VG's or Thrustline mod

[teeweed]

I have a stock 150 Lycoming PA-18A with 31's. What mod would be best if you had to chose between VG's or the Thrustline mod. thanks teeweed

[Luke_theDrifter]

It really depends on what you "want" or "expect" from the mod.

A lot of folks say the thrust-line helps them take off shorter and land shorter, and some folks claim the VG's also help them land/take off shorter.

Not to be a wise azz, but practically speaking the single best thing is experince. Spend the $ on avgas. Take some time off of work, and set a goal to see how many hours, and how much 100LL you can burn in a month. If you take it seriously, even taking into consideration weather days, you can log around 100-150hrs in a month. At the end of that time compare your "perfomance" level before & after and see how much you gain from the experince mod.

[60below]

Luke,

Good suggestion. I had an instructor recommend the experience "mod" to me many years ago when I asked him if he thought I could benefit from a set of droop tips for my PA-12. I had just received my license. (to learn, as he put it) He asked what the price was and then suggested that I put the money in av-gas. Before anyone jumps all over me, I am not saying that modifications aren't helpful; I am saying that I believe he was right at that time, considering my level of experience.

Chuck

[cub_driver]

Luke and Chuck have both given good advice! Nothing beat experience and being current.

I was reluctant to have Vgs installed but I had a friend who had them installed on his plane and he raved about them until I got sick of hearing about it so I finally broke down and had them installed. That was a few years ago and I can honestly say they are a great mod. I really cant tell if they shaved any speed off my stall but what they did give me was good solid aileron control at slow speeds and that in itself is worth it to me.

I don't have the thrustline mod but flew in Christinas cub a couple years ago. Her plane and mine are almost twins with the exception of hers having the thrustline mod. I wanted to see how the thrustliine performed so Christina gave me the controls and we did some stalls. I will say Christians plane fly's faster and slower then my cub hands down. Christina has the VGs so she can utilize the slow speed of the thrustline mod, because she still has solid aileron authority.

If I was looking for a faster cruise I would get the Thrustline mod. If I wanted better STOL performance I would get the VGS, because of the aileron control. If you can afford them both there great mods and do complement each other.

Cub_Driver

[bob turner]

I gotta be the world's worst stick. I don't yet know how to measure landing performance, but for takeoff, I don't see the real advantage of modified cubs. The best performers seem to be the lightest ones with the most horsepower, and a prop that allows the horsepower to develop at that point where you are most interested. Only two or three of us have actual data, and we have posted it. My data says power is everything.

[JimC]

The keys to short takeoff are light weight, high power, increasing the deck angle, and tripping the flow to turbulent attached rather than letting it go turbulent seperated. The latter two are about as important as the first two.
JimC

[bob turner]

My data, sketchy as it is, might back that up. The winner so far is a VG-equipped heavy 160 HP with 8:50s and borer. The stock Cub with 160, 8:00s, and cruise prop is not far behind.

[S2D]

I don't see the real advantage of modified cubs. The best performers seem to be the lightest ones with the most horsepower, and a prop that allows the horsepower to develop at that point where you are most interested. .

Just remember Bob not all takeoffs are are from pavement or hard packed grass strips while empty. Getting out of the muck, goo and snow with a heavily loaded cub is where mods like VG's and TL's help.

[bob turner]

That may be true, but I am at least comparing apples and apples. Do you suppose one Cub might be really superior on level hard surface, and another that takes far longer to get off the ground on such an ideal surface will simply leap out of the muck? Why would a heavier, less powerful aircraft be better in the bush, anyway? VGs would lift it out?

[flynlow]

TeeWeed,
I would put the VG's on , they will be the most bang for the buck. They add a safety margin as well as performance gain.

Put the VG's on now and save up for the TL mod later.

steve

[S2D]

That may be true, but I am at least comparing apples and apples. Do you suppose one Cub might be really superior on level hard surface, and another that takes far longer to get off the ground on such an ideal surface will simply leap out of the muck? Why would a heavier, less powerful aircraft be better in the bush, anyway? VGs would lift it out?

You missed my point Bob. you said you don't see the advantage of modified cubs. You probably won't on a hard surface, cause the difference is minute. But put the same cub heavily loaded in mud or snow and try to horse it out, then you will see a difference between a stock and a modified cub. Same cub not a light vs heavy cub.

[ag-pilot]

Give me the TL any day/every day over the VGs. I did some pretty extensive testing with both mods and in every aspect of flight the TL mod did as advertised. I did not see any decrease in takeoff roll or landing roll and it did not change my aileron roll rate either. they did however reduce my power off full stick aft sink rate from 500+ to around 250 so I left them on. Also, Mark will send you the TL kit and NOT take a dime until your happy with it. Only vendor that offers that deal that I know.
Dave

[ag-pilot]

Steve, of the 2 mods which one do you think had more to do with you not making burger with your cub??? {Quote from flynlowMike,

Mike, I had a similar experience with the TL mod. I was dropping range cubes in 50 lb. sacks and I landed at the DZ to check the debri pattern.

I had approx 400' to take off and when I spun around and was in the process of taking off a 700 lb steer panicked and ran in front of the cub at about 200'. I usually pull full flaps and full back stick and then release stick pressure when the wheels come off. This time I held full back stick and flaps and expected the cub to mush and get very sloppy but it just kept chugging up hill very nose high and felt very, very slow but solid.

I might have missed the steer pre TL but I know the cub wouldn't climb at that attitude previously. ATTA BOY Mark!!

I know which one would have on my airplane.
Dave

[cabinflyer]

How much does a Thrustline kit cost??

[flynlow]

Dave,
"Making burger with your cub" Ha, I had to read that twice.

Ok, now you got me thinking.... The VG's reduced the stall speed and increased control at very low speeds. The TL helped the cub hang in the air and get off sooner.... So maybe both mods kept the steer intact.

My thinking is that you should have both but the VG's are sooo cheap....well at least cheaper, that they would be the most cost effective.

What I noticed most about the VG's was on approach the stick felt 'solid' instead of 'sloppy' and doing stalls ...well the cub wouldn't stall, just hang there with the stick full back level with no tendency to roll off on a wing like it did preVG's. Also the micro's on the tail kept it from 'giving up' in
the flair.

For me, the best way to describe the TL mod is that it made the cub 'lighter'.

Tough call Dave. Buy em both TeeWeed!!

steve

[bob turner]

If you reduce stall speed, shouldn't it make the takeoff and landing rolls shorter? If so, what are your before and after data? I cannot get any "before" data. I have only stock aircraft and other, different modified ones with which to measure.

The best way to get decent measurements is with full gas and dead calm winds on a smooth surface, in my opinion. Launching off of an unimproved surface puts too many variables in the system - such as launching off of a bump?

[Ruidoso Ron]

For me, the best way to describe the TL mod is that it made the cub 'lighter'.

My thoughts, exactly. The way I phrased it was that it reminded me of flying my old J-5.

[SJ]

I think of VG's as a safety mod first, and a performance mod second. I think the correct answer to the question is "both".

sj

[Rob]

Hi Teeweed,

Have you talked with Mark yet? I would recommend that before trying to decide between the two.
The VGs will work on just about any cub (although there was some talk of them exasperating the poor flying conditions of a really out of rig wing)
The thrustline on the other hand, will only improve the flying characteristics of a cub that "measures up" to specs. The bad news is that if your cub is tweaked, you will want to wait until rebuild to straighten it. The good news is that Mark will actually walk you through this over the phone, and will tell you up front if he thinks your cub is not a candidate.
As Steve pointed out... The VGs could actually be considered a safety mod. I didn't notice any of shorter or slower stuff... They did however tighten up the aileron feel at slow speed and help the flair.
Take care,Rob

[KingCub]

I have VG's already on my 180, but am considering adding the thrustline mod. Is there going to be a cowl fit problem with a Leading Edge Exhaust system?

[NimpoCub]

How much does a Thrustline kit cost??

$1800.

[cubscull]

Rob you beat me to it! you hit the nail on the head Mark will tell Tee weed the same thing.

[ag-pilot]

Kingcub, It should fit better. It will give you more room between the exhaust and the firewall at the bottom. My buddy has it on his 160 cub with LEEs exhaust with no trouble.
Dave

[heege-brigmann]

What's about the connection between the exhaust and the cabin-heat-vent.
Will that still fit?

[Steve Pierce]

Doesn't move that much but the SCAT hose makes up for it.