ST .56 & .60 for Super D

[GeneChristensen]

Hi all,
Picked up a couple of U/C Super Tigre, chromed ringed, good bearings and compression, used engines, for Super D. The .56 has the NV through the venturi and the .60 has it behind the venturi. The .56 weighes about 11.5 oz and the .60 is 12.5 oz. I was going to fly these with pressure, remove the NV from the .56, replace with fuel inlet and use a remote NV. I would also like to open the venturi. The venturis on these engines, especially the .60, are quite small compared to other engines.
My cox .15 Conquest is larger. I’ve attached a photo to show their sizes. In the photo the first engine is a K&B 6.5, then the ST .56, then the ST .60, then a TD .09 for comparison. Does anybody know why the venturis are so small and how far should they be opened for pressure.
Are these good engines for Super D?

Thanks, Chris

[DAN BERRY]

Well. one will work for SuperD. Super D requires a .60-.65 and 1000 squares. A .56 isn’t big enough. Ream out the venturi on the 60. Leave about 1/16 ” wall thickness and let ‘er go. There are more powerful engines out there. That doesn’t mean that the ST 60 won’t work.
Start building.

[Anonymous]

Hi Chris

The answer to your venturi question will be found in your description of the previous use for these engines (U/C) the power requirements for U-control are different to Free Flight; they want the 2 – 4 break plus grunt at lower rpm (larger diameter props) hence smaller venturi diameter throat size. Openned up to 3/8″ diameter and on pressure will make them sing.

Ployd in OZ

[GeneChristensen]

Hi Dan,

The AMA & NFFS both list C/D as .301 – .670, whats up with that? Wouldn’t that make the .56 legal?
I’m trying to get some more venturis for them to experiment with.

Therms, Chris

[DAN BERRY]

C/D isn’t the same beast as Super D. Super D isn’t an official AMA event.
C/D can be flown with a 41 on a 600″ plane. Super D is there to satisfy the need for wanting to fly a BIG noisy plane. The biggest I know of is DeLoach’s 1400″ Pilfered Pearl w/ Rossi 65. It gathers attention. It also provides shade between flights.

[JLorbiecki]

You can open them up as far as you like- The 1/16″ wall is acceptable. I usually still like a venturi shape, but many times it makes absolutely no difference. And, as stated, ya need the small hole to run these beasts on suction. With a bladder, cut away!!

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