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Cats - My first time in the rough - what was that?

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Old 03-07-2002, 11:14 PM
  #21
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By "disaster" I was refering to the fact that with certain conditions or combinations of conditions( high speed,improper CG ,over trim, running to fast for conditions) a cat can blow over. As for figuring the neutral trim postion , it has nothing to do with top speed or the position of your trim indicators. To figure it ,place a straight edge on the bottom of the boat(have someone in the boat to work the trim)raise and lower the trim until the prop shaft is parallel to the bottom of the boat. Do this to both drives. Get in the boat and make sure that both indicators are the same and if not make adjustments so they are. Then take pinstriping tape (red is best)and mark on the indicators at Zero trim. now when you travelling at higher speeds you can just glance down and find Zero easily. Finding CG is not a easy. Call the builder and ask where the CG should be. Mark it on your boat on both sides with tape along the the bottom side of the boat. Lift your boat off the trailer and place an object across the bottom of the boat so it can rock fore and aft. If your boat is balanced you should be able to easily rock it fore and aft on that point. If not you will be able to feel excesive weight in the stern or bow. Now you have to only move heavy items (motors, batteries etc) to the front or back of the boat to balance the boat on the CG. Remember with a balanced boat on its CG and zero trim the boat will run the fastest and be the safest for that hull design. Hope that this helps Otto

Last edited by 36spectre; 03-07-2002 at 11:16 PM.
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Old 03-07-2002, 11:17 PM
  #22
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I agree with the to much trim consensus like most boats trim in a little in the rough you don,t want the bow flying. Also a two foot chop should be good water for you . One more comment power into the wave then off as the props clear , a little neg trim and a jab of the thottle should plant the nose done correctly the boat will stay level


practice , practice, practice


justice racing P1-4
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Old 03-07-2002, 11:25 PM
  #23
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Lotsa questions here....... First and foremost proceed with caution. We all agree on that. .............

As to C/G....... does this 25 foot Cat actually have two V8's in it? If so we may have an incureable C/G situation. I can't imagine an antidote for that much weight aft. But let's press on. The answer to the question about the 200 lb woman in the rear affecting balance and C/G is undeniably YES. In my tunnel boat days I had 1,2 and 3 lb bags of buckshot that I placed just forward of my feet....to balance the boat....never used more than 10 lbs...made a WORLD of difference.

C/G location varies from boat to boat but it should sit approximately 1/3 of the way from the stern to the bow. The ideal location should have been set by the designer/builder BEFORE the fuel tanks were installed (There's that "original" design issue again.... T2x just won't let that go). That way you can approximate the proper C/G by balancing the boat on the center of the tanks. To do that you position engines, batteries, trim pumps etc using this as your natural balance point. In this case it's the "engines" issue that is problematical. In his post last night George Linder mentioned that we were laughed at when we arrived at Lake X with our first stern drive 30' Shadow Cat sporting extended drive shafts which resulted from the engines being 15 inches or so further forward in the hull than was the norm at that time. We knew where we wanted that C/G to be from our prototype tests........ some of which were the dreaded "trial and error", but most of it was simple math....well .....maybe not so simple.

We were told(by some well respected people) that "any damn fool" knew that those engines were too far forward. To this day I agree............... if you thought those engines were too far forward ....you were a damn fool. On its first run The boat ran 15 miles an hour faster than 36' Cougar Cats with bigger engines!!!!!!!! and destroyed them in rough water. it held its own against 36 Cigarettes too....in big seas

Conventional wisdom at that time stated that you could control a boat in rough conditions using trim, ballast and tabs. This is true to a point...except all of those things slow you down and hurt handling. Whereas, a boat that wants to stay level NATURALLY makes a lot more headway over the water. Spectre 36 is right on when he says that a boat that shows max speed at neutral (or slightly negative) trim is properly balanced. Let me add that this is also dependent on proper drive height and props.

For those of you scratching your heads about the "slightly negative" trim quote above, remember positive prop rake gives natural bow lift............ but, that's another story. for another night.

Bottom line true performance aint easy, automatic, style conscious, cheap........or necessarily fair....... Let the buyer beware! Buy a Skater.

T2x
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Old 03-07-2002, 11:30 PM
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I think T2X and the other cat owners are correct. I have noticed that if I carry some "heavy" people in the back of my Chris Cat that it shifts CG to the rear, but not to an extreme. We once went off of a "surprise" tanker wake at over 90mph and the CC landed perfectly (still scared the crap out of me ). The CC has the engines set forward with drive shafts and your 26 with the twin engines against the transom plus weight in the back seats has too much CG towards the transom, IMHO.
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Old 03-07-2002, 11:39 PM
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And T2x, if you can't afford a Skater by a Spectre!!! Rich how are you, I'm missing the Jersey shore how about you. Otto
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Old 03-08-2002, 01:35 AM
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As I was reading this story it was as if I had written it. I have experienced something very similiar (more than once). The scariest time was in the ocean inside the breakwater in Long Beach. Me and my passengers got a mouth full of salt water!! Not to mention the salt in my eyes. I have too found that trim makes a huge difference in how the boat handles and lands. PS my boat is a 1998 American Offshore 2600 Procharged 454.
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Old 03-08-2002, 01:50 AM
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Otto , HOw are you ? I thought you left this great site ! I just realized someone switched names on ya ! Do you have the bugs out of the cat yet ? Can't wait to see it and finaly flatten some waves with you ! Later ,JOE
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Old 03-08-2002, 09:11 AM
  #28
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Someone explain to me where the right CG should be on a V bottom hull in relation to the length of the boat.I was always told the farther back the better.This aplication is for racing in ocean.
Randy
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Old 03-08-2002, 09:12 AM
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UT
is sounds like your boat kicked off of the top of a wave
did you start to slow down before this happened? once you get into rough water you have to pedal the throttle and keep the boats momentum and it should fly flat

practice and seat time will help

it was nice meeting you at the boat show and the eliminator plant was awsome now i know why they have such high quality
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Old 03-08-2002, 10:40 AM
  #30
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Couple of answers and a couple more questions:

T2x - My boat is a 26' Daytona Eliminator which measures 26' 10" to be precise. There are two V8's, the new Merc 6.2L (377 ci). I estimated the two engines added 800 pounds - considering the lesser weight of the small blocks vs. the typical large block application. I defiantly run positive trim on flat water to get the optimal speed on the GPS. If its incurable, so be it. But I love the process, so I will keep trying. If time proves it incurable, its my fault, not Eliminators. I was the one who pursued the twin engine application in this boat. Just had to be unique I guess.

36spectre - We are going up to the lake this Sunday for the kids spring break. I will perform your neutral trim test precisely to assure that I am running at positive trim. Cattitude told me to do this months ago and I should have paid attention. If after this week of testing I still have a problem, I will take it to Eliminator and have them lift it up and perform your CG balancing act. Maybe we can move the batteries around or something.

Question - If I need positive trim (forcing the bow up), doesn't that mean my CG is forward, not aft? If its forward, then the extra weight of the twin engines isn't the problem. Wouldn't it make sense, that if there was too much weight on the transom, I would be using negative trim - trying to push the bow down? (had to draw a little picture of a boat for that one )

With a full week at the lake I should be able to spend a lot of time testing. We have a big shuttle boat that takes people back and forth to the casino hourly which kicks out a sizable wake. Think I will go do some test jumping off that (with the proper coast guard approve horizontal spacing of course). Will try it with different trim settings and see how it works. If I can find some T2x like buckshot bags, I will try to move the CG around and note how it effects the flight attitude. Not sure if I can find a 200 lb bag to simulate what happened before

When I get back I will post all the results for you guys - and I promise to be careful!

khadley - Thanks for coming by at the boat show, it was nice to meet you! Glad you enjoyed the tour. If that's a picture of your boat on your card, it sure is a kick-ass boat!
 
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