Poor handling cat

[keithbradley]

I got my twin build done to the point that I could take it out to the water and test it today. Its a 30" Team Lindenau Smiths cat. In an attempt to make it faster than my previous boats, I fitted it with castle 1520's spinning counter rotating x447's. I took it out to run some shakedown passes and it handled poorly. I think I flipped it 5 or 6 times. When I turn it "rolls". It basicly does the opposite what a mono does. It keeps the front end in the air and drops the side outside teh turn into and under the water. Sometimes after turning its like one side comes off plane and drags in the water and the boat sits crooked.
This seems to go away at high speeds, but speeds that are getting on the edge of taking a corner. I would say it flattens out around 35-40mph.

I had the props rotating towards the center.

I came home, switched shafts, and changed the direction of prop rotation so it spins them towards the outside. I also decided to try and run it on 3s instead of 5s to take some weight out of it and see what it would do. It was a little better but still not good. It seems I have a great saw boat, but horrible sport boat.

Do I need to get rid of the 1520's and get some 36mm cans and run them on 3s each (planned setup was 1520's on 6s, or 1518's on 5s). Is it just too much weight?

[Karfrik]

I would try smaller props,i believe 2 447`s for a 30" are too big.But go try the boat with new outward prop rotation first....see how it goes.....

[Flying Scotsman]

Interesting questions, I have no twin motor experience or knowledge of that hull, but the props do look large....Fluid or others???

Douggie

[keithbradley]

Interesting questions, I have no twin motor experience or knowledge of that hull, but the props do look large....Fluid or others???

Douggie

Yeah I did go big with the props...My thoughts were based more on what I could push than what the boat would handle well with to be honest.
I was out for speed, and willing to have an overly aggressive handling boat as a trade off. I didnt foresee anything like this though. It doesnt handle like an overpropped boat either. At least nothing I've seen. At high speeds you can accomplish long, sweeping turns. At lower speeds (under 35ish) it just about rolls over when you turn. At mid speed you can be turning, then one side will just dig in and flip it. As far as I can tell its a matter of buoyancy, and I'm only overcoming it when the boat is at high speeds. I'm just waiting for someone to tell me Im wrong and that I need to spit on the rudder and it will work perfectly, then I can go back to being excited about this thing, instead of buying yet another set of motors and sacrificing more power

[Make-a-Wake]

I applaud your need for speed, by my word.......twin 1520's in a 30" cat.......WOW. The Miss Geico is the same size and runs one 540L motor...............and hits 35 with an x642 on 4s. Twin 1512's would be enough to make it fly.................. You may have too much weight between the motors and 2 x 5s batts.

Since you mentioned 36mm cans, consider the Feigao 12L......for 4s. (x2 of course)

http://www.offshoreelectrics.com/pro...i-540L&cat=116

[Rumdog]

I'd bet it's the weight.

[JMSCARD]

I have twin 10xl's with 3 runs on them in the swap shop...they would be perfect for this hull on 5s and 6s for being crazy...tiqueman runs twin 10xl's in a 32" skunk and gets over 60mph........ they have the slim line H20 jackets too....

[keithbradley]

I applaud your need for speed, by my word.......twin 1520's in a 30" cat.......WOW. The Miss Geico is the same size and runs one 540L motor...............and hits 35 with an x642 on 4s. Twin 1512's would be enough to make it fly.................. You may have too much weight between the motors and 2 x 5s batts.

Since you mentioned 36mm cans, consider the Feigao 12L......for 4s. (x2 of course)

http://www.offshoreelectrics.com/pro...i-540L&cat=116

Yes its overkill on overkill. Lesson learned on too much weight in cats...It has some big steps, so I think it never planes out well enoung to stop the sponsons from trying to drive it straight, while the rudder is trying to steer it, resulting in the rolling turns.

I know the geico (and other cats) have smaller single motors, but 35mph is about 45mph short of where I would like to be

[keithbradley]

I have twin 10xl's with 3 runs on them in the swap shop...they would be perfect for this hull on 5s and 6s for being crazy...tiqueman runs twin 10xl's in a 32" skunk and gets over 60mph........ they have the slim line H20 jackets too....

I think I am going to go with something a little more drastic in the weight reduction area...like 3000kv on 3s each and smaller props. Either that or put the 1518's in it on 6s and just dont turn.

[Make-a-Wake]

Yes its overkill on overkill. Lesson learned on too much weight in cats...It has some big steps, so I think it never planes out well enoung to stop the sponsons from trying to drive it straight, while the rudder is trying to steer it, resulting in the rolling turns.

I know the geico (and other cats) have smaller single motors, but 35mph is about 45mph short of where I would like to be

Didnt know you wanted mach 2 out of a 30" boat.................

Castle has the 1512's in a 2650kv which would work well on 3s.............maybe you can turn with them and the lighter batts........................just a thought.

[keithbradley]

Didnt know you wanted mach 2 out of a 30" boat.................

Castle has the 1512's in a 2650kv which would work well on 3s.............maybe you can turn with them and the lighter batts........................just a thought.

Only mach 1.8...

It was a lofty goal for sure but I have found 70mph with single motor setups in multiple boats so I wanted to go further with twins. Doesnt look like its going to happen.

I actually have a 1512 2650 here. I just sold it and Im waiting for payment to clea rto ship it! Its def smaller than the 1520's and 1518's, but light enough???I'm not sure...I definitely dont want to spend more money adn have the same problem. I am considering seaking 3660's...

http://www.hobbypartz.com/07e-c-sl-8t-3660-blue.html

Anyone have any experience with these?

[Make-a-Wake]

I had one of those once and it fried in a Cen aquajet for some reason..........cant remember why........may have been user error. Its the same motor as this one at Hobbyking and has some decent reviews - http://www.hobbyking.com/hobbyking/s...idProduct=8593

The Feigao 540L is the same size and may be considered a better motor by those who use them(i own a bunch of Feigao's.......good product for the $$)

The 8L or 9L could be on option for you....................

http://www.offshoreelectrics.com/pro...i-540L&cat=116

[NativePaul]

I raced against a smiths cat in last years nationals, it was on a twin 3s setup and while it didnt seem to be displaying the extreme handling defects you are getting I wouldn't say it was a good handling boat, its a stunningly beautiful boat, but too narrow to turn really well in my opinion, I was substantially faster in the turns with my 36"x14.25" Crestrunner cat. that was the only one I have seen and I only saw it once so that could just have been a poor setuo but if it was me I wouldn't invest in lighter gear for it I would fit the 1518s and go to the SAWS on 6s.

While I don't think it will ever be a serious oval racer I'm sure you can get it to turn much better than it sounds like it is doing at the moment without spending any money or sacrificing any straight line speed. Have you played about with rudder caster to try and get it handling better? Angling the rudder so the bottom of the rudder is a little further back than the top will make the boat run wetter in the turns which sounds like it would help you out a lot having a longer waterline instead of a deeper displacement.

[blackcat26]

Keith, do you have any pictures of this baby?

[LarrysDrifter]

Im not dogging Feigao motors,but why not try a pair of Arc motors 540 XL's?They are 4 pole and more efficient.Although they do cost a bit more than Feigaos,they run excellent.