What is a good 6x3 prop?

Master Airscrew, only with the stiffness of a Cox (grey) competition prop.

navion34 wrote:The Graupner 6*3 is a good prop, maybe not easily available on the west atlantic coast... Here in Europe it's not hard to test it...

Thanks, have sent Graupner an email

Mark Boesen wrote:Master Airscrew, only with the stiffness of a Cox (grey) competition prop.

Thanks and shall research this.

The white Grish was a great 6X3. Are you looking for one still in production?

I like the graupner ones, they are a little nicer than the MAS, to me at least.

A 6x3 prop is a little bit too high load though for most .049 engines, the APC 5.7x3 is a better match in terms of load.

Graupner nitro props are hard to find here in western US east of Continental Divide, I've never tried them so don't have a good feel for them. I like the Masters 6x3 as they provide reasonable thrust for the Black Widows and Norvel .061's here at our 4,300 to 6,500 feet elevations. I don't have a .049 Tee Dee but imagine they'd work for them also. I like them because they are reasonably priced and are reasonably durable. They are able to survive dead stick into our brushy turf, which is hard on wood props.

fit90 wrote:The white Grish was a great 6X3. Are you looking for one still in production?

Yes, something can be bought in bulk for resale

Surfer_kris wrote:I like the graupner ones, they are a little nicer than the MAS, to me at least.

A 6x3 prop is a little bit too high load though for most .049 engines, the APC 5.7x3 is a better match in terms of load.

We have plenty of 5" props as well as access to the moulds for those.

However, our 6x3 is a tremendous seller and we have gone through over 6,000 of them so far. The "Tee Dee Crowd" particularly likes them.

Without question the APC 5.7 x 3 is a real performer with Reed and TD's .049's unloads and provide excellent mix of thrust and rpm in the air with good fuel duration. Will need to sell prop adapters for the 5-40 bolts.

The MA 6x3 has a thin airfoil square tips produces more thrust but the drag reduces top end speeds light prop.
The Graupner props have a thicker airfoil and produces good thrust prop is stiff hold its pitch in the air if I recall
they are little more heavy.    

The Cox prop has a thin airfoil and is light weight allows good rpm.
The tornado / grish props are light and thin airfoil rounded tips allow good rpm.

Cox International wrote:

Surfer_kris wrote:I like the graupner ones, they are a little nicer than the MAS, to me at least.

A 6x3 prop is a little bit too high load though for most .049 engines, the APC 5.7x3 is a better match in terms of load.

We have plenty of 5" props as well as access to the moulds for those.

However, our 6x3 is a tremendous seller and we have gone through over 6,000 of them so far. The "Tee Dee Crowd" particularly likes them.

That's funny, that's the last prop I would use on a TD. As would others here, unless they are cutting them down for a more tailored prop.

APC props would be good as would the MA. Both available in the US. I would like to try the Graupner though as they look to be well made and probably perform similar to the standard Cox.

If you choose to stock the APC props look at the 6x2 as this is a good choice for a TD on shorter lines. The lower pitch slows things down a bit.

Phil

pkrankow wrote:If you choose to stock the APC props look at the 6x2 as this is a good choice for a TD on shorter lines.  The lower pitch slows things down a bit.

Phil

I agree!

Cox International wrote:We have plenty of 5" props as well as access to the moulds for those.

However, our 6x3 is a tremendous seller and we have gone through over 6,000 of them so far. The "Tee Dee Crowd" particularly likes them.

I'll have to grab a couple on my next order then.  I was looking for a 6x3 Cox a couple of weeks ago, and I had plenty of 6x4 and a couple of 6x2, but I couldn't find more than one 6x3.

The Pack Rat Mark

If Bernie is able to negotiate a deal with Graupner, I think that will be great. I've never tried Graupner, but there is always a first.

Discounting CL experiences with the Cox Babe Bee, Golden Bee and 290 in the 1970's, most my reed valve experience has been with the Black Widows. I found the 6x3 prop adequate. At sea level, a 5.25x4 or 5x4 performed about the same as the 6x3. However, at high elevation, found the 6x3 a much better performer than the other. But then I was dealing with 78% to 85% of the air density one had a sea level.

Mind you, I may have not been flying at the most optimum power level, but found the 6x3 prop more economical at elevation.

Ditto on the Pee Wee's. Using factory Cox 4.5 inch or so diameter props, found small 1/4-A RC aircraft flew at about the same speed as a Top Flite white nylon 5.25x3 or Tornado yellow 5x3 nyon prop at sea level, but the larger diameter prop turning at a slower RPM extended tank run about a minute on moderate nitro fuel.

I may have violated all the rules in the book, but these reedies are torquey little devils and stand up to some abuse.

I'm using 6x3's and 6x4's on Norvel. Don't have a Tee Dee .049 to compare with, but a 6x3 puts out decent thrust and speed at 4,300 feet elevation.
Worst flight is better than the best day of work.

Do you have access to the original Cox 6 x 2 L/H molds? It would be nice to offer a replacement prop for the PT-19 Flight Trainer.. as there is no outboard wingtip weight on that model.

Those of us (like me..) who use reed-valve engines for C/L.. would benefit from having more L/H props to choose from.. although I do realize that we're the minority..  

roddie wrote:Do you have access to the original Cox 6 x 2 L/H molds? It would be nice to offer a replacement prop for the PT-19 Flight Trainer.. as there is no outboard wingtip weight on that model.

Those of us (like me..) who use reed-valve engines for C/L.. would benefit from having more L/H props to choose from.. although I do realize that we're the minority..  

No we don't but we have a few thousand of them here that are brittle due to age. We have been giving them away for free with an order with the provision they be boiled before usage; which will restore them for a few weeks or months.

The Graupner props have 4.8 mm screw holes and Cox .049 / .051 / .074 engines use a #5 screw (3 mm). Users of Graupner props use prop spacers for 1/2 engines.

However, Graupner is looking into whether they can make us a special run of 6x3 props with a 3 mm hole as well as 7x3 props with a 3.4mm hole; in which case we will buy. They would be competition props along the lines of the Cox grey ones.

Graupner props are quite high-end, with superior quality. The props retail for aprx. $5 and $6 respectively but we would be in a position to sell them for $3.95 (6x3) and $4.95 (7x3)

Shoot Yeah Bernie!

Good job.

That sounds good with a proper sized hole for the 6x3 props. If they can't do it, it is no big deal one can just put a piece of small fuel tubing.

Their 7x3 props are quite big though, certainly not suited for .049 or .074 (Queen Bee) engines, and I think it would be a little too high load for the 09 TD too. It might work on the Medallion .09 though.

According to Cox documentation, the 7" props are for

Medallion .049 on the large side
Tee Dee .049 on the large side
Queen Bee .074
Medallion .09 on the small side
Tee Dee .09 on the small side

We have much demand for 7" props but no stock. Also, they will be a good match for our diesel engines.

Cox International wrote:According to Cox documentation, the 7" props are for

Medallion .049 on the large side
Tee Dee .049 on the large side
Queen Bee .074
Medallion .09 on the small side
Tee Dee .09 on the small side

We have much demand for 7" props but no stock. Also, they will be a good match for our diesel engines.

Yes, the Graupner 7x3 will be good for diesel engines, the higher weight gives a bit of inertia which helps with starting and the revs will never be very high anyway.

I just think that they are a little thick in their profile to replace the cox 7x3.5 on a high revving .09 TD engine, that's all. There is a Rev-up 7x3.5 that is closer to the Cox prop, in my opinion.

Since a picture says more than a thousand words, here is a little line-up of different 6" and 7" props;



Larger format;

I think the best thing about the Cox 6x3 is the reason it's coined the "Rubber Ducky." Nobody I know of makes props that are as indestructible these days. My direct replacement for my Cox and Norvel engines is the MA GF series 6x3 which I cut down to my preference. They will break but are not as fragile as APC and others. Usually not on a dead stick nose-over landing.

Off topic, but I think 6" props inhibit the power of Tee Dees and other SPI engines that need high RPMs to really do their thing.
Rusty