Carbon V Metal Props

[Reedy]

Hi All,

I have a fairly crude FE monohull that I built myself and am running a 12 Cell Brushless Setup ( http://www.offshoreelectrics.com/pro...=dh-aqcom-1800 ) I recently upgraded it from a 700BB motor and the brushless setup is much faster/more fun to play with.

I have dialled it in reasonably well using a set of carbon props, and have ended up with the 45mm 1.4 pitched prop giving the best performance, 42mm props (both with 1.4 and 1.6 pitches) run very poorly and a 48mm one generates way too much motor/battery heat. The 45 has good performance and heat generated is manageable but perhaps slightly higher than I would like it to be.

My question is, will upgrading to an x445 sharpened & balanced prop yield any appreciable improvement in performance and/or run times or is the difference between like carbon vs beryllium prop fairly negligible?

I'm Just looking for ways to tweak and improve performance further without needing to resort to full rebuilds.

[j.m.]

Generally speaking, a properly worked metal prop will work better than a carbon prop, yes.

[JimClark]

yes for sure plus you can add cup to the metal prop and will give you even more speed

[domwilson]

I would try both the X442 and X445 or even a M445. Carbon prop blades from what I've read and experienced, tend to flex under load. Changing their pitch. It is better to have a few different props to experiment with here. But I could be wrong. Others might have different recommendations.

[Reedy]

How does the M series compare to the X series?

Obviously I could buy a stack of props and experiment with them all but that would cost a bit. I'm more interested to see what kind benefit changing to a metal one will give, and to see what results others have had.
The plan is to experiment with carbon props, see what works best and then pick up a sharpened/balanced metal one that best matches it.

[domwilson]

The "M" series has the "tongue" removed. It unloads the prop at higher speeds. However you will lose some speed in coming out of turns and off the line acceleration. But this does depends on your setup.
You may want to do some reading before spending your cash.

Here is a diagram.
http://www.offshoreelectrics.com/inf...er-diagram.php

Some info.

http://rcprops.com/TechNotes/rcprop_tech_info.htm

http://rcboat.com/prop.htm

http://www.fastelectrics.net/propeller_preparation.php

There is plenty of info. on this site and others have may have more links to some good reading. Egneg on this site does prop work and may have some good advice for you. You may want to PM him to get some thoughts.

[BakedMopar]

I have started doing my own props. While I may not be a pro or quite understand what to add or modify to get what I'm after it is a good learning experience. I use a data logger to jot down the differences each modification does as well as observation and video. I log everything down. I always start with a plain S/B and go from there. Yes theres some that I have gone too far.

FWIW I was doing the same as you. I got a good baseline with the carbon then got similar in metal. The metal props runs much better than carbon.

[Steven Vaccaro]

Its a very hard question to answer. A direct swap from a 45 to a x445 will not always yield more speed. On one of my boats I've had to go from a 42mm carbon prop to a x445 to yield the same speed.

[Reedy]

Yea I suspected as such, I have an X642 prop which you would think would perform alright compared to a 45mm carbon one but in this case it runs a similar top speed but has very bad acceleration and sets my batteries on fire. I guess the real answer is that there is definitely not a 1:1 mapping between the carbon/metal prop ranges and it remains largely trial and error.

Also as a side note, I've read that only metal props are allowed in competition, what's the reasoning behind that?

[Steven Vaccaro]

Also as a side note, I've read that only metal props are allowed in competition, what's the reasoning behind that?

I have not heard that. I have raced and won several races using only Graupner props. People laughed until I ended up infront of them

[Meniscus]

That's funny, I don't care who you are!

While we are on the subject, do the carbon props suffer from burn over time?

[Steven Vaccaro]

That's funny, I don't care who you are!

While we are on the subject, do the carbon props suffer from burn over time?

The edges will nick over time from hitting shore. But unlike plastic, you can file the edge to sharpen them.

[Reedy]

Ok so its not a universal rule then, I cant remember where I read the metal prop rule, it might have been in an Australian Club's rulebook and I couldnt figure out why.

[Steven Vaccaro]

Ok so its not a universal rule then, I cant remember where I read the metal prop rule, it might have been in an Australian Club's rulebook and I couldnt figure out why.

It could possibly be a rule in the USA that I wasn't aware of.
They don't like to spin at high rpm, so there is a danger of a blade flying off. But I have never had it happen to me. Most my setups are in the 20k to low 30k range. I've had great success with them.

Someone posted a link to a guy that ran one at about 50k and it blew apart, but if it didn't his esc would have gone first. It saved his boat from going .

[egneg]

I would suggest an M445 and if temps are ok then an M545.

I seem to remember reading in the IMPBA rules that metal props are required.