RCU Forums - View Single Post - Building second DD w/ FAI GRRT
View Single Post
Old 10-02-2002, 03:33 AM
  #10  
AndySteere
Senior Member
My Feedback: (2)
 
AndySteere's Avatar
 
Join Date: Dec 2001
Location: Columbia, MO
Posts: 243
Likes: 0
Received 0 Likes on 0 Posts
Default Building second DD w/ FAI GRRT

One difference you will note about racing props and standard props is the size of the hub. Especially on the smaller prop-diameters. As a general rule, the racing prop's hub is larger thicker stronger and rated for the RPM's you're going to turn it.

I have been warned by APC that if I'm turning more than 20k to use only the bigger hub size ("D1" I think), instead of the standard-hub ("C1" I think). They don't recommend the smaller hubs above 20K. The props I quoted you are the bigger hub. I have also heard stories about 7x9 and 7x10 sport props shedding blades at high RPM (a VERY bad thing).

Personally, I wouldn't use a wooden prop on this engine at all. There might be some wooden props out there that are designed for racing, but none of them will be as efficient (fast) as the APC.

Here is a picture of my GRRT (slightly older version pipe) with its APC 7.2x8.6. Note the diameter and thickness of the prop's hub:

(click for a larger version)


Now compare that with the APC 7x10 shown installed in these two images:

(click for a larger version)


(click for a larger version)


The 7x10 has a tiny hub in comparison. I haven't and wouldn't want to try it for fear of it breaking (especially after boring it out to fit the large crank of the GRRT).