Correct trim

[John McFarlane]

Is there an easy way to know when a boat is correctly trimmed at speed please?

 

[Dunaruna]

Re: Correct trim

John, <br /><br />There are some tell-tales that will alert you of incorrect trim such as porpoising, sucking air on turns, rooster tails, really bad fuel economy etc. but IMO it comes down to 'feel' and you'll only get that with time. You can even add gadgets such as a fuel computer that will give you optimum economy.<br /><br />Every boat/motor combination is different - experiment.<br /><br />Aldo

 

[Triton II]

Re: Correct trim

Generally when it achieves the highest rpm without any signs of ventilating at WOT. However if the boat porpoises off waves it is generally trimmed too bow high, if it wanders around and the steering gets heavy as the speed increases it is generally trimmed too bow down. If it ventilates in turns or with a following sea it is generally trimmed too bow high. There's no real answer to this question, there are so many variables, but trial and error will soon show you where to trim for whatever the situation. Best of luck.

 

[Triton II]

Re: Correct trim

Beat me to it Aldo!

 

[Dunaruna]

Re: Correct trim

Yeah but your much more eloquent in your delivery <br /><br />Aldo

 

[Triton II]

Re: Correct trim

I think perchance you mean 'you're' and 'eloquent'? Confusing this language ain't it but! <br />Please see question on your carp post.

 

[Dunaruna]

Re: Correct trim

Hey hang on a minute, you're not Mr. Browning are you? (my 5th grade english teacher) <br /><br />Aldo

 

[umblecumbuz]

Re: Correct trim

As has been said - this site is an education!<br /><br />English language only please!

 

[cthru1]

Re: Correct trim

Triton II, what is ventilating? Please explain as if I were a child so I can understand. Thanks

 

[Dunaruna]

Re: Correct trim

Ventilating is when the prop sucks air - basically.<br /><br />Good on a plane, bad on a boat <br /><br />Aldo

 

[Reel Poor]

Re: Correct trim

.....Oh what wit we read.....

 

[Dunaruna]

Re: Correct trim

Just my warped sense of humor at work, Ok ok I won't give up my day job

 

[Triton II]

Re: Correct trim

Mr Browning here. For a change Dunarunna has something of value to show and tell the class. <br />Mr Duna?<br />"Ventilating is when the prop sucks air - basically.<br /><br />Good on a plane, bad on a boat <br /><br />Well done Dunarunna. You are correct. Next time please remember the full stop (period to those of us who have an American education) at the end of the sentence! <br />In plain English, here's an explanation...<br />The boat's propeller rotates at such a speed and close enough to the surface whereby it creates a boundary layer of air over its blades. It does this because the blade tips break free of the surface and literally "suck in air". Boat propellers, as Dunarunna so eloquently states, are not designed to rotate in air, and the thrust decreases as the rpms rise. Ventilating (also erroneously know as cavitating) is this self perpetuating condition where the propeller spins fast in a bubble of air, next thing you know, you're going nowhere fast. It's cured by lowering the trim or straightening out of the turn (if that's where the ventilation occurred). Ventilating is not good for the propeller but isn't as bad for the motor as many people make out - simply because modern motors have rev limiters and no one in their right mind allows the propeller to ventilate for long. Hope this helps.

 

[Dunaruna]

Re: Correct trim

Once again your elowqewsion is impeckable

 

[umblecumbuz]

Re: Correct trim

On the other hand, ventilation is essential for the helmsman, otherwise he will never be correctly trimmed!<br /><br />In which case, he would probably cavitate.... or something.