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An R2AK design

Posted: Tue Oct 17, 2017 7:43 am
by D.Wilkins ... cing-sail/

A fast 27' aluminum design in the works for amateur builders. She could also be built in sheet plywood and epoxy. I'd love your feedback.

Re: An R2AK design

Posted: Mon Oct 23, 2017 11:00 am
by D.Wilkins
Although not as safe, I have changed the companionway/interior access for Buck to a more conventional sliding hatch. Also I have shown the framing, hull stringers, pipe berths and head. That olive green tank is for ballast water. ... cing-sail/

Re: An R2AK design

Posted: Mon Oct 23, 2017 11:32 am
by satchel
Very cool design. I like the simplicity of the hull form from a building standpoint. That masthead kite and huge bowsprit would be pretty fun downwind! I sailed R2AK 2016 on about the most similar boat to Buck that currently exists, an Express 27. The express is 150 lbs heavier than Buck but has 1100 lbs in the keel. The upwind sail area looks similar. Is there ballast in your lee boards? Even on the express we had to have crew weight on the rail more than was comfortable when going upwind in 15+ kts. Additionally, looking at the profile it seems like the center of lateral resistance is significantly aft of the center of lift of the sails, but I could be mistaken.

I like the sliding seat rowing stations but I think the future of human propulsion is pedal drive. Especially if you are designing a boat from scratch, pedal drive is much more effective and comfortable over long periods of time.

I'm glad that there are professional NA's working on designs for R2AK, very cool!

Re: An R2AK design

Posted: Mon Oct 23, 2017 2:20 pm
by D.Wilkins

Thanks for your interest and approval of this design.

Think of Buck as a big dinghy. I started the concept with maximum highway trailer width (8.5'). I bent some fast lines around that and enough sail area for light air and she ended up at 27'. I think the E-27 is a bit less beam. One should be quick to reef Buck. Although standing at the mast in the cockpit makes reefing a whole lot less work.
Her sail plan is quite low and this keeps her CE low helping with stability. I had a version of her with seated hiking racks and ditched them out of simplicity, and were replaced with lifelines.
Your question about lead ("leed") refers to the CE's relationship the the CLR. All monohull sail plans have the CE ahead of the CLR. The amount varies per hull shape, sail plan, etc. This is to counteract the pulling force (twisting moment) the sail has over the hull drag. Keeping in mind that the hull heels and is relatively placed a varying degrees/distance to windward of the sail.
In short Buck is a bit tender and she is shown with more or less normal lead.
Her rig may be stepped fore or aft, or raked, and her chainplates (although not shown) will allow varying positions. All tweaked post shakedown. You raise a good question as Buck is not a typical shape.
Yes, the leeboards will need a bit of lead (metal) in insure they drop with ease.
You are not the first one to sell me on pedal drives. I had started a catamaran R2AK design last year around a retractable, composite propeller pedal shaft. That idea is not dead!

Re: An R2AK design

Posted: Thu Nov 16, 2017 3:29 pm
by satchel
Hearing your methodology makes me understand the design better. I can definitely envision a plywood version built cheaply and competitive for a low budget team that wants to build their own boat!
I look forward to the catamaran design!