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

.15 size shrike w/OS32 Prop?

Reply

Old 08-12-2002, 11:53 AM
  #1  
ckoerner
Senior Member
Thread Starter
My Feedback: (2)
 
ckoerner's Avatar
 
Join Date: Jan 2002
Location: Crest Hill, IL
Posts: 429
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

I have a .15 size Shrike with an OS 32 on it. I am currently running a 9x6 prop with 15% heli fuel. What would be a good prop for the 32? Would an 8x8 be too small? It's very fast with the 9x6, but I want more.
Thanks,
Craig
ckoerner is offline  
Reply With Quote
Old 08-12-2002, 12:04 PM
  #2  
jlong34016
Senior Member
My Feedback: (1)
 
Join Date: Apr 2002
Location: columbus, OR,
Posts: 365
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default prop load

I believe the prop load is diameter squared x pitch. You are running a 9 x 7 = 567 an 8 x 8 = 512. A 8 x 9 = 576.
jlong34016 is offline  
Reply With Quote
Old 09-04-2002, 03:43 PM
  #3  
ckoerner
Senior Member
Thread Starter
My Feedback: (2)
 
ckoerner's Avatar
 
Join Date: Jan 2002
Location: Crest Hill, IL
Posts: 429
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

I tried an 8x7, but it seemed slower. Any other suggestions?
Thanks,
Craig
ckoerner is offline  
Reply With Quote
Old 09-04-2002, 04:36 PM
  #4  
evan-RCU
Senior Member
 
evan-RCU's Avatar
 
Join Date: Feb 2002
Location: Charlotte, NC
Posts: 3,911
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

try an APC 8x8, You have a great combo there, afriend, Guido has almost the same combo, 25FX on one, it'd almost as fast as my magnum...
evan-RCU is offline  
Reply With Quote
Old 09-04-2002, 04:48 PM
  #5  
ckoerner
Senior Member
Thread Starter
My Feedback: (2)
 
ckoerner's Avatar
 
Join Date: Jan 2002
Location: Crest Hill, IL
Posts: 429
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

I will try a APC 8x8. I have another one (Shrike) with a .25FP on it. Mine with the .32 is faster at half throttle then the one with the .25FP. The .25 is boring now. I was thinking of throwing the .25fx on it w/pipe. I had to do a lot of mods to the one with the .32. I also have a Whiplash sitting ready to paint. Hopefully it's faster then my Shrike. I like the looks of the Shrikes better though. They look more like a real plane instead of a flying wing.
Later,
Craig
Craig's page
ckoerner is offline  
Reply With Quote
Old 09-04-2002, 05:48 PM
  #6  
evan-RCU
Senior Member
 
evan-RCU's Avatar
 
Join Date: Feb 2002
Location: Charlotte, NC
Posts: 3,911
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

he is using a macs tuned pipe and running a 7x9 on his .25FX
evan-RCU is offline  
Reply With Quote
Old 09-05-2002, 02:23 PM
  #7  
corey-RCU
My Feedback: (2)
 
Join Date: May 2002
Location: winnipeg, MB, CANADA
Posts: 141
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

I run an apc 8x7 prop on my .32sx with a mac pipe and get 17500rpm... very fast!
corey-RCU is offline  
Reply With Quote
Old 09-05-2002, 08:01 PM
  #8  
PAINLESS
Senior Member
My Feedback: (19)
 
Join Date: May 2002
Location: Los Alamos, NM
Posts: 432
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

jlong,
What do those prop load numbers mean? Does a higher or lower number mean more speed? Does prop efficiency figure into that some how? Inquiring minds want to know.
PAINLESS is offline  
Reply With Quote
Old 09-05-2002, 08:38 PM
  #9  
jlong34016
Senior Member
My Feedback: (1)
 
Join Date: Apr 2002
Location: columbus, OR,
Posts: 365
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default prop load

There are many people with alot more knowledge than me to answer this. My simple interpretation may not be entirely correct and i don't proclaim to be an expert by any means.

The load on the engine is determined by the diameter squared multiplied by the pitch. This number is a ballpark way to compare what changing props will do to your rpm's of a given engine. To get more speed you want more pitch, to get more thrust you want more diameter. A larger load will decrease your rpms, a smaller load will increase your rpms. Obviously there are many more variables but this is just a quick way to see where you need to go with the prop dimension to get the desired result.

The original question was about going from a 9x6 to an 8x8. The poster wanted to know if the 8x8 was going to be too small. The load of the 9x6=486, the 8x8=512. The smaller diameter prop is actually a bigger load on the engine and will slow the rpms down. So did he want the rpms up to get the engine in the power band? or did he want more speed? or did he want more thrust? We can say for sure the thrust will be less and the rpms will be less but the speed we cant say because of other variables.
jlong34016 is offline  
Reply With Quote
Old 09-05-2002, 08:46 PM
  #10  
PAINLESS
Senior Member
My Feedback: (19)
 
Join Date: May 2002
Location: Los Alamos, NM
Posts: 432
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

I did a search on "prop load " and found this: (apparently there was a chart that went with it but I didn't find it)


"Engine Load = Propeller Diameter Cubed x Pitch 1. Find your prop diameter in the first column and follow across to the pitch of your prop to find the relative loading factor. The larger the number the more load the prop will place on your engine. i.e. An 11/3 prop with a load factor of 3993 will load the engine the exact same amount as a 10/4 with a load factor 4000. 2. If you want more R.P.M. go to a prop with a lower load factor. 3. If you want more speed go to a prop with a higher pitch. If you want more acceleration/vertical speed go to a prop with lower pitch. 4. If you need more thrust you can also go to a larger diameter prop. "

Based on this and your last post, it makes sense to me now. Its really just a way to compare props to each other. There was an article in one of the model mags recently about this.
PAINLESS is offline  
Reply With Quote
Old 09-05-2002, 09:02 PM
  #11  
PAINLESS
Senior Member
My Feedback: (19)
 
Join Date: May 2002
Location: Los Alamos, NM
Posts: 432
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

Actually if you cube the diameter instead of squaring it the numbers come out different. 9x6 = 4374 and 8x8 = 4096, so the 8x8 would load the engine less than the 9x6, which should mean a gain in RPM. At this point I don't know which is correct, squaring or cubing.
PAINLESS is offline  
Reply With Quote
Old 09-05-2002, 09:10 PM
  #12  
jlong34016
Senior Member
My Feedback: (1)
 
Join Date: Apr 2002
Location: columbus, OR,
Posts: 365
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default prop load

It will be different for different engines. Some sites say they use 5th power. The square rule has been proposed for engines of our size. Only way to tell is to test it. I have two jetts, one nelson, four ys, and two os engines. I have just started with these speed planes late this summer. I have alot of props to try out. Plan on collecting data and plotting. Just curious ckoerner, did you tach these props?
jlong34016 is offline  
Reply With Quote
Old 09-05-2002, 09:16 PM
  #13  
PAINLESS
Senior Member
My Feedback: (19)
 
Join Date: May 2002
Location: Los Alamos, NM
Posts: 432
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default .15 size shrike w/OS32 Prop?

Agreed, testing would be the definitive solution. Although, the artical I found did specifically mention model size props and engines, I didn't paste the whole thing.
PAINLESS is offline  
Reply With Quote

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


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service