Larry Marshall <  > contributed:

About his Braun razor, George Penniket wrote, "... leads me to the conclusion that R/C model flyers should keep a log of performance and charge times for all the battery packs they use..."

This is very useful. I tried. Gave up as it got in the way too much of having fun. What I do, however, is cycle my batteries every once in a while and compare the numbers to those I've stored in a spreadsheet for that pack.

"...the Braun razor has a green LED which lights up while the battery is charging, and goes out when the battery is fully charged. Does this mean that the charging circuit includes a peak charge detector?"

No...I've been into my own Braun and changed its cells (there are two 600 mAH cells). Most simple charge circuits are simple voltage- detect circuits that stop charging at a particular voltage (probably 6V in the case of the Braun). These devices are not as worried as electric flyers about getting every last electron into the cells, and thus the more conservative (two AA nicads would peak around 7.5-8V) charge termination. It's also easier to do, as they know the cell number, cell resistance, and don't have to worry about detecting change, which is harder than detecting a fixed voltage value.

"...could this charging circuit be used successfully to charge small battery packs for microlight R/C models?"

A different question. If your battery is 6V, yes. You could probably take the electronics from your Braun and charge with them. Seems a hard way to get a couple of simple components though.

Joe responded to some of George's queries with, "...the 'reduced charge' phenomenon you mentioned is what's generally called 'memory effect'. Some authorities claim that it doesn't happen -- yet I have experienced it for years with my videocamera nicad packs."

I think much of the confusion on this comes from equating what we do with electric flight and what you do with videocamera batteries. The former typically charges and drains the cells quickly, breaking up salt bridges that otherwise form with really low charge/drain currents.

"Discharging the packs to 1.1V per cell; recharging; then repeating this a couple more times is supposed to 'erase nicad memory' and restore full capacity."

I'd be dropping those cells down to .9V per cell rather than 1.1V if you want to have much of a beneficial effect from this.

"Doing that to one pack didn't help. I disassembled that pack (had to destroy the plastic case to do so) and found one shorted -out cell..."

A different problem :-) They sure don't want you to replace the cells in those silly cases do they? I did this for my dad at one point. In fact, I used higher capacity cells which improved the duration considerably. But, as you say, you have to break the case open to get to the cells. I was able to do this in a manner that made the case reusable, though it was a couple years ago and I can't recall how.

For what its worth, I have memory problems with the cells in my dustbuster but have never had any such problems with my electric motor power cells.

Cheers --- Larry

Dereck Woodward <  > remarks:

Patrick LeRay wrote: "I had two Jedelsky-type all-balsa 6 x 36 wings I'd made 16 years ago hanging around. Gonna use them. BIG under-camber, right? Flat stabilizer, enlarged slightly from the proportions of the Golden Oldie. Building this one as an experiment with foamboard, slab sides, built-up rounded decks, balsa nose."

I can send you a "plan" of my electric "Twig-E" all sheet profile bipe that flew quite well on two wings that size! Mine were made from 3/32" balsa sheet over TLAR ribs, an idea shamelessly "borrowed" off MA's Bob Kopski. Sadly, they proved inadequate to the task, but the model flew very well until one wing fell off. Mk2 will have simple built-up wings -- nearly as cheap, and not all that much fuss to build. The model had about 3 degrees top and bottom, flat-plate stabilizer, some downthrust and sidethrust, six 1700 cells and a 19 turn ferrite geared 3:1 into an APC 10 x 7 electric fan.

The plan is not much over the basic outlines; was going to gussy it up when the model became repeatable. Much of the idea revolves around developing a set of numbers for a low-power electric biplane for the seven cell set. Could maybe take those numbers and add a full fuselage later -- not too removed from a Gere Sport, Currie Wot or S.E.5 if you have an imaginative squint.

Right now, the plan is a lot of doodling in my DesignCAD files; can export it as .DXF or .DWG also. A paper printout would be largely meaningless as it has doodles all over the place. I just select bits to print out and build off.

Regards, Dereck

Bob Peterson <  > queries:

This hasn't been talked about much, but has anyone had any problems running any of the small (.018) Mills-like diesels being offered?

The only one I've attempted to run was very un-Mills-like in handling. It would fire when primed but would not keep running. It had good compression and "felt good" as well but just wouldn't run for more than 4-5 seconds. I was using Aerodyne fuel that ran all my other engines just fine. The props I tried ranged all the way from 5x3 to 6x3. What am I doing wrong??

Thanks, Bob

Glenn Bolick <  > wrote:

The SMALLnet people are the greatest! Asked about the problem I was having with the Astro-Flight 217D controller and got nice responses from Dick Evans, Larry Marshall, and Bernard E. Cawley, Jr. From their inputs I am able to determine that my experience is far from unique. Apparently A-F did not put all the information in the brochure which would help one to properly use the controller.

Anyway, all will be glad to know I have substituted an old reliable controller and put the 217D in a Dumas PT-109 boat, where its problems will not affect flight! By the way, I did fly the APACHE yesterday very well with the new controller, with take-off from a grass field, and about a four-minute flight. Need to tweak in a little more aileron, and will be all set.

Thanks again for the input on this quirky controller!

Glenn Bolick

Sam Brauer <  > submitted:

Jim Branaum was wondering if the Easy Built Spitfire (50") could be converted into a .25-powered R/C model. I've had some experience with the 50" rubber-powered P-40 (also Easy Built) so think this is pretty applicable.

The short answer is that a .25 would be a tad overpowered. My P-40 came in at 8 ounces (sans rubber); maybe a little less. I haven't really flown the airplane that much, just a couple of 30-second flights of a circle or two. Basically I'm too chicken, plus I think the wings are quite fragile. I'm worried about the airplane catching a tip and cartwheeling, shedding pieces across the landscape.

I've been toying with the idea of using one of Dick Miller's MG1 motors for conversion to electric. Right now, the airplane is flying on a 14-inch hand-carved prop and 3 loops of 1/4" inch rubber, so I think this motor may hack it.

When I built the P-40 I downsized the 1/8 inch square stringers to 3/32 and I lightened up the fuselage in general. It's still a bit overbuilt, but that's hard to avoid with this kind of complex shape. I should have beefed up the wings; the only spar is a piece of 1/4" by 1/16". That's OK for flight loads, but not OK for any kind of ground contact.

I also built the airplane in one piece to save weight, but transport is a bit tricky. I've been thinking about converting it to a 3- channel R/C airplane. The rudder is already built separately, it would just mean modifying the existing stabilizer and adding some spiderwire for controls.

I'm assuming that the Easy Built 50" Spitfire is a pretty similar airplane. Clearly that airplane is not going to fly on a .25 without extreme modification. It would be easier to start with a kit that had been designed for that size motor to begin with.

I've also built the Easy Built 44" Spitfire that was designed for an 05 electric. The kit was a real bear to put together -- the fuselage called for being fully planked with balsa. (I substituted 1/64 ply instead.) I don't know how the stock airplane flew; I used a Cox 074 (which was a little shy of oomph) and then a Webra 10 (nice quiet motor). I think the weight of the airplane with the 10 was around 30 ounces. The specifications on the electric version showed weights that were a good 10 ounces more. The airplane flew quite slowly on the Webra 10 but looked pretty realistic. The airplane would loop (maybe with a little dive) and rolled OK, but it wasn't going vertical. I've still got the airplane but it looks a little tired.

Anyhow, the landing gear was barely adequate for the airplane at 30 ounces, and the wing spars are marginal. I'd lay long odds that if this airplane flew heavier and faster, that wing is coming apart.

Sam Brauer, Norwalk, Connecticut

John <  > reports:

I have been a fan of small airplanes for many years, but my preferences lean towards 36-inch-span aircraft powered by tuned- pipe-equipped high performance engines. I have a pair of Not For Sales powered by piped O.S. 25 FX's and they are a blast to fly.

I prop them with the APC narrow-bladed 9.5 x 4.5 and they will go literally straight up forever. As well, they will perform every stunt I can think of and land at a crawl.

Have a Sig Wonder with a re-timed T.T. .15 and it is piped as well. Terrific performance. My theme in all this is that small does not always mean low performance, rather it means lower cost and easy transportation.

Future plans include shrinking down the Hobby Hangar profile Gee Bee to a 36-inch span and powering it with a piped .25. The "forty-size" version is a blast, so a small version should be terrific as well.

Anybody out there share a similar passion? John

Carl Risteen <  > informs us:

The 5 micron stuff has been made commercially for about two years, and the 3 micron is quite new. It can be used to cover very light structures - I can get away with 1/16" square leading and trailing edges, with rib spacing up to about 2", with almost no distortion.

It weighs about ll grams per square meter, depending on color -- the darker colors weigh less. Warps can be very easily removed with a hot sealing iron; desirable warps -- washout, etc. -- can be added easily, and they stay, unlike with Jap tissue.

Microlite is available (5 micron) in l5 colors currently, and about 6 or so in 3 micron. The 3 micron material is about 65% of the weight of the 5 micron, but is less opaque.

We can only make about 100 24"x48" sheets, or 200 24"x24" sheets a week, so have not advertised the product. Having a devil of a time getting it into quantity production -- normal film coating machinery won't handle such thin film.

It is available from David Lewis < homefly.com > and Skyhooks & Rigging, or, if anyone has trouble reaching these dealers, they can reach me at the e-mail address above.

Keep up the good work. Carl Risteen, Risteen Associates Ltd. Phone: (506)454-0276

Walter Legan <  > has a problem:

I have been flying a Herr 36-inch Piper Cub with electric power, built with wing washout as so many recommended. I am trying various configurations of motors and batteries, with everything from a 7- ounce flying weight to the present 10 ounces. The last condition was with a Speed 280 direct drive and a Joz 6 X 2.5 prop cut down to 5.25 inches. Until my last flight the plane had been flying nicely at all these different setups (though very little aerobatic flight was attempted). I have only been trying to optimize flight time and climb rate.

My last flight started terrific, with the plane climbing out so nicely I started to get a little giddy. At about 300 feet altitude I reduced the throttle and tried a spin using up elevator and right rudder, I believe. That worked great, and the plane recovered immediately when I neutralized the sticks.

I climbed to recover some of my altitude and then tried a spin using left rudder. However, when I neutralized the controls, the plane kept spinning. I tried to increase the throttle, but by then the Cub had crashed.

Please advise what happened and what I can do to prevent it from happening again.

Thanks, Walter Legan Orlando, Florida

Bob Slater <  > wonders:

I plan to build a scaled-down Cabin Playboy for sport flying as an Old-Timer R/C Assist plane. I want to mount the engine radially, which lets out O.S., since they have stuck on that remote needle valve. The engine will be a plain bearing. .25. Obviously, it needs decent power, and an excellent carburetor, since much of the flying will be at lower power settings. Does anyone have any feedback on the Thunder Tiger plain bearing .25?

Thanks for the help. Bob Slater

Gary Edson <  > contributed:

I finally received my new Thunder Tiger .07 from Sky Hobby. The engine comes up to TT standards in appearance, and the purple anodized head and spinner nut are certainly distinctive! Bore is 0.472 in and stroke is 0.393 in, for a swept volume of 0.0688 cubic inches.

Crank diameter is 0.2942 inch. The exhaust port opens at 100 degrees after TDC and the duration is 160 degrees. The transfer ports open at 115 degrees after TDC, and the duration is 130 degrees. Intake timing is hard to measure because the carb does not come off, but appears to open at about 135 degrees before TDC, with a duration of about 190 degrees. The engine weight is 3.35 ounces. That's definitely heavier than Norvel; but this may be good, if the extra weight means better rigidity of components. The crank is bushed, but the connecting rod is not. It does have an oil hole at the big end, though.

The needle valve is nicely sealed with an O-ring. However, the fuel inlet nipple on the carb is in an awkward location and does not hold the fuel tubing well. There is no gasket or O-ring on the backplate, but my engine has no air leak there. I discovered that the head was screwed on only finger tight. Another disappointment was that the engine was rather dirty inside -- not metal shavings -- just dirt.

To me, it looks like a combination of "little" and "big" engine design. I.e., "little": screw-in backplate and screw-on head and combination beam and radial mounts like old OK Cubs and Wen-Macs.

"Big": slip-in cylinder liner (pinned), schneurle porting, and single- chamber muffler with pressure tap retained to exhaust stack with 2 machine screws. Three items of special interest: (1) The literature says ABN (TT has perhaps adopted truth in advertising...). However, the plating on the liner is bright silver color, not yellowish, as I expect nickel to be. The liner also has metallic dark gray areas around the edges, whatever significance this may have...

(2) The head is 2-piece, with a disk-like head threaded for the glow plug and retained by an externally threaded (purple) finned "cylinder head lock nut" (their terminology) that screws into the top of the cylinder part of the crank case casting, retaining the head against the top flange of the cylinder liner. The glow plug is deeply recessed into the purple head, rather like car engines, only not so much so. Unfortunately, with the two-piece head, the disk-like head can rotate under the purple threaded head piece when one tries to tighten or loosen the glow plug.

(3) The air-bleed carb body is part of the crankcase casting. Looks simple and effective, and the throttle works smoothly.

The piston fit is good. One can hold the piston at TDC and the engine will maintain compression seemingly indefinitely. There is also a strong piston-pinch at TDC. The warranty is for three years, affirming Thunder Tiger's confidence in their product.

The engine comes with a flat wrench (kinda like the Coxes), some fuel tubing, and a plastic isolation mount for use behind the radial engine mount. That's supposed to lessen vibration and noise.

An unexpected feature is an attachment point behind the cylinder for a safety wire (like used in control line combat).

Now, let's cut to the chase. Using an old Cox ThimbleDrome 6x3 prop (which allows little engines to rev up pretty good), Omega 10% fuel with 4 ounces extra castor, and an OS #8 plug, I get a reliable idle down to 4,000 rpm and top end of 18,000 rpm WITH MUFFLER! This is definitely acceptable to me because of the high-oil, low nitro break- in fuel and because the engine is still very tight after 20 minutes running. Even immediately after running, with the engine hot, the compression is good and the piston-pinch at TDC is still very apparent.

Without the muffler, the engine is not loud, and with the muffler it is VERY quiet for a little engine. Best of all, the muffler causes very little loss in rpm (how much I cannot tell, since the engine is still breaking in and increasing speed with each run). For a little engine, it throttles very well, having little hesitation with sudden throttle opening from idle. Only downside: my engine did not start easily by hand. The first time running, I could not start it by flipping.

However, it lit off readily with the electric starter (there is a thin washer behind the prop driver to take the thrust of a starter). By the end of my bench running I could start it by flipping.

I anticipate that when it is fully broken-in, and as I learn how it likes to be handled, it will start better by hand.

My son, David, is standing behind me, reading over my shoulder and fondling the TT .07. He wants to put it in the half-size Dazzler he is building. Will I ever get this engine back? Bob Slater