Puff (oz15177)

About this Plan

Puff. Free flight sport model for electric power.

Direct submission to Outerzone.

Update 19/3/2024: Added article, thanks to RFJ.

Quote: "One of she last models I designed in the early 1960's was a 60 in wingspan shoulder-wing sports power model using one of the - then - readily available German 2.5cc diesels. It was, for its time, a lightweight model built on the 'Stick and Tissue' principle using ideas that I had used for many years, hence its identity - Type 57 (Heinz 57!).

Today, some 35 years on, we are seeing the return of the free flight sports model aeroplane as we used to know it but using electric, CO2 and the new miniature diesel engines in place of the inevitable Dart, Merlin and dozens of others long out of production.

Puff: The basic design was reduced to a modest 26 in. The one main difference, however, was the use of really light balsa replacing the medium hard and hard strips used originally in order to save weight for the intended power unit, a direct drive German made R21 type 4.5 volt motor listed by Opitec in their catalogue. This motor is one of a range and weighs 1 oz, costs 85p plus VAT and can be fitted with an Elektro Star propeller of 130mm diameter at a cost of just 95p plus VAT - and it comes complete with a spinner! For power, Opitec have a 1.2v cell at £2.49 plus VAT of which three are required. As a matter of interest, this power unit is sold as part of their 'Bumble Bee' free flight electric powered 40 in span motor glider, the stated output of the R21 being 4,800rpm with the resulting 3.6v. Taking into consideration that the total cost with charger is about .g.20.00, Opitec have really entered the aeromodelling market with something to offer at reasonable prices.

Now to the model drawn and renamed Puff' because that is how it flies - almost out of power but then, it is electric and much slower than a similar model with, say, a new Mills .4 cc on board.

The basic fuselage is built flat using 1/8 sq strips to form the basic sides, the second being built on top of the first for accuracy and both left to set before separating and constructing the fuselage.

Bend the U/C from 18 swg wire and firmly fix to F2, also cutting out the remainder of the formers for assembly of the fuselage ensuring it is nice and square being such a small model. Cover the top of the front fuselage with 1/16 sheet also adding the 1/4 in x 1/16 sheet gussets where indicated and sanding down the 1/4 gusset flush with the outline of F2.

Mark the position of the wing space and cut away the planked portion, putting it to one side should it be required for wing fairings. Add all the 1/8 x 1/16 stringers and 1/16 sheeting at the underside of the space between F2 and the first upright and the space under the tailplane mounting and the fuselage is almost complete with just the tail skid to be added.

The cowling is built up from 1/8 soft sheet with the motor - in the original model an Opitec R21 - a push fit which, after initial flights, is cemented more securely. Any alternative electric motor can be used with, if required, an extra former or reinforcement can be fitted between Fl and F2.

The wing and tailplane are straightforward in construction but should be built with care using light grade balsa, adding all the 1/16" sheet gussets that give added strength.

Covering is a matter of choice but having used Jap tissue for all my free flight models, this is recommended owing to its ease of application and general lightness after doping using, of course, the lightest. grade. The colour is up to the builder but orange looks very nice with black trim. Two thin coats of dope should be applied thinned at least 50/50 for the fuselage and wings with one coat on the tailplane..."

Supplementary file notes

Article.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction