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Help! .074 lil swamp buggy prop choice

Post  Lukemiester Wed Feb 03, 2021 11:20 pm

What size prop would be ideal for my queen bee? It’s soon to be on a Dumas lil swamp buggy in a tractor configuration.
I got 16500 RPM on a cox black 6x3 if it helps any

Thanks
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Help! Re: .074 lil swamp buggy prop choice

Post  Cribbs74 Thu Feb 04, 2021 12:02 am

The instruction manual has 2 props listed. 6x3 and 7x3.5

I am out of my league with boats, but like anything it’s best to just play around with props until you find one that works best for your application.

Ron

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Help! Re: .074 lil swamp buggy prop choice

Post  davidll1984 Thu Feb 04, 2021 1:03 am

Dont expect mutch power from the .074 than the .049 Reed valve engines its just hevy and tend To over heat heatsink modified may help as its Not plane ad weight Not trouble for the prop To use tink 6x3 6x4 wil do the job tink the .9 at that point is mutch bether from far for this application if it nead lots of power try To Find the .9 rc the tee dee .9 performance compare To its weight
About the same weight as the .074 wit mutch more rpm and power To run larger pitch like 8x4 at 25.000 rpm max
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Help! Re: .074 lil swamp buggy prop choice

Post  OVERLORD Thu Feb 04, 2021 2:36 am

I'd use the prop that Cox indicates for that engine. Never mind wether the engine is on a plane or airboat. Don't go too wild on engine choice. Dumas designed it for a .049. A bigger engine gives more torque and might turn over the boat, not so much on a perferct flat water surface, but when suddenly little waves appear, the engine can turn the boat around due to torque. Remember the engine is high above the boat and the boat's attitude is not comparable to an engine that is mounted in the hull. Also, nowadays, the RC gear is a lot lighter than what it was 40 years ago and you will have less draft. I turned my hydro-bat over on snow with only a product engine with a TeeDee head and less that 10% nitro. The Hydro Bat has the same dimensions as the Lil Swamp Buggy.
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Help! Re: .074 lil swamp buggy prop choice

Post  Lukemiester Thu Feb 04, 2021 10:03 am

Yeah I know it doesn’t have too much power, and is much heavier than the engine designed for it. I think mine has slightly more power than a reedie .049, but I’m building this boat for this engine because I want to use it on something and I figured an airboat would be perfect since it would be kinda heavy for a plane. I know an .09 would be a better choice but I don’t have one yet, plus this engine was a gift to me. Also I saw a video on yt of a lil swamp buggy with a OS 10 on it, so I’m sure it could handle the brick that the .074 is.
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Help! Re: .074 lil swamp buggy prop choice

Post  Lukemiester Thu Feb 04, 2021 10:05 am

my question is pretty much if it could handle a 6x4... i want to go fast tongue
it runs good on a 6x3 but I don’t really know if a 6x3.5 or a 6x4 would be too much pitch for it
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Help! Re: .074 lil swamp buggy prop choice

Post  davidll1984 Thu Feb 04, 2021 11:03 am

Try a Good 6x3 the engine wil like dont wory the .074 can run larger prop litle faster than .049 u can go up To 7x3
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Help! Re: .074 lil swamp buggy prop choice

Post  Cribbs74 Thu Feb 04, 2021 11:16 am

Lukemiester wrote:my question is pretty much if it could handle a 6x4... i want to go fast tongue
it runs good on a 6x3 but I don’t really know if a 6x3.5 or a 6x4 would be too much pitch for it

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It’s not going to hurt anything to throw a 6x4 on it. It either loads it down or it won’t. You may find a smaller pitch works better because of increased RPM’s
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Help! Re: .074 lil swamp buggy prop choice

Post  Lukemiester Thu Feb 04, 2021 11:43 am

Cribbs74 wrote:
It’s not going to hurt anything to throw a 6x4 on it. It either loads it down or it won’t. You may find a smaller pitch works better because of increased RPM’s

Alright thanks for the help- from what David said and what you said I think I’ll try a few different ones
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Help! Re: .074 lil swamp buggy prop choice

Post  davidll1984 Thu Feb 04, 2021 11:56 am

Is the engine run in pusher configuration??
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Help! Re: .074 lil swamp buggy prop choice

Post  Lukemiester Thu Feb 04, 2021 2:05 pm

davidll1984 wrote:Is the engine run in pusher configuration??  
no, it's tractor configuration
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Help! Re: .074 lil swamp buggy prop choice

Post  Surfer_kris Thu Feb 04, 2021 3:02 pm

Lukemiester wrote:my question is pretty much if it could handle a 6x4... i want to go fast tongue
it runs good on a 6x3 but I don’t really know if a 6x3.5 or a 6x4 would be too much pitch for it

My QB didn't like the 6x4 prop, it would sag a little at prolonged full throttle runs.
For more power you could try a better glow head, I'm assuming that you are using a regular glow plug?

A Turbo plug should give you at least another 1000rpm. For better throttling you can also make the carb mods shown elsewhere on this site.
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Help! Re: .074 lil swamp buggy prop choice

Post  Lukemiester Thu Feb 04, 2021 3:12 pm

Surfer_kris wrote:
My QB didn't like the 6x4 prop, it would sag a little at prolonged full throttle runs.
For more power you could try a better glow head, I'm assuming that you are using a regular glow plug?

A Turbo plug should give you at least another 1000rpm. For better throttling you can also make the carb mods shown elsewhere on this site.

yes i'm using the mecoa .09 head and a k&b medium heat idle bar plug. i did the carb mods as well. i posted on pages 3 and 4 in here: https://www.coxengineforum.com/t12983-cox-074-queen-bee-nelson-plug?highlight=queen+bee
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Help! Re: .074 lil swamp buggy prop choice

Post  Lukemiester Tue Feb 16, 2021 10:48 am

i cut down an APC 7x4 i had laying around to a 6x4 and it ran just fine. looks like i'll be be buying the rev-up 6x4 on ex model engines along with some car engine parts
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Help! Re: .074 lil swamp buggy prop choice

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