what kind of speeds are the 428 racers reaching?

Also, what kind of speed might i expect from GP Viper, OS 46AX mini tuned pipe,25% Nitro?

thank you!

428 planes average in the mid 160's.

A Viper with Normal .46 AX will hit around 125mph.

You may get an extra 5-10 mph with your setup.

A few years ago, Rusty Van Baren was flying a Vortex with a Nelson. He was flying at the local field and flying a tight course. I was standing in the flight path as he was coming out of a turn with a radar gun in hand. From I remember, I saw speeds in the 170's with the highest reading 176 mph.

170mph-176mph for a 428 airplane? The radar gun was somewhat optimistic. Dave had it right, listen to the people that know.

Or do the arithmetic, 9" pitch prop at app 19,000 rpm.

Ed S

176 mph reading is possible, since the 428 Nelsons tend to unload to about 22K in the air. Also most people don't notice a 5 mph breeze, and even a slight dive will add 3-5 in the trap. But in race trim pulling Gee's very few will crack 170.

On the other hand, parrallax error will result in a slower than true speed. If you are standing just 7 degrees off axis from the path of flight, you have a 1% error.

Bob,

There's your lucky seven degree figure again!

I have seen low 170's also, but that would not be the Norm. Most 428 'ers are in the low 160 range. It takes a good airplane, with a well needled strong engine to break 170.

At the Winterfest, Travis did 171 on Fred's radar gun going away from him to pole one (from pole3)....

Hi Bob, Hope the ribs are healing well, I would love to have you come and race with us this year and then possibly go to the nats or a big gold cup race... FYI Our own testing has confirmed what Henry Nelson and Dave Shadel and Fred Burgdorf have stated, unload on the quickee version nelson is about 21,500 max unloaded rpm in the air.... Average engine about 21k... A stump puller and a higher timing will get in around 21,500rpm, but I have heard of no more than that and of the 5 planes and engines I tested, the best was right at 21,500.... Dave says there is a dead spot in the pipe around 22k, If you are approaching that number, you are wasting energy and are propped too light....

PS... Another insight into speed was the max dive speed on a qm with Fred and Travis testing I think Fred said 224mph stragiht down and it reached maximum velocity... No matter how long you hold the dive, the speed never goes up any higher than 224mph with a qm 40. The prop is being overun by the airplane... In 428 I heard around 208mph with a Jett motor straight down in a long dive....
Food for thought....

Randy Bridge's FAI racer ran 204mph in a shallow dive in Phoenix at Winterfest.... I heard Mike Helsel was clocked at over 200mph with a qm Polecat and Dubb Jett engine....

JZW

I tested with Fred years ago right after I won my first Q500 Nats. We took that same plane with a 8.8 x 8.75 prop and put it in a big long dive. If I remember correctly it only went 187mph. My FAI in Phx was not too good, we were kind off trying some different timing stuff and not really set up like we flew it at the trials. I got kind of put on the spot out there to fly it at lunch.

Fred took his FAI and put it in a huge dive and it went 245mph and then the engine blew up. So to say the least, I wasn't too interested in diving my FAI and waiting for the rod to pop...

RB

John,

Ribs are at about 90-95% and I will be racing this summer.

Randy and John's numbers-

187mph in a dive would be around 22.5K with the 8.75 prop.

Years ago in F1, Gary Hover showed up with an audio tach at a Phoenix race. On the ground he was propped to turn 22K. In the air, it would only pick up the engine noise when flying away from the pilot. The airborne rpm was also 22K, but when you do the math from your friendly physics book (the section on Doppler efect), I was able to calculate that the engine was turning around 27K in the air. I relayed that information to Henry who didn't believe that engines unloaded that much. (Back then you had a monthly talk to the piston and sleeve supplier.) Over the phone, I heard, Clunk (sound of a heavy dusty book htting the desk), flip, flip, flip (pages turning), click, click.......click (HP calculator), "Hmmmmm, you're right! Wow!"

Of course, an open exhaust engine can turn up to whatever. With the magic muffler style pipe, there is a hint of lock-in to limit the upper RPM. With any engine/prop combination there is a horsepower curve. Your airplane's top speed is related to the power and drag by a cubic function. Diving just converts potential energy back to kinetic. Want to go faster in a dive? Pitch up the prop, fly richer, and add weight to the airplane.

I always thought that Vecter ad claiming 208 mph was a real disservice (knowing it was also completely meaningless BS).

Fred's dive would have increased the rod loads by about 50% (a guess), it would take a few hours to dig out the books for a true analysis.

Now for a common myth - people seem to be confused by prop efficiency and prop slippage. Prop efficiency is a measurement of how much engine hp gets converted to power actually dragging the airframe. It usually runs around 80-85%. So say your quickiie engine has 2.8 hp (this hp is not static, it's on a curve related to rpm) and the prop efficiency is 82%. All this means is that the airplanes speed is related (cubic function) to it's drag when it is absorbing 2.3 hp. So picking the correct prop is finding the right pitch for the day where the engine is peaking on the curve for the airspeed. Where a lot of people seem to go wrong here is they think the 82% figure is a measurement of prop slippage. Of course, for real entertainment read the extreme section where warp drive is just on the horizon.

Randy and Bob, thanks for the information, wow 245mph thats smoking, I am not sure who Fred tested with when he got the qm numbers of 224mph. That V-Vector was clocked in a dive with a Jett motor to get that 208mph reading, like you said, that ad did not help pylon racing in my opinion, we are of course much slower on the course... my own testing with my data recorder showed simular information that Randy stated in 428, The max I saw was 177mph, but I only dove it straight down for about 3 seconds, it scared me, thoughts of flutter, linkages and rods exploding kept creeping into my mind as I dove from high in the sky... I wish I knew how to make a better wood prop for those changes in atmospheric conditions... I am not quite sure what you are talking about when you discuss prop efficeincy, 82% is a good number, does it matter if it is because of drag and hp or actual prop slippage? The end result in speed loss is the same right? If I calcualte out prop diameter and pitch/rpm and the 80% efficiency rate, that should get me close to the speeds I can expect in the air??? The qm motors also unload close to 27k in the air, so a light prop that easily reaches 27k will accelerate better and reach top speed faster, but that top speed will be lower than a higher pitch prop that does not accelerate quite as fast, but reaches a higher top end straight away speed and reaches its 27k closer to the end of the starights... Thats my question, is it ideal to just reach top end speed right before you pull again, or is it better to reach the top end speed half way down the straight. Even though its slightly slower top end speed at half way in the straight, what is better, a little slower, but reached quicker or just reaching a higher top end speed just before you pull again??? That is what most of my testing has consisted of, testing lap times against different props that reach different speeds at different points on the course, and of course acceleration in and out of the turns...
JZW

John,

No, the efficiency of a prop has nothing to do with slippage. It is just a measurement of energy conversion efficiency. I don't think that our racing props slip all that much, but I don't have any trustworthy data. Props are the extremely complex to understand, really more difficult than the rest of the airplane.

About the only way to accurately determine the drag of an airplane (short of a wind tunnel) would be to haul it up to altitude on a "mother ship" and then drop it without a prop. With a data logger, especially one that could measure both the rate of altitude loss, and airspeed, a "J Curve" graph could be generated. Since the rate of descent is the power inputed vs the speed of the plane, you can calculate the equavant flat plate drag of the airframe with a series of drop tests.

Once you have this data, then you could compare engine power inputed vs actual speed and determine prop efficiency. Of course this too would require a bunch of testing where you measure engine rpm and torque at multiple loads and rpm's to determine the horsepower curve vs rpm. And there are also the other variables of atmospheric pressure, temperture, and humidity. Then the internal variables in the engine setup of crank, and sleeve timing, as well as head clearance and design (combustion chamber). Throw in a few different fuels, props, and plugs and the data universe explodes.

In full scale, this curve tells some interesting things about the airframe. The very bottom of the curve is the minimum power point at which the airplane can maintain level flight. This speed is usually the one where you can glide the furthest (this also depends on the wind, as with a headwind, you must glide faster than the so called best glide speed to get the maximum distance).

Then there is Carson's number which is a line from the origin to a point on the curve that is tangent to the curve. This is the speed that give maximum fuel efficiency for greatest range. We race a lot further up the curve

The left side of the curve which is slower than the best glide speed is the so called "back side of the curve". That is where giving more up causes the airplane to drop out of the sky faster while going slower. A good place to be IF you are too high and want to lose altitude to make a landing. But to land, you have to drop the nose and speed up to get back to normal pitch response or your landing is likely to be a very bad arrival.

recap:
So for airframe development, glide and measure.
Test engine setup to adjust shims for conditions and prop so the engine delievers peak hp. Simple eh?

Yea, that sounds very simple and would only take a few years to calculate... I think I will stick with lap times and my data recorder to show me what is actually going on.... So any thought on my questions about where to reach max speed? Half way down the straights?
3/4 of the way in the straight? just before you turn? Any thoughts on the best ideal location to reach maximum speed?
Lap times, of course, help most of all to answer these questions, but I would like to hear what you have to say in theory???

John,

The definition of "insanity" is to continue to do the same thing and expect different results.

IF everyone is using the same engine, the same prop, the same airplane....well you see where this is going.

Bob

Ok, I get what you are saying, but what I am talking about is different props with different diameter and pitch, which of course give me different levels of performance, not to mention a high rpm timing and compression compared to a low timing and compression ratio...
If I am running a cf prop, then I can only try new timings and new head spacing, but I am talking about making props that have different levels of performance, some are good in the turns, accelerate good and reach top speed half way down the straight away...
Then the next up is a prop that accelerates a little less, but is a few miles an hour faster and reaches top speed at 3/4 of the way down the staright... Then I have another prop, it accelerates even slower, but reaches a top speed 2mph faster than both previous props, but does not reach this until right when its time to turn... I was hoping you would have some theory behind this and what prop would be ideal for our course.... I now realize I should not be discussing this on an open forum and there by giving away all my prop secrets!!!
Thats funny.... I cannot even make a prop that goes as good as the V-2 cf prop, oh wait out of 15 props I made, 1 was about as good, I better get to it, I broke that one, if I make 30 more at 2.5 hours a piece, I will have 1 or 2 as good as a 7.50 cf prop!!!
Wow, even at 10.00hr thats 750.00 bucks for 2 props... 35.00 bucks does not sound so bad now!!! Whats Delponto's number???
JZW

Is this forum slip? Let's talk 428 here and move the other to 422.

I guess that is a no....

i have seen nelsons with the 9.25" pitch propo turning easy more than 20k's on the ground how is that possible?

Don't know Ray, my planes are competitive speed wise with just about anyone, and I'm lucky to hit 19,400 peaked on the ground, backed off to about 19,000.

I've never had one hit higher than 19,600 with that prop ever!

Sounds like a screwed up tach or worked prop. The most I’ve ever seen from mine or anyone else’s on a perfect day is about 19600 on a pinch. That same engine and prop the next morning (cold) was about 18800.

Barry

I guess I need to engines, I've never been seen over about 19,400 with the 9.25....

Gary, at the Winterfest, in the mornings I was lucky to hit 19,000. After lunch I was hitting 19,300-19,400 with both of my engines on the pinch. Nothing special, just newer Nelson versions set at .191 and .011.

I just ordered a new one with the fuel line nipple on the top like yours. Thanks, you just cost me $400

Damn Dave, I didn't pay nearly that much for the needle assembly...then again I didn't order mine with the optional engine attached. Back to the props, I rarely run the 9.25 prop anyways, I usually run the 9.5NN.
GS

I have a few of the 9.5NN props, just not convinced I can fly smooth enough to use it.

Hard to argue, since thats about all that Fred uses. Not many others use it, I have a few, but they tend to sit at the bottom of the prop box. Definately not a beginner prop, takes a nearly perfect course to maintain the top speed with it.