Thorp Air Command - T18.net

Hi!

Quick info what do you think about the third hole on the bending square tube.
Is it possible that the third hole is a starting point for a possible rupture?
I'm not a Thorp specialist but I never want to loose this weight on flight.





I need to sand blast the arm and see if some small crack is begening.
I want to know your idea about that!
Thanks again.

_________________
Thierry
French Canadian T-18
C-FPVE #091

I would be very cautious ! I am not a welding guy , but it may be possible to close up the 3rd hole with a torch ? Or cut and splice a new piece in . Or make an entire new weight/arm . Or buy one ?

RB

That's a mild steel Tube Thierry, The hole is not in a spot being of high stress. Clean it up,spotless, 45degree countersink the hole to get into some fresh material and Tig it closed, Make sure there are no cracks, make sure the tube doesn't get hot enough to loosen the lead weight at the end of the Tube........Dan

You can also put a piece of solid rod in the hole that runs from one side to the other and use it for filler,It would make the hole easier to fill and allow for less heat to close it up,weld bothe ends of the rod this will also reinforce the area with the hole in it if you are worried about the integrity of the tube. Dan

I open my AC43-13 and I see some interesting document. Dan your apsolutly true. I think a small welding with a inside doubler was correct.
I send you pictures after the reapir!!!

Merci.

_________________
Thierry
French Canadian T-18
C-FPVE #091

Hey guys,

Tried about 5 attempts to pour lead into a plaster mold with steel arms in it. Made nice patterns, nice mold, etc., but casting lead just doesnt work for me. I think plaster has too much air or something and I get a lot of bubbling. Let plaster sit for a week and in the oven 250F over an hour to get rid of any water vapor and still pretty poor castings. I've seen some that others have made and they look pretty rough too. I was hoping to come out good. Searching old newsletters I find nothing about making these.

Anyone with ideas on this, or a source of good ones to put on a new bird, please let me know. By the way, I recommend anyone to look back at the old newsletters. It's been a while for me and they're really fun.

Thanks, Les Krumel
Albuquerque

I made a mold out of thin steel and shaped it like a cookie cutter. Foiled taped a flat piece steel to close up one side and poured. I also tinned the square tube where it attaches to the lead.

Les,
In my experience, the trick to getting a good lead molded piece is to pre-heat the mold. You can't do that with plaster -because it hasn't got enough mass & other reasons. Steel or even aluminum works well with lead. If the mold is cold, the lead starts to harden as soon as it hits, causing stratification, possible voids, etc. If the mold is not too thin & has some mass, that helps too because it doesn't cool off as quick. I'll heat the mold to 400 or 500 degrees in the oven before taking it out & pouring the lead. I've even heated molds on the range top in the kitchen, while melting the lead right there also. My wife loves that.
It is important to tin the steel arms before molding the lead, as Bill said. Don't splash, but don't "piddle" around - pour it right in so that you're never pouring lead on top of lead that has already started to solidify.

_________________
John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Or you can call Mike.
I'll have the weight molds shortly (as soon as Mike gets healthy) and I'll pour you some.
Cubes

Hey guys,

I'm still in need of aileron weights. If none are available I'll try milling a mold from aluminum. I'm down to a short one-page checklist of things to do before N48LK is ready for airworthiness inspection. Getting exciting now.

Thanks.
Les Krumel,
Albuquerque

Les,

I made my molds out of some scrap strip steel. I cut a notch in the cookie cutter looking mold to let the arm with pin in. The whole thing was placed on a plate for the pour. Easy to knock it out once cooled. Don't make the project harder than it is.

_________________
Bob Highley
N711SH
SN 835
KLAL

Les, I have a few sets of spares. You're welcome to a set.

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

I can make some too. Let me know.
Cubes

Thanks for the response guys.

Bob, I tried 5 times with the mold I made and a couple of times the problem I had was springing a leak. Just a small crack and what a mess! I think I did good with the rest of the project and wanted to a nice job with this too. I might be able to get it but I'm real close to the finish line; the best thing at this point is just to get a pair already made.

Lee, if you already have a good set please PM me and let me know what I need to do.

Thanks again,
Les K

What is the approved aileron balance? I see some people are adding aileron trim which will move the CG aft. How much does this affect balance and how critical is the aileron weight (for example, how much weight can the aileron trailing edge have)?