber like WRC at 350 kilos per cubic metre
= ~ 35 kilos.
...............................................................................................................

So extra weight overall on boat = 98 kilos.
The resin coverage on a boat that size is around 120 liters, so you might say you double the resin.

The planned bare hull weight was around 500 kilos, so you could say you increase the boat weight by nearly a fifth. BUT there needs to be over 200 kilos of permanent ballast, so at least 1/2 of the extra 98 kilos can come off that figure. So an "extra 41 kilos". The other benefit is that the timber strips are separated by a thick glue line, which may be handy from a longevity point of view. Since the extra resin is around $2,000, you would hope so.

So, its not as good as my previous attempt, but not nearly as bad as Pars estimates looked.

You would never use this technique on a hull that wasn't going to be fully encapsulated with glass/epoxy. Even Mark Bowdidge says his engineering calcs just consider the wood and filler to be a high density core, which is in line with all commercial standards.

But being able to lay out and fit all the planks, fit in the stealer planks ahead of time then have a one time "glue-up", seems to merit serious consideration.

I think you could fairly drop the gaps to 2.5-3.0mm & still squeegee a bog slurry through the planking. Not so good for clear finish on the inside if that's part of the strategy. But the division/encapsulation is a good point, though you get similar with a consistent glue line. Personally I'd just brush a juicy layer of resin/colloidal mix to butter both faces & just keep moving with a bit of squeegee work over the joins then a solvent or even a quick metho wipe to smooth the ooze factor. Some satay skewers or similar can be drilled for & driven when required to maintain alignment of planking between station molds.
Jeff.

 

[TOALL]

50ft strip plank sailer

I commissioned my own design. Have a joinery business with staff. very used to building complicated items

 

[TeddyDiver]

Having considered many building methods I decided on a sheathed strip plank hull. Not having built a boat before I looked at the different methods but ultimately was scared away from using a foam core because people were reporting delamination after even small knocks and collisions.

There's not delamination risk with foam core more than strip planked has in an oneoff built boat. You laminate the skins on the core and see the result all the time during the process. It's totally different from a mould built boat where the outer skin to core bond stays hidden untill it fails.
What comes to weight there's no gain with foam cored vs strip planked heavy skin composite. Foam core needs additional fiber directions along the hull where strip planking doesn't.. depending of the loads and engineering of course but you get the picture.

BR Teddy

 

[rwatson]

......
The Boat has been professionally designed.

Does any one think I should be building it differently?

Based on your joinery experience, and careful preparation, I would say its going to go OK, as long as you don't try to build it right way up like you mentioned.

Pars mention of moulded plywood, perhaps diagonal planking is very valid, but that might mean a hassle with a bit of re-designing. Sheathed strip planking is a pretty close call.

I am assuming that the hull has lot of of compound curves as a good sailing boat should have. If it was just hard chined, or even multichined, plywood would be the more sensible solution.

Foam core might be best to avoid on a first build, as it requires some experience to do it right. The last copy of Professional boat builder has a story about a professionally built foam hull that was mostly voids, and had to be nearly rebuilt .

Finally, PARs advice about the size of the project is the killer point. 50ft is a huge project, and really, the main part of the hull is barely 10% of the problem. If you have staff and premises , you are off to a good start, but its still a huge project.

Jolly good luck to you.

 

[rwatson]

I think you could fairly drop the gaps to 2.5-3.0mm & still squeegee a bog slurry through the planking. Not so good for clear finish on the inside if that's part of the strategy. But the division/encapsulation is a good point, though you get similar with a consistent glue line. Personally I'd just brush a juicy layer of resin/colloidal mix to butter both faces & just keep moving with a bit of squeegee work over the joins then a solvent or even a quick metho wipe to smooth the ooze factor. Some satay skewers or similar can be drilled for & driven when required to maintain alignment of planking between station molds.
Jeff.

Yes, true, the gaps can be much closer than 6mm - I was being overcautious in lots of those figures..

The way that Mark does it requires no real alignment hassles. He just lets the strips go their own way, and adds the stealer planks afterwards as required.

Not having to wrestle with glue as you pin the strips is a BIG bonus. Especially as you can adjust the strips dry, and not have to worry about them being hard glued into place when you see that there is a wave in them. Being able to eyeball the hull, and even take out some high spots with a sander before you commit to a permanent gluedown can save a lot of fairing compound and elbow effort I would think.

 

[LP]

I did a 24' hull by similar means. Still building actually, but past the hull portion. I used tongue depressors for spacers and used a pneumatic nail gun. Planking went decently. I am bright finishing large portions of the hull and the glue joint are fairly attractive.

I would run about six planks and then bog them to set them in place. I worked from one end to the other. I would bog a section with a fairly loose mix, scrape up the push-through and use it on the next section, mixing more as I needed it. Pushing up around the turn of the turn of the bilge, I started widening the gap some and mixed a thicker bog that would stay in the vertical gaps. The only part I need help with was closing up the hull. I need a set of eyes on the inside to tell me if the seams were fully bogged.

Enjoy you project. 50' is a lot of boat.

Here is where I start planking my build.

http://www.boatdesign.net/forums/wooden-boat-building-restoration/blackrock-24-build-46526-6.html

 

[rwatson]

I did a 24' hull by similar means. Still building actually

Enjoy you project. 50' is a lot of boat.

Here is where I start planking my built.

Looks a good effort, made more painful by going for a bright finish.

I was particularly interested in one of your comments on the build

" I may have used an entire six gallon pack on the seams plus some minor bonding of planks to frames, bulkheads, stem and transom. The early seams took less, but as I rounded over the turn of the bilge, I had to thicken the mixture more so the seams got wider to get the mixture to be worked in with a reasonable amount of effort. By the end, I was putting in a cup and a half of fillers into 6 oz. epoxy. 1 cup of CS for strength, 1/2 cup of wood flour for color and 1/2 cup of microballoons for post cure workability."

In my recent estimate on a 28 ft of 25 gallons (98) liters) using the "dry plank" method, (which it seems you used to some extent.) sounds reasonable, or even quite pessimistic.

Thanks for the feedback on the topic.

 

[TOALL]

50ft strip plank sailer

Had a quick look at your link LP. looks ever so relevant. Will look in detail a little later this evening
Did you feel the dry process of planking saved you any real time, and would you use it again?
I'm sure its much easier to fair without the hard glue line

 

[LP]

Had a quick look at your link LP. looks ever so relevant. Will look in detail a little later this evening
Did you feel the dry process of planking saved you any real time, and would you use it again?
I'm sure its much easier to fair without the hard glue line

There may have been some time savings. The dry planking process is more fulfilling as you can get more on at a single go. A major benefit of doing it this way is that the goo factor decreases significantly. Instead of having your fingers (gloved of course) in the slop for the endless hours of plank, goop, plank, goop, plank, goop, plank, goop, .......... etc , etc, etc ....... And on and on and on....., you plank, plank, plank, until you feel you need to stabilize everything, then you have an hour or so of goopiness and give it all a break until the goop goes hard.

I did a 16' stripped hull where I glued each strip and edge nailed by hand on each strip. After a couple hours of this, everything you are touching is a tacky mess, no matter how hard you(I) try to work clean. There is was no avoiding getting fingers in the mess.

For my given hull form, I would do it again. I have other techniques I want to try so I may never do it again. I want to do a lap strake sometime. I'm also messing with a small catamaran design and that will definitely be S&G.

As far as glue lines go, I feel that there wasn't a significant difference in fairing the fat line or the thin edge to edge lines of my previous build. The fillers I used in the gapped seams softened the lines to an extent. I initial fairing with a block plane, followed by fairing boards with a firm to hard backing so the harder seams would not be left proud. The orbital sander use was kept to a minimum and was only used to smooth the fairing board marks.

 

[rwatson]

....

I did a 16' stripped hull where I glued each strip and edge nailed by hand on each strip. After a couple hours of this, everything you are touching is a tacky mess, no matter how hard you(I) try to work clean. There is was no avoiding getting fingers in the mess......

A Bl*&^dy MEN to that. Working clean and quick is the whole aim and purpose.


Mark has put a promotional video Youtube.

If you turn the music down, have a look at some of the plank layouts in the bits "between", you will get an idea of how little bending he does.

He just lets the planks lie on a natural plane, and doesnt fight the "edge set". Just fill in between with lots of stealer planks. Its only a core after all.

If you are not doing something silly like finishing a bright hull, this is definitely the way to go.

 

[rwatson]

This is what PAR was talking about.

Worth a watch. Bungee cord to hold the fg cloth on looks like a good idea.

 

[Steve W]

I have not read through all the posts so please forgive me if this has already been mentioned but while laying strips is rather tedious it is a good method for someone, novice or otherwise, who wants to build a large hull, single handed in their spare time as they can just lay a few planks every evening after work. Back in the 1960s a guy in Auckland designed and built a 67ft skinny A class harbor racer stripped, edge nailed and resorcinol glued by himself in his backyard. Of course he had the huge advantage of not having a bunch of folks on the internet telling him he couldn't design such a boat as an amateur and that he should just go out and buy a boat or that you cant use resorcinol without tight fits and huge clamping pressure, he just got on with it without distractions and if he did have detractor 50 odd years of successful racing have proven them wrong.
I have personally built a couple of 34ft keelboats with wrc strip planked cores and just used square edged planks which give a nice tight inside fit which makes for a beautiful bright finished inside visible through the glass while the more open outside seams are fine with a painted hull. I see no advantage to ant of the machined edge profiles, I have built a 12ft sailing dinghy with bead and cove strips so I do have some experience to base a judgement on.

Steve.

 

[rwatson]

"Of course he had the huge advantage of not having a bunch of folks on the internet telling him he couldn't design such a boat as an amateur "

Yes, you can tell you haven't bothered to read through the previous posts. There were no detractors, just lots of good advice, peppered with concern on the size of the project, from people who have a even more than "12ft bead and cove dinghy" experience. And, several people suggested that shaped edges may be un-advantageous.

It sounds like you are suggesting a complete novice can loft, layup and build a 67ft wooden boat with no experience.

That "guy" who built a 67ft skinny was obviously brought up in a family that had, or just raced boats, and he probably got the initial lines off someone he had watched build using that method.

You remembered it because it was a one in five hundred success story, and the other 499 are lying half finished in backyards, in the back lots of marinas, and standing out in lonely farm paddocks.