Tri gear to tail wheel weight and balance

[GoingHawgWyld]

Is there anyone that has done the conversion from tri gear to tail wheel that can tell me how it affected the weight and balance? I am currently sitting at 13.93 solo and 15 with a passneger. Will I have a more forward or aft C.G? I have a Series 7... I ordered the Matco 8" from Kitfox. It came with a 3 leaf spring set up. Looks super heavy duty. Do I really need all 3 springs or could I eliminate one and save some weight? I won't be flying on any rough stuff...

[DesertFox4]

Bump to keep this question alive. I know John McBean has done the conversion back and forth so when he gets time to log in he may enlighten us on the CG.

The 3 leaf tail spring seems to be the answer to preserving your rudder from damage if the two spring system fails which I read frequently that they do.

[akarmy]

Is there anyone that has done the conversion from tri gear to tail wheel that can tell me how it affected the weight and balance? I am currently sitting at 13.93 solo and 15 with a passneger. Will I have a more forward or aft C.G? I have a Series 7... I ordered the Matco 8" from Kitfox. It came with a 3 leaf spring set up. Looks super heavy duty. Do I really need all 3 springs or could I eliminate one and save some weight? I won't be flying on any rough stuff...

Yes get the 3 spring. There is quite a bit of weight on the tail of a series 7 and you don't want it to break!

I've had mine in both configs, however I don't have the trigear W&B in front of me, I'll have to dig it up. As a TG my empty moment is 11.53 and two up with baggage 15.17 with full fuel. I think it's slightly further aft than the tri gear.

These are my arms and weights, maybe you could plug them in with your values to compare.

EMPTY WEIGHT CG
Weighing Point Wht. (Lbs.) Arm, (in.) Moment
Left Main, (- tare) 387.00 -2.00 -774.00
Right Main (- tare) 383.00 -2.00 -766.00
Tail Wheel (+ tare) 67.00 167.00 11189.00
Nose Wheel (-tare) 0.00 0.00 0.00
TOTALS 837.00 ^ ^ ^ ^ ^ ^ ^ ^ 9649.00

[HighWing]

I can't imagine removing a fairly heavy structure from the nose of an airplane and replacing it with a fairly heavy structure over 4 times the arm at the rear and not having significant changes to the W&B. For the sake of argument, take a twenty pound item at a + 36" arm and you will have a moment of +540 inch pounds Take the a ten pound weight and mount it thirteen feet or 156" aft of the datum and you have a negative moment of 1560 inch pounds. It has to move the CG aft unless the nose wheel assembly weighs about sixty pounds - as the tail wheel spring and wheel will be close to the ten pounds.
Lowell

[akarmy]

I can't imagine removing a fairly heavy structure from the nose of an airplane and replacing it with a fairly heavy structure over 4 times the arm at the rear and not having significant changes to the W&B.

Keep in mind it's somewhat offset by moving the main gear forward as you are moving the gear, wheels and brakes as well.

but yes, I think it does move the cg aft a touch...

Would be better to have both before and after on the same plane with real numbers, then we would know.

[HighWing]

Very Good point. Did some prelim numbers and the CG might actually move forward a bit, but just guessing on my part. Good call.

Lowell

[Geowitz]

Forget all of the calculations and work. Just go with this setup...

http://www.aero-news.net/index.cfm?do=main.textpost&id=4f6bcd4a-c70a-434d-81f4-570ba8a7b088

Much more versatile in my opinion.

[rwaltman]

That article doesn't mention the optional Middle-Of-Nowhere-Attach for the counterweight. (Still under development when the article was published.)

With the MONA add-on, you can avoid installing the trim crank, sliding rails, and both the nose and tail wheels, landing and taking off on the remaining four wheels in full baby stroller configuration.

Roberto.

[GoingHawgWyld]

Looks like converting over will move the C.G. aft somwhat. Guess I will find out next week when I do the conversion. I have a fresh W&B now so I can compare then and post the results... Thanks!

[jdmcbean]

There are always other things that change... but for reasons of argument the CG moved slightly aft (.7)

Of course there are things like wheel pants, larger tires, different tail wheels etc... that will effect the overall change..

[GoingHawgWyld]

Funny how this article is on April 1st... Hmmmm.....

[Geowitz]

Sorry, wasn't trying to throw your thread off course... We know it's fake... Just threw it in for a little laugh. :p

[GoingHawgWyld]

Actually I was going for it. Might be a doable idea. When I started reading about shifting a weight to move CG rearward to be on the tail I kinda thought that was a tad off and then noticed the date.... Now if one were to put a set of rails under the plane to crank the gear forward and backward that would work... Glad people have a sence of humor!

[GoingHawgWyld]

I finally got around to finishing my conversion from tri gear to tail wheel yesterday. The weight and balance and as a tri gear the plane was 853 pounds empty (Included a 35 pound BRS and no wheel pants). The C.G. was at 12.72 inches.

After the conversion the plane weighed in at 863 pounds in the same configuration as before and also now includes the wheel pants and a GPS. The C.G. is now 14.74 inches. So I got a rearward movement of 2.02 inches. Would have been even more without the wheel pants and GPS. Seems high to me but I have had several people look at it and the numbers are pretty simple... A really small amount of weight hanging out there 167 inches while moving a large weight forward near C.G. makes a big difference!

After adding in for full main tank fuel, header tank, pilot and passenger it will end up at the most aft C.G. at 16 inches.

Not where I wanted to be but guess will work...

[rwaltman]

After adding in ... it will end up at the most aft C.G. at 16 inches.
Not where I wanted to be but guess will work...

Or not. Be VERY CAREFUL there ...

Roberto.

[Av8r3400]

The plane will handle beautifully at 16".

I've seen these planes flying on floats and handling fine over 17".