new hardware finally coming together

[kookie_guy]

ok, did the tub test. the boat is nice and level in the water, but I think I got the rudders mounted too low. Look at the pic, and when the boat is floating, the water is up to the rudder brackets. I will move them up, use the upper mounting hole for the lower screw, and drill a new one higher.

[HOTWATER]

Ditto on getting rid of the fins...I don't think they are going to help you at all, especially the way they are mounted! Not enough angle. They should be kicked out some, not at a 90 degree like they are now. Turn fins like that are much better suited for a mono...Just my opinion...

[kookie_guy]

ok, took her out yesterday for testing. Unfortunately it was a pretty windy day, so the pond was rippled enough that a high speed pass was not a good idea.

Anyhoo, here are the findings.....the rudders are mounted too low like I thought. I will have to moove them up. The X642 adds some sickening punch. The few times I was able to get on it, the boat hauled pretty good. At low speeds however, it seemed like the prop would cavitate too much.

As far as handling, on plane at about 50% throttle, it turns like it's on rails. It actually turns too well, and is very sensitive to any kind of steering input. I will be removing the turn fins as suggested.

That's all the updates for now. Once I get her moving pretty good, I will post a video.

[rcboatfan]

that looks awsome!!

[nate]

Looks really heavy.

[Meniscus]

I have a few ideas once you move the rudders higher on the transom. I'd do that first and get a benchmark before you do too many things.

=> Change one thing, test, then change another.

[kookie_guy]

Looks really heavy.

after removing all the stock stuff, it doesn't really add any significant amount of weight.

[kookie_guy]

I have a few ideas once you move the rudders higher on the transom. I'd do that first and get a benchmark before you do too many things.

=> Change one thing, test, then change another.

good point. I'll probably do that.

[kookie_guy]

more updates.....had it at the pond this morning. With the turn fins removed, and the rudders moved up, she is solid as can be. Still wanted to cut too hard for turning, but after really dialing down my servo travel, I was able to find a very happy middle point. So still turns like a champ, but does not want to roll as soon as I touch it.

The new problem is water getting into the hull pretty bad. It's all sealed, so I am pretty certain it's coming in through the flex shaft. I will tub test it to see what I can do. I've seen someone on here use some tubing with a lot of grease to act as a waterproofing sleeve, so that's what I will do.

Anyhoo, very happy with the way this thing runs on lipos with the X642. Video next time after I sort out the leakage.

[crabstick]

looking good,

Just an observation , the trailing edge of the strut, I see you have rounded it, is there any reason for that ?

Normally to reduce drag they have a square edge. Obviously its mostly clear of the water once planing though so not much of an issue.

[kookie_guy]

looking good,

Just an observation , the trailing edge of the strut, I see you have rounded it, is there any reason for that ?

Normally to reduce drag they have a square edge. Obviously its mostly clear of the water once planing though so not much of an issue.

after speaking with guys at work who are really into 1:1 boats, they pointed out that it's better to have a round edge, almost like an airplane wing so the water will come back together nice and smooth. They explained to me that a hard edge would disturb the flow of the water, making mini swirls and causing drag. It makes sense, so I did it. It's important for the radius to be even on both sides, so I did it on the mill with a radius cutter.

Now, whether or not it has any effect on rc boats, meh, who knows. But if it's good enough for 1:1 boats, it's good enough for the rc one.

[crabstick]

hmm strange, because water breaks away from SHARP edges easier..

anyhoo

[Jesse J]

Yes, I agree with the Crabstick. Difference between planes and boats - the Reynolds number. planes rarely see laminar flow of air, while boats live in the laminar world. What is this? Basically laminar is when the fluid flows at high speeds and does not swirl, stream lines (or the paths of individual molecules) are parallel, while turbulent flow is when you have the little swirls. In water, fast boats separate stream lines then let them pass and re-attach. If you round edges you actually "pull" the stream lines back together and this force is the drag Crabstick is talking (rightly so) about. So, listen to the airboys, but also to your fellow boaters, for water is orders of magnitude denser than air, so principles tend to break down when designing planes vs boats. Clear as mud? sorry, just trying to add some practical explanation to "theory".

The equation goes like this: Re = (velocity*diameter)/(kinematic viscosity). We can leave diameter out when comparing air to water and say that the main differences are captured in this relationship: Velocity/viscosity - velocities are pretty similar, but viscosities are much different as are the compressibility of air vs water. I know, "I was told there was going to be no math" but though I would add this since I mixed them up in my earlier post (before waking up fully and now editing).

[bigpapa]

looks great cannot wait to see finished product

[kookie_guy]

makes sense. I can always take it off and run a pass on the mill to sharpen it back up again. However, I'm on a temp layoff from work (yay automotive) so it's gonna be a while til I can jump on the mill. Unless I sneak in after hours, but ya.

I'll be sure to take a vid of it next time I'm out.