Subject: [harryproa] Off group. Ply trailerable cruiser [5 Attachments]
From: Rob Denney
Date: 1/26/2013, 9:48 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 
[Attachment(s) from Rob Denney included below]

G'day,

Preliminary, very rough drawings attached for discussion.   Comments and explanations after your requirements.

On Wed, Jan 23, 2013 at 10:28 PM, dproasit <knic0014@bigpond.net.au> wrote:

The Job

- Generally semi sheltered waters with ability to handle short coastal hops from creek to creek on a good day.

Easily 

- "Race" at/or capable of 10 kn but ideally cruise around 5-6kn.

Can alter size and type of rig to achieve this.   I have scaled down a "normal" rig, but it can be whatever you want.

- Handle reasonable bar crossings.

Rudders are liftable and kick up in a grounding, without damage.  Long lee hull will help a lot, as will low windage rig and the motor not at the end of a hull.

- Sail in shallow water.

Ww hull draws ~300mm with 1,000 kgs load, which is way more than it should have.   

- Easy, low stress to sail.

Very, as drawn,maybe even easier with a different rig. 

- Self steering ability.

Schooner rig and liftable rudders should make this easy.

- Use as a camper trailer when travelling to and fro.

Yes, although a little clambering to get on and off.   Maybe a ladder for the ww side of the ww hull.

- Trailerable unit dimensions 7'ish m x 2.1m x 1.5'ish m.

See drawings.  It grew a bit as I was drawing it, but can reduce the hull lengths easily enough.  To get it 1.5 high instead of 1.9 would mean making the ww hull a pop top.  This is possible, but adds weight, complexity and leaks for a not very large gain.   Your call.

- Wheel track of 1.7m.

Sits on a flat bed trailer, so no problem.  Maybe it could sit between the wheels (easier launching, lower loaded height) if max width could be extended. 

- Quick, easy and cheap to build and maintain.

Could not be much easier, with ply.   No compound curves, few angled joins.  Glue and clamp stringers to ply edges, assemble, use the shape for the next piece of ply, etc.   Internal join of the deck filletted and the outer edge rounded to make it look smother.

- Fold "on" water.

The scissors join will allow this very easily.  The hinges on the hull, mid beam (not shown, yet) and masts will be very easy, and an overlap (also not shown) on one end will ensure it locks and will be very strong.  Adding these may alter the overall width, but won't affect the folded width.

- Ply, fibreglass and epoxy.

No sweat. 

- Biiiiiig berth, 2.1m x 1.5m. with plenty sitting head room.

Yes, although the height and width taper. 

- Stand up galley with chart/comms.

Yes.  Non bed end of the hull is available for this, as is the area under the seat.  Access into the hull will require removing a section of the seat, which is a bit of a nuisance.  Other option is through hatches in the cabin top (not shown).  These will be there for light and ventilation, but will mean stepping onto the bed.  Or use the one in the non bed end.  

- Fast set up at launch < 1/2 hour. 20 mins would be good.

Slide it off the trailer (large roller on the back edge of the trailer, lift the bow of the boat and push), open the scissors, which will tension the tramp, insert the masts (can be done on the trailer) and rudder boards, hoist the sails and off you go.   

- Outboard that can stay "in place".

Mounted on a bracket attached to the rudder case.  Only remove it for long distance traillering.

- Rudders that don't need to "demount" or are really simple to install

Yes.  Can also be removed easily if required by removing a single pin and sliding the whole assembly out of it's socket in the hull. 

- Beachable and dry out and get on and off easy.

Beachability will depend on ply thickness on the bottom, you might want to consider short shallow keels for rocky beaches, although fenders or planks can also be used.  Lee hull is 900mm high so easy enough to get on and off.   

- Able to motor up narrows folded/partially.

Can motor completely folded 

- Keep out the mossies.

 Screens on the hatches.

- Produce beer, red wine, cook and provide entertainment.

Your department! 

Some random thoughts

* WW hull does not need to be symetrical for and aft, cabins/cockpit?
* Offset timber masts in tabernacle to lay above LW hull deck?

I have drawn it with the booms and sails permanently attached to stub masts.  The masts are then gin poled into position.  Would be very little extra work, but a fair bit of weight to make the tabernacle above the boom and leave the masts on as well.  Can play with this as the design evolves. I think it is easier (and cheaper and lighter) to build a carbon mast than a wooden one.  

* Tabernacle would need to be forward of beam/deck.
* Foam bows could Hinge horizontaly but would be limited to 2.1m minus LW hull width?

yes, although removing them would "only" involve removing the hinge pins. 

* Bows could hinge vertically but possibly foul mast tabernacle?

Not enough room to rotate them through 180 degrees unless we make it longer. 

* Bows could slot in and remove to store between hulls, is there room?

Yes, but not necessary at this stage, although for long trips, maybe remove them and store them in the ww hull. 

* Some slatted deck would be good for when travelling and anchor work?

Much better than a trampoline, but need to remove it when the boat is folded, which is messy  Could include a solid floor (extension of bunks bases and the seat floor)  the width of the lee hull if required.  

* Balanced Lug Sails, 2 lines low stress, easily handled?

Optional, but less easy to use as they get bigger.   

* Cockpit in Hull, probably prefer not, but space may dictate  

* Poptop running from galley over cockpit and section of berth?

* Anti-vortex panels for leeway resistance,less rudder area needed?
http://www.ikarus342000.com/Antivortexp.pdf

Rudder area is good for slow speed steering, but easy enough to experiment. 


* How do we get to sail in shallow water with regards to rudders?

They can be lifted to draw as much as the ww hull.  With the rig to help, they should be able to go upwind in as little as 300 mm of water, with acceptable leeway.  Other courses, no problem.

* What about leeboard?

Lots of hassle, and unnecessary with the rudders 

* Deck clearance does not need to be great, just enough to clear LW hull when folded. Don't have to absail out of bunk or use winch to climb in?

1100mm off the floor.  Easily add some steps if required 

* How do we fold it?

Pull 2 pins, or undo 2 lashings and pull on the tramp and it will scissor.  Unfolding will take a bit more effort,  probably a block and tackle on the overlapping part of the beams. 


All thoughts, comments and solutions gratefully accepted but don't expect me to like them all. - Frinstance "Tell'im that ees dreamin"

Ditto. 


Now we need to get this sorted pretty quick because I've only got a house to finish rennovating, a new house and shed to build, a few k of fencing to do, calves, lambs and kids to mark, chooks and pigs to butcher, fires, floods and droughts to fight, fruit to pick and trees to plant.

So, wer'e lookin at the end of the year.

If you boatbuild at the same rate as you will need to work to get that lot done by the end of the year, you will be sailing by the middle of  next year.

regards,

rob


Thanks All - Darrell


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