Sometime last winter I bought some white silicone tubing from McMaster Carr. I also bought some of the traditional black latex tubing and some red silicone that is of a higher durometer number.

For making Combat bladders, the black latex is a known item.  When it is fresh, it works perfectly.  After a period of time, more than a week and less than six months, it deteriorates.  It gets gooey and will eventually develop pinholes.

Bladders made from the black latex, white silicone
and red silicone fuel feed tubing.

The white silicone with very limited testing failed at the engine end two or three times before developing a pinhole in the middle, I assume where it goes through the bellcrank.  This is with less than half a dozen flights.

The red silicone with slightly more runs has failed at the engine connection twice, but otherwise given no problems.  Because of the higher durometer, it might not work with the internal shutoffs.  The best feature of the red is that it costs about one third as much as the others.

If I could only use one, it would be the black latex.  Since I have a choice, I will use the red for test flying as it gives no problems that can't be tolerated.  I will use the black latex for contests and discard it when it gets bad.  I will find uses for the white silicone, but not use it in contests unless I have no other choice.

Lots of props -- and a vintage Johnson Combat engine.

I just purchased a batch of 9x5 and 10x4 Master Airscrew propellers for Speed Limit Combat along with APC propellers for ½-A and Fast.  These had been available at my local hobby shop so I got used to using them.  When I needed more, I learned the hobby shop could no longer get them from their distributor.  It seems there is only one distributor left in the U.S. for model airplane-related merchandise and that distributor no longer stocks everything you might need. So I had to order online.

When the props came, I put off getting them out of the packaging because I dreaded the work that would be involved with getting them ready to use.  In the past with Master Airscrew propellors I have always had to drill the center holes because they were just a bit too small to even be able to force them onto a standard ¼" shaft.  Also, the flashing on the blades was so bad you had to be very careful handling them to keep from cutting yourself.  This took several minutes per prop to clean up.

When I finally took them out of the package I was pleasantly surprised.  First, the size was clearly marked on one blade so I didn’t have to squint at the tiny printing on the hub.  Next, they now slide easily onto a ¼” shaft.  Finally, while there is still a bit of flashing on the blades it can easily be cleaned up in just a few seconds per prop.  Hooray for Master Airscrew!

I have just gotten stared on the July 20202 issue of Model Aviation magazine.  Many longtime control line modelers complain that everything in this magazine is dedicated to R/C and drone flyers and they refuse to read it.  As a builder, I try to learn from everyone and rarely if ever read a copy of this magazine without learning something.

This issue has an article done by Charlee Smith of Bob Smith Industries about their adhesives on Page 24.  It is an absolute must read!

While I really like all of the adhesives I’ve used from Bob Smith Industries, I must confess most of my building is done with adhesives from Harbor Freight.  I don't know who makes their adhesive products but I have used nearly all of them.  I use their super glue and super glue gel almost exclusively for building.  The viscosity is perfect, the small tubes are really handy, and it's cheap enough that when the nozzle clogs you can just throw it away and grab another one. I put fresh tubes of these along with accelerator in my pit box before each contest.

I mostly use Bob Smith epoxies because they come in bigger containers.  I think the Harbor Freight 5 minute epoxy is a superior product, but the tubes are so small I was always running out.  I do keep that in my toolbox.  Another Harbor Freight epoxy to keep in your toolbox is their 90 second epoxy.  I’ve used it a number of times to get myself going at a contest.

A good supply of balsa is essential in any workshop. Lane Puckett's spreadsheet helps calculate the weight.

Lane Puckett posted an Excel spreadsheet for calculating balsa weight in the MACA Facebook page recently.  I used it as the needed inspiration to finally weigh this much of my balsa supply. (EDITOR'S NOTE: An error in the balsa spreadsheet was corrected on Dec. 24, 2020.)

That’s it for this month.  Here’s hoping we’re all back to normal sometime soon.