Shes FAST but pulls to the right at wot.

[Woohoo\o/]

This is a Bancroft big storm I purchased from motion rc about 2 months ago. Nothing about this boat is stock except for the motor mount and servo and servo linkage.

Rocket 3660 3250kv 4 pole
Flycolor 150a w/ose cap bank (overkill)
4s 5200 100c ovonics
Kingval 110mm centerline mounted
42mm 2 blade (traxxas m41 prop)
Outboards are fake

The boat seems to pull to the right under full power (wot) and I'm suspecting that the prop is pushing the rudder to one side (right in my case)

The servo pushrod seems kinda flimsy and the geometry isnt perfectly straight. so I'm going to replace it with a 2.5mm rod and mount a stronger servo so that its pushing the rudder straight.

Is there any advantage/disadvantage on running a centerline mounted strut/rudder on a catamaran?

[Woohoo\o/]

Here are some more photos just in case.

[don ferrette]

You're on the right track on going with a more robust steering servo and linkage. Also ditch the plastic prop and get a sharpened and balanced equivalent in metal from one of the prop guys on here like Chris Hoffmann (dasboata). A dull prop can create nasty prop walk (pull) and plastic props will never keep a sharp edge.

[Fluid]

The OP has multiple issues with his boat. First, his motor KV is rather high, 3250 on 4S is SAW territory; as long as he’s aware of that I suppose it’s okay. Second, a 42 mm prop on a narrow 25” boat is bound to cause major prop walk issues. Third, the rudder being directly behind the prop will cause wandering and reduce its effectiveness in keeping the boat straight. Forth, while difficult to see, the prop seems to be running rather deep. And fifth, as stated the prop linkage is way too flimsy for a boat this fast.

The easiest fix is to go with a smaller diameter prop. A 35-38 mm prop with a 1.5 to 1.7 pitch ratio will keep the speed up and reduce prop walk. Strengthening the linkage will increase steering reliability but probably not too much of the prop walk. Where is the CG on the cat, measured from the back of the sponsons? And does he have a few degrees of left trim in the rudder?



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[Woohoo\o/]

Thanks for the response. I will definitely start with a more robust steering system. I will most definitely contact chris for a good prop.

From the research I've gathered the downside to running a centerline rudder is less speed. The advantage of an offset rudder is that you can use a shorter rudder for less drag.

[Woohoo\o/]

The OP has multiple issues with his boat. First, his motor KV is rather high, 3250 on 4S is SAW territory; as long as he’s aware of that I suppose it’s okay. Second, a 42 mm prop on a narrow 25” boat is bound to cause major prop walk issues. Third, the rudder being directly behind the prop will cause wandering and reduce its effectiveness in keeping the boat straight. Forth, while difficult to see, the prop seems to be running rather deep. And fifth, as stated the prop linkage is way too flimsy for a boat this fast.

The easiest fix is to go with a smaller diameter prop. A 35-38 mm prop with a 1.5 to 1.7 pitch ratio will keep the speed up and reduce prop walk. Strengthening the linkage will increase steering reliability but probably not too much of the prop walk. Where is the CG on the cat, measured from the back of the sponsons?



.

Yeah I can agree there are lots of wrong setups on this boat. I'm new to this. I will iron out these issues over time. Today I'm receiving a 36mm 2 blade cnc prop.

Yes SAW is what I'm seeking for this boat. I may eventually change to an off center rudder if the upgrade servo and linkage doesn't help. I also plan to get a 2500kv motor. Had this one on hand so I gave it a try. Thanks for pointing these out for me. That's why I appreciate this forum.

[RC boat addict]

You should go to YouTube and watch ironclad Rc that guy has a few cats running fast you could glean plenty of info from his experimentations

[Woohoo\o/]

Yeah we chat here and there. In fact his black jack 24 ran the same motor in this one. He recommended a 40mm prop for general boating. Right now I just threw in a 36mm 2 blade cnc. Gonna give her a try tomorrow to see any noticeable improvements in handling.

[Woohoo\o/]

Also forgot to mention I have the ch 35% from the transom.

[Woohoo\o/]

After replacing the servo and linkage the boat now rides on rails. I tried raising the strut but it got extremely violent so I lowered the strut deeper than what was shown here and it gets on plane. I can do about 7 laps and shes in at 3.8v per cell. Temps are warmer than ideal but boy oh boy!! Thanks to all those who chimed in. I will be getting my tripod out soon for some video. I have nobody to help record.