If Gale’s numbers are twice as high as they appear by the stamped hp, do we have to divide Guy’s answers in hp by 2? Or, is there something missing in Guy’s letter or is it me?

Please enlighten me. I sure would appreciate it. - Marvin Babcock, Parsons, Kansas

A.  Dear Marvin - You’re not crazy and there’s nothing wrong with your math computations. The problem comes with listing a 65 hp Continental as having 250 cc of displacement and turning at 2700 rpm. In reality, a 65 Continental has 171 cc of displacement and is rated at 2350 rpm. So, if you put those numbers in the equation, you get a more realistic answer of 76 hp:

171 x 2350 / 5252 = 76 hp

Better yet, using a more realistic cruise rpm of 2100 gives the hp at 68:

171 x 2100/ 5252 = 68 hp

I’m not sure where Mr. Schmidt was obtaining his figures for the 65 Continental. - M.J.

Q.  Dear Mary - I notice that our editor never seems to be shown flying her plane. This seems like the unseen neighbor’s face on the TV show "Home Improvement"?

On a more serious note, who out there in experimental land has flown a diesel-powered, Rotax-powered two-cycle diesel? Model airplanes fly better on diesel - cooler exhaust - larger props - more reliable? Why not a Rotax 277 diesel conversion?

Yours truly - Eric M. Peterson, Falmouth, Massachusetts

A.  Dear Eric - Help, I don’t want to be the "unseen neighbor"! His life seems a little dull! The reasons you don’t see my face flying my plane are twofold: One, I don’t own an airplane - yet! And, two, there are better things to put pictures of in the magazine!

I have had the opportunity to fly in most of today’s popular ultralight-type models on a number of occasions, including a really eye-opening ride in an Air Creation trike at Oshkosh ‘95. Wow, what a fun machine!

Don’t know whether anyone has fooled around with diesel power for a Rotax, but let’s ask the question and see what response we get. - M.J.

Q.  Dear Mr. Bronson - With your name and address posted in the EXPERIMENTER, I am sure that your mail box will soon be overloaded. I would really appreciate your opinion on a couple of things concerning VW engines. Sold my Starduster Too in 1984 and retired to Arizona. It didn’t work out; too hot for Dorothy and myself. Six years later we were back in beautiful Montana. While in Arizona, I raced dune buggies around the desert and learned how wonderful those little air-cooled engines are. Only back in Montana after a few months, the old building bug bit me again. I picked up a project that was about 50% completed; it was an Aero Sport Scamp. I completed it, and then built up an 1835 cc VW using all new components. It so happened that I had a Hegy 54 x 30 prop to start out with. It did not work out at all, so I ordered a 58-inch two-bladed Warp Drive. With it, set at 8 degrees, it takes off at 3000 rpm fairly well, cruises at 2900 rpm, indicating around 80 mph. In your opinion what size wood prop would give me that same performance, also should I use a higher rpm. I have heard that the Warp Drive prop is breaking VW cranks. I would like to switch to wood until I hear more on that rumor.

Number two problem was ice in the induction crossover tube. I cured that by welding a length of pipe split down the middle to the crossover pipe and then fitted the engine oil line to it and then on to the filter. It worked great and gained a bit of power on take off. Evidently the induction tubes were full of ice crystals. My worry now is, how much heat is too much? What would your opinion be on that?

Only had a chance to fly it for an hour and then winter set in. However, in that hour it did tell me the oil heat to the induction pipe was the answer. Also, have a 12-inch heat muff on the exhaust system, but it would not take care of the problem by itself. When I pull it on now, I get a drop in rpm, which I never did before in the 54 hours of flight that I have on it.

Laurel Airport is 3500 feet above sea level. The Scamp weighs 560 pounds empty. - Richard F. Chapple, Laurel, Montana

A.  Dear Richard - Thanks for your letter. I’ll discuss propellers first. I just replaced my 54 x 24 Marlo wooden prop with a 54 inch tapered blade from Warp and an ultralight hub. Doing the "trig" told me that 54 x 24 gives an 8¡ pitch angle. At this setting my engine would only turn 2400 rpm, so I had to reduce the angle to 6-1/2¡ to get my 3000 rpm take off value. I have not yet flown it due to weather, but have made the following assumptions:

1. The Warp Drive must be much better at coupling to the air given the great reduction in rpm.

2. There was an almost total absence of prop noise with the Warp prop, which leads me to believe the gain is due to lack of cavitation or stall along the imperfect curves of typical wooden props. The Warp prop is perfectly formed.

3. Everyone I know who uses the Warp prop has higher speed, which doesn’t seem to jive with the reduced pitch settings used. Warp explains this as "constant speed prop" type dynamic. I, however, believe that the rpm increase we note when we get airborne with a typical wood prop is just the imperfect portions of the blade "unstalling" or exiting the near stall region, and thus yielding up the wasted rpm. The Warp prop, on the other hand, pulls along its entire accurately shaped airfoil, without inefficient areas. The higher speed, in my opinion, is due to a surplus of static thrust which "seems" to contradict the conventional view of pitch versus speed. No free lunch, but rather just more pure thrust with a ratio change similar to a torque converter.

Your 54 x 30 prop had a pitch angle of 10¡, and you don’t say why it was bad (climb or speed?). Your Warp at 8¡ has 25.5 inches of pitch, which should be a good mid-range compromise between climb and speed. The 3000 rpm is good, too, with a slight pitch reduction, would get you to 3200 with an improvement in climb.

If my figures are correct, a similarly thin blade width wooden prop with a pitch of 31 inches would give comparable performance. I would make sure the prop maker would let you exchange it for a different pitch should you need more climb (less pitch), or more speed (more pitch).

Your oil cooler sounds similar to what I am doing, with similar good results, and the carb heat scheme is also the same.

Good luck and stay in touch. - Bill (Bronson)

Q. Dear Bill - I am relatively new to this sport and am a member of EAA Ultralight Chapter 12 in Minneapolis. I am requesting information from your Engine Q&A column in EAA EXPERIMENTER. I recently purchased a used plane with a 35 hp Mosler two-cylinder, four-stroke MMCB - 1039 cc with a Zenith carburetor and Fairbanks Morse magneto. I have been unsuccessful in obtaining a complete Mosler manual to coordinate tuning and maintenance for the components. For instance, when I bought the plane, the spark plugs were Bosch W9DC with a gap set at .030. I called T.E.C. (Total Engine Concepts) for a manual and received a partial manual and was told to use a Bosch W7AC gap set .016, and yet another manual I received on the Mosler engine from other sources says the spark plug type for the MMCB should be a NGKBP5ES. It also further states in the partial Mosler manual, and I quote from the manual under Maintenance and Rebuilding: "Most procedures can be found in any good shop manual on air-cooled VW’s which we urge you to consult for more detail. Clearance, however, must be adhered to as per this manual, as they are different on engines used for flight. This section covers those operations common to all Mosler engines. Specifics for each, when necessary, are referenced throughout this section."

Would you as the doctor feel comfortable tuning to VW specs? If not, I need specific answers to coordinate the existing components.

1. Recommended spark plug name, number and setting.

2. Zenith carburetor float setting and adjustments.

3. Fairbanks magneto setting and recommended timing

4. I also need to install a carb heat system to fit existing Zenith carb. Is there a kit available to modify? Who and where to purchase from? If no kit is available, your recommendations are appreciated.

Be advised the engine is equipped with ASI, CHT, EGT, oil temp, oil pressure, tach, etc.

Sincerely - Richard Vohnoutka, Eden Prairie, Minnesota

A.  Dear Richard - Thanks for your letter. I’ll discuss how I’ve adjusted my own engine, a 1/2 VW, for which I sell at 61-page narrative called, "How I built a smooth 1/2 VW."

1. I set my points at .016 inch.

2. I field set my timing when required by loosening the mag bolts, rotating the mag body in the direction of prop rotation. Next I turn the prop in its normal direction (with magneto grounded, and plug wires off for safety) to 6¡ before TDC. Then I firmly grip the mag and rotate it opposite prop rotation until the mag "fires." Having carefully noted the exact point the mag fired, I tighten it in this setting. When the engine starts and gets past 300 rpm, the spark retarding impulse coupler cuts out, and adds another 20¡ of advance for a total of 26¡. You can use this as a guide to vary your own setting to match the fuel you burn, and your field attitude.

3. On plugs, I have tried several, and keep coming back to the "Bosch Super Plug," which seems to work better than gold palladium and other plugs. The old Mosler spec of .016" is to insure the spark occurs in your spark plugs and not in the coil windings. Don’t forget, this is a system where the coil has each end of the high side ending at a spark plug, with no center tap. Therefore, your total gap is actually .016" + .016" for a total of .032" gap.

4. I always use carburetors with factory float settings. If it doesn’t "fade" on full power climb out or "load up" at idle, I don’t change it. Many off field landings are the result of "diddle-sticking" with adjustments.

5. As I mentioned, I sell a 61-page narrative on my engine, and it contains drawings of my carburetor heat system. I also use a "tuned length exhaust" and silencers which gave me about 50 more rpm.

6. I adjusted my valves to the VW specs, and if I had noticed any "off seating" of valves at higher temperatures, I would have increased the gap a couple of thousandths. In 100+ hours of operation, this has not been necessary.

If you need a set of my narrative, just send a check for $75 and allow a few days for delivery. Thanks for your letter and stay in touch. - Bill

Q.  Dear Engine Q&A - I’ve been receiving the EXPERIMENTER for a few months and find it very interesting and enjoyable reading.

I’ve noticed a lot of people use Subaru engines on experimental aircraft and there seems to be a wealth of information and parts available.

I, on the other hand, am interested in converting a Honda Civic engine to use on a Kitfox I plan to purchase in 1996. Except for the CAM 100 I can find no information for converting my engine. It is not the same engine used in the CAM 100.

I have a 1500 cc, 16-valve single OHC, aluminum alloy inline four cylinder with only 800 miles on it. I have the factory ignition and throttle body injection but feel it is complicated and, with the distributor directly over the flywheel, not practical. I believe it would be impossible to install a redrive.

So, in conclusion, I would like to ask for information, suggestions and your opinions on building or buying a cogbelt redrive. Also, on an acceptable carburetor and distributor ignition.

I’d very much appreciate any help.

Sincerely - Todd N. Young, Mechanicsville, Virginia

A.  Dear Todd - I’ve had leads on folks converting Honda Goldwing engines for aircraft use and we’re very familiar with the CAM 100 conversion, but other than that we haven’t heard anything in the rumor mill. So, again, we’ll toss the questions out to readers and see who responds. - M.J.

Q.  Dear Don (Bouchard) - I am, at present, building a Europa kit aeroplane and am looking at the various powerplant options available. At the moment I am considering a Subaru EA-81 package from a vendor located in the USA. Recently, however, I have seen some veiled reports and heard rumours that some of the conversions being offered are suffering from overheating and other problems in the engine department along with some difficulties with the drive system fitted.

Could you please advise me of any problems you are aware of and any areas to be wary of when considering purchasing one of these packages. I realize that, for liability reasons you cannot be too specific, however any assistance would be appreciated.
John Bean, Oxfordshire, England

A.  Dear John - It’s certainly nice to receive a letter from as far away as England. The Europa is a nice looking aircraft. There was a fellow here yesterday from north Texas who was having trouble with overheating so he trailered his aircraft to my home to have me look at it and find the cause of the heating. It’s a KR2S, a beautiful aircraft. He had an EA-81 with redrive, a nice setup similar to the Stratus conversion but of his own device. The aircraft would cruise around 170.

The cause of this overheating was cavitating of the air in the water system. I think a lot of problems result from not getting all air out of the system. Another problem is anodizing the engines causing the engine to lose their ability to breathe. Leaving the engine plain or using proper paints would help keep the engine cool, too.

It’s a hard to make a decision about which manufacturer to buy from. All the manufacturers have good products. I’ll enclose some pamphlets and you can pick your choice.

Good luck with your Europa project. We’re hoping to do a story about this KR with the Subaru engine in an upcoming issue of the magazine, so stay tuned. - Don

 
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