Airwaves

Model Airplane News, Jan 2002

Our readers write back

BACKYARD FLYER FAN

I've been out of RC for about 10 years, but recently, while visiting the local hobby shop, I saw a park flyer, bought it, and I'm hooked. I loved the premiere issue of Backyard Flyer, it will be framed and hung alongside my premiere issue of Classic Toy Trains. Look forward to your first quarterly issue. Thanks. [email]

AL THAGARD

BACKYARD FLYER AEROBAT

I really appreciated your review of the Great Planes Laser Mini 3D kit in Backyard Flyer. I ordered the model online the day I read the article! I wondered whether author Vic Bunze had had the opportunity to test his model with the Astro 010 he mentioned as a possible hop-up motor. I've already started building my kit and am looking forward to doing aerobatics in my front yard. Thanks for the new magazine; you've got my subscription!

[email]

JOHN SULLIVAN

John, I agree; a fullhouse electric model that's capable of 3D aerobatics but that isn't a carbon-rod stick plane is very appealing. I haven't yet swapped the Astro 010 into the Mini 3D because before I can do so, I need to make some structural modifications, such as changing the firewall position and the opening in it. I might also need to lengthen the landing gear to accommodate a larger prop. Also, remember that the battery cells need to be mounted side by side in a single row (not up) to fit in the compartment under the wing.

At the NEAT Fair earlier this month, I saw a Laser Mini 3D equipped with a Hacker B20 brushless geared motor, and it was an impressive combination. This model was equipped with longer carbon-fiber landing gear. The Laser Mini 3D is light and has enough wing area to easily support a heavier, more powerful motor. I hope this helps.

VIC BUNZE

RCV REVIEW

I read with great interest your report on the RCV 120-SP rotating cylinder-valve engine in the September 2001 issue of Model Airplane News. But you gave no hint of its performance compared with a conventional 120 4-stroke. In the absence of direct comparison, I felt that your article condemned the RCV with faint praise. Am I wrong?

Will the RCV 120-SP turning a 16.5x13 prop produce a flight performance that's similar to, say, a Magnum 120 turning a 15x8 prop? I noticed that the RCV produces 1.8hp at 5,800rpm. I do not know what horsepower the Magnum produces at 8,300rpm with the 15x8 prop.

The RCV is an interesting proposition if power outputs are comparable. Please advise. [email]

ROB HULL

Rob, I was impressed with many aspects of the RCV 120 and would not condemn it in any way. The reason I did not directly compare the engine with other 4-stroke engines of similar size is that it would be a case of apples and oranges. The real test is yet to come when I get a chance to power a model or two with the RCV engine and see how they perform. It would have been unfair to both our readers and the manufacturer to simply say that the RCV 120 is the best match of "Brand X" engine. When I do the inflight testing, I will report my findings. The RCV engine was able to turn a 17x13 APC prop at 5,550rpm, which is very close to its maximum horsepower rpm.

I can say that the engine is very easy to start and has almost instant throttle transition. It has a lot of torque and is built using very high-quality standards. GY

CUSTOM-CUT METAL

I noticed that several companies will now custom-cut wooden parts for modelers using laser technology. I have sent my CAD files out and in short order have received beautifully done wooden parts to build my models with. It is a great time we live in.

My question is: do you know of any companies that will laser-cut metal parts for modelers? I want to build a scale model, and several metal brackets need to be reproduced. Is it possible to have these parts cut out as well? The wood-cutting companies that I've dealt with say they cannot do it. Your help will be appreciated.

HAROLD YOUNG

SIDNEY, AUSTRALIA

Harold, the laser cutters that are used to cut balsa and plywood parts have a power output of between 15 and 30 watts. Much more power than that is required to cut metal, but owning such a powerful tool is not cost-effective for the average wood-cutting model company. An alternative to lasers is to use high-pressure waterspray cutting. As strange as it sounds, water cutting is just the thing for metal parts.

The technology is several years old and is used in industry to cut out many products, from disposable diapers to intricate leather pieces used in boot making. The water is first filtered and then sent to a super-high-pressure pump called an intensifier. The water is then routed to a cutting wand at more than 50,000psi pressure. In the end of the wand is an industrial diamond disc with a 0.002-diameter hole in it. The extremely fine spray of water from the wand does the cutting. Controlled by CAD/CAM computer programs, water cutters are capable of cutting very precise patterns through several layers of sheet metal.

The only water-cutting service for modelers that I am aware of is offered by Jamie Johnston of Arizona Model Aircrafters. There is a setup fee as well as a cutting charge, but once you have the first parts cut out, each cutting session thereafter is less expensive. Give Jamie a call at (480) 348-3733 or fax him at (480) 348-3773; www.arizonamodels.com.