dasquirrelisme

My Feedback: (81)

I have an Irvine 46 and a 10x7 prop doesnt give me enough clearance. Would a 9 inch prop over rev my engine?

blvdbuzzard

You could try a 9X 3 blade prop?


http://www3.towerhobbies.com/cgi-bin...&I=LXGYM7&P=ML

Buzz.

fiery

My Feedback: (2)

A 9x8 will be fine.

buzzard bait

For most planes I think the 9x7 3-blade would be best, above, unless you're going to the races, in which case the 9x8 should be OK. But it will scream on that prop.

NM2K

My Feedback: (14)

The load placed upon the engine is what matters, not the numerical size of the prop's diameter.

The 9x8 or 9 should load the engine sufficiently. Landings may become a bit more challenging, however. I've used three blade props before and wasn't impressed with their performance.


Ed Cregger

pe reivers

A 9x11 will give you the same engine load as a 10x7
a three blade would have to be 9x7.5x3 for the same load

jaka

Hi!
There is not such thing as "over-rewing" when it comes to two strokes! At least not in the same sense as we talk about it for four strokes.
Two strokes deliver their best performance within a certain rpm band, same as four strokes. But when it comes to four trokes we have valve flutter to deal with at high rpm, no such thing for two strokes!

Go ahead and use a 8x4" or whatever prop you like ! It will not destroy your engine. But "best" prop in your case would be a 9x7, 9x8 or 9x9 APC prop. But for a large slow flying model a 12" or 13" prop is more suitable.
But...There migh be a three blade prop that works equally well too (though I doubt it...).
Have you tried a 9,5x6 APC?
Why can you not use a 10" prop? How is your engine placed on the plane?

pe reivers

Jan,
If you would use these props at racing rpm you suggest, you would get banned in most Dutch clubs.
10x7 is a very decent prop that has excellent pull and flight envelope.  Task is, to find an equivalent prop that runs at about the same rpm, and provides the same thrust. I did that in my previous post.<br type="_moz"/>

airraptor

My Feedback: (66)

pe reivers is correct. The APC10x7 prop preforms the best one most all 45-47 size engines for club racing and general sport flying. It is also the fastest prop on the WM T-34 telemetry proved so.

As far as the 9x11 prop goes though you will see a large loss in flight performance with that prop on most sport planes that are below 100 mph. If you really need prop clearence ie: only .5" more then just use a 1" bigger wheel and keep the 10x7 prop as the you will see less spped loss with the larger tire than you would with a smaller prop.

dasquirrelisme

My Feedback: (81)

Thanks for the help. Just so you know the engine is on a GP Viper and will be used for racing or atleast racing around at my club field. I also have a MVVS 40 engine I might use instead. I know the MVVS is made more for racing than the Irvine. The Irvine is my favorite sport engine and would probably be better in a different model.

Recycled Flyer

I thought the 'task' here was to answer the question posed in the original post, that of 'Would a 9 inch prop over rev my engine? '

And Jan answered that well.

airraptor

My Feedback: (66)

recycled flyer .......

some of us can see the real question being asked and respond correctly.

Yes jan may have answered the question but Pe reivers and others knew what he was getting at.

Run a 8x10 on that irvine. You didnt tell us what plane it was for in the first post but run as much pitch as you can on her and have fun....

Recycled Flyer

Ok, but looking 'through' the question and interpreting it I would think that the correct answer would be to extend the under carriage half an inch or simply
bend the undercarriage down a fraction.

The issue is caused by a self admitted lack of ground clearance, not by a bad prop choice.

jeffie8696

IN my experience Ihave run into fuel delivery issues with small props running at high RPM with my Irvine 53, your 46 may not suffer the same but it can challenge a marginal fuel system. Ihave had a lot of issues with ground clearance at our field , it is rather rough and I fly smaller planes.

pe reivers

I compared the props I quoted earlier.
the 10x7 would provide about 130km/h top speed, with impressive prop howling.
the 9x11 provides 210km/h top speed, and pulls better than the 10x7 above speeds of 30km/h
the 9x7.5x3 will have a top speed of 140 km/h, and outperforms the 10x7 above speeds of 95km/h

jaka

Hi!
On a Q-500 racers like the "Viper" we use 10x6 or 10x7 here in Sweden for our .40 engines with standard silencers. Best prop (So far) is the British RAM or German Graupner "Cam-prop"! APC 10x6 or 10x7 load the engines too much. But we use .40 engines! For .46 engines APC might work too.

The best engines (Webra .40 GT, Kyosho .40 GX and TT .40 PRO SE) turns these at around 14000-14500rpm on 80/20 fuel.
Top speed is around 160-180km/h using these props.
I have higher landing gear available, suitable for 10" props.