F200 – An introduction to Indoor Free Flight

This class is an excellent introduction to indoor rubber free flight. It uses the Ikara Butterfly prop, prop hanger and rear hook, easily obtainable from Flitehook and Sams, and also from members of the indoor free flight group if you ask nicely.

To build the model you need some wallpaper insulation foam. You don’t need much as the basis of the model is a piece 200 mm by 100mm, hence F200.The rules state that the wing, tailplane and fin must be cut from a piece that size, the maximum length of the model 200mm and the maximum motor length measured from prop.hook to rear motor hook is 100mm. You also need to use a Butterfly prop. Don’t bother to flatten the foam as it will be curved when it comes off the roll, but use the natural curve to form the airfoil section. Cut your 200 by 100 blank so that the 200 is straight across the roll and the 100 is on the curve, cut out the bits as shown.

Glue the foam together with Uhu Por, or some fast grab PVA. If you use the latter, use a bit of low tack masking tape to hold the joints until dry. The trickiest bit is forming the dihedral. What you need to do is to cut an arc in the wing centre section and then glue the tip on. Don’t try to sand it as you would a balsa wing, the foam tends to crumble. If you see me I’ll give you a card jig to do it, but the foam is so cheap that you can experiment yourself. The dihedral is 30 mm under each tip, but it’s not really critical, a bit more or less is all right.

The balsa bits should be made from some medium/hard balsa. If you are an RC flyer you will think that this is really soft. I mean about 7 or 8 lb/ cubic foot balsa. (a sheet of 1/32 x 3” will weigh 7 gms, 1/16 will weigh 14 gms, and 1/8 will weigh 28gms.) You can use lighter if you have it and it is stiff enough.

Make the fuselage/motor stick first, the fin and wing posts fit on the port side. Glue wing posts to the left of centre rib first and let them dry. You can use any glue for this, normal balsa cement works well. Make a paper tube by tightly rolling a strip of tissue
or light copy paper round a piece of waxed 1/16 square, unroll it and apply glue and wind it up again and hold it until it starts to dry, the push it off. You might have practice a bit, use balsa cement for this. The tube needs to be tight enough to hold the wing post. When you have your tube push it over the rear post and glue the front post and the tube to the fuselage, glue on the rear hook and the prop hanger. The prop just pushes in. You can glue on the wing now but don’t use balsa cement or cyano, uhu is fine, don’t forget the strengthers, they really help. Glue on the tailplane and the fin, use uhu again.

Hopefully by now you’ve got a recognisable model, all you need is to come along to one of our sessions. They are held at the Scout Hall / gymnasium attached to Bradway Primary School (formerly Sir Harold Jackson Primary School) Bradway Drive, Sheffield S17 4PD. The sessions are held from 2 pm to 5pm on the first Saturday of the month.

You can download the plan for the F200 here.

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