2 blade 3 blade whats the differance ????

[magnum500sw]

yeah i know the 3 blade has one more blade than the 2 blade , but the real question is what is the differance in a chopper vs a full face or round edge blade ? from what i've been reading a prop used on a mono is less then ideal or no good for a hydro . how about some explanation and some cause and effect . i have some boating under my belt but never really had any method to selecting the correct prop . i`d like to expand my knowledge base on this subject .

[sailr]

good topic. I,m anxious for answers

[Fluid]

This topic is far more than can be adequately covered in a post or two, but here is a little:

A low-lift prop like an Octura X, Y or M series can work well on monos, cats and hydros. Lifting props like Octura's 1400 and 1600 series or ABC's H-series generally don't work well on monos but can work on cats and especially hydros. (A lifting prop is one which directs some of its thrust cone downwards, lifting the prop out of the water.)

A mono needs the stern planted in the water, so low-lift props do well. Hydros need the transom lifted and can use lifting props to do it, or they can use low-lift props with a bit of down angle on the strut. Cats can use either, although low lift props usually work better.

The terms "chopper", "cleaver" etc. describe the blade shape but by themselves don't say a thing about lift. Most props with these blade shapes are lifters, but a lifter can be changed into a low-lift prop by cupping the leading edges. Props with 'pointed' tips are used mostly for higher speeds but 'rounded' tips can be as fast or faster and often pull stronger out of turns.

Prop choice is not always simple, but the most fool-proof designs are the Octura X props. They usually give good results on almost any boat. Other props may work better, or not. Few props work optimally as-is, small to major mods can make a big difference in performance - or not. The most common mod is to remove the tongue of an X prop, this often results in a modest speed increase.

The best starting point is a prop that is used by others with the same hull/motor/cells...and not just one guy. If three or more folks have good luck with a certain prop - the x642 on the BJ26 comes to mind - it is a good bet to start with. Minor tweaking may increase performance a bit, or not. Prop choice is more art than science.


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[GP73]

It would be really cool to create a chart of which props are best for certain, well-known, hulls.

Like you said: BJ26 - X642

MG - Prather S220?

[fatboyelectric]

As far as the 2/3 blade part of your question, a 3 blade offers more bite or less slip than its 2 blade counterpart as there is always a blade in the water, while a 2 blade twice in each revolution will have very little blade area in the water. It is for this reason that the 3 blade will provide a smoother yet increased torque load on the system.

[magnum500sw]

So a selection of props is a must for a competitive racer. To accommodate the ever changing conditions you may encounter in a day. So what would be used on a hydro on a slight chop ? You would want less lift from your prop correct ?

[bbosncali]

Wow what a great topic and as stated I ish there was such chart but a lot of what is said makes sense especially for someone like me who likes the higher rpms a 3 blade would probably benefit me more than a 2 blade but cause more amp draw if I'm understanding this correctly. I run a cc 1518 1800kv and usually run 6s which I know is considered way to high of rpms anyways I run either an m545 or m645 and I hit so far my best was 62.1 and I have a buddy who is running a genesis with an x642 1500kv and he hit a best 63.7 and I didn't understand why but after reading this I think I do thanks for the help

[jamie]

I have this stored as a reference ... gives a pretty simple explanation and a chart all on the same page.

http://www.astecmodels.co.uk/props.htm

[magnum500sw]

I have this stored as a reference ... gives a pretty simple explanation and a chart all on the same page.

http://www.astecmodels.co.uk/props.htm

wow!!! that is a great post i am going to send that to the printer.

[bbosncali]

I just ordered an octura 942 3 blade which is a 42mm prop just like my buddies x642 except with more pitch and an extra blade. We both have genesis he's running an 4082 1500kv and hit a best of 64.7 now I'm running a cc 1518 1800kv we wil both be running 6s but now ill be able to put that extra rpms to god use now I hope. Basically its the same prop with more pitch and an extra blade.. I hope I read this thread right i

[fatboyelectric]

I just ordered an octura 942 3 blade which is a 42mm prop just like my buddies x642 except with more pitch and an extra blade. We both have genesis he's running an 4082 1500kv and hit a best of 64.7 now I'm running a cc 1518 1800kv we wil both be running 6s but now ill be able to put that extra rpms to god use now I hope. Basically its the same prop with more pitch and an extra blade.. I hope I read this thread right i

The only things the V942/3 and X642 have in common are being made by Octura and being 42 mm diameter. V series props are basically saw props. They are very aggressive, high lift, high pitch props that are seldom used with great success on anything but hydroplanes.
Your unloaded rpms are just under 40k. Thats alot for sport running. Efficiency is the name of the game. With higher rpms look to prop down in diameter or pitch or both. This also could be good for the handling characteristics of a narrow track width single drive cat such as yours. My point is to consider that a smaller prop at good efficiancy will be faster than a bigger prop at poor efficency considering the rpms your running and would be less likely to cause damage to electronics.

Good Luck,
Kevin

[bbosncali]

That's basically what most of my runs consist of is saw runs.... I also ordered a 646/3 for my df 33 (all trial and error) but I'm running a cc 1717 so I was told to prop up. Not sure if I'm going the right direction considering I've never used a 3 blade prop I mostly stick to x642 and m 445 545 and 645 which I've had success with all at some point. Would the 942 run better running on 5s? My biggest problem is that when I'm running such high rpms a lot of them are wasted

[magnum500sw]

That's basically what most of my runs consist of is saw runs.... I also ordered a 646/3 for my df 33 (all trial and error) but I'm running a cc 1717 so I was told to prop up. Not sure if I'm going the right direction considering I've never used a 3 blade prop I mostly stick to x642 and m 445 545 and 645 which I've had success with all at some point. Would the 942 run better running on 5s? My biggest problem is that when I'm running such high rpms a lot of them are wasted

i am just a noob but it sounds like the three blade is worth a serious look

[fatboyelectric]

That's basically what most of my runs consist of is saw runs.... I also ordered a 646/3 for my df 33 (all trial and error) but I'm running a cc 1717 so I was told to prop up. Not sure if I'm going the right direction considering I've never used a 3 blade prop I mostly stick to x642 and m 445 545 and 645 which I've had success with all at some point. Would the 942 run better running on 5s? My biggest problem is that when I'm running such high rpms a lot of them are wasted

I dont think the 942 will be better running on 5s, just less load on your equipment, but if you wanna push for speed, and if you can tune that prop to work (V series props can cause strange behavior), then proceed with caution as you may find your equipments limits along the way. Remember that this is just one guys opinion. There are MANY others who are way more of an authority on these matters than I am.

I wonder what a P741/4 would do on your boat......hmmmmmm

[bbosncali]

That's how I learn.... if its not from trial and error its from everyone elses trial and error which in the long run can save me lots of money. I don't have awhole lot of experience with a lot of different props except octura x and m series and the ocassional prather which I haven't had any success with