Flip over problem

[sash]

The X452 was running. I'm thinking detongue the prop will this help the lifting problem??

[sash]

I think I've finally got it through my little brain. Just tested the cog again @ 36 %. To get this thing back to 33 % would take 15.87 ounce over the back of the esc enclosure.That is alot of weight over the prop that would keep it planted I beleive. Is this why I'm having a problem ? The only way to get it close I think , is to fully rebuild the chasis moving everthing back with more drive shaft angle or add extra weight over the back end. Add another 2-3 s over the rear would get damm close with a swordfish 240. 8 -9 s What do you guys think ??????????????

[jcald2000]

Tape a weight back there firt to see if it helps.

[1945dave]

In life as it is in all of nature we tend to fix the symptoms not the problem. Adding weight is NEVER, I say again NEVER the correct solution to a problem except perhaps for NFL linemen. If that isn't strong enough try using a bandaid for open heart surgery. The point I am trying to make is NO we do not add weight to bury the prop and move the CG further rearward on your boat. The only real solution in my opinion is to reduce the lifting nature of the prop. That can be done easiest by choosing a different prop. However, since I am basically cheap and don't take lightly the expense of the tiny props there are several things you can do to a prop to reduce the lifting characteristic. Years ago everybody carried a special pair of pliers that had all the teeth ground off. You could tweak and bend your copper base metal props and evaluate if it was better or worse and undo what you did if it wasn't better. In your case I would curl or cup the very outside of your prop a very small amount. By that I mean by the smallest of margin bend the very outside edge of the prop when looking at the prop nut side toward the propnut direction. Just a very small amount to catch your finger nail. This will take some of the lift out of the prop. Next, without cutting or filing and rebalancing if you bend very slightly the part of the prop that many remove the so called tongue portion of the blade so it enters the water from a more straight up and down direction this will reduce lift as well. Now some doubters will jump in and say you are reducing pitch too. Actually no. The pitch measurement is taken at the 70% point of a single blade. All of the surface area of a prop has a job to do but the pitch ratio is a theorectical concept and nothing of value when actually comparing performance between adjustments. Are you not close enough to other fast electric boaters so you can try to borrow a prop or two and see the difference? I believe the M series Octura props were made for you. If not easily tried and tested borrow and test what you can. I would want to try smaller diameter props than your current X552 meaning smaller diameter than 52 mm and try a higher pitch ratio. Instead of 1.4 like all X4xx series props try a X or M5xx series for 1.5 pitch ratio. Maybe even a X6xx or M6xx series for a ratio of 1.6. The prather props are difficult to work but once finished are very good choices. Finding a used prather 230 prop is almost never seen but it might answer your needs without adding a fraction of an ounce. Don't add weight, please.

[1945dave]

I still stand behind my previous post on prop lift and also to not add weight. However, For the time being what you also could do is remove weight forward of the CG by going with smaller lighter batteries. Forget for the moment about trying to get 8 minutes runs and if you are running a parallel configuration of two batteries try using just one battery to see the difference. I still want to see how a good 4S configuration will affect total performance. The added weight of a heavy set of high capacity 6S batteries could be too much weight for the hull to efficiently carry.

Dave

[sash]

Thanks for that Dave. Here is my attempt for balance and prop detongue.IMAG0197.jpgIMAG0198.jpgIMAG0199.jpgIMAG0200.jpg[ATTACH=CONFIG]75601[/ATTAH]
I have detongued the X452 and the balance is 99.9 % perfect. The Pranther S230 from 80 to 95 % balanced (4 hours in total still not happy ).
I've made a tray over the motor to reduce the COG from 36 % down to 32 % for test runs only. I realise the turning will be affected by the height raise but I'm after straight line speed . That is the best i can do at this stage. When my new flexdrive arrives I will post the videos of COG differences and props.

[sash]

More pics IMAG0201.jpgIMAG0202.jpgIMAG0203.jpgIMAG0204.jpgIMAG0205.jpg

[sash]

And more IMAG0206.jpgIMAG0207.jpg

[1945dave]

Looks like you did a great job on reworking those two props. I believe you will like the Octura prop much more now. The lifting characteristic should be reduced dramatically. I am not so sure about the battery movement but this is only for testing purposes so tell us all how this affected your performance. I am thinking you will want to go back to the old CG.

Lets assume you really like what you have done on the reworked X452. The first thing I would do after the test session is make a "prop-duplicator". Essentially a small piece of wood, a 3/16 bolt inserted through that and tightened and then a glob of Bondo about golf ball size mounded up around the bolt. Push the prop over the bolt into the Bondo and carefull scrape away any Bondo that is not needed surround the prop and above the lowest part of the prop as it rest in the Bondo, let it harden. You don't need both blades done, one blade is good enough. What you then have is a casting of the prop that will let you hammer out any dings or minor bent blades that sometimes occur and also will help you in the future to duplicate another.

Dave