Air waves

I enjoyed reading your articles about Zenoah engines and the "Gas Engine Guide" in the May 2002 issue. I have an older Zenoah G-38, and my prop keeps spinning off, even though I tighten it securely. What's wrong? The engine sat for a few years, and now it always sounds as if it is running out of gas. Is the gas tank wrong, or does the carburetor need a rebuild?

JIM HALPIN Milton, DE

Jim; with the few details you supply, it's difficult to know exactly what is wrong, but I'll tackle some of the basics for you. Be sure to use the large prop washer that comes with the engine. If you just tighten the bolt head against the prop, it might come loose while the engine is running. Also, be sure to use an attachment bolt that is long enough to secure the prop properly; the bolt should thread into the hub for at least an inch. You must also balance your prop. If it isn't balanced, it can cause enough vibration to loosen even the tightest bolts.

Your engine should not sound as if it's struggling to get gasoline. If it does, it might be tuned too lean. You shouldn't have to rebuild the carb if it is pumping fuel properly and your engine starts without difficulty. The high- or low-end needle valve has probably been set too lean. Close both of them completely, and then open them 1114 turns out (turning counterclockwise) and run your engine. This will be a good place to start. See the "Gasoline Engine Guide' in the May 2002 issue for details on proper carb tuning. Also make sure that your fuel lines and gas tank are clean and equipped with gasoline-compatible hardware and tubing. GY

FUEL QUESTION

I read Dave Gierke's article on break-in and decided to use his method to break in my Rossi 23840 2-stroke. Our hobby shop sells two popular fuels, but their labels don't indicate their oil content. One has all-synthetic oil, and the other is a synthetic/castor blend. Could I assume 18 percent oil and add enough castor to bring it up to 20 percent? [email]

FLOYD MAIDMENT

Floyd, you could add castor oil to these fuels, but how much? Why "assume" anything? Switch to a fuel whose manufacturer divulges its lubricant percentages. Red Max, Wildcat and Sig list their fuels' ingredients and percentages on their labels. Why take the chance of running too little lubricating oil in your new engine? Dave Gierke

MORE 3D AEROBATICS!

Wow! I'm not sure I could ever pull off the "roller-coaster" [Quique Somenzini's freestyle maneuver described in the April 2003 issue], but I am in awe of his incredible aerobatics skills, and I really enjoyed reading his article. I'm looking forward to his articles on freestyle techniques; I want to pick up a few pointers so I'll be able to show up my buddies at the flying field! [email]

ART DERRY

Thanks for letting us know how much you enjoyed Quique's article, Art. More high-end aerobatics articles are in the works; stay tuned! (And what makes you think your "buddies" didn't read Quique's article, too!) DS

PAINT PREP

You guys must know of all the great products that are on the market, so I hope you can help me. Other than a fiberglass cloth and polyester resin finish, which covering material would you recommend to cover a model that I would like to paint? [email]

ED SROKA

Hi, Ed. There are several alternatives to a fiberglass and polyester resin finish. The first that comes to mind is a fiberglass and epoxy resin finish. There are several brands, and I've used Pacer Technology's Finishing Resin. It is very easy to apply and to sand, and it's available at most hobby shops. Alternatively, you could use a water-based polyurethane varnish in place of the resin. Products used to refinish wood floors, e.g., Minwax and Red Devil, are very easy to apply; just position the glass cloth and brush the varnish on. It does take a little longer to dry, but it doesn't have that offensive odor.

If you want to avoid using fiberglass cloth altogether, consider F&M Enterprises' Stits Lite finishing system. A heat-shrinkable cloth and adhesive covers the model, and then a specially formulated primer and paint produce the final finish (F&M Enterprises [817] 279-8045; stits.com).

Though not as durable as the other techniques, you can also paint over Mylar film coverings such as MonoKote and Ultracote.

Just clean the surface thoroughly, lightly scuff it with fine steel wool, wipe it with a tack cloth, and then use a fuelproof spray paint. Let the paint dry for several days before you mask it off for trim colors. Hope this helps. GY 4