SMALLnet post387

Dave Segal lamented that Tower no longer carries Ultracote. The information we have is that Horizon Hobbies has bought the Ultracote line and will be distributing it, so I don't imagine Tower will ever have it again.

I have also had a little trouble getting several colors of Ultracote lately. All my usual sources were out of certain colors. I thought it was just high demand. But I found out yesterday what might have caused the problem.

Look for HANGAR 9 Ultracote in the near future! So you should have no problem getting it at your local hobby shop, or from Horizon.

In response to Dave Segal's comments about Tower/Goldberg. I seem to remember a report a while back, I believe in R/C Report, that Goldberg was NOT going to sell their products through an intermediate source. While Tower leaves a lot to be desired sometimes, I don't think this was Tower's decision.

I read Dave Robelen's article in a recent model magazine, and would like to know what is meant by a "severely-restricted Cox .010 engine. How does that affect the engine, and how do you do it?

Also, what is the Mabuchi N-20 motor?? I may have some of these but I can't tell. Maybe you could tell me their size?

There has been mention recently of good-quality razor blades made in Germany that snap cleanly when bent. A sample was being offered at 4 for one dollar. Can anyone help in steering me to the proper reference?

Please take a look at the variety of plans and kits offered -- and do bookmark the site! Thanks / AL

Guys using the L-2 size Rapier motors are finding that they fly 85-90% reductions of Jetex 50 (old version) models. I've just gotten a set of KeilKraft Panther plans, reduced to 90%.

I have been working with a few others to get the Rapiers approved for import into this country. As for the thrust available from the Rapiers and Jetex, data follows:

L-1 5.6g .20 ounce 10mm x 39mm L-1A4 7.6g .27 ounce 11mm x 39mm L-2 10.7g .38 ounce 11mm x 48mm L-3 22.9g .81 ounce 14mm x 59mm L-4 33.4g 1.18 ounce 14mm x 59mm

J-35 .50 ounce J-50 .60 ounce J-100 1.20 ounce J-200 3.00 ounces J-350 4.00 ounces J-600 6.00 ounces

If you do the math the Rapier L-2 should fly a model of 91% of the Jetex 35 size, and 86% of the Jetex 50 -- but it is close enough. The L-4 and the Jetex 100 are equivalent, except that it has proven to be almost impossible to start the new Jetex fuels and keep them running.

Also, these little motors run about three times hotter than the old Jetex, and so are a bit more of a handful to operate safely. If flight is not achieved with the model, it can start a fire very quickly.

Carlo, Chief Chemist: Rocket Science Institute of New Mexico Hey, does that make me a rocket scientist?

...Yes, Carlo -- consider yourself SMALL's Official Rocket Scientist! BTW, I might add that the data that came with my Rapier packs (bought from George at SAMS about a year ago) differs somewhat from the numbers given for the L-2 Rapier. The claimed average thrust is only 90 milliNewtons ( 9.17g). Maybe an improvement in the fuel has been made?

Also, the "run time" of the L-2 Rapiers is stated as 23 seconds. That seems to me a bit longer than I used to get with Jetex 35's and 50's. [JW]

Anybody got any plans or pictures of a PVC pipe knock-down rack to put inside a van to haul bunches of little planes around with?

I'm going to the SMALL fly-in in Maumelle again this year and don't want any more damaged little planes from "layering" them between blankets! I'm going to take out both rear seats from the old Windstar and fill it with planes and stuff.

Just wanted to give you all a heads-up: ehobbies has O.S. .10 FP RN engines for $39.99. I just got one today! Get one before you are stuck with blue LA's.

Also, if you like "historical" small R/C planes, check my posts at < http://www.pclink.com/dfritzke >, I have some old Howard McEntee and Aubrey Kochman photos and plans posted there. Kochman was flying CO2 R/C planes decades ago!

Hello once again! I have found a new outlet to vent my SMALL modelling obsession. Someone mentioned a G-Mark .031 engine, so I have found myself one that is in running order; similar in size to a Cox .020 but with what looks like a sensible carburetor up front. Surely the way forward for some manufacturer, since micro R/C gear is very good and is obviously going to get better.

Anyone up for that? In the meantime, does anyone think it's still possible to get G-Mark .030 glow heads? Or does anyone think it possible to drill out and tap the existing head to accommodate a normal glow plug?

...Micheal, the G-Mark .031 is indeed a neat little powerplant. It was designed and made some years ago by a most ingenious Japanese gentleman, who had a product line that included a .12 opposed twin and a .30 5-cylinder radial.

Bill Cannon (the micro-proportional R/C pioneer) was the exclusive importer of G-Mark products into the USA. I bought a pair of .031's from him. These engines needed as much careful break-in time as a "big" glow engine; but once they were fully broken in, their throttle response was exceptional.

The G-Mark maker died suddenly, and so did his engines. Someone bought up all the remaining parts and tooling and had them shipped to America. Unfortunately, on the sea voyage salt water got into the G-Mark material, and ruined it beyond salvage.

I still have both my G-Mark .031's. I just went out to my shop to check the "glow head" configuration. It's more like a fat glow plug than a glow head, and should be easy to adapt to accept a standard glow plug. Just make sure that the glow element of the plug is positioned in the same place as the original. That may require spotfacing or counterboring. [JW]

Would just like to thank all who answered my request for OBOGO plans and Mills .75 parts. A wonderful response...as usual. I even got replies from far-away India! Regards, Peter

My carb problem has been solved. I still can't believe the number of responses I got, from the UK to Shanghai. This is really one bunch of helpful people! Tried to say thanks to all, but if I missed anyone: Thanks. Norm Dial

The wind finally abated today. Calm all morning until I got into the car; then the breeze picked up from 12 to 10 PM!

Anyway, the model flew great: level flight at less than half throttle & a steep climb at full throttle. I had also increased the rudder throw by one more hole on the rudder horn. Made the rudder more effective -- also the model more twitchy.

With the rearward C.G. the model now also rolls to the left. Previously the left roll was more of a barrel roll. Rolls to the right are almost flick rolls. I find that it is more difficult to do an Immelman now, as the model wants to keep on rolling. The pilot needs more practice!

The stall turn to the left is now good & very enjoyable to do. I forgot to try a stall turn to the right. Spins are really easy in either direction: throttle back, stick into the corner & away we go! Managed 15 turns to the right, then chickened out.

It took a burst of throttle to straighten out, together with opposite rudder. Spins to the left are similar, but I only tried 3 turns as the fuel was running low. It is only a 2-ounce tank, so the landing was dead stick.

A fun session even if it was only a single flight. Both pilot & plane survived. It doesn't get much better than that! I now have a model which is a lot of fun & more challenging to fly, so I expect to have more enjoyment from it.

Thanks for the help & advice. I have learned a lot (that it is over-powered with the OS 20) & confirmed again that ailerons are not a necessity with the correct amount of dihedral, enough rudder throw -- but most importantly, that the CG is not too far forward. Or too far back!

I read Bob O'Neil's request for information on the old Ensign kit from Scientific Models. I built one of these way back in 1940 when I was living in the Canal Zone. It was my first "big" free flight, and was powered with a beautiful Ohlsson 23.

I entered it in the first model airplane contest held in the Canal Zone on the Fort Clayton army base. Anyway, I won first place in Class B and the prize was a round-trip flight across the isthmus of Panama to the Caribbean side and back.

Each winner, and there were four, received this prize that was contributed by Pan American World Airways. We flew on a DC-3, and for all of us it was our first flight and did we ever enjoy it.

Unfortunately I no longer have the plans, but that model provided me with many enjoyable flights. Bob, I hope you can get the plans and have as much fun as I did. Somewhere I may have a photo of that model. If I can find it I will be happy to scan it and send it to you. Let me know.

Last July you gave me considerable help suggesting I use Polyspan for lightweight model covering when I complained that Koverall was distorting the wing I was covering.

I've since tried it using your methods, which all worked very well. The problems I'm now having are related to finishing. I'm trying to learn to use dope (Randolph) and think, at this point, that the methods used with fabric are not entirely appropriate using Polyspan.

What I've done is to apply a coat of nitrate dope using a brush, sprayed on two coats of butyrate clear and two coats of the same with talc added. I sanded lightly with 600 grit paper between coats until I got to the talc/dope stage.

I found that the 600 grit paper would not do much at this stage as there were brush marks that could not be removed unless I went to 400 grit. Big mistake, as you probably know.

I didn't notice the damage until I sprayed the aluminum coat, and found those black lines that appeared were actually cuts though the Polyspan where an open bay and the supporting structure meet. I plan on stripping the Polyspan and re- covering (fourth time).

Maybe I'm up the learning curve far enough to do a better job this time, but don't want to ruin it again trying to get a nice dope finish.

The questions that came to mind are: Can the initial nitrate dope coat be sprayed on Polyspan without the problems that would cause with fabric? Do you use any sort of sanding primer in the finishing process? Is it necessary? Wondering if a talc/dope mixture could be sprayed?

I use one of those great little DeVilbiss EGA-503 Spray Pistols in my work and it is what I have been using to spray the dope. I seem to recall that you mentioned that you use this gun and was wondering what pressure you use to spray 50/50 dope/thinner?

Many thanks again, Joe for the suggestions for using Polyspan and also for any suggestions you may have concerning the finishing process.

...Chris, it seems like each kind of model covering material has its own unique quirks and techniques. A couple of other SMALLsters have also asked recently about Polyspan methods, so for their benefit, here's ONE technique that WORKS. (It may not be the only one, but it's the only one I know.)

Apply three coats of plain nitrate (NOT low-shrink) dope to every wood surface that will touch the covering. Sand lightly after each coat dries, just enough to remove the fuzz.

Polyspan applies like tissue, except that moisture hasn't the least effect on it. That means you must position each piece of Polyspan carefully, so as to minimize slackness and excessive material "within the perimeter". Polyspan heat shrinks -- but to a rather limited degree. It's best to apply the covering with that in mind, even if it means covering a wingtip with an extra piece.

I place each piece of Polyspan where I want it, then brush a 50-50 mixture of nitrate dope and "retarder" around the perimeter ONLY. I burnish down the covering and do any minor positioning adjustments that seem needed.

After each section of Polyspan is attached, I trim the outline (usually with sharp scissors) to provide nicely-even "wrap- around" material.

Now comes the trick! Polyspan fibers are quite springy, and it's just about impossible to wrap the material around, say, a trailing edge, and adhere it with dope. It won't stay.

Instead, with a Q-tip, brush a thin coat of Sig's "Stix-It" onto the underside of the "wraparound material" AND a corres- ponding area on the "mating part". Let that dry.

Now with a hot "trim iron" (the flat foot works best for me) you skmoodge the Polyspan margin around the outline. This may take a little practice, because three things take place at the same time here. The foot of the iron acts as a rounding-over tool via PRESSURE (not TOO much!) -- and as a contour-former via its tendency to stick to the Stix-It. (This allows a certain amount of "pull" action, to make the Polyspan conform as it is brought around a curved leading edge.)

And the HEAT softens the Polyspan, shrinking it too as the loose edge gets "turned under" and adhered. This allows the seams to be "ironed down" almost to the point of invisibility.

...OK, once the entire model is covered, careful and progressive use of a heat gun will remove almost every wrinkle. Warps can also be eliminated with careful heat application -- but it's far better to avoid those in the first place.

So far as I know, EVERY type of paper or fabric covering for aircraft needs one or two BRUSHED coats of nitrate dope. This seals the surface, adheres the covering to wing ribs and fuselage stringers, and the action of the brush bristles physically forces the dope deep into the fibers (or weave) to provide maximum adhesion.

(Butyrate dope's adhesion is FAR less.)

...After I applied the first coat of clear nitrate to my first Polyspan-covered model, I let it dry, then lightly sanded the (expected) surface fuzz. I think I used worn 400 wet-or-dry. All seemed well, and I brushed on a second coat of nitrate.

When dry that produced FUZZ GALORE. Horrid. Loathsome!!

This reminded me of a couple of earlier "miracle model coverings": Dave Brown's "Skyloft" and Midwest's "Microlon". The fuzz from these awful materials was IMMORTAL.

I was in despair until my son David came by, and provided THE SOLUTION. That was some exceedingly smooth "abrasive pads", of the sort used by plastic scale modelers. (A set of these is available from Micro-Mark, under the name of Micro-Mesh Pads.)

I couldn't see HOW such smooth-feeling (1200 and 2400-grit) "abrasives" could tame the fuzz that doped Polyspan generated. Maybe the action is a "burnishing" one -- but IT WORKED.

I went all over my fuzzy airplane lightly with one of these pads. That made everything nice & smooth -- and the next coats of dope went on without a trace of fuzz re-appearing.

...I haven't spray-painted a model since I moved to Alabama. I've gotten to like the "brushed finish look" -- and in fact I don't even fill grain any more. I mean, my models are built from wood -- why be ashamed of that? And as long as the overall appearance is consistent, visible wood grain under the dope doesn't look objectionable to me, nor apparently to those who view my models. And I save weight, time, aggravation, and MONEY.

When I DID spray paint, I used pressure between 25 and 35 psig. I found that reduced pressure minimized overspray, and allowed me to apply "wetter" coats. (Too much air pressure seems to make dope dry "in the air" before it gets to the model.) [JW]

I recently bolted down my Norvel AME .061 to my stand and ran it for the first time to break it in. I used Byron's 25% and a starter and it fired up instantly. I followed the break-in procedures to a T, and after about 8 runs, I increased compression by removing one washer and leaned it out.

According to my tach, it peaked at 19,800 rpm with a Grish 5.5 x 4 prop. I was really hoping for more rpm; however, I am not following Norvel's recommendation of using crankcase pressure rather than pressure from the exhaust (which makes me wonder, since the muffler doesn't seal too well.)

The last two runs held their needle settings and it ran solid. I was hoping some of the SMALLsters could let me know what their engines are turning and prop size/fuel/pressure setups. My fuel choices are limited to K&B 1000 and Byron's because I live in Alaska and 1/2A isn't that popular here. Both are good fuels, though, that I have used in the past -- so that isn't my concern.

...Craig, what are you gonna DO with all those rpm? A 4-inch pitch prop at 19,800 is about what you might want in a control- line speed model -- maybe 1/2A Team Racing (if such an event still exists). That's because if the propeller is working at normal efficiency, its model would travel close to 80 mph.

Seems mighty swift flying to me -- 115 feet per second if the prop is working well. And if its NOT, the engine's wasting its energy output in noise and prop turbulence. [JW]

I'm certainly planning on being at Maumelle as usual. Bring better weather this time! Eric

SMALLnet Posting post387