Ty,
Tough one to answer. Kind of like when the wife asks,"does this dress make me look fat"
no dear it makes you look hot 

I have given serious thought about replacing the ST .46 with a ST .51. 

Mine started life with a very good ST 46 but just wasn't quite enough. The retrofit was a bit of a challenge but it came out pretty well. I drilled another set of rear holes in the 51 to match the 46 mounting holes. The engine shaft is a bit longer, had to go to a Dubro plastic spinner with the recessed back plate to make it look right.

The skylark is a great stunt ship but has a thick wing and needs a really strong engine to do it justice. If your Skylark is the same wing area as mine your wing loading is 13.37 oz/sq ft. That isn't too bad, I know one expert from Dallas that says he builds for 13 to 14 oz/sq ft and feels it helps in the wind.

You are going to add two ounces with a 51 which will push the wing loading to 13.84 oz/sq ft. still not bad enough to make it a wall hanger and with the extra power it will be fine. You will need at least a 5 1/2 ounce tank and maybe a little tail weight depending on how it balances with the 46.

Good luck and hope to see it at a contest some day..

BTW: The best flying stunt ship I have is 13.83 oz/sq ft.

HI Pete. Mine has 667 sq in of wing area. 58 x 13 x 10.  It is a Marks Models kit. I have three ST .60, so maybe one of them would be better    I am sure the RSM kit would have come out lighter. Also UHP is coming out with the Lark by Ed Southwick. If theri balsa holds true, it will be very light.

That changes the picture.. forget everything I said except to say a 46 is for sure not enough motor.

Thanks Ty:  The original plan shall remain unchanged - build the 614 Sq In version and use a ST-46 in it, that is why I am glad to hear that yours is the bigger version.  I remember seeing Ed fly his 60 powered Skylark at Whittier Narrows many moons ago.  A good flier, I think it did have an ST-60 and a Disney character for a pilot.  He is missed.  RE the Lark - Phil Granderson had one a few years ago - probably still does.  Like all of Phil's planes, first row finish and very light. I will look forward to the UHP version.   

I think the original Argus was in the 29-32 oz. range, with a Fox 29.  The extra power of the Aerotiger should help, but I wouldn't expect blazing sharp corners.

I guess the plane feels lighter kinda like the Mustang did with a new Rolls Royce Merlin in it. Purely in my mind and lonely too.


I don't know if you know this, Ty, but an Allison powered A model Mustang is thirty mph faster than a D at the same power settings. Set 36 inches and 2450 rpm on both, side by side, and the A model just walks away. It's lighter and smaller (really, the fuse is four inches taller on the D) with less drag, both induced and parasitic.
Chris...

Ty     You know I have used ST/46 in 90% of the planes I have flown since 1980. It's a great motor up to 55 ounces and 620 sq inch wing. Lots of people use them in 700sq" wings and 60 ounces but many problems start to come up with the motor when that is done. If used in a smaller model 610sq" they will go a 1000 flights with little problems. All the old problems are gone with the ABC conversion but they still have about the same power.Years ago when people flew 60 size models with the ST/46 they were constantly chasing a new ring.The USA-1 is a good example.Billy was always looking for more power but he made it work. The ST/51 is a great replacement for the ST/46. In the 80's I won a lot of contests with a 690 SQ" 60 oz 46 powered plane. I later gave it away and the guy put a ST/60 in it and it was a much better plane. I flew it and thought WOW if I had had that I would have done even better.
Ed