My Boat Videos - Gotta Love the 351

Pete, I thought your comment was classic and I know you and Craig are pals. I think indirectly I was probably justifying my own longwindedness (is that a word?) and looking for company in Craig, since I'll give anyone a run when it comes to babbling on.

I fortunately or unfortunately share Craig's interest in the prop calc's but they continuously stymie me and mostly in the area of slip. I just keep playing with the numbers and along the way you learn prop sizes/results, engine power and speed as a function of rpms, etc., all the stuff a gear head or speed freak likes to know.

Luciano, Tim (TRBeng) was doing a big summer test on props. Tim, Did you ever finish the prop testing and compile the results? The slip results should be very interesting because it is the big vaiable!!

TRBenj wrote: 8122pbrainard wrote: Luciano, Tim (TRBeng) was doing a big summer test on props. Tim, Did you ever finish the prop testing and compile the results? The slip results should be very interesting because it is the big vaiable!! Prop testing is finished and I have a bunch of numbers. I havent crunched them yet, but have a pretty good feel for what I would recommend on all the 1.23 direct drive boats. There isnt a whole lot that would help all the 1:1 guys, as I was dealing with a totally different set of props. I will be putting together the full writeup and having Keith post it. Its on the to-do list.

Is it the same thing you've always recommended for the 1:23 boats? Any surprises?

Jumping backwards a bit (didn't check in for a while), Thanks Ried and Pete! So it sounds like I've got the green light to ramble on & on & on & on...! Wait, I think I feel a three pager coming on!
Just kidding.
It was interesting what you were mentioning above about the flex factor of the NiBrAl. You usually see a lot of comparing between aluminum and stainless and folks don't mention the NiBrAl a lot. It's like "Oh that's what goes on an inboard" and that's about it. This has been a cool thread with a lot of neat info.

I had always noticed the huge differnce in the typical inboard props pitch (as compared to sterndrives and outboards). Didn't know for a long time that most inboards were close to 1:1 ratio. I think I just assumed it (in my ignorance) since the were direct drive and the pitches were so low. Most outdrives ratios are in the 1.5:1 or more (the old Volvos for V8's being largely 1.61:1 and then for 4 cylinder engines, as much as 2:1 and I think even higher). Noticed above the mention of 1.23:1 inboards.

Ried; you're right, the main wild variable is the slip factor. It's like that's what you're really calculating if you have known actual speeds, and then theoretical speed, rpm's and gear ratio. It's fun to try to predict the numbers. As mentioned, cup does some things too. Most of my rambling has been from memory from reading, experimenting, and talking to the guys at the Donzi web site. I gotta dig out my old Mercruiser "All you need to know about props" book. It is very cool and full of great info.

Wow; that's all I could come up with. I must have web writer's block.