Savoia S13 (oz2770)

About this Plan

Savoia S13. Peanut scale model of the Italian Schneider trophy racer. A biplane pusher seaplane design.

Quote: "A super Peanut scale model by Lubomir Koutny of the Italian winner of the 1919 Schneider Trophy.

Don't be put off by thinking that a flying-boat biplane pusher will not perform well. The S13 has the right proportions for an excellent flier, and it will do just that providing you take notice of my trimming instructions.

Building: Light weight is the key to good performance and it's worth repeating. Use light high quality balsa, use a light glue as sparingly as possible (I thin down PVA) and get the lightest tissue you can find. If you haven't got any one of these - buy it or think about building something else.

The wings are built with sliced ribs. All dimensions are on the plan. Please use a slightly stronger wood for the ribs which are attached to the struts or reinforce them with an extra strip. The fuselage sides are built over the plan and then made into the basic box. After fitting the nose block and the centre longeron it is covered with 0.5mm balsa. The tailplane and fin are made with separate rudder and elevator. This is both realistic and useful for trimming. The floats can either be made from 0.6mm sheet balsa or from suitable foam. The nacelle is a balsa box with provision for the motor stick.

Take particular care over the propeller. The four blades are made from 1.5mm balsa shaped using a hot iron. The spinner houses four paper tubes into which the bamboo dowels are glued. Make up a jig to ensure the blades are set in the hub accurately. (See pages 52 & 53 of the March 94 issue for more detail of this method of making scale props.) Don't forget to make a 'Czech hook' for the rubber on the prop shaft.

To cover the model you can use Jap tissue in the right colour or condenser paper and spray with Humbrol enamel. I used the latter. For most of the covering I use PVA with three parts water. I only use full strength at the strut attachment points. Using my home made spray equipment (an old fridge compressor) I mixed the Humbrol with nitro-cellulose colour at 1:1 and then acetone thinners. Most of these Italian racers were either red or red and white. This S13 was red on the top and sides and white on the bottom with roundels only on the bottom of the lower wing. The detail I have used is that of the winning plane but the one used by Janello for an acrobatic demonstration shortly after the race is slightly different. I have a photo of the actual winning plane which varies from some of the three-views I have seen.

To assemble the model you must use jigs. Glue the central struts to the fuselage and those to the top wing. Carefully glue in place the nacelle and double check with the plan position. Position both wings with a jig and glue in place with the remaining struts.

Complete the rigging with fishing trace or dacron. Glue on the floats, their struts, the tailplane and fin. Finally check that everything is as it should be. Make up the motor from Tan II. My model is 8 gm and needs 350 mm of 2.5 x 1.1 but it depends on the weight of the model and the pitch of the prop.

Trimming: Double check all the rigging angles again. The CG must be at 40% of the top wing. This is peculiar to this sort of layout where the thrust line is well above the centre of drag and produces a down moment. The model glides very slowly but you still need the traditional soft grass and no wind. Adjust the glide with the elevator. When this is OK try about 600 turns on the motor. With this power it should fly level and in a left hand circle about 6-10mtrs dia. Use the rudder to get the turn correct. Start increasing the turns and adjust as necessary. Be careful if it tends to straighten out and go right as it can then spiral in. Give more left rudder or shorten the motor stick by 5mm because with this model a forward CG will tend to make it spiral right. If the left turn is tight you can warp up the TE of the top right wing a little.

My model won the ELSE CUP for seaplanes in Pardubice 1995 and it was the Open Competition winner too when it flew 53 and 59 secs. It would be good for electric or CO2 as well although it would need to be a bit stronger and perhaps larger. Stephan Gasparin liked it very much and intends to build it for one of his small motors. I wish you good flying, and have fun."

Update 18/8/2023: Added vector format plan, thanks to DavyJones. This was posted by RamJet64 on the HPA site at: https://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=12404.

Quote: "Savoia S13. Schneider Trophy Racer. Peanut Model. Designed by L Koutny Brno. Digital: Dai Buckley 2021."

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