Advanced Cat Driving
 

Going on my second year of ownership and still learning a ton about these amazing machines.

I have taken Tres Martin but he teaches turning techniques and safety and not really how to maximize the performance of your boat.

I learned something new this weekend and made me realize there is a bunch more to this and more than one way to skin a cat (sorry, couldn't help it).

My lesson today….

At 125mph rpms were about 5500. Boat felt great and was "loose". My guy (who I will not name because I don't want any drama) started to tuck the drives back in a little at a time. Boat kept the same speed but rpms went down to about 5000 and it flattened out. Then we kept tucking to see when it would "catch" and it was a pretty remarkable feeling. My understanding is this is how to get your ideal prop slip numbers. Keep the air packed, put some prop back in the water, and flatten the nose a bit.

I'd be curious to hear about other things like…..

How you approach big waves…bow down or bow up?

I tend to go bow down (Tres advice)

What do you do with hop….any trimming or just power through it?

I power through and may tuck the drives a little but when the hop rhythm goes away I trim up again slowly.

What do you do to set up a turn….tuck the drives or leave them be?

I use Tres's advice, tuck the drives and if going a little too fast slow down 2-300rpms but reapply throttle back in the turn

Cool post. Looking forward to the responses, I miss threads like this...

when racing the Talon id run the boat pretty flat. Bring the drives up a bit in the straights and then bring them in neutral coming into a turn. Usually nose in around a hundred to a hundred and five then back on the sticks hard as soon as Ed would start to turn the boat but keep in mind these were supercat 750's they lack big torque and would contunue to slow down throughout the turn. its not big changes either between running down a straight and setting up for a turn (at least not in that boat)

Run big water pretty flat as well. those guys that are always trimmed to the moon only think they are running fast and thats only because the out of control nature "feels" fast. theres only a few mph in that last few clicks of trim and its at the cost of control

When you trim down in turns you don't feel the boat start to want to hook and start rotating?

I had a 28 Daytona, my only cat experience, and you could feel it pivot on the inside edge of the inner sponson, if you trimmed up more you could kind of slide it through the turns, trimmed down a little it would turn harder but you had to keep your butt in tune with the rotation or it would spin out. I spun it on purpose several times around 40 mph just to feel how it would happen, never tried it going faster. Boat never hopped.

Big waves were not an option in that boat, great until they got more than 2-3.

I imagine a Skater handles different with a real tunnel.

I really miss the speed and driving it though, much more fun than the v-bottom

I tend to use a mix of what your describing from your guy and add in a slight wheel correction to see where he boat feels best. Slight left or slight right turn.
Considering how flat the water was running with you Saturday I'd say ya have a lot figured out already considering the boat didn't seem to hop much at all. Between the Tres class and your right hand "guy" you've got the boat working very well.


Pstorti,
The center pod boats are a different animal all together. Both my 25 and the 30 eliminator handled way different than my current shallow true tunnel. It doesn't get that hooking feel the center pods did.

Of course results may vary

We were pretty light on fuel so she was ready to take off. Less fuel = less hop. That's why we only put 75 gallons a side (about 1/2 tank) when we get fuel. Otherwise, the boat isn't nearly as fun to run until it gets to that level.

liking this thread. more info is a good thing. I would imagine each manufactures hull will respond a little different (size, weight, hp ) but use the same drive/trim input technique. Where's Tres on this? or does his info come with course payments only LOL just kidding :party-smiley-004:

If you don't have a tunnel tab you are sort of stuck w/ the hop which is load dependent as you mentioned (fuel on board, passengers as well). You can try to compensate w/ trim tabs but what I found was that it just loads the bow & scrubs off speed requiring quite a bit more throttle to achieve the same speeds. It just feels bound up. Keep in mind the leverage on a 30' boat is a bit greater than a 40' too. Prior to installing the tunnel tab I noticed flat conditions were worse than 1-2' chop when it comes to porpoising but in all conditions putting a little wheel into it will cause the sponson to dig in minimizing the hop. It's not as if you have to tack back & forth like a blow boat but next time you are out just put some wheel in it & I think you'll notice it settles down some.

My boats sweet spot is 100mph. You can trim out to pack air but if you negative trim slightly at 100mph (give or take) it's as if you are in Pro Stock car (slightly exaggerated) whereas it feels as if the bow is lower than the stern (stern to bow rake), the boat is extremely smooth & stable as if it's taken a set, the tunnel is doing it's job of carrying the boat & the large flat deck is providing just the proper amount of downforce to keep the boat stable.

I'm no expert but these have been my experiences as I've tinkered w/ my boat as a bravo drive boat then started the testing & tunning all over again w/ the ILMOR Indy drives

its funny you say that, Lightning Jet on here has a 33 Elim Daytona that does low one thirties but has a hop that varies according to condition, sometimes it is pretty bad other times not much at all but a little wheel left or right does minimize it.

Mine used to porpoise between 65-90 mph. So to say you are just going to power thru it all the time means you'd always be buzzing around near triple digits or have to keep it below 60mph. Just too large of an unusable range of speed in my opinion.

Did you add a tunnel tab to stop the porpoise? I have been experimenting with the tunnel tab on my 338 and after talking with Peter @ Skater I should have it neutral with the tunnel or maybe down a bit. I previously had it up and it was planting the ass end off the boat. It really helps the porpoise. I have not tried using it throw the hop when accelerating. The boat rides the best at the century mark. Any information is great as I have very few hours in the boat.

Yes I did add it for that specific purpose.

Neutral w/ the tunnel is basically like having a tunnel extension to a degree because it provides a longer surface for the air exiting the tunnel to provide lift BUT there are no sides so not as efficient as a true tunnel extension or lowering the tunnel tab which restricts the air escaping & creates more lift.

I think the advise you'll receive from most regarding a tunnel tab will be relatively conservative b/c if not monitored & used properly it can be dangerous. I use my indicator to monitor where mines at, only use it when necessary & always raise it prior to entering a turn. I also raise back to neutral once above the century mark or below 65mph where it's not needed.

so far with the outboards on mine, it hops but not near as much as the 28... the 308 is not quite as responsive to throttle due mostly to the weight i'd think and same scenario on minimizing the hop is turning slightly left or right. I don't have a tunnel tab.

I noticed your turning out, was it set up like that from skater or did you experiment with rotation? Im turning in and thought about trying the other way as well. Does turning out create more stern lift and feel looser?

It's funny b/c what I've experienced is opposite what Bill Pyburn states as being most efficient for Skaters & I hold Bills opinion in high regard b/c IMO he has the most seat, test & tune time of any Skater pleasure boat owner I know of. His comments are in the new 338 thread ( I believe that's on PBN's site)

My boat was originally an IMCO/Bravo boat, 5 blade props spinning in. When upfitted w/ the INDY drives by Skater they spun them both directions but Peter says the 30 or that size range boat prefers out so I received the boat w/ the drives spinning out. Of course I had to to test his theory for myself so we swapped the drives so they'd spin in (way more work than swapping props on a Bravo & running the sticks in reverse only to have to return them to where they were b/c guess what PETE was RIGHT!!) Spinning in provided way too much stern lift & a very loose feeling. Again this is opposite of what Bill states one should experience w/ a Skater w/ less than 800hp / side. I want to believe that prop diameter & drive height also affect the performance & lift of a boat. With that said I returned mine to spinning out b/c it wasn't very comfortable at 90mph on a flat lake w/ no other boats around. Based on my seat of the pants experience I chose not to push my luck. I can run in the 130's comfortably spinning out w/ solid acceleration so I settled for that.

I have wondered if #6's perform different than Arneson's when it comes to rotation since a few newer boats have been built w/ them.

I have been told not to use it bye some, but after I have used it there is a need for it in certain areas. I have been careful not to have it more than a couple of inches negative. How far do you think I can lower it when going from say 65-100? When you turn are you bring it to neutral or higher? I also notice my tab indicator moving up and down when I have it in the negative in rougher water at say 75. Do you find that normal.
Thanks for all your information.

NASCAT- yes Bill talks about it in the 388 thread on PBN... I think he also said that the size of boat matters to. Cause I've been told by two top throttle men that on the 388s the out rotation creates stern lift. But you say on your 30 that in created to much stern lift. This is just what I've been told and read. Man this stuff can be tricky.

Helt- Ben Robertson custom fabricated mine. He said never to go more than 30* or 2.5 - 3 on my indicators but I have to be honest I never placed a digital angle finder on my tab at that setting to know what it measures & even then I'd be doing so w/ the boat on the trailer not the way it sits in the water at speed.

My drive & tab indicators are the cableless potentiometer type (sp??), similar to a throttle position sensor (see pic). But to answer your question YES my indicator light will fluctuate between 2 numbers in certain conditions when I'm not really at speed or forcing it to work. Under load it reads pretty steady. My tab rams mounting tubes have some play in them b/c there's a rubber insulating tube within the SS mounting tube / eyelet that the mounting bolt goes thru.

I never run mine above level at any speed b/c I don't think it really alleviates much pressure at that angle & ultimately I don't believe it affects the handling of my boat in a negative fashion in the level position at any speed. I normally don't lower it until I'm upwards of 50mph, just out of habit & my commitment to not over use it or abuse it. Occasionally I do use it to get on plane if I have a full fuel load & 4-5 passengers on board but in reality I don't need it to get on plane. I also don't really trim my drives b/c the boat gets on plane & runs best in the neutral position.

PS- with regard to above level if you imagine that everything from your cavitation plate & above are out of the water at speedso raising the tunnel tab above neutral just seems rather in effective. Get one of your brave buddies & strap him to your hatches to verify this!! :party-smiley-004:

I actually did some nose cone testing for ILMOR so I had some GoPro video of whats going on back there. It's somewhere on youtube. Try searching Mr. NASCAT (i think). Don't get too excited there's a lot of water splashing around back there so no super clear shots. Can't access you tube at work or I'd post it.

The porpoise on the early 33 Daytona's was standard equipment directly from Eliminator. Eliminator was also kind enough to throw in the added feature of an significant outside lean in turns.

Added features at N/C can't beat that! :daz:

Lol

Tunnel tab bad events occur when tab goes deeper than the rail and takes water from the rail. Also can be bad if left down going over big waves as it can lift transom and lead to stuffing. I believe that keeping the tab level presents no danger as was mentioned before is just an extension of the tunnel.

What are you referring to as the rail??
The step that trailer bunks support the boat when it's on the trailer?
I ask in an effort to understand & have never heard that term used in reference to a hull other than a splash rail.

I would be careful putting that tab down below level until you get more seat time. At high speed with waves or chop it can make the boat a bit unstable from my experience on the 28'. I always waited to play with the tab when I had a good driver I trusted and decent conditions with no traffic. This way later when you are driving and throttling, watching traffic, water, passengers, and winches, it won't be such a handful. Just my $.02 for what its worth.

With not all boat's being the same here's my $.02
I ran my Eliminators outboard to get the best handling and cruise speed, for the brief time that I had naturally aspirated power. I found that it was more difficult to get thru the hop than with the greater HP. The hop for me was only noticeable in flat water less than a true 6" to 1' chop. Aother factor I've noticed is wind direction can change the speed at which the hop occurs (wind over five MPH), cross wind is also something to pay attention to, I've been on LOTO a few times running fast and you reach an cove, or lower elevation bank and a sponson dips due to cross wind. What I try to do is correct in small increments, if it continues reduce the power a few 100RPMs until you get into more stable conditions.
When I ran the MTI "out" I would add a .5" spacer as Nascat was saying the boat feels looser, not to the point of no control just not that comfortable stable feeling you want in a pleasure boat. Running outboard it wanted to hop from 50 to 100 that setup was strictly for testing to get the highest speed and fastest acceleration. The hop running "in" was only around the 75mph mark if I ran 70mph and it crept up to 75mph it would start and take longer to correct than if I throttled up to 85mph than backed down to 80mph. The best cruise was around 110 to 120 the boat set perfect and steering felt great as long as the conditions allowed. The Eliminators needed trim to run, but the MTI I don't think I needed more than 2 numbers on the indicators to run the boat. Get on plane neutral trim up a bit during acceleration and as you reached speed start bumping the trim down a little at a time until the gps shows it that you had gone too far (until you have figured out where it likes to be on the indicators), then back up one touch. Be aware if you are holding tension on the steering wheel one way or another, possibly due to cross wind, unequal drive height or a bigger problem with a skeg. If you are following this method you don't need much trim down to turn the boat when you start your turn it will automatically scrub some speed off allowing the boat to settle and make the turn. The important part is small input into the steering wheel when at high speed.
This probably should have been the first line but check your equipment every time you go out, look for bent skegs small cracks in the gimbal ring, look for broken or damaged control linkage as you ck the oil and ck power steering lines for leaks. It seems like common sense but it can easily get overlooked with the excitement and rush to get going.

The rail is what your skater is resting on. All cats will have these. They are what allows catamarans to carve turns. Imagine making a left turn. As you turn the left sponson will dip somewhat the boat will want to slide to the right. As the boat starts to slide surface water is forced up the inside face of the sponson til upward flow is blocked by the rail. This allows the left sponson to carve or hold its inside position. At the same time the right sponson is sliding along the deadrise of its sponson. Hooks or spin flips occur when the rail is lost.

That's the type of stuff I want to learn…I think I knew this kinda, but that was a great description. I also watch my thrust drive (outside on a cat, inside on a V) RPMs. If they go up and the bow is going down, something bad is about to happen.

Thanks Ski doc!

You can contact me anytime. You remember that I tell every person that goes through my course can contact me for information and helpful hints with everyday skills. I am here in Havasu and will be in LOTO next week.

Thank you SkiDoc , now I understand why my cat tends to want to slide in the turns , I have no rails . I have learned to deal with it by dipping the drive ever so slightly when entering a turn till the boat takes a set .