PM 38 Why the difference in prop length

[Wild Bill Kelso]

Re: PM 38 Why the difference in prop length

Isn't it nice to have an 'errand boy' to do all your shopping for you?

Yes it is, but I wouldn't call him that if I were you.

[Big_Jim]

Re: PM 38 Why the difference in prop length

Yes it is, but I wouldn't call him that if I were you.

Oh, I'd just blame it on my brother.....

[FlyKidChris]

Re: PM 38 Why the difference in prop length

Engine/prop program first. Airframe cleanup next. I'll have a scoop soon, and wingtips are in the works.

That's great news. Is there a website for PM fan attire? I'd like to contribute to the cause.

[Scotty G]

Re: PM 38 Why the difference in prop length

Is that 64 mph an apples-to-apples testing number with altitude and TAS figured out of it? Or is that race speed? I seem to remember a 453 being the fastest lap/race the airplane had ever flown.

[Tigercat24]

Re: PM 38 Why the difference in prop length

The 64 MPH is the difference between last year's and this year's qualifying speeds. She ran just over 399 MPH last year, placing 12th. This year, she qualified 64 MPH faster and placed 3rd (4th behind Furias )

[Randy Haskin]

Re: PM 38 Why the difference in prop length

Oh, I'd just blame it on my brother.....

Oh, am I in the 'insult Kerch' business now?

[Randy Haskin]

Re: PM 38 Why the difference in prop length

The reprofile was a different way of thinking than any other Griffon powered racer yet. Most guys before just cut the tip off and left what Kerch calls the baseball bat part of the airfoil. With fancy 5-axis CNC machines we have these days we swept the tip and cut new airfoils all the way to the tip. What type of airfoils the last 14 inches is the big secret. The results were quite shocking even for me! A 64 mph gain on the course all from the propellers. No other mods were added!

I don't know weather I'm amazed that more teams (owners, maintainers, and pilots alike) don't take this kind of systematic tact to making modifications, or if I'm amazed that this 'simple' change had such a significant impact on course speed.

Either way, I have to say its wonderful to see N6WJ getting some TLC and looking on the course as a result.

Can't wait to see what you guys do next to the last of the Super Mustangs.

[Big_Jim]

Re: PM 38 Why the difference in prop length

Oh, am I in the 'insult Kerch' business now?

No, he just 'really likes' you, and would probably just laugh it off.

[440_Magnum]

Re: PM 38 Why the difference in prop length

The results were quite shocking even for me! A 64 mph gain on the course all from the propellers. No other mods were added!

Thanks for the info. It really is amazing- all those years the poor Griffons were developing all that power... just to turn it into heat shredding the air with inefficient props.

[Wild Bill Kelso]

Re: PM 38 Why the difference in prop length

The 64 MPH is the difference between last year's and this year's qualifying speeds. She ran just over 399 MPH last year, placing 12th. This year, she qualified 64 MPH faster and placed 3rd (4th behind Furias )

And that is what matters. Along with that World's fastest Griffon Mustang at Reno title, and beating The Whittington's fastest lap in the airplane. That has always been a personal goal of mine. Checked it off the bucket list 9/11/12

[RAD2LTR]

Re: PM 38 Why the difference in prop length

I was just looking at a pic of MA2 this morning and it got me thinking. about a couple things. First off, what was the fastest MA2 went, also, what was the fastest Red Barron went?

Next I noted that the cowling on MA2 lacks the scoop up top, were they running a different version of the Griffon, or did they effectivly move the scoop somewhere else? Either way, its a lot cleaner front end. They did however still have the squared off prop blades. Also, with the NACA radiator duct, did it work, was it faster, and could something like it be implemented on PM?

I honestly can't wait to see what you guys come up with on PM. Super Stangs are now a rare breed, especially when it comes to running a Griffon rather than a Merlin. Its got to feel great finding 64 mph with a years worth of development knowing there is more to be found with a little work

Will

[RichH]

Re: PM 38 Why the difference in prop length

I was just looking at a pic of MA2 this morning and it got me thinking. about a couple things. First off, what was the fastest MA2 went, also, what was the fastest Red Barron went?

Next I noted that the cowling on MA2 lacks the scoop up top, were they running a different version of the Griffon, or did they effectivly move the scoop somewhere else? Either way, its a lot cleaner front end. They did however still have the squared off prop blades. Also, with the NACA radiator duct, did it work, was it faster, and could something like it be implemented on PM?

MA II did have a scoop on top. It was a NACA duct. As far as speeds on the course, I believe RB was in the 430's and MA II was in the 440's...

[440_Magnum]

Re: PM 38 Why the difference in prop length

Next I noted that the cowling on MA2 lacks the scoop up top, were they running a different version of the Griffon, or did they effectivly move the scoop somewhere else? Either way, its a lot cleaner front end.

MAII used a Griffon with less supercharger, but its still a downdraft setup and had the carb inlet on top. At different times they tried different scoops. I THINK this photo is a conventional setup set back on the top of the cowl, I've kinda forgotten the details:

http://www.rcgroups.com/forums/attachment.php?attachmentid=4267344

And they tried a NACA scoop (which didn't produce enough pressure rise as covered in another thread):

http://i150.photobucket.com/albums/s95/Wingmanphoto/R98-Miss-Ashley-101.jpg

Frankly, I think PM's scoop is probably more effective than either setup MAII used. That's just a guess on my part, but putting a scoop right at the leading edge puts it in clean air, and is just an "upside down" version of the proven Merlin mustang inlet. In addition to the constant volume / low pressure rise nature of a NACA inlet, there can be a low pressure area a short distance back from the leading edge of a curving surface such as the top of a cowl, which would act against air entering the scoop (eg. a Ford Mustang shaker hood from the late 60s or early 70s which was later proven to be in a low pressure area and was trying to suck air back out of the carb at speed).

[RichH]

Re: PM 38 Why the difference in prop length

A 64 mph gain on the course all from the propellers.

I think Whittington's speed in 1988 proves the 64mph gain from last year to this is from more than just the props, being nearly as fast w/the old setup...

[Big_Jim]

Re: PM 38 Why the difference in prop length

I was just looking at a pic of MA2 this morning and it got me thinking. about a couple things. First off, what was the fastest MA2 went, also, what was the fastest Red Barron went?

Next I noted that the cowling on MA2 lacks the scoop up top, were they running a different version of the Griffon, or did they effectivly move the scoop somewhere else? Either way, its a lot cleaner front end. They did however still have the squared off prop blades. Also, with the NACA radiator duct, did it work, was it faster, and could something like it be implemented on PM?

The fastest qualifying speed of any of the races the Red Baron participated in was 441.9 in qualifying at Reno '79. Fastest race speed was 430 in the 1977 Championship race.

As Rich explained, MAII had an NACA scoop on top between the cylinder head bulges. But while it says "Griffon", comparing MAII with the other Griffon racers is not really fair. MAII had the single stage supercharger Griffon, while the other two had/have the dual stage supercharger that can go into 'high blower'. Kind of thought of as the "little Griffon" and the "big Griffon". There was a significant difference in horsepower output, and that was a definite hindrance to MAII's overall performance numbers.