SMALLnet post427

Another of our old faithful SMALLsters died last week. Phil Davy passed away unexpectedly after a bout with pneumonia.

...A while back I mentioned a fine-quality electronic digital scale selling for about $20 from a few US discount dealers. It had a capacity of 4 pounds. I bought one, and found it exceedingly useful. However, some other SMALLsters weren't able to find a local source for these.

However, the current American Science & Surplus catalog (#174) lists another digital scale as an "on-sale" item at $9.95.

The scale I bought at Sam's Club for $20 has a 4-pound capacity, and was intended for Postal use. The AS&S unit goes up to 5 pounds, and was designed as a food-quantity measuring scale. Made by Sunbeam, it looks like a fantastic bargain for modelers.

Source: Scales, Digital

Vendor: American Science and Surplus

American Science and Surplus is at P.O. Box 1030, Skokie, Illinois 60076 -- (847) 982-0870. < http://www.sciplus.com >.

These folks carry a plethora of model-useful stuff: materials, tools, and components. Examples: Dremel clones and accessories -- Variable-speed 110V rotary tool @ $33; Mini version $20; $2 for a pack of 4 solid carbide rotary rasps...)

...Speaking of tools, George Schaffner < http://www.bbtools.net > sent me one of his new "Classic Cutters" to evaluate. This is a shear-action wire cutter, made in the USA, and costs under $20.

This tool is capable of making clean, non-distorted cuts in stranded cable up to "garage door lifting cable" sizes.

The "002" unit can also cut "hobby shop steel wire" -- K&S for example -- up to 3/16" diameter, and genuine music wire (not often seen in today's hobby shops) up to 3/32".

The difference between the Classic Cutter and other types of wire-cutting hand tools is that the CC uses a true shearing action, with hardened cutting jaws shaped to "surround" the wire being cut.

As most of us know from experience, cutting stranded cable -- such as for throttle actuation -- with a pair of "dikes" produces a flattened and flared-out end. The Classic Cutter doesn't do that. The freshly-CC-cut end of an R/C flexible push-pull cable enters neatly into the socket of a threaded brass "solder fitting". No re-shaping or filing off sharp points is needed. [JW]

I am interested in information about two Cox .049 variations. One is called the "Killer Bee" and the other is the Cox "Venom." I think I remember seeing the Killer Bee advertised but the Venom, supposedly a very limited production job, is not familiar. Can anyone tell me about these two in terms of appearance, performance, etc.?

Excuse me for bringing up the hated C*x but since I fly 1/2A, .020 Replica, PeeWee 30 and 1/2A Texaco, I have a little trouble avoiding them.

Larry Renger < > (who designed those engines while he was chief engineer at Cox Hobbies) responds:

Special crankshaft with a thicker web, but crescent-moon cutouts around the crankpin, and a hole deep into the crankpin to provide improved balance.

Special cylinder with slit exhausts, but the bottom one deep enough to provide sub-piston induction; and the piston and cylinder were taper-ground like the Tee Dees. Available in both .049 and .051 sizes. Anodized case, gold color.

Stainless steel washer behind the drive washer to allow use of power starters; "no drag" (old style) spring starter; Big Bore venturi (don't recall the dimension, but I could measure one, if it really matters). Black for the .049, red for the .051.

Very short needle valve top with a lightweight plastic extension Standard glowhead (Required by NFFS to meet their whacko rules, as was the strange cylinder)

I really don't know the production figures, but probably something like 5000 Killer Bees were produced before Est*s gutted it.

The Venom was basically a competition Mouse engine. I was in touch with Paul Giebault at the time, and he let me in on what they were doing. We did that and more. The crankshaft was out of the Killer Bee. The cylinder was Tee Dee, but the piston had the wall thinned down from .020 to .016 as I recall.

Because we had a free hand on this one, it used the high- compression head and several (4?) head gaskets. The tank was black, the crankcase red: the opposite of the Texaco engines.

There was the SST washer behind the drive washer and no-drag starter spring as above. The venturi and backplate were opened up, I think to .093, but I'd have to measure one to be sure.

If you get a Venom, break it in very carefully or the top of the piston will separate from the skirt (oops!).

Performance was as good or better than the Killer Bee, but they were pretty close.

The discussion of Durham's Rock Hard putty in #426 brings out a really great product. In addition to the obvious uses that were mentioned, it is a great mold-making product. I have used it for nacelles and canopies by producing a foam base just a bit smaller than needed, and then "icing" it with Durhams.

A tip is to sand it within 48 hours, then allow it to set some more. A final fine-grit sanding can put a mirror finish on it. This last bit is time-consuming, but produces a hard glossy mold.

Detail can be scribed or built-up, and then normal fiberglass procedure follows. I have also used this to produce fine looking canopies using a heat gun (carefully) and soda bottles. The Durham's works as a kind of heat sink, so one-off work is a lot easier. Hope this helps spring some ideas.

A week or so ago, on the Jetex list I think, we briefly mentioned the Tail Volume theory. This can be very helpful in determining the balance point of a new model -- especially one of those old-timers that has no balance point shown on the plans. The calculations aren't that difficult -- so do take a look.

I recently finished building a Jetco Thermic 50 kit that I won on eBay. You can see a picture of it on the web at:

This started off as the free flight version (not the Thermic 50 R/C), to which I then added a 2-channel radio and a Pee Wee .020 power pod. It climbs to 300 feet on a full tank, flies sedately, and most importantly it looks good in the air!

I covered everything in yellow Japanese tissue, and doped it with clear and red trim. I recently noticed that Penn Valley Hobby Center < http://www.pennvalleyhobbycenter.com > offers a modern reproduction of the Thermic 50 kit for $29.95, for those who want to build one of your own.

Another R/C model I've been fooling around with is a strange design that can be seen at:

I got the idea for the configuration from watching the first stage of a multi-stage rocket gliding back to earth. I was amazed at how stable the 3-fin arrangement was, even as a free flight glider. My version is R/C, has a 20-inch span, and weighs 11 ounces. It is made of 1/4" square sticks and covered in tissue. The duct on the front is not needed, and is best omitted for less damage on landing.

The aircraft has '3 Fins', and all fins have a moveable control surface. Power is from a Norvel .049 and the radio is 4-channel with a GWS receiver. Using a computer radio, I mix the surfaces so that the turns are perfectly flat: i.e. no banking to turn. Of course it will fly 'inverted' just fine! What seems strange to me is that it flies well at all. I can do loops, rolls (3 per second!), and other basic stunts with it, but the flat turns are the coolest. It has enough power to hover, but I will need some gyros to slow down the dynamics enough to accomplish that on such a small model.

The MDS .18 is a great motor. When they came out, the makers claimed that it fit the space of an O.S. .10 FP. From what I can tell with the hole spacing on the motor lugs, muffler/carb placement etc., this is true. The case is a little wider, but nothing a few passes with a file wouldn't remedy.

Weight-wise, the O.S. .10 FP comes in at 5.7 ounces with the O.S. spinner nut and muffler. The MDS .18 is 7.7 ounces with the muffler. Power is very good; much better than any of the plain- bearing .15's on the market.

One thing though -- read the directions before you attach the carb to the case! I assembled it to see it 'together' before I read the instructions, and found out the hard way that the carb installation is nearly permanent. The retaining screw and nuts draw on the carb from both sides and make it very difficult to move if you don't seat it all the way down, or get the carb on crooked. This is what happened on mine, just by tightening the screws lightly. Dave

Don Garry was asking about the MDS .18. I have had excellent luck with mine, but MDS quality is variable. It starts with an easy hand flip, idles well, and revs up nicely. Not a torquey engine -- they recommend an 8x5 or 8x6 only.

Find and caulk all possible air leaks! I have mine in a Hobby Hangar 1/12 scale Tempest (in-line engine) and it is a little rocket.

The muffler did not fit in front of the firewall, so I chopped off the back, turned a plug for it, and fixed 2 new outlets in it with JB Weld. Took a while to get the breathing right -- my first attempt took away too much power.

I just got a new PAW 0.5cc R/C engine, as my old one got worn out flying my Yard Bee. I think it is salvageable, but no harm having a spare. This new engine confirms something I found with all my other PAW's: that the factory-recommended needle valve setting of 2 or so turns out is way rich. Both mine seem to do fine at 3/4 turn open.

Even at 1 turn open they fatten up and really slow down. I wonder is it because I use smallish bore tubing for my fuel line.

I wonder if it makes the draw from the tank much more efficient. We argued this topic to death in another forum, producing more heat than light along the way. I don't have the tank up high or anything like that. William Adams

Regarding Don Garry's inquiry, I have an MDS .18 which I used in an R/C scale combat model before we changed the rules to allow .25's. I found the MDS .18 to have good power for its size, easy to start, and had reliable idle (not that we used the idle much in combat...)

Jim Rundle asked about methods for notching ribs for spars. I use the same method Jim uses for shaping the ribs: plywood templates with the balsa ribs sandwiched between. However, I also notch the plywood templates for the spars. After sanding the ribs down to the rib pattern, I use an X-Acto saw to remove the bulk of the balsa from the spar notch area, and finish up with a sandpaper strip glued on a stick. Gene Smith

I too have noticed the lack of information on the MDS engines; one of the local hobby shops here in Houston has several left on display, but again I noticed he does not push them as he used to. (This could mean nothing at all.)

What I do know is that most of the shops, when confronted with a customer looking for the best bang for his buck on engines, are pushing the Thunder Tigers and Magnums -- both of which seem OK.

I really like the MVVS engines, and they are a good value. You can buy these direct from < http://www.justhobbies.com > here in Houston. I believe they also bought the rights to the fun-fly models when Morris Hobbies sold out.

I have two MVVS engines: a .12 and a .15. MVVS also makes both of these as diesels. Both of mine idle well, and the silencers work well. Top end is there when you need it.

Please note that you have to purchase the mufflers separately. They are actually tuned silencers. If you remember the original Lazy Bee box and the articles about it in the various magazines at the time recommended and used the MVVS .12 with the tuned silencer, and an extra piece of silicone heat-resistant tubing to funnel the gunk to the back of the tail.

K&B is back in business under new ownership, and they have an .18 that looks good, and is priced nicely as well. Check them out at < http://www.modelengine.com/ > Clarence Lee had good things to say about the new owners recently in RCM.

My web page is < http://www.modelflying.com >. You can see my mug and my Lazy Bee there. Regards, Joe Ross

Yes, I was aware of Joe's design intentions for the Dakota, and it is a magnificent small-field free flight model. When we were running a Dakota contest at The Eastern Canadian Open at Gananoque, we ran it as a power ratio event -- in other words the ratio of glide duration to power run.

As you say, the usual figure was around 1:1. But Roy Bourke suddenly showed up and got about 3.5 to 1. Most disconcerting! And he was using an elderly Cub of less than .049 displacement!

I live in hope (not much, but some) that the NFSS will sort out their Dakota contest rules. It is obviously a mistake to allow serious contest fliers to produce rules for a fun event. They completely miss the point.

Specifically they will only allow a very restricted list of engines and they allow the use of mechanical devices like timers. There is an almost infinite range of engines suitable for, and appropriate for, the Dakota, and there's no reason to allow anything more sophisticated than an eyedropper type tank for timing of the engine run.

It's just great to have a plane in which one can put nice old engines to use and have fun. Most of the lighter diesels between .03 and .06 cu. in. would be fine, and I'm often tempted to build a Dakota for a personal favourite small glow engine, the McCoy 049 which had a combination induction system of crank- shaft valve, and spring-loaded valve in the venturi. I would be slightly worried about the possibility of burning out a glow head, but suspect I would get away without this happening if I just used a NiCad for ignition.

...Dave, it seems to me -- and is one of the main reasons that Randy and I started SMALL -- that it's detrimental to set up ANY competition regulations for model airplanes.

As the late, great George Aldrich liked to say, "All you need to do to ruin a popular modeling activity is to make it an official AMA competition event."

My outlook is: why should ANYONE tell YOU what to build and fly for your own personal enjoyment? And why should anyone even attempt to judge YOUR model to see how well it conforms to THEIR standards and ideas?

Not many modelers compete anyhow. It's always been that way: In my old home town (New Castle, Pennsylvania) for more than a decade there was enough model airplane activity to support two hobby shops, plus model kit counters at the local "Five & Tens" (1940 equivalent of Wal Mart). Yet whenever our club put on a model contest in those days, only 2 or 3 locals would enter...

The Flying Aces Club (FAC) holds "low-key" model contests at Geneseo, New York every July. These are well-attended -- but even low-key competition can KILL.

Yes: two modelers that I know of have died at Geneseo FAC meets: exerting themselves too hard to get their mass-launch entries back to the starting line in time for the next "heat"...

SMALL is utterly non-competitive, and will remain so as long as Randy and I can keep it that way. That's why SMALLnet rarely posts notices about competition events.

Yes, some SMALLsters DO fly in contests. But the whole idea behind SMALL-style model flying is just having FUN. Who needs a trophy, anyway??? [JW]

Raj mentioned in Posting #426 a source of smaller Enya engines in Singapore. Another source is Richmond R/C in Canada: < http://www.richmondrc.com >. They list the .06 for $50, the .09 for $47, the .15 for $54, and the .25 for $60.

Raj is right, the smaller ones look like throwbacks to the 1950's design-wise, but my .049 and .06's run just fine. I did have to do a bit of filing of the clamshell muffler to get a good fit around the cylinder head though. Richmond also has a decent inventory of parts, and it IS possible to get the older parts from Altech.

Like Raj, I also recommend the CX .11, a great little engine on a par with the late great OS .10 FSR. (I may have to order one of those .09 diesels from Hobby Shack Singapore!)

I'm working on the old .01 Cox TD-powered "Littlest Stick" originally published in RCM around 1975. (Built one about 17 years ago that barely flew, due to the heavy radio -- but now we have *micro* flight packs!)

Anyway, I got the plans from a web site and was also looking at the dwx CAD files and noticed some updates.

The new improved L-S has longer wingspan, which I'm using; and 0 degree right thrust, since we now have proportional radios. That I understand. But what about the reduced wing incidence from 5 to 3 degrees? Is that because the new version uses an elevator? If I keep it rudder-only, should I keep the 5 degree incidence?

...Chuck, this topic was covered in SMALLnet before, but since you're new, here's the information again.

A rudder-only R/C model is more or less just a guided free flight. While the engine's running, the airplane climbs; after the motor quits, the plane glides back to earth. Usually the power-off part of the flight lasts at least as long as the climb.

For that reason, R-O models use a couple of degrees of right thrust: so that the airplane turns the same in response to transmitter commands, power on in the climb, or power off in the glide.

Most high-wing rudder-only designs use downthrust too, to reduce the climb-out angle, AND to minimize spiral-diving tendencies. (In a banked power turn, downthrust tends to keep the circle from tightening.)

R-O models use more decalage than 2- or 3-channel designs, because they're normally trimmed to fly a trace "tail-heavy". That way, in a gentle banked turn under power they'll maintain altitude. And in a STEEP banked turn; i.e. a deliberate spiral dive to build up speed -- when the plane straightens out, the decalage acts as "up elevator", and permits zooms, stall turns -- even loops.

I've flown a lot of rudder-only, and still enjoy it. I use the "decalage effect" to flare out in landings. Circling my model over the field as it loses altitude, I wait until it's about 3 feet above the grass; then quickly straighten out. The slight extra speed my plane built up in its banked turn then makes the stabilizer work like "up elevator" -- and my model flares out nicely into a 3-pointer. (When I do everything just right, that is...) [JW]

I seem to be having centering and resolution problems with my micro servos. I have used FMA S-100's and Hitec HS-55's, and they just don't seem to return to center (and hold it) with the same repeatability as a standard size servo, say a Futaba S-148.

Also, my S-148's respond to just one click of the trim lever, whereas the small servos aren't moving until 2 or 3 clicks of the trim lever. Is this common for the micro servos? Are any of the micro servos better in this regard than others?

...Mark, the problem lies in GEOMETRY. The feedback pots in R/C servos move angularly -- but their change in resistance is proportional to the DISTANCE they travel.

The pots in micro servos use much smaller-diameter resistance units (C-shaped carbon film paths) than the larger servos do. A 5-degree angular movement of the feedback pot brush thus moves much farther on its track in a "standard" servo -- and produces a correspondingly- larger change in resistance -- than one in a micro servo. And as far as I know, all R/C servos employ the same "decoder" circuit.

I'm not sure whether they're still being made today, but Bill Cannon's micro servos operated with good precision. That's because they used a compound gearing setup that Bill developed. But Cannon micro servos have one fault: if you rotate the output wheel (or arm) by hand, you'll strip the gears.

I've used Cannon servos myself since they first came out, and enjoyed excellent service from them. But they CANNOT stand much abuse. [JW]

SMALLnet Posting post427