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New boater looking for some advice

Old 08-06-2010, 11:45 PM
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highlandcrawler
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Default New boater looking for some advice

Hi all,

I am somewhat new to the world of actual hobby grade boats. I have messed around with different boats of different design since i was a kid and here recently got a somewhat "real" boat. Its a 32" v hull with a water cooled 540 and solid shaft drive. It had foul electronics when I got it . First thing i did was take out all the crap and stuck in a Tekin fxr and a Spektrum system. I am having tons of fun with this boat but am greedy and want more. I'm a rc crawler and scaler by nature and the fast electric thing is a little new to me. I am looking for a patient person on here to help me with some newbie questions. First thing I was wondering is about props. I'm not sure on how they are measured? What are the dimensions that are given? How would I go about measuring and figuring out the prop I have now. The reason I'm inquiring about props is now that ive added a little more power it seems that my boat wants to "burn out" sometimes and loose momentum. Any help would be greatly appreciated and there are many more questions to follow
Old 08-08-2010, 07:29 AM
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siberianhusky
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Default RE: New boater looking for some advice

"This has been covered many times but is still worth repeating. Regarding Octura props, the letter refers to the blade shape on their more recent props.
X - low lift prop
M - same as X with tongue removed
V - cleaver style blade, pointed
P - non-progressive pitch, lower-lift version of 1700 series

The numbers refer in couplets to the pitch ratio and the diameter in mm.
1640 - 40mm diameter, 1.6 pitch ratio = 64mm pitch
X640 - 40mm diameter, X blade shape, 1.6 ratio = 64mm pitch

A general rule of thumb is that when moving from a 2-blade to a 3-blade of the same design, reduce the diameter to 80% of the 2-blade. This will give approximately the same load with both props. Replacing an x646/2 with an x646/3 will increase the load a lot, by about 25%. The 3-blade will be more efficient. Three-bladed props are often used to supply adequate thrust and load in a smaller diameter to reduce torque roll and poor handling effects."
This was posted by Jay Turner on another forum, not my work and I take no credit for it. Great answer though.
I don't understand how Prather figures out their props, Just ahev to look at a chart to see what 215, 230 or whatever means
GrimRacer props have both pitch and diameter shown on the labeling, an "L" in the name indicates a lifting prop I believe. Could be wrong though I've never bought or used a GrimRacer prop.
Without knowing the boat, motor and battery pack it's kinda hard to make any recommendations.
Old 08-08-2010, 08:39 AM
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res3567
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Default RE: New boater looking for some advice



You are correct about the Grimracer prop....I have one for my SV 27.

40 x 52/3= 40 is the diameter, 52 is the pitch, /3is a 3 bladed prop.

Old 08-08-2010, 11:05 AM
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highlandcrawler
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Default RE: New boater looking for some advice

Thanks guys thats what I was looking for. As for the hull I'm not sure of its origin but am pretty sure its Chinesse. The motor is an old silvercan I had around and for batterys ive been running a thunderpower 3s 30c and a 2s 40c. The problem I'm having is that it just seems like im overpowering the prop sometimes. The boat will loose lift and the motor speeds as the boat slows. Its really bad after a sharp turn and i have to feather the throttle to get it to hook in again.

Old 08-08-2010, 11:14 AM
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res3567
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Default RE: New boater looking for some advice

What is happening is called cavitation. The prop is pushing air istead of water. Once the boat gets "up to plane"....that is the prop grabs correctly, the boat will move through the water normally. Also remember...the prop spins in one direction. So if you turn to sharp in that direction that it is spining, the boat will spin out. You need to list the motor specs as well as your prop specs and more pics will help as well. In boating, EVERYTHING needs to match up correctly...from to motor, to the ESC, to the batts., to the drive train, and finally the prop for you not to have consistant problems. No I am not saying it needs to be PERFECT, just close.
Old 08-08-2010, 11:32 AM
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highlandcrawler
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Default RE: New boater looking for some advice


ORIGINAL: res3567

What is happening is called cavitation. The prop is pushing air istead of water. Once the boat gets "up to plane"....that is the prop grabs correctly, the boat will move through the water normally. Also remember...the prop spins in one direction. So if you turn to sharp in that direction that it is spining, the boat will spin out. You need to list the motor specs as well as your prop specs and more pics will help as well. In boating, EVERYTHING needs to match up correctly...from to motor, to the ESC, to the batts., to the drive train, and finally the prop for you not to have consistant problems. No I am not saying it needs to be PERFECT, just close.
Hmmmm I see. You are very right about the cavitation being worse in one direction. I had never even thought about that, good info thanks. The prop is 40mm tall and am still a little unsure on how to figure out my pitch. Its about 12mm long if that helps. The drivetrain upon closer inspection has some sort of a gear reduction on it? As far as pics what do you guys need to see? I will post up pics of whatever helps. As far as the motor I would say it was a 27t out of a tc

Old 08-08-2010, 11:41 AM
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res3567
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Default RE: New boater looking for some advice

I guess the better question is can you get specs on the boat and we can start from there. All we are doing right now is guessing.
Old 08-08-2010, 11:50 AM
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highlandcrawler
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Default RE: New boater looking for some advice


ORIGINAL: res3567

I guess the better question is can you get specs on the boat and we can start from there. All we are doing right now is guessing.
Well on the specs I would assume you know more than me on this boat. I got it 2nd hand and not from original owner. It was cheap so I picked it up to start into rc boating. Its 32inches long and ran a 550 stock is all I know unfortunatly. Im heading out to run it righ now but will post some more pics and try to find more info on it when I return. And thanks I apreciate you willingness to help me out. This is just a boat to get me used to all the ins and outs of the boating world before i get a real boat and spend a lot of money on something I dont know anything about or how to set up and drive properly.

Old 08-08-2010, 11:57 AM
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res3567
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Default RE: New boater looking for some advice

Ok. Go out and run it. Open up the hull and take pics of the insides. Take pics of the rudder and prop as well. I will try todo research, but right now I am like you. I have no clue....yet....but I think i have seen this boat before....just gotta remember were......
Old 08-08-2010, 12:17 PM
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highlandcrawler
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Default RE: New boater looking for some advice

Sea twister from what I just found. Mine is minus the graphics i guess. From raidentech I think.
Old 08-08-2010, 01:15 PM
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res3567
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Default RE: New boater looking for some advice

Ok got it. This thing is on the edge of being a toy and hobby quiality. There are no upgrade parts available and specs are limited at best. I am modding a Traxxas Blast, and when I am through, I will post my results.Some of those sameparts may fit on your boat and you may be a lot more satisfied. This is my latest mod and I hit a snag.....but once I overcomeit this should run way better.....


http://www.funrcboats.com/ProductInf...d=PROPKITBLAST




Old 08-09-2010, 12:09 AM
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highlandcrawler
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So I went out and ran it some more and encountered a few issues. First the pinion came off inside the gearbox and sent me swimming for it. While i was repairing that i figured i would swap the motor out for a 580 size I had lying around because the other would get pretty warm after a few minutes on the 3s. Back out on the water the boat was a beast. Speed jumped considerably and temps dropped on the motor and esc. Now another problem I'm having is with high speed stability. The boat is very twitchy and the rear wiggles around at speed. Now that its faster it has a hard time holding a turn without spinning out or skipping sideways. So I'm wondering is this an issue I could solve with trim tabs and turn fins? Also was wondering if someone knew or had a rough idea how the weight should be distributed in a boat or this size and style? wondering about my COG After some reading around these all sounded like they might help me. I will try and throw up a video tomorrow so you can see exactly what I'm talking about. Here are a few pics of the boat.




Old 08-09-2010, 12:06 PM
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Default RE: New boater looking for some advice

You may think I'm crazy, but I would try it without the gearbox. That bigger motor looks like it's too much for that gearbox. You would only need to reverse the rotation of the motor and make some motor mounts. As for your spin-out problem, try a turn fin . You need to make sure the fin is at 90* to the bottom of the boat and not parallel to the boat's side
Old 08-09-2010, 10:15 PM
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res3567
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Default RE: New boater looking for some advice

Nice pics. The more info available the better to help you out. Go with Hydro Junkies advice....lose the gearbox. Weight and COG is going to be trial and error if no one else has modded this boat. Realize this also....the faster you make it go, the more unstable itmight become.


EP = electric power....usually a brushed motor and ESC, and a plastic or ABS hull....not very wide which leads to instabilaty at very fast speeds. (Faster than stock).

FE = fast electric....ususally a brushless motor and ESC (and the ESC isalso watercooled)... single or DUAL batts. Fiberglass or equivalent typehull, WIDE transom, with turn fins AND trim tabs.
Old 08-10-2010, 01:46 AM
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highlandcrawler
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Default RE: New boater looking for some advice

Thanks for all the info guys. Today I finally gernaded the gearbox altogether so it got tossed in the garbage. I built a mount and turned a new coupler on the lathe as the two shaft sizes no longer matched. Its all in back together now waiting to go back out in the morning. As far as the high speed stability what can i do to give the boat a more locked in feel? Or am i fighting a loosing battle there. IO have also added a turn fin into the mix but have yet to have tested. I will let you guys know how It turns out. This is a fun learning process so far.
Old 08-12-2010, 11:09 PM
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Default RE: New boater looking for some advice

The turn fin should help a little trim tabs too. With a submerged drive at high speed and the shallow vee hull it's going to be a hand full.
Since you got the bug for boats you may want to consider the new SV 27R great boat right out of the box just add a Lipo shield and lipos
and you have a boat that will go 40 + with a little work 50 I own two of the earlier ones that have been modified and love them. Check out this link
http://forums.offshoreelectrics.com/...ad.php?t=11601
I also own a Hydro called a Vac-U-Pickle that run 45+ the boat ROCKS
http://forums.offshoreelectrics.com/...ad.php?t=15304
Good luck Wiz
Old 08-17-2010, 10:35 PM
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ORIGINAL: wizard122

The turn fin should help a little trim tabs too. With a submerged drive at high speed and the shallow vee hull it's going to be a hand full.
Since you got the bug for boats you may want to consider the new SV 27R great boat right out of the box just add a Lipo shield and lipos
and you have a boat that will go 40 + with a little work 50 I own two of the earlier ones that have been modified and love them. Check out this link
http://forums.offshoreelectrics.com/...ad.php?t=11601
I also own a Hydro called a Vac-U-Pickle that run 45+ the boat ROCKS
http://forums.offshoreelectrics.com/...ad.php?t=15304
Good luck Wiz
Those sv27s are a pretty cool looking setup for sure. Somewhere down the line I might try one out. I only got to test my turn fin for a few passes before i had some mechanical issues. I am thinking of adding a second one to the other side as well. Do you think this is a good idea? In blowing up the gear drive i was left with some motor mounting issues as well. The tube the prop shaft goes through(sorry don't know the technical name) is vevy close to the bottom of the boat. Like so close the motor needs to be about 3" from the tip uf the tube before it can be lined up. My mount was pretty hack so I ordered up this one from OSE http://www.offshoreelectrics.com/pro...prod=ose-80230
along with this flex couplerhttp://www.offshoreelectrics.com/proddetail.php?prod=grp-3344. Between those pieces i should be able to make it happen. But with the flex coupler I'm thinking I will need to secure the end of the prop tube. Is this correct? I was also wondering what would the effects of raising the end of the tube about 1/16" or so? I realize it will change my prop angle also but am not sure if it will cause poor handling or lifting?

Old 08-17-2010, 11:06 PM
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Default RE: New boater looking for some advice

Here are a couple of pics of what im talking about


Old 08-24-2010, 01:38 AM
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Default RE: New boater looking for some advice

I got all my parts in and put on and wow what a difference. While I was at it I added a Velineon I had spare at the moment. I have been reading and researching a lot about different handling characteristics and hull setup. COG was way off for this or any boat for that matter. Ive been playing with balancing it at around 30%-32%. With the turn fins on both side and a pair of trim tabs toward the center of the transom the hull is glued to the water now. All hopping and porpoising is now dialed out. We ran it on the river today and bested 26mph up river and a few passes down at 31. Its pretty amazing now to watch fly by (for a novice boater). I have a new lower kv motor coming and a ton of props to play with from OSE. I'm also thinking of changing out the rudder to a better quality alum. unit with a water p/u and fill the hole in the transom. Any recommendations? I am thinking of this 3" one from Kintech



Old 08-24-2010, 10:28 PM
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Default RE: New boater looking for some advice

Now you are helping me out.....I am in the process of converting my dad's Traxxas Blast (which is quite slow). I am looking to add another rudder and a surface drive stinger similar to the one on my SV 27.....I like your pics....mine is an ongoing project as well. I want to get this thing redy for the VXL setup as the XL5 setup with the Titan brushed motor is faster than stock.....but not by a lot. What kind of flexshaft and collets are you using?Also, were did you get your trim tabs and turnfins?I like that setup in yourboat as the u-joint setupin the Blast is not working well at all with the increased torque.I will track your progressand you can track mine....

Check it:

http://www.rcuniverse.com/forum/m_9951504/tm.htm

Here is a VERY NICE setup....but it aint cheap. Some will say it is just better to buy a RTR such as the SV 27. But the hobby is also about building and improving by upgrading.
This would fit very nicely on my Blast....

Check it:

http://www.offshoreelectrics.com/pro...od=ros-monosys
Old 08-25-2010, 12:01 AM
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highlandcrawler
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Default RE: New boater looking for some advice

Thank you much I appreciate the interest in my project. Its kind of discouraging seeing so many people go by with nothing to say good or bad? The flex shaft is a Graupner piece I got from OSE. The tabs I cut myself in the shop. Since I wasnt sure what i was looking for I made some quick ones to tune into my liking, then will mill some nice ones outta billet after I have sizes figured out. Like you said its all about just building and improving on things that makes me happy. I wouldn't mind picking up one of those sv27s after I have a little more time on the water and a better understanding of how everything works and why. That darn u joint set up is a pain. I had that on a mini v i had before. I ended up scrapping the joint and using a cvd axle off a Losi mini crawler modified to fit. I ran 3s lipos and a crazy big prop i got from the LHS and it never failed. The boat literately exploded and it was one of the only pieces not destroyed. There was no turn limit with it like the u joint either. Watch that VXL it makes my 32" boat do wheelies!
Old 08-25-2010, 12:31 AM
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res3567
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Default RE: New boater looking for some advice

With all of the upgrades you have done to your boat....you calling yourself a novice? If you can post vids, that would be very interesting to see....

Keep on upgrading....I am right there with ya!
Old 08-25-2010, 12:37 AM
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Default RE: New boater looking for some advice

One of my good buddies got a cheap deal on this same boat. He blew out the tranny in his even faster than me. He didn't want to drop more money into it as he just bought a new ul1 also. I decided to see if there was a way to fix up the tranny to make it a little stronger and live for a while. Everything about it stock brings the suck pretty bad. The shaft is bowed and midsized, the gears are plastic, and all this rides in egg shaped bushings. My solution was to scrap everything but the case.

This shows the parts new and old.
I turned down a piece of stainless stock to 4mm and put on a couple flats. Next I found some gears that are the same size, pitch, and count. Pretty easy they were maxx gears i think. I bored one out to fit on the new shaft and key to the flat spot. Next were those darn bushings. I kept feeling like I had a bearing of this size somewhere???? I looked around in my parts forever and found them. They are the exact size of a Losi mini t bearing for the front wheels.

So with that find I pressed them into the case and had all my new parts. I figured with all reliable pieces on the inside i would beef the case a little also in case it wanted to flex under heavy load.The case is held together with screws threaded into weak pegs. I drilled them to 1/8" and through the back of the case. I used long 3mm stainless screws with nuts on the back to squeeze it all together and keep it there. This setup will also give him the option of different ratios. If he was to run a 19 to 19 he could have a 1:1 drive with the stock case. Would be a good mod for anyone else that might buy this boat



Old 08-25-2010, 12:56 AM
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Default RE: New boater looking for some advice

The only way to tell is for you to test it out yourself. One reason alot of people don't respond is because the boat is not a very popular one....as I found out the hard way with my dad's Blast. It looks good to me as you have upgraded it with stronger parts. But it will haveto be tested and with thenew upgrades to your boat, I don't see you regressing back to the gear reduction drive as you seem plenty satisfied with the way the boat runs now.....
Old 08-25-2010, 12:58 AM
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Default RE: New boater looking for some advice


ORIGINAL: res3567

With all of the upgrades you have done to your boat....you calling yourself a novice? If you can post vids, that would be very interesting to see....

Keep on upgrading....I am right there with ya!
LOL novice boating for sure but my passion is building. I have a small business scratch building scalers and comp trucks for people. I will get some good videos after my motor arrives and I get back out on the water. I have lots of everyone else but never get any film of my own stuff.
Here area couple of my other land based projects







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