F12 design and development

Maugan,

Need a source of oakum ply that will ship. Seems most, if not all, wooden boat building suppliers are on the coasts. Have you done any sourcing yet yourself?

You may want to contact one of the kit kayak companies that buy in huge volume, they might be able to give you the name of a good supplier. Do you think this hull would be built using the sticth and glue method that the kayak kits use? It's supposed to be very easy but I have not tried it yet. Maybe, once the design is finalized, we could get one of the large kit kayak companies to put together a hull kit with all the wood and precut panels? http://www.clcboats.com/boats/sharpie.php

For Okoume or Merranti
try Boulter Plywood in Mass. they ship country wide and stock everything plywood. Wonderfull to deal with

http://www.boulterplywood.com/

4x8 3 mm is 39$ each, 4 mm = 45$

I could see me building one of these suckers for screwing around on a local lake

Eric

Thank you Eric,

By far these are the most reasonable suppliers.

I noticed for an additional $59 they will scarf two sheets to make one 4' x 16'. Shipping penalty for this oversize length would be an additional $30.

Any merit to 4' x 16' stock?

At least if you build Blade F16 you don't need to do that yourself <img src=

alt=

/>

Seriously the bulkheads could be done from the 4' and deck from side of the panel if designed carefully. This way it should be just plotting and then cutting thus saving the trouble of joining the panels.

--
Valtteri

Good source for cheap fixed or telescoping tiller extensions is to use a fixed or telescoping paint roller handle - available at home centers in a variety of lengths/materials. Not very bling, but certainly up to the needs for this boat.

The 5-chined wave-piercer will be

stitch and glue

for certain if building only 1 boat.

What I'm trying to do it design it in such way that only 3 joints need to be stitched-and-glued with the remaining 2 joint being a simple screw and glue after routing the joint rod to the right angle.

And if more then one boat is made by a builing group a joint rod can be made for all joints allow all additional hulls to be simply

screw and glue

. This should save time. Another idea I have it to have one guy build a prototype and make an angle tool of this hull for all joints and have him sell routed joints rods for all chines to other builders. This would allow all other builders to save time and would recoperate the cost of the prototype. Definately a win-win situation.

I hope this answers your question, Tim.

That is an excellent idea Tim.

The already offer another multihull, the

Pacific Proa

http://www.clcboats.com/boats/pacificproa.php

I think I will contact them after the design is finished and sell these plans through them.

Wouter

Of course you can have them make the scarf but not glue it together yet.

That additional saves shipping charges and you only need to spend a little time glueing the platse together yourself.

Also less risk of damage during transport ? Afterall a 6 x 2 foot package is alot easir to handle then a 12 x 2 foot package.

Wouter

Good idea,

Noted, thanks.

Wouter

You got that right, I would personally LOVE to have one of these F12's for the days and evenings when I don't have enough time to rig the F16. In my case that would be most weekday evenings during summer.

I had been thinking about buying myself on old laser 1 dinghy but experiences held by other laser owners at my club say that the surf on our beach make going out and coming back in difficult. A catamaran is much more suited to traversing the surf, sandbars and associated breakers.

In my case I will just clip my F16 rudders and tiller extension to the back of this boat and use one of my spinnaker sheet autoratchets for the mainsheet. And of course I just use my class 5 landyacht mast for the sail. Hell I got enough spare blocks and bolts laying around to complete fit out this boat as per current plans.

Yes, I think I'm designing a boat that I will be sailing myself as well.

Preliminary drag/saildrive calculations show speeds beween 9 and 14 knots both upwind and downwind.

OHHHHH yeah !!!

Wouter

Having attended a seminar on stitch and glue building by Chris, I can tell you he is multihull fan. The Proa design is very interesting, and I had asked him if he would ever consider a kit or plans for another multi (I was thinking of a cat based on the basics of the Proa main hull). He didn't rule it out, but had nothing planned, as something like that might be bigger than a practical kit. This, however, may just be the thing that gets their interest. If nothing else they may be willing to share some tips that would help the design be a success from a mass building sense.

Here's the linesplan to the drawing I posted earlier:

I can tweak the design very quickly to accommodate any changes that Wouter or anyone else wants.

One little thing about that design above, I know little kids will ram those things into each other and the dock, etc. so how about making the bows plumb top to bottom instead of pointy at the waterline? That would spread out the impact stress and hopefully NOT cause holes in the hull of what ever they hit, and protect the bows of the hitter as well.

Also, I asked them (CLC) about doing a wooden Blade F16 kit but he said it would be too hard to it as tourtured ply (for most beginners) and it would also be quite a big job to convert tourtured ply plans to the stitch and glue plans, since that method does not lend itself to a nice round hull bottom. However, he did not rule out any stitch and glue type hulls. We would probably want to specify the mast/sail set up to keep it as a one-design type boat. BTW, this is exactly how the Opti started. The

Optimist

, a charity group from the Tampa area, had a contest to design a small sailboat out of a single sheet of 4x8 plywood. Perhaps the F12 could be the

New Opti

?

Maybe out of 3 sheets of 4x8 ply?

Like this Tim?

John,

Correct me if I am wrong but the designs that you and Wouter are presenting are still a tortured ply design, i.e. the side panels have curvature in more than one direction and so the ply sheet still has to be tortured i.e. bent in two directions at the same time. Although by keeping the amount of curvature in one of the directions small you are making the torturing process easier.

I don't think there is any way around this to produce the kind of hull shapes (which I think are good) that you are proposing

Does the software that either of you are using have the facility to produce flat panel patterns for the side panels that you are designing?

Gareth

You realise that the hull shapes and sizes that you are proposing are quite similar to those of the international moth. 3.35 length 2.25 beam with a planing bottom. It may be worth looking to some of their construction techniques.

http://www.moth.asn.au/building_registration.html
and

http://www.moth.asn.au/download/building_ply_skiff_moth.pdf

Gareth

Jalani, yes, that's probably more safe for the kiddies, and anyone near them! <img src=

alt=

/> (I have 4 kids, I can tell you they can hurt each other and you, even with a baskettball!)

My designs are definately not

tortured ply

, but I'm afraid to say that those of John are.

My designs ONLY bend the plates in one direction and therefor do not require any torturing. And therefor it is of course understood that my hulls will look a little more crude as a result.

Able to make the hulls out of flat panels bend only in one plane was one of the very first design criteria on my list.

Maybe later we may be able to twist the panels a little bit by making use of the natural flexibility of the panels but we'll develop that after have gained experience by building a few prototypes. Calculating the panel shapes is a whole lot more difficult when twisting the panels.

Yes.

Tim, I would like to have a wave-piercer bow, but the hull shape I'm working on now (simpler) has a straight bow.

The deck of my hull design arcs down towards the stern and bow. So that is also a difference with the picture made by John.

Wouter

I always thought it would be fun to connect two of those foiling moths with carbon cross beams, create a foiling cat!

Hi All

Firstly, I found over here that companies aren't too keen on shipping the ply sheets scarfed but unjoined, they don't like the risk of damage to the scarf during transport, and having to replace it.

Second, I can't remember, I'll get back to you. <img src=

alt=

/>

Regards

Hi All

Now I remember, I was thinking the other night about wave piercer type bows, I wondered if it would be good idea or not, because if one were to include WP bows in their design that was for junior use (I realise other age groups might use them as well) but, having the most forward surface of the bow at basically waterline, there would be a greater chance of damage to others, as opposed to having the foremost part of the bow at the gunwale. I'm sure we probably had our share of mishaps or near misses when we were young, and probably still have them now.

I wouldn't dismiss the idea, but just a thought.

Regards

Hopefully I will have posted an old picture of an Impara Cadet, this would have to have been around 20 years ago. I haven't been able to get to the club to take any photos showing the hull shape bit better. It is very similiar to the Arafura in its rig, however the hulls are rounded tortured ply. Not quite a small mossie, but good little boat just the same.

Regards

Another good reason to pursue this design <img src=

alt=

/>

At the moment I can't see how you are doing this then, the two plots you have presented so far seem to show a near vertical bow combined with non vertical side walls. I know you haven't finished yet but I don't yet see how you can have those two features without a small amount of torturing.

A small amount of torturing is not a bad thing it just makes getting the flat patterns more difficult.

I am keen to see how your design progresses, good luck.

Gareth

I can't see the problem with a small amount of stressing the ply. In fact, I would say it is highly desirable since it induces more stiffness to the design than would otherwise be present plus it looks better! Also, Wouter, I have to agree with Gareth - the sketch you provided indicates some bending of the ply in two directions. I don't see how it could otherwise be made.

The amount of twist is VERY small and developing the shape is very easy indeed. I'm going to make a stiff card model of my second sketch (as amended for Timbo) and see how it works out.

I agree, can freeship, calculate the panel shapes once you introduce twist?

Folks,
I'm surprised at the number of posts that are being entered on this. Just a couple of responses below:-

Phill eluded to a homebuild ply box and rudder here somewhere?

John,
I did and it is dead easy. You could be building the rudder setup while waiting for resin to cure
on the hulls. Just takes a bit of planning. The ply rudder setup will be a fraction of the weight
of a rudder system from a H14 and probably better all round.

How easy or hard this project is to complete in a short time span while not compromising on the final product will get down to well thought out building instructions. These can't be written up in detail until the design is finalised.

**********

Of course you can have them make the scarf but not glue it together yet.

Wouter, once the ply is tapered for the joint it is extremely prone to
damage even if it does not leave your workshop. There is no way I would ship it at this stage.
There are a number of different ways of tapering the ply for the scarf join.
However anyone not confident in any of these should just us a simple lap joint.

***************

I can't see the problem with a small amount of stressing the ply.
In fact, I would say it is highly desirable since it induces more stiffness to the
design than would otherwise be present plus it looks better!

Janali,
I agree with you on this. Apart from stronger and stiffer the hull will give the appearance of being fairer as well.
*****

Regards,
Phill

Just thought I'd look at the drag for the different hull shapes.

Hull1 is a conventinal

blade

design, hull2 is a moth planing bottom design similar to what Wouter and John are proposing, hull3 is a Gcat type Deep V design. All hulls are 12ft long and are displacing 120kg. The slimmer Gcat hull has the lowest drag, but there is not a great deal in it.

With regards to hull 2 this program does not predict planing so if the F12 will plane at higher speeds then there could still be a benifit in going that route.

Gareth

Gareth,

All my designs up till are made with panels that only bend in one direction. All the rest is optical illusion which I'm actually applying to make the hulls look nice !

See here :

Also my bottom panels are significantly more flat then those shown earlier in Johns picture. Afterall I'm trying to achieve some planing properties with this boat. This version has straight sides and a straight bow. The one with the wave-piercer bow is the same but with slightly inward canted sides. The amont of side canting needed for swept back bow is so small that we probably can get that by just twisting the ply inward at the bow.

Work is continuing.

John,

How or where do you see it ?

Gareth,

Can you alter the box hull shape in your drag simulation to have 25 degrees keel panel angle. Meaning each panel moves up from the keel line at 25 degrees ? That is a promising hullshape and it will resemble the red hull much closer in shape and I hope in drag so too. while still presenting a relatively flat keel that hopefully allows some planing. Not full planing but just a little amount so that 2 or 3 knots can be added to the top speed.

Thanks you all it really helps when other people do portions of the work.

Wouter

From the cheap seats.

I'd strongly suggest keeping with the wave piercing bow to give this boat as much a modern look (within homebuild reason) as possible,
or as Phill said,

It will look like a bicycle with training wheels

.
And also per Phill, if it's deemed an issue add a layer of glass