bought a batch of various size props on flea bay. what engine is best for a 7/8?

Props of that type are suited for .10-.15 sized engines.

Have a look at this chart;
http://www.uoguelph.ca/~antoon/hobby/propchrt.htm

Hi!
I would say None!
7x8 is such an odd size that no one uses it. Could be used however in engines from 3,5cc (.21) and up to 6,5cc (0.40) depending if it's an APC or not.

Likely older high RPM applications specific for RC pylon, freeflight power and controlline speed. And displacements up to .40.

Thanks guys,
I had recently lost my photo library including that chart in a computer crash so thanks

I bought 24 yellow grish props NIB on fleabay for a buck a piece. I think the 7/8s might be fun on my .15 on a Lil Streak.
I have 12 of the 7/8s and some up to 12/4, so they should be fun to play with on various planes.

The white grish tornados were popular in controlline applications. The 12/4's were low RPM stunt specific props. If they are white plastic boil them in water for ten minutes or so.

John

Actually, it's a good idea to boil any old props that look like they're nylon. Nylon dries out and that makes it brittle. Nylon actually has a moisture content and loses it over time. And needs it.

Boiling actually just speeds up the hydration process. Just soaking works too.

BTW, the early nylon props did have a history of throwing blades at really high rpm. Don't ever stand in front or directly beside them when they're running except when starting the suckers. And keep them pointed away from others.

Thank you darock, Yes I intended to mean all the pure nylon props, I was trying to differentiate between the pure nylon and the wood Grish props, don,t want to boil those

Pure nylons in something over eight nine inchs will separate at relatively low rpm's that todays engines exceed if not boiled.

Actually if you have bolted wing especially with shoulder or high wing with nylon bolts these will be less prone to breaking if boiled.

John

Hi!
7x8 is way to much for any .15 engine!
7x5, 7x6 or 8x4 APC if its a fast airplane ...8x5APC if its a scale type airplane (like a Kyosho PBY Catalina)

OK I think it would be at the max but not nec. to much. the O S Site lists up to an 8x5 for the 15 LA. Since I have 12 of the buggers I may try making one a 7.5 x 8 just to see the difference. Nothing like answering your own question
and we'll be having PROP SOUP for lunch!

7/8 is a .40 size pylon racing prop,the st x-15 engine could only swing a 7-6 berore being loaded down

I see [sm=idea.gif] I don't really fly my 40 size birds in that speed envelope so I may trim one down and try it as^.5 or 6 x 8.
Thanks guys appreciate the input.

Has anyone tried to find the fastest prop for a tower .46. My club has pylon racing but we have two rules. You have to use a engine made in china and the airplane has to be a stik. We all use this cheap Vmar stick sold by richmond rc. I raced for the first time yesterday and got whopped using a magnum .46 with all the props i tried.
Thanks

Hi!
Whopped!???
Try an APC 9x7!