Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

model tech mach racer

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Old 05-29-2008, 07:49 PM
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russm
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Default model tech mach racer

flew mine for the first time today. handles well, but the speed even in a dive was dissapointing. i am guessing around 85 mph. have a 46ax w/ a mac muffler,9-7 apc prop,and 15% synth fuel. tached it at 14300 on the ground. i really figured this setup would be a lot faster. it is a very lite airframe and does not seem like there would be a lot of drag. any thoughts? thanks, russm
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Old 05-29-2008, 09:15 PM
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Crazy4Flight
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Default RE: model tech mach racer

http://www.jettengineering.com/
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Old 05-29-2008, 09:24 PM
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russm
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Default RE: model tech mach racer

ya,ya,ya, i already new that. have a sj50 siting on a shelf. when i put this plane together, it was in use. good answer though.
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Old 05-29-2008, 10:35 PM
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Duane-RCU
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Default RE: model tech mach racer

I have a ST .45 with a t/pipe (maybe not tuned good yet, this is my first try) 9X7 APC, getting a little over 16,000 on the ground. Flies ok I guess, manual suggests not diving at full throttle, I guess things might blow apart (flutter!) I like how it slows down to land, this is my first delta. No radar or speed guesses, but I figure it's a little over 100mph? Nothing like when the ST was on my Viper (Jett muffler) turning the 9x7 over 17,000, that was fun...
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Old 05-29-2008, 10:56 PM
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Default RE: model tech mach racer


ORIGINAL: russm

fhave a 46ax w/ a mac muffler,9-7 apc prop14300
If you are using a BLACK Macs muffler it may not make more power than stock. A Macs tuned pipe will make more power....when the header is tuned. A Macs "pre-tuned header & pipe" is in the ballpark.

The tricycle landing gear is a ton of drag if you are using it.


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Old 05-29-2008, 11:06 PM
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freakingfast
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ORIGINAL: Duane-RCU

I Flies ok I guess, manual suggests not diving at full throttle, I guess things might blow apart (flutter!)
I can’t imagine marketing/selling a plane that’s obviously designed to appeal to the speed minded and than tell the customer not to put it in a power dive.[:'(] Maybe it’s just me.
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Old 06-03-2008, 04:11 PM
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Default RE: model tech mach racer

I test flew my second Mach racer this past weekend.
The first one met an unfortunate end on it's maiden flight. It was powered by a Jett 50. For some reason I put the power switch in the hatch where the directions indicated. BIG mistake when after less than 2 seconds the hatch blew off. You guessed it, the switch flew off still attached to the hatch. After a graceful arc topping out about 200 ft in altitude, the largest piece left was the hatch that blew off.

[link=http://homepage.mac.com/amerikiwiusa/iMovieTheater106.html]Mach Racer[/link]

Anyhow, the new one I moved the switch off of the hatch (Just in case) and powered it with an OS 55 AX with an Ultra Thrust racing muffler turning an APC 10x6 at 16,800 rpm! (And that is a brand new engine with maybe less than 20oz fuel through it)
Maiden went well except for major flutter in a shallow dive. (No Damage)
After I sealed the hinge Lines and changed to a 10x7 prop with no reduction to speak of in rpm, 2nd flight went well to (Except for more flutter in the shallow dive)
Now, I'm working on sealing the hinge lines top and bottom, trying to reduce any movement in the control pushrods to try to remove the flutter!
If there is any interest, it was clocked at 124 mph on the first flight and 128 mph on the second!

Anyone else have any suggestions on stopping the flutter?
I'm also going to invest in an APC 9x8 and 9x9 props to see what effects they have on the speed etc.
Needless to say, I have a new favorite fun plane to fly!
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Old 06-03-2008, 06:00 PM
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Default RE: model tech mach racer

My suggestion is to make sure you have mechanical advantage on all servos, i.e. use the inside hole on the servo and the outside hole on the control horn at the control surface. If you need more throw, increase it with the transmitter. You could also use ball joint style clevises to reduce slop. If you have sealed the hinges on one side that should be sufficient.

Blessings, Terry
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Old 06-03-2008, 06:51 PM
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Kmot
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Default RE: model tech mach racer

georbeckha: The remains of your Reaction 54 accident is the most amazing crash picture I have seen! [X(]
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Old 06-03-2008, 07:19 PM
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russm
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Default RE: model tech mach racer

tried a 9x8.75 apc prop. 15200rpm. slower yet. put a jett muffler ands 10x6 wood prop on it. will see if that helps any. geo, thanks for the heads up on the flutter. excellent #s on the radar. that is about what i am looking for.
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Old 06-03-2008, 10:32 PM
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Ed_Moorman
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Default RE: model tech mach racer

I flew my 2 with a Magnum .52XLS with a Rossi short pipe and an OS .50SX with a Jett. Both used 9-7 props.

First, my testing on the black Mac's muffler is that it will cut your rpm, not increase it. The stock muffler without the baffle will be faster.

Second, a 10-7 will be a better prop for the .46AX, in my opinion. It's not a revver like the .50 or the TT .46.

Third, I always replace my pushrods on anything that can flutter with 4-40 size rods. The 2mm stuff that comes in the kit is pretty flexible.

Fourth, Mine were built without the gear and launched. Lots of drag on the gear.
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Old 06-05-2008, 06:10 PM
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rexracer
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Default RE: model tech mach racer

I don't know a lot about speed planes, but I do have a 46AX and it likes a lot of load. I have a high drag plane (Funtana 40) and I'm using a MA 12x6. It turns close to 12000 on the ground if I remember right, and unloads a lot in the air. I bet I'm getting over 14000 rpms flying into a 15mph headwind.
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Old 06-08-2008, 07:22 PM
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planknheli
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Default RE: model tech mach racer


hey ed,
i would like to put dual rudders on mine, am i crazy?? the reason i ask is on the maiden it went into a flat spin & i couldn`t pull it out so it went into a tree. we got it dwn. next flight it did it again but i clicked on the high rates & pulled it out. i let my friend fly it & guess what? inverted flat spin . before he could pull it out = deadstick. he flattened it out before it hit so there was no damage. i put the 700 mah 4 cell flat pack behind the elevon servo`s & with a magnum 52 it balanced at 8.25 . took the nose gear block out & no mains, cowl or canopy. weight is 3lbs. 4 oz. it needs alot of down ele. to hold it inverted. would this be causing it to flat spin?? i fly my 3d profiles hands off upright or inverted. i`m thinking of adding tail weight to bring the cg back but i`d rather cut out the 2 vert. stab. & add 2 rudders & the servo instead of lead. then i could flat spin on purpose & of course hover & tail touch. lol.
thanks,
conk
p.s. it climbs at full throttle. will the cg change fix this or do i need to add dwn. thrust??
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Old 06-09-2008, 02:16 PM
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Default RE: model tech mach racer

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Old 06-09-2008, 06:00 PM
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Default RE: model tech mach racer

Plankinheli,

I got my second one into an inverted flat spin and, no matter what I did, it wouldn't come out. I cut the power and it plopped down in the grass. The only damage was both fins are cracked. I have also done flat spins with two other deltas. They seem to do them pretty well. My twin comes out very nicely.

Here's a landing photo. You can see where I cut off the rear, curved section of the fin. The rear spar is already in the fin. I used 2" aileron stock for the fins.

I moved all me servos to the top and am using Hitech 5245s, mini digitals. OS .50SX & Jett pipe.
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Old 06-09-2008, 08:09 PM
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Default RE: model tech mach racer

Please forget my first message above! I got it backwards. Starting over, I have a Mach Racer that had 4 oz of lead on the tail when I bought it. Did not do a CG check. It had an OS 46ax. Flew great. Found out the correct CG I took off the lead. come to find out it is still tail heavy even without the weight. Now I do not know how it flew so well. I have put an OS 50 sx with jett muffler. Are all mach racers real tail heavy? How will this effect flight? I do not use landing gear. The CG is about 10 inches back instead of the recommended 8 inches. Any solutions?
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Old 06-09-2008, 08:53 PM
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Default RE: model tech mach racer

My Mach Racer balanced out perfectly at the 8 inches with the os 55 ax and Ultrathrust muffler WITHOUT taking into account the amendment to the extra 3/4 inches or so of distance between the firewall and spinner backplate.
Incidentally, I changed to a 9x9 APC prop (From a 10x7) and the rpm stayed the same at 16,900 and speed at about 130mph
I managed to break that prop when I ran out of fuel and the prop stopped at top dead center and I had to make a downwind landing. No other damage though so was lucky there.
I changed to a 9x10 APC prop and again, the RPM stayed at 16,900 but the top speed went up to 143 mph level flight. I still have the flutter at top speed but I suspect it is the elevon pushrods flexing as there is no movement or slop in the control surfaces. (I did change to the hole right next to the center of the servo horn which helped until I went to the 9x10 prop.)
Next will be to change to maybe a carbon fiber pushrod to rule out the flexing. I'll have to let yous guys know how that works out! (The flutter combined with the RPM scream makes it sound like a hotrod flying past. It sounds neat but has an ominous tone to it)
One of the guys out the field took some video and with his permission, I'll put it out when I am able to for comments from the peanut gallery!

George
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Old 06-09-2008, 10:23 PM
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Default RE: model tech mach racer

Thanks George. How could mine have flown that tail heavy? What prop would you use on my 50 sx. And I have a choice of mufflers, a jett or a macs marine pipe. What do think? And how do you measure COG on this plane??
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Old 06-11-2008, 06:32 PM
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Default RE: model tech mach racer

thanks alot ed!
thats just what i had in mind. your way is simple compared to what i was gonna do.
what do you think about my down thrust / cg issue? i added 3 oz of lead to the tail but i still need alot of down ele. when inverted. i added washers under the back of the motor to give it some down thrust but it still climbs pretty good at full throttle. do you think it`s because of the up trim in it from the tail heavy condition?
thanks again,
conk
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Old 09-22-2014, 06:36 PM
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vasek
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Default

Love it ! Here's a vid wth a HK pulse jet.
https://www.youtube.com/watch?v=TTc6MmHRlsQ

I saw a review where it states it's sold by YT International in the UK, but did not find it on their site. Can I get this delta in EU ?
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Old 06-21-2018, 08:22 AM
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The elevons are kinda' twisty. Wondering what has been done to possibly stiffen them. Since flutter seems to be an issue with this airplane, could anchoring the outboard ends of the elevons allow enough control authority while eliminating flutter?
Anyone substituted different elevon design here?

Not looking for all out extreme speed - just want to avoid flutter with a stock muffled Rossi .40 or similar and airplane equipped with the L/G.
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