Thrust Line Conversion

[flathorn]

Does anyone have any information about doing a thrust-line conversion on a T-Craft, specifically an F19?
I know that there are many being done on the local PA18's and PA12's through STC, but wasn't sure if anything was available for the F19.
I also understand the F19 could benefit from this conversion more than the BC12D, as the thrust line is different. Is that true or hearsay, to anybody's knowledge? I'm helping rebuild a PA12 this was done to, and am very interested in it, as I could recoup some of the speed lost through modifications.
I know there are several jerry-rigged ones being done, but haven't talked to anyone with personal experience so far. Unless the entire cowl is rebuilt planes with the conversion are easy to spot as the uplift on the engine requires a strip be added to the side and bottom of the cowl to cover the gap.

Kathy

[jgerard]

Re: Thrust Line Conversion

I hang out with a lot of cub pilots and for sure the thrust mod is one of the best things you can do a pa-18. Not sure how the T would respond, totally different airfoil. P.M. me and I'll give you a few hints on making the T a better short field airplane.

Jason
N43643

[VictorBravo]

Re: Thrust Line Conversion

Jason, I'd be glad to hear your experiences about making it a better short field airplane too. And I'd love to hear just what a "thrust line adjustment" means. Which direction of thrust line adjustment are you saying makes a difference in a Cub, T-craft or whatever?

[jgerard]

Re: Thrust Line Conversion

http://www.supercub.org/phpbb2/viewtopic.php?t=3856&highlight=thrustline

this should explain what the pa18 guys have been up to

Jason
N43643

[Robert Lees]

Re: Thrust Line Conversion

That's quite interesting. Page 9 of that thread shows some photos of the length of the mod at the firewall...looks to be about a 2" extension for 4 degrees of engine lift.

What's the thrustline of the 65 Taylorcraft?

[birdlegs]

Re: Thrust Line Conversion

It reads like an oversight from the enginnering staff at lockhaven, Bet Forrest knows where the "Thrust line" is on the Taylor designs.

[Jim Hartley]

Re: Thrust Line Conversion

Jason, I'd be glad to hear your experiences about making it a better short field airplane too.

I think we all would like to hear Jason...

Jim

[jgerard]

Re: Thrust Line Conversion

Now don't jump all over me at once for what I am about to post. I would recommend you take everything on this forum with a grain of salt

The Tcraft wing responds nicely, well at-least mine does, to removing the washout from the wing. More lift is created from removing the negative AOA at the out board part of the wing. Some may say that it is dangerous to fly a plane out of rig from the factory specs, Mater a fact your insurance Co. may not cover you if they find that the crash was a result of improper rigging. So do what you want and please don't say "jason told me it was ok change the washout...ect." Add a set of Vg's to your now flat wing and that will give you back all the feedback and smooth Tcraft style stall. I DON'T have a set myself yet, but will in the near future. You can also rig the ailerons to hang low from the T.E. about 1/4" with a flight load. this will slow you down a bit, but we are not concerned with speed here. The slightly drooping ailerons also increase the camber at the outer section of the wing which helps delay the stall also, just like washout would.

Bigger tires help you take-off and land shorter. Better angle of attack for takeoff and you can bring it in just a bit slower with a touch of power for landing and not have to drag the tail-wheel across the ground with the mains still 6-8" off the ground. Plus the lower tire pressure you can run with the bigger tires helps slow you down quicker and reduces the tendency to bounce. Good breaks are a must. Anyone that can't figure out how to make the shins work can buy me (or Rob Lees , nice pics on your website man!) a plane ticket and I'll come out and show you how to properly set them up. They work fine when maintained and adjusted properly. My breaks are strong enough to lock up and skid 8.50's, and can hold a full power run-up easily. for more info on shin brakes use the search function of this forum.

Long flat props = better takeoff and landing. An engine is rated for max continuos HP at redline. 2150 rpm on takeoff from an A65 is not 65hp, Doesn't matter that you are at full throttle. HP is a derivative of RPM. You can't hurt the engine by letting her spin to to max rpm. There are a few of the larger cont and lyc. that have a max continuos and a max never exceed rpm usually limited to 3 min for take off. Just don't operate out outside the manufactures recommendations and she'll stay to together all the way to TBO. For short field work you want the longest prop allowed for your engine. This also helps with landing by creating a larger disc area to help slow the plane down. 70 to 74" equals more than 4 square feet disc area.

Pilot technique is more important than any mod to the airframe when operating off airport. Knowledge, skill, and judgment are the 3 basic principals in flying. Do I know what to do? Can I actually do what I need to do? Should I bee doing this? I am not an instructor by any means but if people want to talk about short field techniques we should start a different thread. There is enough of us who use these planes for more than the $100 hamburger that combined we should be able to provide at-least some info on what does and does not work. Practice continuously to stay sharp. What works in my plane may not work so well in yours. There is no room for hesitation or lack of confidence when working a short strip with a technical approach. The most important instrument here is your butt, so make sure you understand what it is telling you!

Jason
N43643

PS - Keep it Light!

http://gallery.taylorcraft.org/view_photo.php?set_albumName=N43643&id=skykomish_river_1

[birdlegs]

Re: Thrust Line on "T" cart's

Rob; I was reading my specs book/manual last night,it reads....(Quote)The thrust line is parallel to the line at the top surface of the Horizontal stab. (Enquote) This is the same surface used to level the airframe when rigging the wing wash. Sounds like a zero degree thrust line like a J-3.to me. anyone concur?

[VictorBravo]

Re: Thrust Line Conversion

Uhhh...Boys.... take a gander at this.

Using "up-thrust" instead of downthrust is all well and good, but it will put your airplane out of trim at cruise speed. It will likely have a very good effect on STOL takeoffs.

However, just like Dancing can lead to Marijuana (in the old anti-drug films of the 60's), up-thrust can lead to re-rigging your incidence angles, which can lead you to fly the airplane at aft CG, which can lead to dancing (not the good kind). IMHO, someone can experiment with the up-thrust at their own discretion but I would not let it lead to aft CG experimentation.

Removing the wash-out sounds fine for slow speed work but remember that the OTHER reason for washout is to reduce the structural loads at high G loading. This is called "geometric washout" and it serves two separate functions. Be aware of both before you start screwing in the strut clevises.

I have to vote strongly against drooping the ailerons. It ain't safe.

FIRST, it makes the tips stall faster than the rest of the wing. This is WORSENED by taking out the washout BTW. VG's might exacerbate this as well. My understanding is that with the VG's the airplane waits longer before it stalls, but when it lets go it lets go. IF THAT IS TRUE then drooped ailersons will create an unsafe situation.

Second it increases the aerodynamic loads at high G loadings.

The big tires and flat props make totally good sense to me.

Bill

[flathorn]

Re: Thrust Line Conversion

A quick update on the Thrust Line modification:
I talked to the owner of Thrust Line Inc. (he lives in this area), and he didn't do a mod for the F19 because he said *theoretically*, from what he was told by the present Taylorcraft ownership, the F19 was zero thrust-lined on makeup, but that the BC12's etc, could benefit from the mod. He did say though, that he'd had some difficulities dealing with the present ownership of the company and wasn't comfortable with the expertise of the information given him, but was going with that answer at the present time.
I just wanted to pass on what I had learned, since I brought this question up. The owner of TLI said he would get back to me after he does a little more research, so I'll let you know if this information changes.
Kathy
3585T