Small craft EN ISO 12215 clinker boat

[Niik]

Hi everyone, I have to calculate an existing "fishing" (pratically it is only hull, with no deck) clinker boat made of plywood by following the stardard EN ISO 12215. My questions are:
1) I've read the standard many times and I haven't found a single mention to clinker technique and I am afraid that I am only wasting my time. In particular, the frames are located in quasi-random position along the boat (I mean with no equal space between them) and the "b" of the planks are not the same but they change at each plank. So do you know if I can actually do that?
2) If so, my idea was to consider the overlap of the timber as stiffeners, with the height of it as the sum of the thickness of the two planks (attached screen). Can it be correct? Also, should the section be considered as a rounded one or hard-chined?

Thank you.

 

[Waterwitch]

Your second drawing has the planks lapping opposite of how lapstrake boats are usually built. The bottom edge of the sheer plank would be lapped on top of the plank below it. The faying surface of the laps of the planks are usually beveled so they lay flat against each other, so they would not be the same thickness as two planks thick along the entire width of the lap.

 

[waikikin]

Hi Niik,
The standard description seems to exclude traditional construction.
Maybe there's historical exemptions where you can improve buoyancy etc to pass, we had to do that with an old timber work scow, added foam filled buoyancy under the thwarts and got a letter from an accredited surveyor. Different part of the world but surely there's provision for existing vessels that met whatever standard when constructed.
Jeff

 

[AlanX]

Hi Niik, questions 1 and 2 seems to refer to ISO 12215-5 which is mostly about design pressures , design stresses/stresses/moments and scantlings.

Q1: Hull panels and frames
I am not aware that the standard requires equal frame spacings.
You just need to check that each panel scantling meets the panel design pressure.
A panel can be a group of (glue) planks.
Of course the overlap joint needs to be strong enough that the planks act as a panel.

Q2: Panel cleats or longitudinal stringers
Sure you can include the glued plank overlaps in the panel scantlings and in the hull SM calcs,
but I suspect they don't add much and their contribution is probably ignored (extra work for little gain).

I think the main advantage of a glued overlap is to increase local loads, here I added cleats so I can stand on the sole of my canoe:
View media item 28785
There are other structures and loads you also have to consider but this is not the question here.

Regards Alan

 

[wet feet]

A couple of points;yes you probably can consider the plank laps as stiffeners and you almost certainly can't consider the hull to be a hard chine hull.A traditional hull wouldn't have the frames at quasi random locations as the frames are needed at fairly regular intervals to avoid the situation where only the fastenings of the plank laps are there to resist any forces applied and this situation would lead to split lands-a situation that can still occur with frames in place.I don't suppose the formulators of ISO 12215 had clinker hulls at the forefront of their considerations as it would only represent a tiny subset of the commercial maritime world.It might be a very useful thing to seek out and carefully read on old set of building guidelines there are versions of Lloyd's yacht construction scantlings and you may be able to find the equivalent guidance from the White Fish Authority.

 

[AlanX]

If you want to use traditional boat building methods then I would look at Gerr's "Boat Strength for builders, designers, and owners" for advice on scantlings.
It's not ISO 12215 however.

AlanX

 

[Niik]

Thank you very much for all of your answers. This is my first study in this field so I am learning and doing at the same time. I will give a look to Gerr’s book and Lloyd’s one. Thank you.
Regards Niik

 

[Pablo Sopelana]

Hi Niik,

We are preparing an online video-based course "Scantling with ISO 12215" which will be available soon:

- The course: Scantling with ISO 12215 https://navalapp.com/courses/scantling-with-iso-12215/

You may be also interested in the other courses we have so far:
- Courses: Navalapp Online Courses https://navalapp.com/courses/

Hope this can be of any help.

 

[Niik]

Hi Pablo, very interesting. Can’t wait to attend it. Do you know when it will be available?
Niik

 

[Pablo Sopelana]

Thanks Niik for your interest.

Our internal launching date is the End of May, and we are working hard with this date in mind.

We could also open the registration before End of May with an Early Access Program where students enrolling in Early Access will benefit from a reduced price and be the first to experience the course content as we upload it.

My suggestion to you is to sign up at Navalapp. There are different membership levels ( https://navalapp.com/sign-up/ ), but you can also sign up for free here: Sailing Yacht Design & Performance https://navalapp.com/account/checkout/

You will receive all the updates related to this course.

 

[Pablo Sopelana]

Hi,

Just wanted to confirm that the course is now available:
Scantling with ISO 12215 https://navalapp.com/courses/scantling-with-iso-12215/

 

[Pablo Sopelana]

And this is a link to an introductory video: