In this new addition to my home page, I am introducing my latest project in large scale model aircraft - a 100inch Raven.   This model is the latest addition to my stable of large scale model aircraft, as you may have already seen by browsing through my home page.

Specifications:

Wingspan            100 inches

Weight                 25lbs

Engine                  3W70B turning 24x10 Menz propellor with custom built mufflers

Construction         liteply/balsa fuselage/tail feathers, foam wings balsa covered

Finish                   Solartex covered - two-part epoxy paint

Accessories         custom built smoke system - gearpump using separate channel in both mufflers

Equipment           JR 388 using a separate channel for each elevator and for each aileron -

                           4231 servos for ailerons, 4721 servos for elevators, 605 for rudder, 517 for                              throttle

click on thumbnails to view larger picture

Flying

Initial flights  were done using a 24x8 Top Flite propellor with the engine using a mixture of 40:1.

With the engine running at 6,300 rpm, take off was perfect, no trim changes were found necessary and the model showed no vices at all.    The only comment was that the engine seemed to over rev a bit on the downhill and change tone considerably on the uphill.   Landings were perfect and the model can be slowed down appreciably with no tendency to drop a wing.  No aerobatics  except a roll were attempted on the first flights.

Other flights are planned using a 24x10 Menz propellor and 50:1 petrol mix.

Flying the Raven - update

Next flights were made with a 24x10 Menz propellor and a 50:1 petrol mix.  Performance did not improve, but the engine kept at a constant revs in normal flight.  The model was flown successfully in the Association's Annual event, and it was observed that when going inverted, the engine seemed to fourstroke and then pick up again in the upright position.  The engine was turning at 5,500rpm.

The photograph below shows the Raven  with Wendy Hostetler at the controls (Wayne Handley lent her the plane!) and with the inset in flight belching smoke from both its exhausts.

We went back to the workshop and tried to analyse the problem.  We fitted a trumpet to the carburretor and opened up the cowl to let more air in freely, but the engine kept fourstroking when inverted and took a long time to pick up from idel, whatever setting we made.

Finally we found out that the engine was not exhausting properly due to the rather small exhaust outlets and the silicone tubing attached to them.  A quick modification to the home made exhausts and Bingo! The engine is now very happy swinging the 24x10 prop at 6500rpm and getting more than 30lbs thrust!

I am looking forward to other flights.....