Building 23 foot cabin cruiser

I hope to start building a 23 foot cabin cruiser as a retirement project, using plywood on wooden frames. I bought the original plans from Hartley Boats about 8 years ago and in their booklet they mention that frames should be made of Iroko, mahogany or sapele, or they can be made up of laminated plywood.
Is white oak suitable for the frames? If laminated up from plywood what thickness should the finished frames be?
I don't really feel comfortable of learning to epoxy that is why I want to stay with the old way of doing things.
Any advice will be greatly appreciated.
Regards to you all
Ken

 

I am sure some others will share their personal experience with white oak.
I can only say that the quality of the wood you find is often more important than the species. Some kinds of oak is hard to glue with epoxy. Laminated frames could possibly be a little thinner than solid frames.

When I searched for data on white oak I wound this page,
http://www.jmjoinery.ie/hardwoods.asp

You may want to look up the strength properties somewhere. For frames I would estimate that if oak is 10% stronger you can use 5% smaller dimensions.

 

White oak is a fine frame material and most adhesives work well with it. Epoxy can cause difficulties with white oak.

Laminating up frames from plywood, will make heavy frames to gain the strength the solid lumber will provide (pound for pound). This is an option, but you'll like cutting them from solid stock better then gluing up bits and pieces of plywood and it will look a bunch better too.

Sapele and mahogany are similar in weight and strength, Iroko is dense stuff and I'd think you could do with a lighter frame material. White oak is also dense. In your area there should be a wood that has reasonable rot resistance and a dry weight around 40 pounds per cubic foot. The two mahoganies you listed are just over and under 40 pounds and the oak is 46 or heavier, with the iroko being over 50 if memory serves me (I didn't look it up). You'll be looking for a tight and straight grained species between 38 to 46 pounds per cubic foot, that ideally should be rift or quarter sawn, knot free (or near so) and have good rot resistance.

The frame thickness should be listed on the plans (laminated ply versions), if not make them the same thickness of the solid wood frames.

 

Many thanks to both Ragnar and Par for your extremely prompt replies to my queries yesterday. You have both given me things to ponder over and I will spend some of my time today on the internet checking weights and density of different woods.
Once again many thanks, I'll try to keep you informed of my progress as I go along
Ken

 

23 foot cabin cruiser

I think the first thing to consider is the type (species) of timber available to you ,I don't know much (that means anything) about Malta,but I guess boat building timber would be pretty scarce there ,and would mostly be imported which means expensive ,and also taking into account the wastage involved in cutting frames out of solid timber,particularly if much curvature is involved ,I can see why you are leaning towards cutting them out of plywood ,and that means laminating them,and in my opinion that means epoxy(a boat builders best friend),however doing this(laminating plywood) is not going to result in a top job ,as has been noted in another post,so decisions ...decisions
Now what I am going to say apply's to my neck of the woods ,far removed from Malta .Some years ago ,with the advent of modern glues (formaldehyde and epoxys) we used to laminate solid timber for frames ,and that timber was flooring as used in the buillding industry,I am not talking about rubbish timber here ,but virtually cabinet grade ,one species was rose gum,if not the most beautiful timber in the world it would run a close second ,looking back on those days it was almost a criminal waste .this timber was cheap because it came from the building industry and not from boat building suppliers .So I would suggest ,as someone else has ,look to the quality of the timber not only the species,look to the building industry ,and most importantly learn to like and use epoxy(your boat will last longer)

 

Alternative woods

Further to my previous questions about building a 23 foot cabin cruiser. I still have a couple of outstanding questions or queries.
Firstly, is it alright to mix different types of wood. ie, 'frames white oak', 'stringers maybe pirana pine', 'keel mahagony' etc?
Secondly is there any formula for working out what the head room should be in cabin and wheelhouse? Or is it a case of 'if it looks good to the eye, it is alright'? I know this might sound like a rather stupid question, but the on the plans I have, a hole is left in the roof of the cabin for the helmsman to stick his head out of. I have re-drawn the plans and made standing headroom in the cabin, with the helmsman having to stand on a raised platform in the wheelhouse. If any body can give me some sound advice on this I will even post a picture of my updated plans to help them out.
Anyway for now this is all from me as I have to get back to the internet and check some other things out.
Regards
Ken Cocks

 

Hi Ken,

Mixing woods is OK. I don’t know exact formula for calculating the headroom, but standing headroom on 23 fts boat looks too much. Personally I will stick to the original design, since such small boats didn’t tolerate many changes. However somebody with more knowledge on this design can give you better advice i guess.

CapKos

 

I am afraid it will look bad with standing headroom, but that's a matter of taste.

You have to consider the weight of the roof and cabin structure though.
More weight high up and more windage can be dangerous.

 

One of the most difficult aspects of design work, on small craft, is providing standing headroom. Many tricks can be employed, built down garboards, hollow keel wells, raised or broken sheer, etc. On 23' power craft, it's extremely difficult to produce a handsome vessel, that has standing headroom, without the pilothouse looking tall, boxy or generally out of proportion. Excessive freeboard can help this situation, but it too then becomes awkward looking. Sometimes this can be hidden with a cove stripe or second, lower rub rail, but many design styles can't tolerate this treatment without having other aesthetic issues crop up.

Another key issue that is common among backyard builders is adding weight, with changes to the design. Small craft are very weight sensitive and seemingly small additions can alter the trim and balance of a boat. Changing a runabout to a cabin cruiser for example, may place enough weight forward, that she can never be expected to lift her bow clear and plane off, without a huge HP increase (which may strain the structure past her limits). Now this may not be the case with your boat, but changes have to be well thought out and the weight accounted for.

Post a picture of your revised plans and we'll have a much better time of it, in as much as offering reasonable suggestions.

 

For these and similar questions I recommend these forums:

http://www.woodenboatvb.com/vbulletin/upload/forumdisplay.php?f=1

Kaa

 

update and drawings

Sorry to all of you out there for taking so long to get back online, but family commitments had to come first and this is the earliest opportunity I have had to get back to my drawings. I have enclosed two drawings of the proposed cabin cruiser I would like to build, so that those of you out there in the know can give me some advice whether they are workable or not. I would much rather have a little disappointment now, rather than half way through the build. Your comments are asked for, so please be as brutal as you like.

 

I think it's workable, but I don't like this kind of hanging knees

 

ah Raggi you have fine sense of humour
may I say this boat will most definitely need trim tabs , as she will heel heavily into the cross wind, but thats ok trim tabs once you get used to em are fine

 

As you say, better a little dissapointment now....
And not to throw bad aspersions on any Hartley designs - thousands have been successfully built over the years - but, for another approach - and a similar sized boat that has standing headroom, take a look at Tom Lathrops Blue Jacket 24 www.bluejacketboats.com

 

The Blue Jacket's hullform looks more efficient!