Metal versus plastic prop instability

[Heaving Earth]

I dunno why you blow it up man. If you don't know about something just take your own advise. There's ALOT to learn.
As far as Prather props, they are 1.5 pitch. Puts them in between the octura 1.4 and 1.6.

[J.W. Pepper]

I dunno why you blow it up man. If you don't know about something just take your own advise. There's ALOT to learn.
As far as Prather props, they are 1.5 pitch. Puts them in between the octura 1.4 and 1.6.

What made you think I blew up?? I started out by recommending he read the Octura X or M prop thread. And tried helping after that, my intentions were good, unfortunately I got in over my head.

I've got a lot on my plate right now, bought a NIB PB IM-31 with all kinds of high hopes and the dam thing has become a nightmare... You need these bullets, no you need these other bullets, no the stock bullets work just fine,

Then along comes this prop soap opera with all the conflicting / confusing info involved in trying to figure which one to use. What's the next soap opera going to be?? It just wears you down after a while. So yesterday (05.07) I finally got fed-up with all the B.$ & said f*** it and boxed the boat up. When I can find the time, I'll take pix and get it listed in the swap shop.

As far as Prather props, they are 1.5 pitch. Puts them in between the octura 1.4 and 1.6... And the diameter puts them in between the x440 & x442.

Now take somebody like me who is new to FE boats and he's trying to tune it. The x440 is too small diameter & not enough pitch. x442 is too big diameter and still doesn't have enough pitch. So what am I supposed to do?? Make my own??

I thought of a great analogy for this whole mess...

What if Traxxas used gear type "A" for they're rigs?? And Team Associated used gear type "B" for there's, HPI used gear type "C" for there's, DuraTrax used gear type "D" for there's, Axial used gear type "E" for there's.

Now add in ARRMA, Venom, Tamiya, Kyosho, Thunder Tiger, and all the others.

None of the gear types are interchangable, none are compatible, none have the same tooth pitch type and so on. Can you just imagine the havoc that situation would cause??

So why hell does it have to be that way with boats?? There's what... at least a 1/2 dozen manufacture's all using they're own system to define the size of they're props, none are compatible, all use different methods to define type & size, non are interchangable - just one big stupid a$$ hodge podge B.$. mess.

And you wonder why I get frustrated??

[martin]

One of the best ways to burn the electrics down in a boat is by over propping, you get no second chances as its all over in a puff of smoke. The amp draw can go through the roof with the wrong props.

[paultbg]

@Pepper-you get it slightly wrong: there are no wrong props (except the ones way to big or way to small); instead of trying to buy the perfect prop for your setup, try to adapt your setup to your prop.play with the boat settings: trim tabs, cog, prop angle and see what is the best setup for that prop; there is a lot of information here in this forum but you need to select what you need at your stage; I would never reco to a beginner to alter the blades of the props in any way; that is an advanced technique used by the racing guys in order to gain 2-3 more mph; if you boat is bouncing on the waves or is not stable in turns, for sure you do not need to alter the blades...
Now,back to your problem, why do you say that a particular prop has not enough pitch? What actually means this pitch for you? Is your boat running to wet, is not on plane? Please explain what problem do you want to cure.
Regards

[J.W. Pepper]

@Pepper-you get it slightly wrong: there are no wrong props (except the ones way to big or way to small); instead of trying to buy the perfect prop for your setup, try to adapt your setup to your prop.play with the boat settings: trim tabs, cog, prop angle and see what is the best setup for that prop; there is a lot of information here in this forum but you need to select what you need at your stage; I would never reco to a beginner to alter the blades of the props in any way; that is an advanced technique used by the racing guys in order to gain 2-3 more mph; if you boat is bouncing on the waves or is not stable in turns, for sure you do not need to alter the blades...
Now,back to your problem, why do you say that a particular prop has not enough pitch? What actually means this pitch for you? Is your boat running to wet, is not on plane? Please explain what problem do you want to cure.
Regards

Paul,
Thanks to you and the other forum members who have made positive contributions, I do appreciate it. I've had a lot on my plate lately, so I tend to get cranky at times without realizing it.

The PB IM's come with a SS prop that is horribly out of balance, there's several posts about it, think I saw them in the Impulse threads in the PB section of this forum. It's the same size as a Prather S215. I have no intentions of using it because of the issues I read about + excessive weight.

I like Jan's CNC'ed aluminum props because they're basically ready to go out of the bag. I use sandpaper to get rid of the tooling marks and give it a satin finish like it says to here... http://www.aquacraftmodels.com/acces...op-tuning.html - scroll down to the bottom step #4.

That said, I have 3 of Jan's props, x438, x440 & x442. The x440 is a bit smaller diameter than stock and the x442 slighly larger in diameter, both are 1.4 pitch of course. In post #16, heaving earth states the prather's are 1.5pitch. Ok, so if I'm reading things correctly, I need a x541 prop, one small problem, there's no such thing - that I know of anyway.

Regarding your other suggestions...
I got a set of SpeedMaster trim tabs from Steve to make precision adjustments posible, manual says to bend them with large pliers.

I also removed that rediculous post the battery lid goes on, filled the hole with a small piece of wood & epoxy. I have 2-sets (4-total) of velcro straps, the idea was that it would be much easier to move the batts fore 'n' aft to dial in the COG.

Darin Jordan has done several really informative posts about the IM's (V1 & V2), I copy / pasted one of them into a MS Word document so can reference it anytime I need. Still trying to find the others so I can do the same thing with them.

As far as my IM goes... as you can tell from post #17, I've pretty much thrown in the towel. The reason I addressed your suggestions was courtesy; if someone is going to put the effort into addressing one of my posts, the least I can do is acknowledge them in a polite manner.

Regards,

[paultbg]

@Pepper- please leave aside that pitch is not that important as you may think.your boat will sail ok with 1.4 and 1.6 as well.
I have read the post again but I am not able to see what is actually the problem with your boat? What exactly you don't like?
A clear description of the problem, maybe some pics of the setup or even a video of the boat running will give us the opportunity to help you.
in the mean time, you can read here about the rules/setups general available for any model boat:

http://fastelectrics.net/fe_manual.php

Regards

[BHChieftain]

Now take somebody like me who is new to FE boats and he's trying to tune it. The x440 is too small diameter & not enough pitch. x442 is too big diameter and still doesn't have enough pitch. So what am I supposed to do?? Make my own??

Hi Pepper,
I have an "unusual" prop in my prop box, an Octura x637. It happens to be awesomely sharpened, thinned, and balanced-- tuned up real nice. It has more pitch than the x442 but less diameter. I don't need it anymore and would be happy to mail it up to you for you to try it out. If it works you can buy if from me for $40 later. If not, just send it back.

X440: 2.198"
X442: 2.310"
X637: 2.368"

bye,
Chief

[jstolz]

Don't give up on the 442 metal prop. Metal props run more efficiently than plastic props. The only boats that I have ever run plastic props in we're my N1 Mono and Crackerbox. Both boats had low efficiency 27t brushed motors. With the more powerful and efficient brushless motors, plastic props are distorted in shape. They are a cheap way to test a new prop on a boat. Once the right plastic prop is found, you can purchase the comparable metal prop. In your case the plastic prop runs ok and keeps the boat stable. With the 442 and the boat properly trimmed, you should get better performance.

You need to be open to all options when trimming your boats. I would adjust the strut to a neutral setting with the strut bottom parallel to the bottom of the boat. Set your center of gravity at around 30 percent. Keep the trim tabs parallel to the bottom of the boat. You can make small adjustments to the strut, center of gravity and trim tabs to get the boat running stable in the water.

How is your strut adjusted on the transom? I suspect that the strut is adjusted low on the transom. Can you move the strut up? Don't change the angle of the strut. You can trim your mono by moving the strut up an down on the transom. I think that when you run with the 442 prop, the whole boat is lifted out of the water and making it run unstable. By moving the strut up on the transom a slight amount, your boat will settle in the water. It will run more stable. It takes patience and trial an error to get a boat properly set up.

[Skullcracken]

Sure did, sharpen balance and polish. I realize that just because its metal it's going to better, just surprised it led to much more instability. I guess I need to fine tune the trim tabs to see if I can dial it in, otherwise I will go back to the plastic prop.

Try trim tabs down more and angle the drive up slightly. Spartans are bad about chine walking because they are too buoyant. Not enough hull in the water. You're likely increasing thrust with the metal prop, but with the instability and chine walking, losing top end.

[jetnfast]

Back from more testing....this time with a de-tongued x442. The good news is the stability is now rock solid, the boat is stable with little to no chine. The bad news is the temps on the T180 are 150F and the stock motor is up to 110F. With the tongued x442 and the stock prop is was around 110F on the ESC and 100F on the motor, both which I was comfortable with. In terms of speed, with the stock plastic prop I was at 49.7mph and the latest run on calm water with the detongued x442 was 47.2 mph. Not a huge difference, but with the high temps, I think I want to try other prop options. My batteries were centered with a 30% CG and a neutral strut BTW. I am thinking about trying an M445 next and then maybe a x642.

Any idea why detongue-ing the prop increased the temps? Maybe the load on the motor?

[madmikepags]

detounging should have less load on the motor less punch off the line and higher top end, (the motor should turn more rR's) is the boat running the same with both props? by that I mean is the attitude of the boat the same? what batteries are you running? 4s 5s 6s lipos? I can't believe that size boat only uses a 42mm prop? my similar sized boats (cats and monos) use between 52-57mm props?

[jetnfast]

I am running 6s Gens Ace 120C lipos. Strange I am not seeing higher top end, but the boat is way more stable than just a regular B/S x442 not detongued. Maybe I detongued too much? I have another x442 that I might just remove a small amount off the tongue. I am also thinking about ordering an S-215 (Copper), and an x642 to experiment further. At this point I gotta get the temps down, since stock prop was running 110F on the ESC, 150F is way too hot for this boat based on my past testing. The boat is running about the same attitude as with the tongued prop except the detongued runs much more stable with almost not chine on smooth water.

[jstolz]

Any idea why detongue-ing the prop increased the temps? Maybe the load on the motor?

Is the detongued 442 sharpened and balanced? If you detongue the prop, the blade from leading edge back has to slowly transition from sharp to thicker mid way back into the prop. If rework is not done properly, you could get higher temps than on a sharpened and balanced stock 442.

[jetnfast]

Yes, it is sharpened and balanced. Maybe I need to thin the prop more? You could cut a steak with the prop it is so sharp!

[kevinpratt823]

Though I do agree we would all benefit from standardizing the prop sizing between manufacturers, there are charts out there listing equivalent props from different manufacturers. As far as comparing it to cars, well that is a whole other story, and I think a more fair comparison may be due. First of all, for gears there are 32,48,64, and mod-1 pitches, which in boating that could be compared to different flex shaft/drive dog sizes. A pinion may be interchangeable, but that is about it, spur gears, diffs, etc ARE brand specific. While a boat has a handful of adjustments, cars have dozens. The characteristics that a prop contributes to, in car language, would be a combination of gear ratio, tire selection, and clutches primarily, but also affect the equivelent of supension, ride hieght, camber links.....and then some.
I know I have been doing cars for some time, and I still have quite a bit to learn about tuning all that stuff, so don't get discouraged. Take your time to learn what you can, especially with searching the forum, and enjoy the boat.