Thorp Air Command - T18.net

I just borrowed EAA326 club scales.
I'll be at the hangar tomorrow morning to weigh FEISTY and my son Peter's RV-4.
It's been decades sinse these planes have been weighed.
Can someone please tell me how to establish 'level' in pitch on a T-18?
I have the platform jack to raise the tailwheel, I need to know where I place the level.
I just weighed my RV-8 project. It's 1073 Lbs, and using a W&B spreadsheet, I have distributed the weight well. I still have radios, fairings, interior panels & seat cushions to add, so I'm hoping to weigh in at 1099 lbs
Which would be very light and well balanced for a turbocharged auto conversion.
So any help so I can get toward a valid W&B would be greatly appreciated.

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Scott Emery
EAA Chapter 326
T-18 N18TE

Level along the reinforcing strip below the cockpit entry (WL42).

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Bob Highley
N711SH
SN 835
KLAL

I used the WINN Weight and Balance CD from Spruce . Very easy to use . Just plug in the data and you get what you need. No complicated math . You can configure for every possible situation and it will tell you if you are within limits. I used the basic W & B data from the Forum to verify the WINN Data and it was VERY close to those numbers . Not a bad deal for $19.99 . I hate math !

RB

Now I gone and done it!
I got tired of the old starter, getting weaker and slower.
I got a Skytec flyweight starter, and today, in cold sunny weather I changed the starter out.
Even at freezing temperature, the skytec starter cranks the engine over quickly. although my fingers were numb
It's also about 6 lbs lighter, so tomorrow I'll do the weight & Balance.
My fuel sounding rod is marked right off the newsletter guide, indicating just under 22 gallons on board. I de-fueled the RV-8 to weigh it. I suppose it's better to de-fuel ol' FEISTY than to guess how much fuel is aboard....
If the W&B permits, I hope to remove the 27 lb battery + fiberglass box, and mount an PC680 battery farther forward. Like under the copilot seat or on the firewall.

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Scott Emery
EAA Chapter 326
T-18 N18TE

Ya, now ya done it, done gone and made me envious , I could use some quicker starter power, my prestolite starter is acting kinda old and feeble lately.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

I worried;
Intially, I decided it was the starter, but then, over on the vansairforce site, the problem was frequently the $10 starter relay. So I worried that I bought the expensive part, and did not solve the problem. Although I'm perfectly happy to shed about 6 pounds from the plane ( on me it's harder)
So, glad I was that it cranked mightily. I had contemplated wiring around the starter relay, (the starter has a relay built-in) as the wire to the starter was now too short, but the ships power came off it, and the wire from the relay was clamped and spaced so nicely to clear and avoid the fuel hoses & fuel pump. I hate to mess up legacy work that was done so well, just to pull a 'Short' wire until it can do the job. I found a short piece of appropriate wire and got on with it.

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Scott Emery
EAA Chapter 326
T-18 N18TE

Scott - I'm 2 beers into the playoff game, but if you remove something heavy and add something light, yet wish to have the same moment and hence, CG, dontcha gotta move it farther away, not closer?......maybe I just don't know where your battery boat anchor is located.

Did you get the SkyTec with the KPS ? Kickback Protection System .

RB

Fraser,
It depends on where you are moving the heavy item to balance things out. In Scott's case he remove weight from the front of the airplane and his battery is in the aft part on the plane so he needs to move it closer to the CG. If he moved something in the front he would have to move it away from the CG to make things balance. Clear as mud, right?

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

I feel what your puttin down

Scott,

I control my SkyTec directly from the start switch, eliminating the start solenoid/relay also. Keep in mind that the normal keyed ignition switch w/start position may not be adequate to do this without the threat of damage to the switch. The SkyTec solenoid will draw considerably more amperage than the separate external solenoid did because it is mechanically engaging the starter as well as completing the motor circuit. I used a separate heavy-duty start switch.

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

It's generally accepted that airplanes & boats gain weight over their service lives, and FEISTY seems to fit this category.
I used the EZ-Weigh scales we have in EAAchapter 326' tool room. The ramps & tail wheel jacking platform are for RV's, so I had to do some scrounging to get FEISTY level.
I stripped it out, noted 6 qts oil and defuelled it until the siphon quit, which I'll call 1 gallon unusable fuel. Fred Ferguson, the builder made a nice W&B page with profile view and arms for the wheels.
I easily (but for the math) multiplied the weights by the arms to get the moments, added the moments, and devided by the total weight:
LF=431. RF=447. =878 * 53.95 = 47368.1
TW=65 * 214.08 = 13915.2. Total moment = 61283.3 devided by total weight 943 = 64.9875"
Empty weight 943 (6 quarts oil and 1 gallon gas)
CG= 64.98
Did I do it right?

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Scott Emery
EAA Chapter 326
T-18 N18TE

So I added 27 more gallons fuel to top it off, weighed in myself, my wife, the headsets, seat cushions iPad etc, guessing 375# add 10# baggage for the little box of junk we all need, and Ol FEISTY is 1490# and CG is 68.49". That's about 2/3 back from 61 toward 72"....
Anyway, the 65# tail wheel weight is a full 10# more than the legacy weight of 55#.
And No, I did not add that Mercruiser trim pot and indicator! Little did I know at the time how little I would need it, and how important weight can be 'back there'.

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Scott Emery
EAA Chapter 326
T-18 N18TE

At a quick glance, it looks like your math is correct. 65 pounds on the tail sounds very, very high. Should be closer to 50. But if the balance works, go with it.
Cubes

Incidentally, I rely more on percentage CG, than straight arm. The percentage CG should be 15 to 32.
Cubes