Scale Matters

View from the 707. Photo from Internet. All other photos by Orin Humphries unless noted.

Potpourri

By Orin Humphries
July 2025

Lore

The 707 Roll

Our mechanic, Ben, shared this one night on the phone when I’d said that I had bumped into famous test pilot Tex Johnston in the Pilot Shop at Boeing Field back in 1990.

“I ran into Tex,”,Ben related, “and asked him about rolling the 707 over Lake Washington during that Seafair.”

But first, let me set the scene as we, the public, heard about it after the fact through the media. The press interviewed Tex about this, of course, and Tex had to carefully choose his words for the public. What we read in the paper was that the Boeing president called him into the head office for an explanation. Tex said to the press, “I told the president that the fuel, oil and hydraulic systems are designed for a one-G environment. This roll maneuver is a one-G maneuver at all times. The airplane didn’t know it wasn’t right side up.”

Back, now, to Ben’s conversation with Tex some time afterward:

Ben said, “I asked Tex what he had told the company president.”

Tex replied, “I asked him, ‘What makes you think that was the only time?’ ”

“How many times had you rolled it?” Ben asked him.

“Many times.”

Now Ben was curious. “Have any other Boeing airliners been rolled?”

“ALL of them.”

(Pause)

“What about the 747?” Ben asked.

Tex paused pensively, choosing his words with care, “Not for public dissemination.”

By the way, the non-pilot public calls that maneuver “barrel rolls.” “Not so,” corrected Ben. “It is an aileron roll.”

I have always wanted to know how that is done, so I asked Ben.

Ben explained, “You place your feet on the floor.” (That is, you do not use rudder.) You push the stick forward to get a 10-degree nose-down attitude for speed. Then, you pull the stick back to establish a 10-degree nose-up attitude. Once you have that, you throw in maximum aileron and take the back pressure off the stick for neutral elevator.” You keep the stick over until you stop the maneuver.”
(A barrel roll is a different maneuver in which you do use rudder.)

Basics: Soldering

There are two kinds of soldering tools, two kinds of wire that we modelers commonly deal with, and two kinds of soldering flux. There is a 25Watt soldering pencil and a two-level, 100/140Watt (or so) gun. The wires come in two different surfaces: bare (shiny) and black (oxide coated). Flux is resin or acid.

The tools are used this way: For wires 1/16inch and smaller, use the 25Watt pencil. More heat than that will burn the wire which then won’t take the solder. For wires over 1/16inch diameter, used the big gun. But for relatively smaller items, use only the first click on the trigger, 100Watts. Use the higher power, second click,140Watts, for the larger jobs.

For shiny wire, sand the wire first to break a likely-invisible oxide coating that, even though the surface may look clean, metals pick up from the air over time. Then use the resin core solder, or common, non-acid soldering pastes from the hardware department to facilitate the soldering. Pre-tin the surfaces to be joined. Clean the resin flux away with alcohol or paint thinner and oil the joint to prevent the bare wire next to it from rusting.

With black-finish wire, first sand away the black oxide protective coating. For this wire, use acid core solder, as resin core will not work. Note that even if your sanding job looks complete, the soldering won't be absolutely even; it will have very tiny blotches where the solder didn’t stick. For the acid core jobs, rinse the area with a solution of baking soda to neutralize the acid, and then oil the area, especially for these acid core jobs.

In either case, “heat the work, not the solder.” I do have to start the whole job by getting a drop of solder on the hot tip for good heat conduction to the job. Then, flow enough solder into the work to fill the gap, and do this for both sides of the job. Get the solder hot enough to flow around, looking shiny.

.049s: Siphoning and Needle Valves

Silicone "standpipes" help prevent fuel siphoning from tanks.

On my little twin 1/2A bird, a Grumman XF5F-1, the cylinders of these engines have exhaust ports that face aft enough to blow over the standpipes on the tanks. I noticed that some fuel siphoned out during runs thanks to Herr Bernoulli. On Cox engines, the cylinders thread into the crankcases at random “clock” directions, and some wind up with exhaust ports facing somewhat aft.

B-25

My model is in my right hand.

At the 2024 Regionals, I couldn’t get my engines on my B-25 to run. This was early before the wind came up. This was a mystery, because the day before we packed up the van to go to Roseburg, I had purposefully run the engines in my garage in Lynnwood, Wash. At the contest the needle valves were so far off the plane was not going to fly that day. I couldn’t believe that they could be that far off. I disassembled the engines/tanks to eliminate variables. Finally, I recognized that they were extremely rich, so much so that I looked around to see if Noah was pulling up to the dock (…) I tried turning the needle valves up to a half turn to get a good mixture, but no joy. I then flew by bigger birds, and returned to the 1/2As afterwards. By the time I finally got them running, the wind had come up and the B-25 didn’t fly that year.

It had taken an entire 360 degree turn of the needle valves to get the right mixture. Back home, in my garage it again took an entire 360 degrees the other way to get the engines to run. My first guess was perhaps an altitude difference between the Roseburg Airport and my Lynnwood garage. However, Ben got me the altitude of my garage, and it was only 17 feet different. That could not be the explanation for the extreme (to me) difference in needle valve setting. I finally had to accept that the difference was due solely to the difference from one day’s atmosphere to the next. For our .35, etc., size engines, how much do you change your needle valve settings from one flying session to the next at your home field? That’s what had gotten me at Roseburg.

Callie Graphics

This is the Stinson logo on the fin of my new project.

For years I have read about other modelers ordering various markings for their projects from Callie Graphics and have seen the results in the magazines. I have always assumed this company to be a big graphics house that would logically charge quite a bit for one-off orders, so, I never checked it out. I had to go to “them” for the Stinson logo for my SR-6. What a pleasant surprise!

Callie, the fellow, sent me three pairs of the logos and gratis, three more of a plainer version, postage included, for $10! The stickers are rub-on type and are made of vinyl so that they are fuelproof. I have since ordered N-numbers for the top of the SR-6’s rudder, and similar for my venerable Staggerwing, plus Beechcraft logos for the fin of my Staggerwing, cost $8 with postage. Okay, so as I finally got up on this horse, I have ordered Hamilton-Standard decals for my scale SR-6 prop and a representative manufacturer’s label for the dummy engine’s front case, $10.

Callie has many markings already in his files, so I didn’t have to send him a copy. His service is punctual.

12v. Battery

Many of us have a 12v battery in a line box, and we wonder how much life is left in it when we head to the field. Well, that’s falling off a log easy, it turns out. First, this short piece in no way is here to cover the subject of all 12volt batteries. It is about only the ones we use to spin our starters and run our fuel pumps. By the way, the bible on all 12volts and their myriad uses is the book, is “Living With 12 Volts” and is on Amazon for $13.

We use sealed batteries and their ilk. For them, the state of charge is found by simply using your voltmeter. The max charge is 14.4volts, and the minimum safe low is 12.2volts. the amount of discharge at a given point is simply the voltage at that moment, in between those two numbers. As most but not all know, the voltage drops in some fashion with usage. It does not stay at any steady level.

Example: Mine was at 13.6volts when I checked. Well, as you can see above, there is a 2.2voltage range between the max charge and minimum safe discharge. My battery, then was discharged to a level of 1.4/2.2. (12.2 – 13.6 = 1.4; the range is 14.4 – 12.2 = 2.2.)
But, don’t put your battery on the charger this afternoon and come take it off sometime tomorrow. Check in on it and take it off when it reaches 14.2volts. Some types can be harmed if left there.

Building Boards

I have a balsa building board made in butcher block style. This approach is supposed to be warp proof. However, in the usual humidity range of the Puget Sound region, I found that mine did in fact warp a little. I solved this by screwing the boards to the underlying table.

Composite Rod with Large Holes

I use composite (com-POS-it) rods for pushrods as they eliminate the need for pushrod guides. The hole in the composite rods is larger than the wire that we put the clevis on. To adapt the wire up to the hole diameter, I use two sizes of telescoping brass tube. I leave a small pocket in the adaptor for glue security, and I use epoxy glue. Since both ends of the composite rod are to be so plugged, I use a small diamond-tipped router on my Moto-Tool to make an air relief hole in the rod. Otherwise, in pushing the adapted rod into the rod’s other end compresses the air inside and tries to eject the new end. I got the diamond-tipped routers from Micro-Mark.

Heat Sinks

Sometimes we need to solder things that are in contact with soft materials that could be damaged. Rather than spending money at the hardware store for a specialty heat absorbing product, I use materials at hand. Such as, extra nuts or washers and scraps of aluminum.

Rib Trimming

In some kits or plans, we have the desire to have at least the appearance of flaps or ailerons. That may involve trimming ribs. I built a jig to hold the rib in place for a razor saw, and durable aluminum bars to guide the saw.

Profile MLG Mounting

Old kits and plans for Profile models had us put the ends of the right and left landing gear wires into the same fuselage hole, meeting at the fuselage centerline. We always lined the holes with brass tubing, hoping that would have enough strength to resist the torque of landings, especially on grass fields. We all know that never worked. The penetrating ends of the gear wires overcame the reaction torques that the fuselage wood and the brass tube could provide.

To solve this, we make the upper ends of the gear wires of different heights. Each gear leg has its own, separate tube-lined hole. The part of each leg that penetrates the fuselage must reach all the way to the opposite surface. It is the 1/8” plywood on the far side that provides adequate resistance to twisting inside the fuselage from grass landings.

Further, 1/8-inch diameter wire for gear legs on .35-size modes and up was never adequate for landing on grass fields. We were forever straightening the legs after maybe two or three landings. Use not less than 5/32-inch diameter wire, where weight is not a consideration, and you are on grass.

Gary’s nacelles

A former student of mine from the Libby Jr. High model Club, Gary Dowler of Spokane, Wash., is scratch building a Boeing XB-15. He shares his project photos with us on how he made his nacelles.

Gary made his cowl lips by mounting a block on a frame to turn it on his drill press, not needing a lathe.

This is the lip mount.

He built up the sides of the nacelles with strips to be sanded. He then added blocks for the accessory section of a nacelle as you see in the next photo.

He fitted the nacelle to its place on a wing section building tool by sliding the nacelle along sandpaper on the wing.

The final product.

Basics: Framing

When we build, we commonly start with one side of the frames (formers) pinned over the plan. When gluing on the other sides of the frames, we worry about getting them straight across. This is what I tried for my Stinson project.

Break-in Stand Use

Everybody has their own break-in stands; this is mine. It has one small quirk that I will share.

I had to get all four of my P-3’s OS .30 engines tuned up and ready for flight someday. I got down my break-in stand and threw it in the trunk, heading for the field. My stand has a 16-fluid-ounce tank, which makes the distance from the tank’s clunk to the spray bar about one foot. I noticed as I was fishing around for the settings for these old carbs (1970’s vintage) where if the engine were at mid-range and I suddenly opened the throttle, the engine would just die sharply. That was no bueno. This was a mystery for a couple of days as I went from engine to engine.

One the evening, the light came on. Jamming the throttle open creates a very sudden demand for a big increase in fuel flow. This setup is on muffler pressure feed, mind you. However, the fuel train in the feed tube was a significant mass to be accelerated; remember that in my setup the fuel column is 12” long. In a model the fuel train is normally about 3 or 4 inches, right? Muffler pressure was not enough to accelerate the fuel stream. Mystery solved. On this stand, open the throttles slower.

Phew! That was a blast. (Test is Tuesday, though! Just kidding.)