Airwaves

Model Airplane News, Jul 2000

Our readers write back

DUCTED-PAN JET FAN

George Leu's article on jets was a welcome sight! As one who returned to aircraft modeling two years ago (after a 20-year hiatus), I was astounded to discover that the little 1/2A-size Berkeley ducted-fan jets (really just noisy gliders, not effectively propelled models) of the late '50s and early '60s had grown up!

I did note one piece of misinformation, however. The new K&B ducted-fan engine is not a .48, as is widely thought, but a .45. The model number is 4825, and the crankcase does have much in common with K&B's new .48 sport engine, but with a bore of .850 inch and a stroke of .800 inch, it displaces just over .45ci, not .48ci.

Also, with the exception of those from O.S. and K&B, ducted-fan engines can be frustrating for beginners to find. It should be pointed out that the Rossi .53 shown in the article can be found at Czechmate Distributing, the MWS folks (www.mws.com). Rossi's former distributor, Sig, now handles Irvine, which also offers a .46 ducted-fan engine that has very small external dimensions. Dubb Jett (www.jettengineering.com) has two fan engines available as well.

George could also inform prospective jet jocks of "The List" for jet modelers. Hosted by Bob Parks, this is an electronic forum for beginners and experienced jet fliers and builders. Email rc-jets-on@lists.kidsource.com, type "subscribe" in the subject header, and you're in! Again, thanks for a fine article!

GEOFF SANDERS

Portland, OR

ANTENNA QUESTION

The article, "How to Custom-Fit your Cowl" in the March 2000 issue couldn't have come at a better time. I'm building a Lanier Stinger .60 and have been dreading figuring out how to cut the holes in the cowl. When I read the article, it made my day; now I can't wait to get to that part of the assembly.

One question: I've noticed in most of the photos you use that the antennae rarely hang out of the planes. I've only been back in the hobby for a few years, and it has been awhile since I've done any building; is it safe to keep the antenna inside the fuselage? Thanks for your help.

CRAIG BUCKLIN

Oxnard, CA

Craig thanks for the kind words. To answer your question on antenna placement: in most cases, mounting your antenna within the fuselage is fine, if you keep it away from any servo and battery leads. This can be difficult to do if you have servos in the tail, and you run long extension leads back to them; the antenna can pick up electrical interference from these leads and shorten your range and/or cause erratic servo action.

Also, if you use the new Ultracote Supreme covering material (with aluminum pigment backing), you should not install an internal antenna, as the aluminum will effectively shield the antenna and cause a much-reduced radio range. Whichever way you install your antenna lead, do a static range check with the engine running to be certain of your radio's operation.

SMELLY STUFF

I enjoyed John Tanzer's article in the May 2000 issue on the use of nitrate dope to attach light fiberglass cloth. Nitrate adheres better than butyrate and is a logical choice. After many decades of modeling, however, I found the odor of these products to be objectionable. There are now water-based, polyurethane products on the market that do a good job of making lightweight fiberglass, silk, Polyspan, etc., stick to balsa. I have also tried a water-based acrylic, but it didn't have as strong a grip as the polyurethane in my test. Either of these will do fine as a substitute for "dope" in filling Polyspan, etc., on open structures. Shrinkage does not seem to be a problem. For those who need to avoid the odor of dope to get along with spouses, neighbors, etc., it's worth a try!

A friend of mine who was a traveling salesman used to carry modeling materials with him on trips and use them at night wherever he was staying. One night, there was a knock on the door; the local police had been called to arrest the "dope fiend" who had been reported to the manager by concerned neighbors. Seems the smell had been carried by the ventilation system to all the rooms in the motel!

BILL BAKER

Norman, OK

Bill, thanks for the information and the amusing story. Yes; the new water-based paint and finishing products available at hardware and home improvement stores are welcome additions to the modeler's workbench. 1 have also tried Minwax's polyacrylic floor finish to attach fiberglass cloth to balsa; it's an excellent substitute for smelly polyester resin. Besides being almost odor-free, nearly all of these water-based finishing agents are better far our environment than the paints and thinners we've traditionally used. I guess you could call it a win/win situation.

LASER-CUT PARTS

I've heard a lot about the new laser-cutting technology, and until now, I thought it was just for kit manufacturers. A friend told me that the price of laser-cutting has dropped to a level where almost anyone can get parts cut for any plan he might want to build from. Is this true? What's involved? Any help would be appreciated.