Forums: Whisstock Designs: Design123 (20' 4 Berth Yawl) New Topic Post Reply
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yorkcoparamedic
Posted: Mar 10th, 2009 at 02:01   |   Subject: Design123 (20' 4 Berth Yawl)
Hello! I have been thinking about building a sailboat for a couple of years now and I think I am ready to tackle the project. As a first time builder I hope a 20'er is not to much, but I really dont want anything smaller. I would be cruising the Chesapeak Bay (upper bay area) around Middle River. Anyway, approximately how much money will be invested into a project like this. From start to finish, including motor. I am not concerned with the amount of time it will take because I am in no hurry.

Thanks for your time,
Charles
debenriver
Posted: Mar 10th, 2009 at 21:45   |   Subject: It is not easy!
It isn't easy to estimate build costs because there are so many variables. There are many different qualities of material, though generally medium to good quality is better and more economical in the long run. Also it does depend somewhat on the hours you are prepared to put in. Making the spars yourself will be very much cheaper than having someone make them, for example -- and full instructions for pretty much everything (including making the spars) are included.

Some builders can make their own ironwork and fittings; some have to send out for these to made. Few builders make their own sails because this is really difficult - but some do. And so on.

For the "average" builder, preparing his/her own timber from sawn material, making their own spars, but buying in fittings, sails and so on, I would estimate the cost to be in the region of $20,000 - $25,000, including the outboard engine new.

George
Rolando
Posted: Jun 30th, 2009 at 07:46   |   Subject: Some questions on Design 123
I tried posting but it disappeared so I'm trying again.

I am likewise interested in Design 123 and have some questions.
To start:
1. Please comment on how it is to sail a yawl. I am intimidated by the number of strings to pull :)
2. I currently have a 2-stroke 5hp short-shaft Mercury. Is it adequate to use as the auxiliary?
3. What is the hull weight?
Thanks.
debenriver
Posted: Jul 2nd, 2009 at 13:57   |   Subject: Some questions on Design 123
Sorry you had difficulty posting - we did have server troubles for a while on the 30th. To answer your questions:

Lots of string!

It is true that a cutter-headed yawl looks a little complex - and of course it does have more ropes and sails than a simpler rig.

A plain cutter rig version is available - you can see this on Plan No. 123-011-02 on the Study Plans page. I would guess about half the boats built to this design have been rigged like this.

However, once you get the hang of sailing a yawl, it is no more difficult than any other rig. In fact it can be easier in some respects: reefing for instance can be easier because you can, as a first reef, simply drop the mizzen. As a second reef, you can roll up the jib. The boat handles very well under mainsail and staysail, and you have reduced sail area without having to go through the hassle of reefing the mainsail.

The thing to do is start your sail trials with your new boat on a nice quiet day. Make sure everything is good and that the engine starts OK. In fact we advise carrying out engine trials first before even pulling up a sail, so that you get confident about handling the boat generally. Then start with the main and staysail and see how she handles on all points of sailing. Then proceed from there to build up your knowledge of the boat, the rig and her capabilities. Try out other sail combinations - mizzen and staysail for example can be a good rig under some conditions. That way the rig will never seem complicated because you are at ease with it.

The real bad thing to do is to go out and start hauling up sails and then find it is blowing too hard, or something doesn't work properly, and get in a muddle. I think proper sail trials over several days and in increasingly heavier weather are as vital a part of building the boat as any other.

If you are going to sail with several people and feel that the mizzen just adds too much clutter to the cockpit, or simply prefer a plain cutter rig - then that's the way to go for you!

When I was young (about 10 -12) I was allowed to have the mizzen as "my" sail, which I guess kept my interest in sailing going when otherwise I might just have become bored by it all. I remember getting really mad when my dad made me pull it down (because it was getting too windy).


Outboard engine.

Engine power is usually reckoned in hp per ton displacement. About 1 hp per ton will get you up to hull speed ok, but it is not really enough to maintain hull speed or give you good control in adverse conditions. 2-3 hp per ton used to be considered sufficient. The tendency nowadays is to go for 5-6 (or more). This is partly because ancorages and marinas have become more crowded so more instant manoeuvrability is needed and partly because on larger yachts a lot of power-absorbing ancillary stuff is being run off the engine

I usually reckon on about 4 hp per ton minimum. But I would think that your 5hp (= 3.5 hp per ton) would be adequate. I'm not sure if the short shaft model would get the prop deep enough however - you would need to establish that from measurement. The design dimension from the bracket to the prop centreline is 680mm, but this can be changed.

Hull weight.

The weight of the bare hull, deck, superstructure etc. is 458kg (1,010 lbs).
The ballast keel weighs 518kg (1,142 lbs)

The remainder of the weight of the boat is the interior furniture, spars, sails, fittings, gear, outboard engine, etc.

Hope this helps -- George
Rolando
Posted: Jul 2nd, 2009 at 15:37   |   Subject: Now for more questions
Thanks for the reply.

Now for more questions:
1. What are the issues to look out for in building the lapstrake version?
2. What thickness plywood is specified for this hull?
3. How easy/challenging is it to loft the individual planks and to lay them on the frames?

Thanks again.
debenriver
Posted: Jul 2nd, 2009 at 17:31   |   Subject: Subject: Now for more questions
Lapstrake issues:

None really. Lapstrake is simple, relatively straightforward and strong. It is the laps (which are 30mm - 1.25" in this case) that give the strength, because they effectively become longitudinal stringers. They and the transverse frames break the hull skin up into quite small panels.

You have to get good at filleting (applying an epoxy/fibre fillet joint). This kind of looks simple but is actually quite hard to get right, so that you end up with nice smooth fillets and not too much mess all over the place. Lapstrake planks are filleted (in the 'corner' formed by the laps) inside and out. You are aiming as much as possible for a 'first time finish' because sanding them up a lot after the epoxy has cured is not much fun.

The lapstrake skin is 9mm ply.

The plank shapes are discovered from the frames set up on the building jig. They are not lofted as such. Basically you measure around each frame and divide the resultant length by the number of planks (typically 11, 12 or 13 for this boat). This gives you the apparent width of the plank and where it runs on the boat. You add the width of the lap (30mm) to the apparent width to get the actual width.

To arrive at the developed shape (the shape on a flat sheet that will be correct when bent around the boat) we use an age-old boatbuilding system to derive plank shapes, carvel, clinker or lapstrake. We have a long, wide batten (made from several pieces of ply screwed together) and bend it around the boat. Because it is relatively wide (say 150mm) it won't bend on edge.

By taking measurements from the (say) top edge of this batten to the top-of-plank marks on the frames, and ticking off the frame positions on the batten, we have effectively recorded the plank shape. Laying this out flat on the ply sheets, we can transfer the developed frame positions and the top-of-plank shape to the flat sheet. Then it is simply a question of drawing around the marks with a normal fairing batten and then applying the actual plank widths from this line to give the other edge of the planks.

This may sound complicated but in fact is isn't. And once you have done it once and got the hang of it, you just have to repeat the process for succeeding planks, because there is no difference in principle between one plank and the next. The beauty of lapstrake is that you don't have to be quite as accurate as you did with carvel, or even traditional clinker, because the wide lap will absorb the odd error of a mm or two.

The plank sections can be scarphed or butt joined together. A scarph join is simply bonded together. A butt join is supported by a butt strap on the inside. Both are equally strong. You can join the whole sheets together before marking the planks out, or you can do it individually with each plank when the sections are put up on the frames on the jig. The former is good if you have someone to help you lift the planks into place; the latter is good if you are working alone.

Our instructions are much more detailed on this process and they really do lead you through it step-by-step.

We are in the process of creating DXF files of the ply components, both flat and curved, of our designs so they can be CNC cut and delivered as finished components ready to fit. These will include the developed shapes for the hull planking. We are currently working on design 074, but we will get to this design as well in due course.

The DXF files will be available as packs. Pack 1 will cover the developed shapes of the hull planks, coachroof and cockpit coamings. Pack 2 will cover the other flat ply structural components. Pack 3 will cover the flat ply components for the interior furniture.

Builders will then be able to order pre-cut components from a suitable company locally. In the UK there is Jordan Boats. Here in Maine there is CNC Routing and Design. And we will be expanding the list of suppliers.

George




Rolando
Posted: Jul 3rd, 2009 at 03:09   |   Subject: One last question for now
One last question for now:

Do you have a Bill of Materials for the hull so I can estimate the cost?
Or at least the required quantity of plywood, epoxy and fastenings. It will be a self-built boat and I want to be able to schedule the expenses over the 1-1/2 years that I intend to make it.



Thanks for the thorough commentary; I have printed all the study plans and will need to digest all the information. But I owe you a profile of myself:

I am in the Philippines and currently Googling for plans for a trailer cruiser that I can take around our islands. While the sailing will be mostly within sight of land, the weather and currents can be daunting depending on the season, so a "coastal" type boat would be the more comfortable choice for cruising up to a week at a time. It will be parked at home in my boatshed when not in use.

I am more inclined to the yawl rig: the smaller sail areas to be handled should make up for the number of lines to tend.

While there are many good sailing areas here, launch ramps are for the most part non-existent making beach launching the norm. This limits me to a boat length of from 18 to 22 feet--thus my interest in Design 123 (and possibly 146 if I find that the heavier towing weight of the 123 is less practical).

If ever I choose a Whisstock plan, it will be my sixth and largest boatbuilding project. So far my building experience has been plywood plank-on-frame and some stitch-and-glue; doing a lapstrake will be entirely new to me. But I think I have enough skills to pull this off and the sea-kindliness of the round-bottom plus the gorgeous look of your designs should more than justify the extra effort. The CNC option is cool and though I am not optimistic, I will ask around if anyone here can do the service.

Thanks again and I'll appreciate any leads/websites you can give me of previous or current builders of the 123 and 146.

BTW Pls feel free to move my posts to another thread; I'm beginning to feel I've hijacked this thread from yorkcoparamedic.
debenriver
Posted: Jul 9th, 2009 at 00:57   |   Subject: One last question for now
I'm not so very good at Bills of Materials. I spent so many years doing materials (and labour) estimates to build boats - mostly big ones - and mostly getting it wrong - that I sort of shy away from them now!

Designing is the stuff of dreams – bills of materials are reality.

However I can do the ply and epoxy quantities fairly easily and I will post them shortly.

I think you might find that 146 is an easier trail than 123, though she is OK for a trail home in the Winter and back in the Spring – just not intended for weekend trailing.

Back soon ...


George

Rolando
Posted: Jul 9th, 2009 at 10:39   |   Subject: :)
I understand perfectly! Thanks.