Puma 305

The Puma 305 came about by the fact that my previous own designs had not performed well and I needed something new. I had built a Jif 2 / Puma over the Christmas break which sailed well. Would a Footy version be as good? Arranging the formers at 30mm spacing instead of the RG65 65mm suggested it would be broad in the beam but not unattractive. I decided to reduce the deck level by 10mm and with the Videlo Trophy as a target for its first race started building.

Completed the Friday before the Videlo on Sunday. A brief trial in the local canal suggested that the 305mm Puma was a great improvement on my previous boats but how would it do against competition.
First race at the Videlo Trophy it came second – much to my surprise. It was clearly fast, accelerated well, resisted diving, and tacked well. Final result was 5th, beating several ICEs. Could have been placed higher but for a few mistakes by the skipper.

So if you fancy something a bit different, try making a footy version of a RG65. Many of the RG plans give formers at 65mm spacing. It is a simple operation to space these at 30mm for a Footy version. There are hundreds of RG 65 plans free on the web.

If you want to see what a Footy version of an RG65 looks like take a ‘snapshot’ of the hull from a .pdf version of the plan and ‘paste’ it into a Word document. You can then alter the aspect ratio. A Footy is only 47% of an RG65.

Here’s how I built my 305mm version of the RG65 Jif 2 / Puma

The sketch shows the key components.

The Jif 2 / Puma plans are available for free download on http://rg65.free.fr/.
The formers I used are in the Jif 2 Puma folder titled Cuadernas Tres.pdf. I used them as drawn i.e. not reducing them by the thickness of the planking.

The formers were set 30mm apart (instead of 65mm for the RG65 version) and planked with 1/16 sheet.  The deck line was lowered by 10mm and a short bulkhead added to the bottom of former one to finish the lower bow planks on. The lower bow being carved from balsa block, as is the bow. (replacing the rounded RG 65 bumper with a point). There are many articles on planking hulls. Having the formers spaced at 30mm makes it comparably easy. The planks do not have to fit perfectly; small gaps will be filled with the resin / glass cloth on covering.
 
After extensive sanding the hull was finished with a covering of 6oz glass cloth and finishing resin. A few strips of glass cloth were positioned inside together with reinforcement of the area where the fin passes through and the inside given a thin coat of resin.

The fin is made up from laminations of 3/32 by 3/8 spruce and 2mm by 1.5 mm carbon fibre rod. Carefully clamped together dry and then low viscosity super glue applied to the join lines and the assembly left overnight. The surplus glue is then sanded off and the leading edge rounded and the trailing edge sanded to a fine edge.

 The aluminium mast tube is sewn and epoxied to a 9mm extension in front of the fin. A 5 mm length of 4mm aluminium rod is epoxied and crimped into the bottom of the tube.

The fin is slightly wider than the scaled RG 65 width. The trailing edge was set at the former 6 position which put the leading edge slightly ahead of the former 5 position. The fin angle was set by eye at right angles to a line midway between the deck line and the expected waterline. A 1/8 balsa cross brace was fitted to hold the fin in position prior to fitting the deck.

Deck is a 1/16th balsa pre covered with layer of 6 oz cloth and glued to the hull with finishing resin and when set trimmed to the edge of the hull. Prior to fixing to the hull 2mm x 1.5mm carbon fibre rods are glued across the underside of the deck each side of the radio cassette opening and a 1/8 balsa reinforcing piece for the sail sheet deck loop fixing.

The bulb was cast in a short length 18mm inner diameter of aluminium tube and the ends filed to shape with a Surform. Shaping was stopped when the weight reached 8 oz / 227 gm. I always fit the bulb to the fin last of all, adjusting its position and the length of the fin to get all the deck fittings etc. inside the measuring box.

Rudder is 1/16th ply with a 16 swg piano wire inside a brass tube pivot rod inset at the top. The slot where the wire is fitted is covered both sides with 1/32th ply and the whole thing given a layer of epoxy resin. The rudder bearing is a brass tube epoxied to the transom.

Radio installation is in the form of a cassette. My standard cassette uses two ‘Component Shop’ 9gm servos. The sail arm servo has resistors added to the end of its feedback pot to increase it’s throw to almost 180 degrees. 2mm x 1.5mm carbon fibre rods are glued across the underside of the deck each side of the radio cassette opening

Sails are standard Stollery balanced rig with plastic bag sails.

Final weight of my version was 417gms (with the biggest sail) with a keel weight of 227 gm.

I had to round the top of the bow to fit the measurement box. It may be better to space the planking formers at 29.5mm to give a bit more allowance for the bow block.

Paul Risdale