Author: Bob Aberle
Edition: Model Aviation - 2007/07
Page Numbers: 74,75,76
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Frequently Asked Questions

Bob Aberle | [email protected]

FMA Direct Cellpro 4S Charger Adapters

Also included in this column:

  • Selecting balsa wood by weight
  • Hook-and-fastener tape convention
  • 1/2A radial engine mounts
  • Heat-shrink tubing

THIS IS THE 40th monthly column in which I try to give you the best possible answers to questions you have written or E-mailed to me. Each new inquiry is given a sequential number for future reference.

Many questions and answers have been posted to the AMA Web site at www.modelaircraft.org/mag/faq/index.asp. Unfortunately that posting stopped in August 2005 and will not continue until this section of the AMA Web site is revamped. In the meantime, if you can’t find the subject matter you are interested in, drop me an E-mail or letter and I will try to assist you.

Q300

Q: “I just finished building your reduced size version of Joe Wagner’s Sioux, the construction article for which appeared in Quiet Flyer magazine several years ago. My particular Sioux ended up heavier than your own and was, in fact, tail-heavy.

After finishing the construction and recognizing I had a problem, I weighed a typical piece of my 1/16 x 3 x 36-inch balsa sheeting and found that it weighed about 20 grams. I have no criteria as to whether this is too heavy or what.

Can you shed some light on this? Can you also tell me of sources of supply for good graded balsa wood?”

A: I always weigh my balsa using a small digital scale. I use a My Weigh (model MX-120). I tried looking up that scale to provide a reference and found, by accident, a newer version (model 200Z) that weighs as much as 200 grams in 0.1-gram increments and costs only $22.99. You can find it at www.rightonscales.com/web/120z.htm.

I picked a medium-to-soft 1/16 x 3 x 36 balsa sheet from my wood stock (I would guess that is where I found the wood to build my original Sioux). It weighed only 7.7 grams, or 62% less than what the reader found. I’m sure that extra balsa weight caused the tail-heavy situation.

I checked my Sioux, which I still fly, and without a battery pack it still balances at 50% of the wing chord. With the battery in place it balances exactly as shown on the plans: approximately 25% back from the wing leading edge. So please take more note of wood weight.

If you are buying from a hobby shop or craft store, bring the tiny digital scale with you. Most mail-order houses that supply balsa wood are wonderful at grading from light to medium to heavy.

I buy my wood from:

Q301

Q: “I’m beginning to learn that every Li-Poly battery supplier has its style of balance or node connector. This is the connector that allows you to balance all the cells in a pack.

I happen to like the FMA Cellpro 4S balanced charger, but none of my packs will plug into the balance connector on the Cellpro. To make matters worse, FMA Direct went out of the battery business. So what am I to do with their charger?”

A: If you look further into your Cellpro 4S instruction manual or at www.fmadirect.com/products.htm?cat=45&ind=4 you will find that FMA Direct offers adapters that allow you to plug Li-Poly battery packs supplied by Apogee, E-flite, ParkZone, ElectriFly, Poly-Quest, Thunder Power, Hobby Lobby Twenty, and Tanic into the charger. Any of the original FMA Direct Cellpro packs will plug directly into the 4S.

FMA Direct also sells its own node connector and cable so you can separately wire cells in any of your packs that don't have that feature. The instructions supplied with this cable are excellent, but please be careful not to short out any cells in the process.

Q302

Q: "Do RC clubs establish a convention for the use of the popular hook-and-fastener tape? I was thinking of suggesting this so that I could easily share some of my battery packs and radio equipment with my fellow club members."

A: This popular mounting tape achieves its adhesion by having one "hook" and one "fuzzy" surface. When the two come in contact they literally attract like magnets. It is known by the brand name Velcro.

The reader is suggesting that clubs set up a convention so that each member places the hook portion of the tape on the battery pack and the fuzzy (mating) surface on the model. This way, if you are at the flying field you can swap with a club member because every pack will have the hook surface.

We didn't make a thing out of this at my local SEFLI (Silent Electric Flyers of Long Island) club, but everyone seems to have adopted the same convention. My flying partner Tom Hunt and I have done this since back in the days when we competed in the AMA Electrics Nats in Muncie, Indiana.

When flying in competition, it is important that last-minute substitutions be made easily. We even use the same convention when attaching RC receivers and ESCs to aircraft fuselages. You never know when you might have a failure and you need some quick help. It is a good point!

Q303

Q: "I'm having trouble trying to locate a radial engine mount for a Cox Tee Dee .049 glow-fueled engine. I know there were many brands of such mounts years ago. Has the market 'dried up' or can some mounts still be purchased?"

A: I still have several such radial mounts in my collection. The one in the photograph is a Kraft-Hayes type KM-09 (the next size larger) because I don't have a KM-05 (.049 engine size) in my inventory. These mounts were generally made from a molded, filled nylon material.

Kraft-Hayes — Dayton, OH 45424; Tel: (937) 236-2455. The catalog item code is HAY059 — a Kraft-Hayes Engine Mount KM-05 — listing for only $2.25.

I also found fiberglass-filled nylon engine mounts on the Dave Brown Products Web site. Catalog number 0405 is intended for Cox .049 and .051 engines. You can obtain these from Dave Brown Products Inc. at 4560 Layhigh Rd., Hamilton, OH 45013; Tel: (513) 738-1576.

Another popular engine mount in its day was the Fourmost Racing Products Airflo. It was also a beam-to-radial mount, but the bottom was streamlined much like a forward-fuselage cowl. These were intended for use on 1/2A RC Pylon Racing models at the time.

I have no way of knowing if these mounts are still available. The address for Fourmost Products is 4040 24th Ave., Forest Grove, OR 97116; Tel.: (503) 357-2732; E-mail: [email protected]. It might be worth a try!

Q304

Q: "I keep hearing that you should add heat-shrink tubing to wire splices and where the wire goes into a connector block or pin. I picked up some of this tubing at my local RadioShack store, but I have to admit that every time I get the heat from my soldering iron in close proximity to the tubing it tends to melt before it shrinks. Did I buy the wrong tubing or am I applying the wrong kind of heat?"

A: I'm a firm believer in using heat-shrink tubing for almost all my electric wiring jobs. What you bought from RadioShack is fine, but I have found some that is quite firm, or rigid. Alternative suppliers include Batteries America (www.batteriesamerica.com), Radical RC (www.radicalrc.com), and Air Dynamics (www.airdyn.com).

The real problem is that you should never use heat from a soldering iron. As hot as the element gets, you still have to practically touch the tubing to get it to shrink. Invariably you will be close enough to melt the tubing before it gets a chance to shrink.

The best way to shrink the tubing is with a heat gun. These are the same tools we use to shrink iron-on covering and reshrink the same covering when it goes limp on us. You will be surprised to see how well that gun shrinks the tubing.

I pick up loads of this tubing at any of the regional hobby trade shows where they cut it off a reel. It comes in a variety of diameters (sizes), so make sure you always get a good selection. The suppliers I mentioned sell tubing in large diameters, such as 2, 3, and 4 inches.

This kind of tubing can be slipped over a battery pack you assembled. With an application of heat from the gun, you end up with a pack that looks like a pro assembled it.

Q305

Q: "I read your article titled 'The Case for Building Model Aircraft' (November 2005 MA). In it you show a lot of the tools you use for building your own models. I'd like to see more info presented in future articles or in your column."

A: When you get down to it, I don't use much in the way of tools. All the ones I use are referred to in that article. I still use a 20-year-old Dremel rotary device. It isn't modern by any long shot, but it does work well.

However, your request has merit. I'll try to work in more of the "tool"-type items in the future.

I build many airplanes using practically nothing in the form of implements. I balance my models with my fingertips under the wing. My most important "tool" is a trusty balsa-block building board.

I wrote a portion of MA's "From the Ground Up" series in 2004 that amounted to 10 articles. All of the articles are listed on the MA Web site at www.modelaircraft.org/mag/FTGUp/titlespageftup.htm. Parts 6, 9A, and 9B include details about building, assembly, and testing. These should be interesting to you.

I do have one item to share. It will probably sound like trivia, but I buy X-Acto No. 11 blades and single-edge razor blades in boxes of 100. I have definite reasons for this. I change these blades as often as a dozen times while I am building just one aircraft. A sharp blade builds the best aircraft!

Thanks for E-mailing me. I will pursue some of your ideas. MA

Transcribed from original scans by AI. Minor OCR errors may remain.