Opinion about design

[kaor]

Hi, I found this design from Francois Vivier http://blog.vivierboats.com/2011/02/...ff-cutter.html and i really like it, but would like to hear opinion or 2 about it. The keel and building technique is same as Pen Hir http://www.vivierboats.com/albumsen/.../index_en.html .
My questions are, what do you think about this type of keel, what is lifetime of epoxy - ply construction? Is it maintenance intensive?

[michael pierzga]

Its a pretty boat.. You need to buy the plans and examine the construction details. Looks like the keel blade is a separate component from the rudder skeg. Looks like the keel blade is housed in a trunk. It all makes sense , represent logical engineering and is easily repairable but without the construction details its difficult to judge. Properly Epoxy encapsulated marine plywood lasts a long time.

[FMS]

Your links are not working for me kaor.

[gonzo]

The links don't work for me either.

[michael pierzga]

http://www.vivierboats.com/Img/EN_Pen-Hir.pdf

[kaor]

Its not Pen Hir, its just same building method. Here is link http://1.bp.blogspot.com/-Ga5kUquoRH...lhouette_0.jpg or try to google Koalen 26

[kaor]

Uploaded with ImageShack.us


Koalen is the name I have given to a range of boat designs inspired from traditional fishing boats of Britany. After Koalen 22 and Koalen 25, this new design was asked by a home builder of a beautiful Beg-Meil. As per hull shape, I am keeping an intermediate line between pure tradition, with the raked keel of Breton crabbers, and the approach of some yacht designers fitting high tech and deep appendices on a traditional looking boat. A boat must be a consistent whole. A gaff rig is powerful and needs an appropriate hull. A light hull with a deep bulb keel suits a high aspect ratio bermudian rig, not a gaff rig which does not allow the same heading to windward. The keel of Koalen 26 is based on the same principles that the one fitted on my Pen-Hir, which gave astonishing high performances. It is simple to build, being made of a plywood wing, 40 to 50 mm thick, with two half lead torpeedos transversally bolted. With such a keel, the boat keeps most of the behaviour of a traditional gaff cutter: excellent course keeping, easy manoeuvring under sail. In addition, drying out with legs is very safe.
Koalen accommodation are very similar to those of Pen-Hir, with more space and in particular standing headroom and a diesel engine. But above all, Koalen 26 carries an awesome gaff rig with a topsail. The topsail yard takes place into the accommodations.

[michael pierzga]

Nice boat...but without the construction details of her plywood keel and its attachment to the hull its not possible to comment on its longevity. Best to purchase the plans and read the designers comments and build instructions.

[kaor]

You can see on Pen Hir which have same building method

http://www.vivierboats.com/albumsen/...ides/AR01.html

[michael pierzga]

On study plans its not possible to see the engineering details of the keel

[Tad]

The engineering details of the keel are that it's constructed of two layers of plywood bonded together (and I assume fiberglass sheathed) and the ballast is in two "cheeks" which form a ballast bulb either side of the lowest point. This is a clever construction system built using plywood for almost all the parts. I believe amateur builders will find this system simple and not intimidating......sawing numerous foil lifts (of different shapes) and bonding them together with threaded rod might scare off the beginning builder.

But I have to say I don't like this structure, I think it's weak where the boat should (in my view) be bulletproof. The reason it's weak is that the grain in the ply all runs fore and aft or vertically, where the load on the keel is sideways (athwartships). Proper quarter sawn lumber bonded into a keel will resist this side load very well as the grain is oriented perpendicular to the load. For general use this ply keel is probably fine, but in a hard grounding I suspect something will break....but perhaps that's okay.

[michael pierzga]

encapsulated plywood does not like mechanical fasteners penatrating its skin and allowing water to enter. . It should be easy to waterproof , isolate, the mechanical fasteners holding the lead bulb cheeks onto the blade. I would worry about the mechanical fasteners..keel bolts or whatever .. attaching the keel to the hull . How is the keel held to the bottom of the boat ?

[Tad]

Originally Posted by michael pierzga

How is the keel held to the bottom of the boat ?

See the link above....the outer keel fin is plywood which extends up into the boat to become the inner keel, with additional plywood cleats added to it to form a landing for the planking....no mechanical fasteners holding the keel on, just some through bolts for the ballast.....

[michael pierzga]

The keel is only glued into the shallow keel trunk ? No mechanical fasteners ?

[Tad]

There is no "trunk", what I said was that the outer keel extends into the boat to form the inner keel, as seen in these pictures. No mechanical fasteners (AFAICS) as none are needed and there's no advantage to adding them.