Naval Architect Consult

[tomherrick]

The boat extension project is rising to the top of the list again. Too many reasons for its postponement to get into even if I wanted to. The silver lining is that I've had lots of time to consider and reconsider options. I'm considering a further extension - not unlike BeerThirty's idea - but it would be more of a continuation of the hull than a bracket. More cockpit space, potential for cabin extension, a broad swim/kayak platform, hull speed increase, and many more benefits. And yes, it it might be a 29-footer when its done.

I had my current plans reviewed by a naval architect, Jack Hornor, who offered good suggestions and gave the plans a thumbs-up. Last night I decided to contact Jack again about this new extension concept and learned the sad news that he had passed away about a year and a half ago. I certainly didn't know him well, but enjoyed his good nature and the enthusiasm he showed for my project. I last saw him at IBEX in Louisville a few years ago and we got to chat briefly.

So now I'm searching for another naval architect/engineer who might get a kick out of consulting on a small project like this. Some do - some find it a nuisance. Five pages into a Google search for a naval architect in Kentucky came up empty. I know of one nearby - maybe the only one - but he's not my guy. The marine surveyor who led me to Jack suggested another name - but also in Maryland. I'm hoping to find one that I can meet with in person without a nine-hour one-way drive. An email to SNAME for a directory only got a friendly response from the receptionist so far.

Anybody here know of a solid, good-natured NA they'd recommend for this kind of consult? I exported digital design files that Jack was able to bring into his 'real' NA software to review. I can do that again.

Below is a sketch of what I'm thinking...

[thataway]

I don't have a NA name. But the "stretch concept is done all of the time by many fiberglass boat builders. The issue, is often if to add the increased length in about the last 1/3 of the boat, vs the transom area. The major issue with the 22 would be several fold. One would be the already narrow beam, the weight carrying capacity, the amount of rocker in the addition, plus the strength of the bracket/transom, with additional weight.

Being that your boat is a pre 1987 C Dory, it may be easier in several ways. The hull lines aft are flatter, I don't believe that there is the reverse chine, and the core may well be plywood, rather than balsa. One question to ask is if the boat would need stringers with the revision (perhaps with knees). When you are getting close to adding 6 feet that is very significant--as I am sure you have considered. You may pick up about almost one knot of theoretical hulls speed, if this really means anything in a planing hull? The increased room, and functionality--plus the pleasure of doing a project, yes worth it, if you like to work with glass, and this type of project!

[starcrafttom]

Hi, I would not discount a bracket. many people are under the assumption that a "bracket" can not have any lift or flotation. My 84' 27 ft flat bottom cdory has a alum bracket that is designed to be a extension of the hull. The gap between the hull and the bracket is only 1/4 inch.

I did not own the boat before the bracket was installed but i have been told that it smoothed the ride over chop and increased the fuel economy. Both motor's are mounted out of the way and the bracket provides a great swim/kayak enter point.

The length to beam makes it a little bit tipsy but it does not bother me at all. The improvement of handling long rollers and chop to 3 ft is well worth it as is the increased speed. We love our boat and I would not consider a bracket unless it is designed as a extension. It can be done in aluminum far faster then in glass. And I'm sure for less money.

[Sea Wolf]

Tom-

I don't know a qualified NA in your area, but you'll get a lot of very good ideas from our C-Brat friends here.

I'll hold my comments on the design issues here for now, but if it were me, I'd just wait for a CD-26 or CD-27 to come along and start with that competed hull and modify from there.

Would be simpler, might cost less in the long run, and be easier to re-sell later.

Those boats typically come in at around $35k or so, and often require re-powering, but I guessing that the comparative cost and complexity of the modifications would probably put the either project in somewhat similar cost figures after a trade-in /off with the 22 Classic. YMMV!

Still, if you love big projects, have the time and $$$>>>>>>>>>>>!!!!!

Good Luck and have fun!

Joe.

[olsurfdog]

I recollect that someone already did a similar extension of a 22. Don't remember the year or specifics, just that they extended the cockpit and added a bracket. I'm sure a search of the archives would turn it up.
Good luck--sounds like a interesting project.

[Sea Wolf]

[hardee]

Tomherrick,

There are also some pix of a CD-16 that was extended to 18 by Oldgrowth Dave. Here are the links to his album photos:

A CD16 extension of 24”
http://www.c-brats.com/modules.php?set_albumName=album172&op=modload&name=gallery&file=index&include=view_album.php&page=3


The extended 16 now a CD18
http://www.c-brats.com/modules.php?set_albumName=album460&op=modload&name=gallery&file=index&include=view_album.php

He reported a huge improvement in handling, and of course range because he added the saddle tanks, moving weight forward.

Harvey
SleepyC

[tomherrick]

First, thanks all for your thoughtful responses, although I've learned to expect nothing less from this crew. Some quick responses to y'all before I hit the pantry cabinet project in the shop so I can clear the decks for some boat work...

@ Dr. Bob:
· no reverse chine
· core is plywood; originally was CDX with lots of voids - not marine
· basic boat extension that exists now - pre-'bracket' - is 25'9" LOA
· 'bracket' addition could be a stand-alone, but would be glassed as part of existing hull
· I don't think stringers would be needed; Jack Hornor was fine with the extension to 25'9" without; the 'bracket' addition will have internal bracing fore and aft creating three pockets; it'll be epoxied to the transom and glassed in - light but very rigid
· I'd like to spend a lot of time at displacement speeds, so a knot or two might help a bit with fuel costs
· Jack had said that planing speed with the data he reviewed in his software would probably be a coupla knots less and that I could theoretically do it with a non-recommended 40 HP
· so far, I don't like working with glass; can't wait to sand and polish gelcoat...

@ Tom
· I've done a fair bit of checking into 'bolt-on' brackets and the ones I was looking at did add buoyancy and additional lift for planing
· I really, really like the swim/kayak entry point thing...
· a length of Beam can make me tipsy, but I prefer Woodford Reserve
· aluminum would have to be done by someone else that I'd have to pay and hope that they get it and that I communicated well; I own the glass and epoxy and plywood and don't charge much

@ Joe
· I have the $$$>>>>> for this project, but not the cost of a new-used C-dory; that said, I'd buy that diesel 27 longhouse in a heartbeat if the girls at the lotto sales would enter my numbers right - just to keep this boat company
· it would definitely be simpler, but I wasn't born that way

@ Michael and Harvey
· I have spent hours looking at Beer:Thirty and Oldgrowth Dave's projects; they gave me a lot of confidence and enthusiasm that hasn't been too awfully tamped down by the events of recent years

Thanks again,

Tom

[ghone]

Hi Tom. You may try Trevor Bolt yacht design in Richmond BC.
1-604-517-8311
He did a preliminary design for me in 2002 on an Arctic sailboat
He might have some good input
George

[BrentB]

may Darren the engineer who design a tunnel wedge for CD29 could help??

http://www.c-brats.com/viewtopic.php?t=22013