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

Shrike 40 with thinner airfoil

Reply
Old 12-16-2012, 07:41 AM
  #101
MJD
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,602
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

Quote:
ORIGINAL: Speedy-Gonzales
(1) You got some pics of these hinges? I'm interested in anything new or at least new to me!

(2) Have you done anything with the Shrike plans I sent you??

(3) Did you tell ''Santa'' I want a SD kit for Christmas???
(1) Yes.. here they are. I believe I am mistaken about these being a Fourmost product, I was thinking about the gapless hinge extrusion I have in the workshop which is Fourmost. I bought these ages ago and they sat in my pile of stuff until I realized I ought to use them on the .65 Demon. Dimensions are 1/2" wide x 3/8" thick. It would be easy to reproduce with the appropriate hinge material, and a tapered carbide burr on a router table I think. Just laminate a solid piece then cut out the bevel without hitting the hinge material.

On 1/2A models I have successfully made continuous hinges on 3/32" sheet stock with a Dremel router table and the paper-thin circular saw cutter that comes with some sets (that should be outlawed but it works great for this) supported with 1/32 ply. I cut a slot in each side then slid in a strip of Coverite fabric covering, then CA. Works like a champ, but a bit fiddly at first.

(2) Yes, I have made some headway on a CAD design of a revised version, but there is quite a bit of work to do yet.

(3) Santa's cool with that, but it won't make it for Christmas. I am taking two weeks off over the holidays, I hope to make some headway on a kit run with the time off. Progress has been dismal so far, I've been working M-F 10-12 hours/day for ages and sideline tasks keep getting bumped.
Attached Thumbnails
Click image for larger version

Name:	Wu59844.jpg
Views:	9
Size:	311.5 KB
ID:	1830709   Click image for larger version

Name:	Ni24900.jpg
Views:	7
Size:	307.4 KB
ID:	1830710  
MJD is offline  
Reply With Quote
Old 12-16-2012, 07:54 AM
  #102
MJD
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,602
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: Speedy-Gonzales

CBP,
Drop me some names for where I might find CF props in this range from custom manufacturers? I'm always concerned about throwing a blade above 22K with standard GFN APC's. I'm still running on a few 12 packs of RevUp wood pylon props and massaging them with a Prather pitch gauge.
As CP said, Steve Wilk/Eliminator has a wide assortment of CF props indeed. Good source of 1/2A CF props too.

The other source is ZZ Props, you can find them through C/L speed forums (try ZZCLspeed at Ay Oh Ell dot com). His selection is much smaller, but the props come with far less finishing work needed. He has a few props in the right general range depending on the engine:

8x8 (couple of versions)
7 x 7-3/4
7x8
8x8-1/4
7-3/4x8
8-3/8 x 8-1/2

This is where I got all my D speed props.

MJD is offline  
Reply With Quote
Old 12-18-2012, 04:36 PM
  #103
SpeedBoy
Thread Starter
 
SpeedBoy's Avatar
 
Join Date: Nov 2007
Location: Monterrey, MEXICO
Posts: 461
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

Finally some time to play with the engine , I switched the prop to 9x10 APC , fuel Power Master 15% nitro and I added castor oil Klotz to bring it at 20% oil , and tuned pipe 10 cc , tach read was just 17,500 RPM.

I think is time to start with the dremel job on the sleeve to raise the exhaust timing. I did a wheel degree and measured the stock timing wich is 150°. I'm plannig also make the exahust timing wider as it looks a bit narrow compared with the crankcase.

I'll probably start raising 5° each time and have a tach reading between each mod. to see if there is any RPM gain.

GOD bless me !!



Attached Thumbnails
Click image for larger version

Name:	Fd91099.jpg
Views:	12
Size:	166.9 KB
ID:	1831667  
SpeedBoy is offline  
Reply With Quote
Old 12-18-2012, 04:51 PM
  #104
MJD
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,602
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

17,500 sounds to me like a 10cc pattern engine on a 9x10 prop.

What is the pipe length, plug center to fat part of the pipe? The picture could be deceiving but that header/pipe system looks really short, I wonder if you are right off resonance. Bear in mind, for tuning a piped system like this, best to trim a good 10% off the diameter of the flight prop and then trim pipe length to max ground rpm on that setup. If the engine/pipe system is hyperactive enough, 15% is more like it. I'd go 10% with this engine unless you go ape with the timing.
MJD is offline  
Reply With Quote
Old 12-18-2012, 05:17 PM
  #105
SpeedBoy
Thread Starter
 
SpeedBoy's Avatar
 
Join Date: Nov 2007
Location: Monterrey, MEXICO
Posts: 461
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

MJD , please dont pay atention on the picture above as reference on the set I described on my last post , that picture is with the 7.5 cc pipe , it was taken about 2 months ago.

The real measure ( pictures below ) is 11-1/5" from plug center to fat part of the pipe (just behind the fitting) and from plug center to the end of the pipe is 17-3/4".

I'll test with 10% nitro and see what it drops.
Attached Thumbnails
Click image for larger version

Name:	Nl30770.jpg
Views:	18
Size:	168.5 KB
ID:	1831691   Click image for larger version

Name:	Fa84658.jpg
Views:	14
Size:	152.2 KB
ID:	1831692  
SpeedBoy is offline  
Reply With Quote
Old 12-18-2012, 05:26 PM
  #106
Speedy-Gonzales
 
Join Date: Mar 2004
Location: Bryan, OH
Posts: 1,171
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

Have you flown the plane yet? I would give it a throw ( as is ) to see how it performs, get a good feel for it, and see how it comes up on the pipe. 17.5K is low but at least you will have had the plane in the air and get some feel for it before going ballistic with it.

To me it would seem that the airframe presents more limitations than the engine.

I'm sure you will get some "pucker factor" the way it is now!

Speedy Gonzales
Speedy-Gonzales is offline  
Reply With Quote
Old 12-18-2012, 05:39 PM
  #107
combatpigg
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

SB..your plane looks SUPER[:-]!!

Remember that the engine will lose torque when the exhaust pressure leaves the cylinder early...but you gain high rpm ability.
So......your engine will become very critical about the amount of diameter it will turn. You have an airframe that should be clean enough and small enough to make a 8+ inch diameter prop work if the rpm is there. The real work isn't just doing the engine mods. The real work is finding the correct prop that compliments the engine mods. With a high timed speed engine [180 degrees or higher] you want to start your search UNDER PROPPED so that the engine runs cool and stays happy. Gradually you try bigger combinations of pitch, diameter, blade area and blade thickness until the engine starts showing signs that it can't handle it.
combatpigg is offline  
Reply With Quote
Old 12-18-2012, 06:03 PM
  #108
Speedy-Gonzales
 
Join Date: Mar 2004
Location: Bryan, OH
Posts: 1,171
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: combatpigg

SB..your plane looks SUPER[:-]!!

Remember that the engine will lose torque when the exhaust pressure leaves the cylinder early...but you gain high rpm ability.
So......your engine will become very critical about the amount of diameter it will turn. You have an airframe that should be clean enough and small enough to make a 8+ inch diameter prop work if the rpm is there. The real work isn't just doing the engine mods. The real work is finding the correct prop that compliments the engine mods. With a high timed speed engine [180 degrees or higher] you want to start your search UNDER PROPPED so that the engine runs cool and stays happy. Gradually you try bigger combinations of pitch, diameter, blade area and blade thickness until the engine starts showing signs that it can't handle it.
+1 CBP!
Speedy-Gonzales is offline  
Reply With Quote
Old 12-18-2012, 06:13 PM
  #109
SpeedBoy
Thread Starter
 
SpeedBoy's Avatar
 
Join Date: Nov 2007
Location: Monterrey, MEXICO
Posts: 461
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: Speedy-Gonzales

Have you flown the plane yet? I would give it a throw ( as is ) to see how it performs, get a good feel for it, and see how it comes up on the pipe. 17.5K is low but at least you will have had the plane in the air and get some feel for it before going ballistic with it.

To me it would seem that the airframe presents more limitations than the engine.

I'm sure you will get some ''pucker factor'' the way it is now!

Speedy Gonzales
I havent flown it yet , more that 5 persons have told me the same , give it a throw as is , but mmm I really want to wake up this thing , I think I could probably follow this advise if after doing the first 5° raising timing job the engine doesn't have any gain on RPM. Its just that I want to give it a chance to improve the performance before the maiden.

I know this is not a f3D or so , but something tells me that this aiframe could brake the 300km/h mark at some point. Probably a bit optimistic but feels good when dream.

We'll see.
SpeedBoy is offline  
Reply With Quote
Old 12-18-2012, 06:33 PM
  #110
SpeedBoy
Thread Starter
 
SpeedBoy's Avatar
 
Join Date: Nov 2007
Location: Monterrey, MEXICO
Posts: 461
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: combatpigg

SB..your plane looks SUPER[:-]!!

Remember that the engine will lose torque when the exhaust pressure leaves the cylinder early...but you gain high rpm ability.
So......your engine will become very critical about the amount of diameter it will turn. You have an airframe that should be clean enough and small enough to make a 8+ inch diameter prop work if the rpm is there. The real work isn't just doing the engine mods. The real work is finding the correct prop that compliments the engine mods. With a high timed speed engine [180 degrees or higher] you want to start your search UNDER PROPPED so that the engine runs cool and stays happy. Gradually you try bigger combinations of pitch, diameter, blade area and blade thickness until the engine starts showing signs that it can't handle it.
Thanks for the compliment Chuck !!!

I hope you mean about it wont be able to run bigger props like 11x7 APC , or do you mean the 9x10 APC could be too much load to this displacement after raising the timing???

I don't pretend to use something under 9" in diameter for this airframe. Im not sure if a 8" long prop would be enough to overcome the drag of this model.

I'll be careful after doing the first 5° timing job , if no gain there , I probably wont make any more raising timing.

SpeedBoy is offline  
Reply With Quote
Old 12-18-2012, 06:35 PM
  #111
MJD
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,602
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: SpeedBoy

MJD , please dont pay atention on the picture above as reference on the set I described on my last post , that picture is with the 7.5 cc pipe , it was taken about 2 months ago.

The real measure ( pictures below ) is 11-1/5'' from plug center to fat part of the pipe (just behind the fitting) and from plug center to the end of the pipe is 17-3/4''.

I'll test with 10% nitro and see what it drops.
Okay, that explains it.. it looked like it was set up for a propped ducted fan engine.

I would think 300kmh is within reach if you get the engine singing.
MJD is offline  
Reply With Quote
Old 12-18-2012, 07:20 PM
  #112
combatpigg
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: SpeedBoy


Quote:
ORIGINAL: combatpigg

SB..your plane looks SUPER[:-]!!

Remember that the engine will lose torque when the exhaust pressure leaves the cylinder early...but you gain high rpm ability.
So......your engine will become very critical about the amount of diameter it will turn. You have an airframe that should be clean enough and small enough to make a 8+ inch diameter prop work if the rpm is there. The real work isn't just doing the engine mods. The real work is finding the correct prop that compliments the engine mods. With a high timed speed engine [180 degrees or higher] you want to start your search UNDER PROPPED so that the engine runs cool and stays happy. Gradually you try bigger combinations of pitch, diameter, blade area and blade thickness until the engine starts showing signs that it can't handle it.
Thanks for the compliment Chuck !!!

I hope you mean about it wont be able to run bigger props like 11x7 APC , or do you mean the 9x10 APC could be too much load to this displacement after raising the timing???

I don't pretend to use something under 9'' in diameter for this airframe. Im not sure if a 8'' long prop would be enough to overcome the drag of this model.

I'll be careful after doing the first 5° timing job , if no gain there , I probably wont make any more raising timing.

I have never played with any engines larger than .50 sized for speed so I can't tell you about which sized prop will work best for you. All I can say is that 9x10 sounds large to me, but it might be just fine.
My comments are to be taken as general advice. When you want more speed from a 2 stroke engine, you must do mods that raise RPM.
With mechanical engineering, every time you try to improve one aspect.....you make another aspect worse.
If you are serious about speed, it has been proven that 180 degrees of exhaust duration is the STARTING POINT for a properly designed full wave pipe to be able to do it's magic. The trick is to find the best combination of propellor characteristics to fully take advantage of the narrow power band that a high timed 2 stroke engine has. If you expect the perfect propellor is just a phone call away....it might be, or it might take a lot of trial and error to find the prop that marries your engine to that airplane just like a wedding ring.
combatpigg is offline  
Reply With Quote
Old 12-18-2012, 07:44 PM
  #113
MJD
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,602
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

A good data point is the fact that a popular prop used by RC speed fliers in Europe on 10cc engines timed for the low 20's is a CF 9-10. The pattern is from a 10x10 APC trimmed and reshaped so it has better hub strength than a direct copy of the 9x10. The guys who go smaller and higher pitch as in 8x12 or so are flying very low drag pure speed designs. I'd say 9x10 is real close to to the right choice for that airframe on a hot 10cc. If you were leaving the timing as is and running in the higher teens I'd say run a 10-8.

For safety's sake note that if you get that engine really spinning, that APC 9x10 could be a safety issue. Right now you're fine.
MJD is offline  
Reply With Quote
Old 12-18-2012, 08:47 PM
  #114
combatpigg
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

What guys don't appreciate is that unless the compression and nitro % is just perfect, you can't just whip out your ultimate killer prop without taking a big chance on cooking your engine.
A piped engine with high timing [+180 degrees] is a supercharged engine and it will behave like a weight lifter trying to impress his new girl friend if you go for too much load too soon.
It is capable of developing more power. stress and heat than the parts can tolerate..but only for a run or 2.
Piped engines below 180 degrees timing don't hit resonance as brutally..so they don't have the same handling precautions. They have more margin for error
Both Henry Nelson and Dave Shadel will tell you that setting up a "full race" engine is not much different than tuning a model diesel engine. You have to find the balance between load, compression and nitro by working from the safe side towards the most powerful...or else keep these guys on speed dial and give them your credit card number.
Dave was able to finally hammer this point home with me during a call for another P/L/rod set and head button.
Finally, any "full race" speed engine that has a nice idle and good transition to full throttle doesn't have a big enough carburetor.
combatpigg is offline  
Reply With Quote
Old 12-19-2012, 09:58 AM
  #115
flycatch
 
Join Date: Jul 2002
Location: Barstow, CA
Posts: 1,993
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

I flew these airframes while under contract with the US Army. The program was called "MATs" minature aerial targets and used for ground to air target practise.
flycatch is offline  
Reply With Quote
Old 12-19-2012, 11:12 AM
  #116
combatpigg
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

Sounds like a tough way to make a living....

I'd volunteer to play that game if they would just pay my expenses....no salary. Of course I consider an ice chest full of beer "an expense".
I'll bet there are a lot of other flyers who would do the same.
combatpigg is offline  
Reply With Quote
Old 12-19-2012, 04:20 PM
  #117
europatc74
 
Join Date: Feb 2005
Location: summit, NJ
Posts: 215
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

What do you know, a Shrike Forum. Guess I missed it. I build Shrikes all the time. Scratch of course. I have a number of them. A Shrike 40 with an OS 61 SF. A couple of 10s. One with OS 32. Another modified with a Rossi 40 F.I.R.E with pipe. Just needed to widen the fuse. Another in the works with a Thunder Tiger modified buggy engine. I also built the 1/2A with an OS 15 CV engine. You should try the 1/2A with the CV 15. Quite the handful to fly. Such a great flying model. I have modified the frame a number of ways but the original design still flys the best....
europatc74 is offline  
Reply With Quote
Old 12-19-2012, 05:20 PM
  #118
combatpigg
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: europatc74

What do you know, a Shrike Forum. Guess I missed it. I build Shrikes all the time. Scratch of course. I have a number of them. A Shrike 40 with an OS 61 SF. A couple of 10s. One with OS 32. Another modified with a Rossi 40 F.I.R.E with pipe. Just needed to widen the fuse. Another in the works with a Thunder Tiger modified buggy engine. I also built the 1/2A with an OS 15 CV engine. You should try the 1/2A with the CV 15. Quite the handful to fly. Such a great flying model. I have modified the frame a number of ways but the original design still flys the best....
Sounds like a pretty cool fleet you have...!
Was there a 1/2A kit or is that your own version..?
combatpigg is offline  
Reply With Quote
Old 12-19-2012, 06:29 PM
  #119
speedracerntrixie
 
speedracerntrixie's Avatar
 
Join Date: Jun 2010
Location: Sacramento, CA
Posts: 5,340
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

I'm wondering if your Picco is intended for pattern use the same as my Rossi was. My Rossi did not work at all with the short pipe/high RPM approach even though I raised the exhaust port .030. What ended up working the best was a total pipe length of 25" and a large prop. In this case an 11X11. I did try a pipe length of 18" with an APC 9X10 and the airplane was a dog. Changed to a longer header for a total length 21" and got best results with a 10X10. Finally had a section welded to the pipe that increased the inlet ID to 7/8" and made up a 7/8"x 12" header for a total length of 25" and installed a Picco 12mm carb. First tried an 11X10 and it was a huge difference in speed. Tried an 11X11 and was even faster, 11X12 and the speed dropped. Now the 60 is going into a classic pattern airplane and a Rossi 90 is on the way. I'm going to start off with the 25" pipe and 11X12 and see what she does. Lots of engine for a 6 lb 450 sq in airplane lol

I just pulled the Rossi 61 and pipe out of my race plane to get it ready for the arrival of the 90. You can see that the header/pipe is quite long in comparison. You have to love that carb. I'm assuming that the Picco the OP has is fitted with an 8mm carb indicating that it was intended for pattern. It may just be that it develops it's peak power at a lower RPM like the Rossi does.

Attached Thumbnails
Click image for larger version

Name:	Pn37109.jpg
Views:	14
Size:	156.0 KB
ID:	1832084  
speedracerntrixie is offline  
Reply With Quote
Old 12-19-2012, 08:47 PM
  #120
europatc74
 
Join Date: Feb 2005
Location: summit, NJ
Posts: 215
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

Combatpigg
Yes there was a 1/2A kit. I still have a 40, 10 and 1/2A kits which I use as templets. Kits occasionally pop up on E Bay. Pricey, considering the original kit prices.
europatc74 is offline  
Reply With Quote
Old 12-19-2012, 08:52 PM
  #121
combatpigg
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

Thanks for that info about the 1/2A Shrike. That would be a fun 1/2A project to try.
combatpigg is offline  
Reply With Quote
Old 12-20-2012, 08:48 PM
  #122
Quikturn
 
Quikturn's Avatar
 
Join Date: Jan 2008
Location: West Des Moines, IA
Posts: 739
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil

Speedboy, what an awesome job you did on your Shrike. I love it!

Good luck on your flight.

I built one a few years ago. It had a piped OS 40 FSR abc engine. It was fast enough for me. My only mod was to add a dual rudder set up. That was great for snap rolls and spins.

Unfortunately, I sold it but I made rib & former templates so I may have to build another one. My thought was to make it with a twin boom tail to resemble a BVM Bobcat. I have a YS 45FR looking for something to do.
Attached Thumbnails
Click image for larger version

Name:	Fd91532.jpg
Views:	16
Size:	188.0 KB
ID:	1832450   Click image for larger version

Name:	Tp46461.jpg
Views:	14
Size:	100.6 KB
ID:	1832451   Click image for larger version

Name:	Ch97591.jpg
Views:	15
Size:	83.1 KB
ID:	1832452  
Quikturn is offline  
Reply With Quote
Old 12-20-2012, 11:38 PM
  #123
SpeedBoy
Thread Starter
 
SpeedBoy's Avatar
 
Join Date: Nov 2007
Location: Monterrey, MEXICO
Posts: 461
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: combatpigg


Quote:
ORIGINAL: SpeedBoy


Quote:
ORIGINAL: combatpigg

SB..your plane looks SUPER[:-]!!

Remember that the engine will lose torque when the exhaust pressure leaves the cylinder early...but you gain high rpm ability.
So......your engine will become very critical about the amount of diameter it will turn. You have an airframe that should be clean enough and small enough to make a 8+ inch diameter prop work if the rpm is there. The real work isn't just doing the engine mods. The real work is finding the correct prop that compliments the engine mods. With a high timed speed engine [180 degrees or higher] you want to start your search UNDER PROPPED so that the engine runs cool and stays happy. Gradually you try bigger combinations of pitch, diameter, blade area and blade thickness until the engine starts showing signs that it can't handle it.
Thanks for the compliment Chuck !!!

I hope you mean about it wont be able to run bigger props like 11x7 APC , or do you mean the 9x10 APC could be too much load to this displacement after raising the timing???

I don't pretend to use something under 9'' in diameter for this airframe. Im not sure if a 8'' long prop would be enough to overcome the drag of this model.

I'll be careful after doing the first 5° timing job , if no gain there , I probably wont make any more raising timing.

I have never played with any engines larger than .50 sized for speed so I can't tell you about which sized prop will work best for you. All I can say is that 9x10 sounds large to me, but it might be just fine.
My comments are to be taken as general advice. When you want more speed from a 2 stroke engine, you must do mods that raise RPM.
With mechanical engineering, every time you try to improve one aspect.....you make another aspect worse.
If you are serious about speed, it has been proven that 180 degrees of exhaust duration is the STARTING POINT for a properly designed full wave pipe to be able to do it's magic. The trick is to find the best combination of propellor characteristics to fully take advantage of the narrow power band that a high timed 2 stroke engine has. If you expect the perfect propellor is just a phone call away....it might be, or it might take a lot of trial and error to find the prop that marries your engine to that airplane just like a wedding ring.

you want to start your search UNDER PROPPED so that the engine runs cool and stays happy. Gradually you try bigger combinations of pitch, diameter, blade area and blade thickness until the engine starts showing signs that it can't handle it.


A piped engine with high timing [+180 degrees] is a supercharged engine and it will behave like a weight lifter trying to impress his new girl friend if you go for too much load too soon.
It is capable of developing more power. stress and heat than the parts can tolerate..but only for a run or 2.
Piped engines below 180 degrees timing don't hit resonance as brutally..so they don't have the same handling precautions. They have more margin for error
Probably a 9x9 or 9x8 would be a better choice if I start doing the timing job !?!? or do you think is good idea begin with the 9x10 and run it and check again RPM ???

I dont want to overheat the engine and your advices has much sense to me. If the smaller prop is better , I'll start up the engine again with the new prop to have a reading and then I'll work on the sleeve to compare the RPM.



SpeedBoy is offline  
Reply With Quote
Old 12-20-2012, 11:43 PM
  #124
SpeedBoy
Thread Starter
 
SpeedBoy's Avatar
 
Join Date: Nov 2007
Location: Monterrey, MEXICO
Posts: 461
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: MJD

A good data point is the fact that a popular prop used by RC speed fliers in Europe on 10cc engines timed for the low 20's is a CF 9-10. The pattern is from a 10x10 APC trimmed and reshaped so it has better hub strength than a direct copy of the 9x10. The guys who go smaller and higher pitch as in 8x12 or so are flying very low drag pure speed designs. I'd say 9x10 is real close to to the right choice for that airframe on a hot 10cc. If you were leaving the timing as is and running in the higher teens I'd say run a 10-8.

For safety's sake note that if you get that engine really spinning, that APC 9x10 could be a safety issue. Right now you're fine.
Trying to clarified wich prop would be better for the timing job .
SpeedBoy is offline  
Reply With Quote
Old 12-20-2012, 11:46 PM
  #125
SpeedBoy
Thread Starter
 
SpeedBoy's Avatar
 
Join Date: Nov 2007
Location: Monterrey, MEXICO
Posts: 461
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Shrike 40 with thinner airfoil


Quote:
ORIGINAL: europatc74

What do you know, a Shrike Forum. Guess I missed it. I build Shrikes all the time. Scratch of course. I have a number of them. A Shrike 40 with an OS 61 SF. A couple of 10s. One with OS 32. Another modified with a Rossi 40 F.I.R.E with pipe. Just needed to widen the fuse. Another in the works with a Thunder Tiger modified buggy engine. I also built the 1/2A with an OS 15 CV engine. You should try the 1/2A with the CV 15. Quite the handful to fly. Such a great flying model. I have modified the frame a number of ways but the original design still flys the best....
Could you please share what mod. you did on your Shrikes ? would be nice to see if there were some improvement on some point.
SpeedBoy is offline  
Reply With Quote
Reply


Thread Tools
Search this Thread
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -8. The time now is 09:19 PM.