Model Boat Mayhem - Forum

Dry Dock / Shipyard: Builds & Questions => Yachts and Sail => Topic started by: knoby on March 29, 2013, 09:11:58 PM

Title: Rg 65 Racing Sparrow
Post by: knoby on March 29, 2013, 09:11:58 PM
I mainly race marbleheads, but last year built a couple of footys just for fun. Our club water gets quite low during the summer, so have now decided to build an RG 65 Sparrow so as I can sail all year. Although I do have a copy of the book, I have decided to do it a little different ( this could be my first mistake). The frames are cut from 4mm balsa, & the planks are 3mm balsa. I mounted the frames on an old Venetian blind slat, that I have spaced up in the middle 1/2 inch & the supported in-between to give a nice curve. I used the blind for 2 reasons, firstly it is varnished so the frames wont stick permanently to it & secondly, because it was what i had. The frames were glued on with a hot glue gun, checking them for squareness both on the centre line & vertically. when dry I taped all the frames, except 'B' & the transom, so as the planks wouldn't stick to them. I intend to remove all the frames once the hull is finished.I have started planking the hull, but will upload photos of that when its finished. I am fairly confident I can build this very light & strong, but time will tell. My only concern at the moment is how to make the fin & rudder. The profile of these is important to get the best hull speed & as of yet I haven't found a method I really like. Already looked at the commercially available ones, but they are around 100 for carbon ones & I don't want to pay that.
Please feel free to comment, criticise or add anything, I am not offended easily

Cheers Glenn

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Title: Re: Rg 65 Racing Sparrow
Post by: Terry on March 30, 2013, 11:43:19 AM
I remember reading a post on the Racing Sparrow forum, a guy had used Helicopter rotor blades for the fin and rudder, nice profile and made from carbon.

Title: Re: Rg 65 Racing Sparrow
Post by: knoby on April 16, 2013, 06:49:48 PM

Finished the planking, its not perfect, but I am happy for my first attempt at plank on frame. Sanded the hull before removing from the formers, leaving just the first one in to give the bows some strength.

In the end I used an aly centre for the keel. I glued a strip of hardwood to each edge of the aly, then clad the whole thing in 3mm balsa. This was sanded to reasonable profile once dry. The hardwood was useful to give a guide to how much to sand off.

The rudder was made from 2 pieces of 2mm ply. I used 3mm carbon tube for the rudder stock, into which i inserted some stainless steel wire. The carbon tube goes into the rudder about 70mm,leaving about 20mm of wire protruding. I bent the wire at an angle so as the tube would not turn inside the rudder. This was then super glued into position on one side if the rudder. I super glued another piece of carbon tube below this, in order to give me something to wrap the rudder skins around. The 2 rudder skins were then laid out flat on a piece of tape like a butterfly. Then applied epoxy, thickened up with microballons, & stuck the 2 pieces together, clamping them until dry. Once dry the rudder was sanded to profile.

The keel was tacked into place with superglue & then a keel box built around it. The top of the keel box is a plate that will take the sail servo & battery pack. This was all glued with resin & once dry a thinned coat of resin was applied all over the inside of the hull.

A hardwood strip was glued into place from the bow to the radio plate to give a strong mounting point for the mast, along with various cross braces to give some integral strength to the hull.