Daryl Martel

My Feedback: (3)

I have a large self designed fun fly plane I'm trying to tame. Unfortunately at our field we have a .96 DB limit for engines under 1.00 cube and the large open bay structure of my funfly design transmits a fair amount of noise. I had the engine soft mounted and it was very hard to keep an exhaust on! As a result I've hard mounted the engine using a Dave Brown mount. I have a header and a nice large volume muffler on it - that's about as quiet and efficient an exhaust as I can get. I bought a nice 14 X 6 APC prop but unfortunately it metered out to 98 DB, 2 DB too much. I've tried a 14 X 8, and today an APC 16 X 10 APC cut down to about 14" diameter. The problem is the big pitch props pull the plane along too quickly and make the handling squirrely. On top of that, running that much pitch makes the bottom end respond poorly and idle is very difficult to set. I really don't like what's happening here - it's ruining my flying experience! What size prop are most people running on their .90s? 4 pitch seems to be the preferred number I notice. The trouble with propeller noise is you have to keep the diameter and RPM down to keep it quiet - any suggestions?

m.gramling

My Feedback: (8)

try a 14x6 Master Airscrew wood. with the stock muffler I am getting 9500. Trottles good, and transition is good.

Most of the time, the woods will spin about 1000 less Rpms then a APC and that might put you under the limit.

PaulSwany

My Feedback: (45)

I ran a 14 x 6 master airscrew wood prop on mine... I never measured the db's... but it seemed pretty quiet to me.

Daryl Martel

My Feedback: (3)

Tried an APC and Master 14 X 6. I think the engine really likes that size best but it sure lets the engine wind up - I've seen 10,600. As I'm using a header and large volume muffler, the back pressure is minimal, especially considering how quiet it actually is. I'm thinking most of the noise is coming from the prop and airframe. I took the engine off tonight and re-mounted it to rubber "Wellnuts". I doubt it'll make a difference, but we'll see. I'm going back to a 14 X 6 tomorrow, damn the noise, it's just too fast with more pitch. Pretty surprising how quick it clips along considering the wing is 4" thick. Weighed it the other day - 8 1/2 Lbs. Not bad considering it's so big. Shortened the rudder chord to 3" tonight too. The rudder had way too much authority. Thanks for your replys. Anyone try an APC 16 X 4? I see they are available/listed on their website.

T Morelock

I had a ST90 that loved a 15X6 APC....don't remember what the RPM was but it flew my Cap232 like a scalded cat. I wasn't doing any 3D stuff back then, though, so I don't know how appropriate the 15x6 is...The ST90 is a torque monster, so I propped it more like a 1.2 4 banger.

Kevins_RC

My Feedback: (1)

I've run the 15x4W APC on it. The wide version will help with the RPMs that you are looking for though with the 4 pitch. I ran this prop for a while on my ST90 with a Mac Header and long tuned pipe on my Ecstasy. I am now runing a Zinger 16x5 cut down to 15", swepted tips, and thinned blades. I like the spool up much better on the wood.
Good Luck!
Kevin

Daryl Martel

My Feedback: (3)

Thanks Kevin - I may just order an APC 15 X 4 or 16 X 4. The wide blade on the 15" sound good - less diameter equals less noise. Cheers