Jupiter (oz2290)

About this Plan

Frog Jupiter. Free flight rubber sports model. The Jupiter was kitted by Frog between 1947-1950.

Quote: "Jupiter, the bringer of jollity. A Frog kit revisited using an updated plan. Built by David Deadman.

Vintage day at Old Warden is a great event in my calendar and I nearly always see a model that inspires me. Brian Downham (when he's not having a lunchtime doze) makes some lovely aeroplanes, but his Frog Jupiter always seemed rather special. With its low wing, 30's racer look, and seductive shape, it is a beauty. As soon as I saw it circulating the hallowed turf, I knew I had to have one, but I didn't pursue it till I spotted it in Mike Woodhouse's catalogue along with many other desirable plans Visiting Mike to pick up a plan, I took the opportunity to stock up with his special quality balsa (each sheet marked for weight and density), and some Esaki Jap tissue.

which he sells along with hundreds of hard to get items. The Jupiter was a 1947 Frog kit and Bob Jones has kindly re-drawn the plan and added the wood patterns we need, plus prop details - so there's no excuse for delay.

There's a lot of lumber in the fuselage, so you need nice light 1/8, 3/32 and 1/32 sheet and keep weight down as best you can. The fuselage is rectangular aft of the wing, but at the front the sheet sides are pinched in to fair with the scaleish nose shape. If you have used lightwood for your formers with vertical grain, they will bow as you pull the sides in. I modified my formers as shown, to include a horizontal square spacer at the bottom, which helped a lot.

Wing fixing is tongue-in-box, which is a good knock off feature. I opted for 1/64 ply each side of a 3/32 balsa tongue, well drilled to save weight.

Undercarriage legs are spruce, hinged at the back with rubber band springing working through tubes in the fuselage. It's all very practical, if a little heavy. The spats add a lot to the appearance, but I kept them thinner than drawn, to save weight and reduce drag. The wing is tapered in plan and section with rounded tips - all scale like features, which enhance the lines. The only change I made was to reduce the width of the LE, again with weight in mind.

This model calls for a 13 inch hand carved balsa prop, so I screwed up my courage and made one, but l didn't know how to hide the freewheel device in the spinner. My prop hub was too bulky and the balsa too weak to thin down. Fortunately, I still have a 'Paulina' prop given to me by the proprietor of Teddington Models, 35 years ago_ Beautifully carved from a wood that looks like Lime, it is very, very thin. Try as I might I just can't match the exquisite quality of this old prop.

The spinner in the Frog kit was plastic, which must have been an innovation in 1947. I chose the easy way out and made a balsa/ply laminated spinner 'turned up' in the drill and hollowed out. Brian made his in fibreglass..."

Quote: "FROG Jupiter, a 36in span low wing semi scale model of a sports aircraft with snappy flying qualities". This plan shows all fuselage formers, but only the root rib - no patterns for the other ribs."

Direct submission to Outerzone.

Update 12/10/2016: Added new wing layout drawing, thanks to RonaldL. Quote: "Finally found the time to resize the wing layout. It's not the most precise or advanced drawing but should be sufficient to build a wing from. At least it was for me. I would be most delighted to see someone else taking advantage of it. Ronald"

Update 25/05/2018: added article from Model Flyer June 2004, thanks to RFJ.

Supplementary file notes

Wing layout drawing, includes all ribs.
Article.

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