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Oct 22, 2017, 07:38 AM
Chuck Hunnewell
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Advice On 1:12 Scale RC Sailboat of a L F Herreshoff Stuart Knockabout-Design #53


In September 2017, I began constructing a 1:12 scale (28" LOA) hull replica of an L Francis Herreshoff design (#53) sailboat called a Stuart Knockabout. The original was built in 1933. in the late 1980's, replicas were built by Edy & Duff of Mattapoisett, MA with a design prepared under license from the Herreshoff foundation by Bill Harding of Marion, MA. Today, the Stuart Knockabouts are being built by Ballentine Boat Shop of Cataumet, MA.

However, instead of a semi-keel/centerboard with attached rudder which was used in the original design, my hull model will have a fin keel and fin rudder. The mast will be about 32" to 34" in height from the deck and the boom will be about 10" in length. The exterior beam is slightly less than 7". I have not selected the displacement weight, yet.

The 1:12 scale replica hull design was prepared for me by Ralph Perkins of New Mexico using the original design offsets in the Herreshoff design #53. The laser cut wood frames and other components (rudder and fin keel box) were made for me by MR AeroDesign of Quebec Province, Canada. The frame stations are 2" OC. The hull is planked with 1/8" thick x 1/4" wide Balsa planks the are glued with 5-minute epoxy.

I estimate" that I may have about 1.5 "and 2" clearance x 6" width x 8" length to install the RC system (receiver, 2 servos, battery power pack and armature for the jib and main sheets. The problem is that I have no idea what would be a suitable RC system package for such a small RC sailboat. This is where I need advice. I lack any expertise in RC systems layout. My only experience with RC sailboats is a Soling One Meter that i purchased this Fall and began sailing for the first time with the Marbleheaders of Spring Lake RC club.

FYI - Ralph is currently preparing plans for me for a 1:8 scale Stuart Knockabout (42" LOA) which will be about 10"+ in beam. The frames will be cut by MR AeroDesign. The wood frame stations will be 3" OC and it, too, will be balsa planked and epoxy-glued. I plan to start that RC model in CY-2018. I think that will have more space for the RC system, but right now, I need to solve how to desihn an RC system for my 28"-long hull.

Advice and suggestions would be most welcome.

Chuck Hunnewell,
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Oct 22, 2017, 08:13 AM
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At 1:12 should be about 1 kg (2.2 lbs), so look at R/C equipment used on RG65/DF65 size boats.
Oct 22, 2017, 08:38 PM
RB
Displacement for your Knockabout can be determined by floating the hull then adding weight until the hull floats on its waterline. First however mark the waterline for and aft. Once the boat is weighted and floats on its lines, then weigh the whole thing and go from there. Keep an accurate tabulation of the weight of the hull as construction progresses. As an estimate assume 250 gr for a complete rig, 100 gr for fin and rudder, 200 - 250 for electronics, 100 gr for batteries, then the difference is the weight for the bulb. As a check for all this, compare to a known model of similiar size - ie Victoria.


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