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

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Old 03-07-2002, 08:35 PM
  #11
Uncle Toys
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Interesting T2x, my neighbors mom, who was sitting in the back, is rather large (god I hope he doesn't read this). If anything the fuel tanks CG should be forward as they choped something like the aft 15% to make room for the twins.

Semper thought it was the trim also and he has a lot of experience with 26' Daytonas.

HavasuCat, you've see 5 to 6 footers at the lake - DAMN! This was the typical wind blown lake we typically see in the summer monsoon afternoon blowups. Hope I'm drinking beer on the porch next time 5 footers cruise through. DAMN!
 
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Old 03-07-2002, 08:40 PM
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UT

Since your setup it total different then mine but my boat does not like very much trim. after neutral I start losing speed.

With boat out of water check where your trim gauges are & where outdrives are when you are neutral. Then you can see where you go from there. I have ran mine 80+ on ocean conroe (all boat wakes & wind) in about 2' chops & boat just ran level.
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Old 03-07-2002, 09:06 PM
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The CG idea is interesting. In a small boat like this, could an additional 200 lbs in the back seat throw it off enough to change its flight attitude? 225 lbs would be 5%. If I am low on fuel, say quarter tanks of less, and the fuel tanks are forward of the engine compartment, maybe that would change things. HavasuCat, do you go flying across the Lake Havasu 2' chop with people in the back seat?

Turbojack - my optimal trim (using GPS) is a little positive, about number 5 on the trim indicator.
 
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Old 03-07-2002, 09:10 PM
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If in doubt, throttle out!!

Welcome to the big times. On the Chesapeake Bay there can be 5-6 footers mid-day. 25-28' 'lake' boats can't handle it. Best to take a change of shorts and practice, trust your boat, respect the water.
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Old 03-07-2002, 09:19 PM
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Rich, how do you check the CG? I've known about people using trial and error, but is there a more productive and accepted way to determine the proper center of gravity?
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Old 03-07-2002, 09:23 PM
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T2x has a point ! Those motors are a lot of weight in the back of a small boat . Could also have gotten a little too much air under the front . You know some cats in the a bad condition do this thing called "blow over " ! Also my understanding is cats run fastest when the prop shaft is parrallel with the bottom . I assume that this person I got this from knows something as he spends probably 80% of his time above 160 mph ! But There are always more theories .................

Since it only happened once it is hard to diagnose it . Especialy with the panic factor included !! Unfortunatly ,You will have to go back out and do it again ,carefully ! And feel it out.

Good luck with it . And be safe .
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Old 03-07-2002, 10:05 PM
  #17
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you were over trimmed. Plus, these little cats don't really start packing air until 70 plus, hence the sneeze. Let your speed over the water create the lift, not the trim, same as changing your angle of attack. At 100, you'll know it's right. No hunting, sloppyness, just rock solid. Not much you can do about the cg unless you move the helm up to the bow light.
 
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Old 03-07-2002, 10:14 PM
  #18
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I have a Chris Cat but I dont see 2ft in your boat as much of a problem.The trim is my guess I run very little trim when the nose is up it will land harder.The trick is to get it up on top level it out if you slow down water will come over the bow. My boat is larger but the number of people and gas load doesent make much diffrence seat time is all you need a 25 with twins sounds fun!
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Old 03-07-2002, 10:17 PM
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I can only give you my personal experience form dialing in my pleasure cat(36 spectre with 1000HPs and numberVI drives) and my race boat (32 Mealstrom wtih 750HPs and number V drives). The best all round performance and drivability(safety)was with zero trim, that is the prop shaft angle set parallel to the bottom of the boat. The joke with myself and the riggers(Kurt from Kurts Comp in New Jersey) was that we should weld the drives in that position because no matter what we tried the boat only performed perfectly (including top speed) at that position. This can only be used as the rule if the CG of the boat is perfect from the start. The balance of the cat hull is a million time more important than the Cg on a Vhull. Any thing else that you do before you check the CG of your boat with the CG position of the CG that you get from the builder or the designer of the hull. If you call the they should tell you where the CG should be. All of the "bandaids" that people use to fix Cg problems(ie;balast tanks,trimming in, larger diameter props) are a waste of money, time, saftey and usually top speed as each will result in a slower boat when compared to the boat with the same HP , zero trim and the proper CG. With zero trim an proper CG the boat will always reenter the water with the same angle that it left. Rember if the trim is a zero the prop will force the nose down harder in a head wind or against an on comming wave much harder that with the drive trimmed even slightly "UP". That can cause a disaster at high speeds. Best of Luck ,Be safe and listen to T2X, Otto
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Old 03-07-2002, 10:49 PM
  #20
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OK, I will certainly bring the trim down. If I remember correctly, neutral trim is 2.5 on my trim indicator. If optimal trim (per GPS) is 5.0 at WOT, does that tell me anything about CG? $hit, maybe I don't know how to find neutral trim. If I put a rather long straight edge along the bottom and align the prop shaft parallel to that, isn't that neutral trim?

T2x and 36spectre - how do I figure out the proper CG? Trial and error?

Spectre - your last sentence is confusing and with the warning of a "disaster at high speeds," I was hoping you could clarify please. Thanks.
 
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