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St3250 ???????

Old 01-20-2016, 08:45 AM
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Default St3250 ???????

1. Have a scratch built hi-wing plane that I have put a new ST 3250. I've ran about 1.5 Gl of fuel through it for break-in as per post I've read here here at RCU. So my question is which prop(S) would work to give me the best power needed to fly this heavy bird?

2. What is the best way to drill a new prop to fit the ST3250? I have a drill press.

3. This China made engine came with the long round muffler--however, I have another 3250, made it Italy that came with the rectangular ST muffler that looks like a Bison. I was wondering if I might be better the use the smaller rectangular one? Read somewhere that I could block one hole on it and have better pressure on fuel tank---thoughts?

3. !'ve read that too large of a spinner can cause a engine to over heat--and I understand how that might happen by diverting air away from engine. So, what is a good size to use?

4. What formula is used to determine if an engine will be big enough?
I assume Weight, and wing data, prop data?

I tried to post this before but cant find--so sorry if I end up with double post.

Thanks for any feedback
Old 01-21-2016, 09:12 AM
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You can use a 20 x 8 or 18 x 8 propeller, whichever will fly the airplane as you desire.

To drill the prop, center it under the drill press and then carefully drill the hole. Use a backing block under the prop to prevent tearout.

You can increase muffler pressure by reducing the exhaust outlets. You just have to "try and see".

A spinner should not cause overheating if it does not prevent airflow through the cylinder fins. The spinner used would be determined by the cowling, not the engine and propeller.

There is no formula to determine engine size. The airplane designer uses his experience in airplane sizing. The same engine can be used on a wide variety of airframes.
Old 01-26-2016, 03:45 PM
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I pulled out the scales today, I have a total weight of 16.5 lbs ready to fly, less fuel! Not sure it will fly at that weight. The wing alone is at 4 lbs and see no weight removal. However,may find a lighter main gear setup.
Old 02-11-2018, 06:29 AM
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Default 325 super tiger

I fly a 82' Bates P40 with 5 1/2 spinner at 23lbs my 325super tiger with perry pump and f glow plug pulls this plane just fine and with no over heating problems don't worry you self .Your plane is at 16 1/5lbs that ST will handle that with no problem

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