Piper Tri Pacer (oz15285)

About this Plan

Piper Tri Pacer. Radio control scale model. Wingspan 80 in.

Quote: "Free time? Try our free plan! This 80 inch span semi-scale classic light aircraft has been designed for .61 4-strokes and 4-function RC. Piper PA-99 Tri-Pacer, by Keith Humber.

The Piper Tripacer was a follow on design from the old faithful Piper Cub. Initially it was a tail dragger christened Piper Pacer. As trike undercarriages became more in vogue in the Fifties and early Sixties, the Pacer sprouted a nose-leg, hence the Tripacer. It certainly is a very attractive looking machine and ideal for modelling, or so I reasoned 27 years ago to be precise, in the days of Digi Three Propo RC. I designed and built the Tripacer in 1971 using 3+1 Propo radio and a Merco 61.

However, one fine sunny morning I was flying the Tripacer when an aileron failed to operate. Down wind, about a mile, was a fairly large fruit apple farm. Yes you have guessed - the Merco stopped and the model spiralled in - we heard the loud bang from our flying field. We went to retrieve the model with a certain amount of trepidation, and on our arrival we found the bits nicely laid out on the drive. It was well and truly broken. I said to a couple of my fellow club-mates, That's the end of the Tripacer. I duly left the remains in my loft stating that one day I might rebuild her as I couldn't bring myself to bin her.

Well, I was in my roof searching for another of my models earlier this year and I came across the Tripacer remains. It was then that I decided that I could rebuild her using a Laser .61 4-stroke instead of the old Merco, which would suit very well and sound better to boot. So after 27 years came the rebirth of the Tripacer 'Phoenix'.

The Construction: This is relatively simple, it just seems that there's rather a lot of it. The overall construction is of a conventional nature with no difficult areas. However, to make it a little easier for those of you who are thinking of building this model as a first time larger semi-scale model, I will try and assist with some more in-depth instructions.

No special tools are required, but it is advisable to have some PVA, 30-minute epoxy and Cyano glues. Cyano can be used in most areas, but additional strength may be needed in certain areas with the addition of PVA. Use epoxy to join the engine bearers, noseleg torsion bars and bulkhead pieces.

The Fuselage: This is built using two basic side-frames of 1/4 x 1/4 (6 mm sq) hard balsa built over the side elevations (remembering to build a left and right hand panel). These are framed up on 1/8 ply formers F1-F5. Firewall bulkhead, F3, will need to be cut-out to suit your engine's silencer and fuel tank types.

The rear fuselage is constructed using stringers of 3/8 x 3/16 balsa tapered towards the tail. The rear fuselage top is sheeted with 1/16 balsa on triangular 1/8" balsa formers (T1-T3). Internally, there are 1/16 sheet angle reinforcing strips at top/side and bottom/side edges to help stop the longerons from buckling under the covering strain.

A 1/4 (6 mm) balsa sheet tail saddle is fitted between the last 1/4 sq cross-member and the rear fin post. Each side will have a 1/8 (3 arm) balsa sheet infill to strengthen the rear end between the fin post and 1/4 sq uprights. This also acts as additional tailplane support..."

Update 12/5/2024: Added the missing sheet 4 of 4 now.

Supplementary file notes

Article pages, thanks to RFJ.

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