Changing prop diameter

[tiqueman]

I did some quick searching and havent found anything. Just curious, if you have for instance an X447 and cut it down to 45, is it now the same as an X445 or has the pitch or anything slightly changed?

I know there are x445 available so why would you cut a 447 down, but an (R) is not. I cut down both a L and R 447 last night to 45 for a twin I have. And like I said, just curious if anything other than diameter changes.

[siberianhusky]

It still has the pitch of the 47 mm which is 65.8 so it becomes a 1.46222 x 45.

[Boaterguy]

it would change other factors, like siberian husky stated, but a 2mm change (1mm off each blade) would not be so much to affect your setup in any noticeable way. of course do not match an X445 with a cut down 447, but if you cut both, I don't see a problem.

[tiqueman]

So comparitively speaking, it has more pitch than a stock 45? I guess thats what I was getting at. I know that since I didnt physically bend or tweak anything, I didnt change pitch, but a cut down 45 is not the same pitch as a stock 45. Correct?

[Boaterguy]

yes, that is correct.

[siberianhusky]

Lift seems to stay about the same as the larger diameter, at least on the small mono's I've done this on. Boaterguy must have been into the crack again! there is a huge difference in performance! The difference in load is amazing! There is a difference between a 38 and a 40mm prop store bought prop why on earth would you think 2mm wouldn't make a difference if you do it yourself?

[tiqueman]

2mm certainly makes a difference. I got some gps runs earlier today. I'm going to throw some stock 447s on it later in the week for comparison of both speed and temps.

[Rich]

So comparitively speaking, it has more pitch than a stock 45? I guess thats what I was getting at. I know that since I didnt physically bend or tweak anything, I didnt change pitch, but a cut down 45 is not the same pitch as a stock 45. Correct?

The pitch of both props is the same, so is the total pitch after you cut it down, all you have done is made it into an x445. The first "4" in x447 and in x445 denotes the 1.4 pitch of the blade. The 47 and 45 denotes the diameter. The math works out the same. 2mm is a big change in performance especially at the RPMS we run at.

[Boaterguy]

I meant that the pitch that changes with a 2mm diameter larger prop cut down will not have alot of affect, I agree that 2mm is a large change, but a cut down 447 vs a 445 is not much different.

[tiqueman]

Putty shows something is different. If you take a 445 and a 447 cut down to a 445 the blades do not lay the same. My findings cause me to disagree. A 445 and a cut down to 445 is not the same

[Rich]

Putty shows something is different. If you take a 445 and a 447 cut down to a 445 the blades do not lay the same. My findings cause me to disagree. A 445 and a cut down to 445 is not the same

Hmm thats interesting...can you compare a 447 cut down to 445 and a stock 445 with some data? I am curious as to see what happens, since I have an x447 to modify.

[Rich]

I meant that the pitch that changes with a 2mm diameter larger prop cut down will not have alot of affect, I agree that 2mm is a large change, but a cut down 447 vs a 445 is not much different.

Ok I get what you were trying to say now

[Boaterguy]

haha good because I don't even understand what I said.

[siberianhusky]

x445 has 63mm pitch, an x47 has 65.8 divide by 45 and you get 1.462 pitch ratio.
You still have 65.8mm of pitch just in a 45mm prop instead of 63mm of pitch, this is a major difference at these sizes and rpm. Boaterguy at least get a running boat before offering opinions on something you have no experience with.

[Boaterguy]

yeah, whatever you say.