Posted: July 26 2010 at 15:01 | IP Logged

Hello Doral lovers !  Quick question...

We've just gotten a 2004 28 foot Doral Prestancia a few months ago, and I was wondering about the proper 'trim tab' settings.  The majority of the time, we're cruising a small series of canals, (like Fort Lauderdale) which lead out onto our Lake.  Approx. 20 min of dead slow, no wake allowed, then once out on the Lake, we can 'zip' to where ever we want. 

Most of the time, our trim tabs are completely down - for NO WAKE, while in the canal.  However, when up on plane on the lake, I've accelerated, trimmed up the engines a bit, until the nose (bow) dropped.  I continue to trim the engines until the bow feels very 'loose' and the boat actually 'skates' a bit from side to side - but the bow is level.  I noted the trim tab level as well.

Question is:  When I checked with the Doral manual, it indicated that the "normal' or 'optimal' trim setting was practically HALF WAY UP on the trim tab scale, dependant of course on number of passengers, wieght, wave conditions, etc.  My setting, when up on plane and four passengers was only around a QUARTER of the way up. 

Which is better?  Again, when I tried trimming the engines higher, the boat remained on plane, and the bow relatively level, but the steering seemed quite 'loose' and almost 'floating. 

Would that 'feeling' be correct and indicate that I found that 'sweet' spot of success with both optimum planing and trim levels for fuel economy and performance, or not?  (Maybe I should get up on plane, choose the right speed I want, and then raise the tab levels until the bow starts to rise itself again - what the Doral manual calls 'porpoising' (like a dolphin I guess...)  When it starts to rise, I simply 'back down' the trim tab to level out, and leave it there...(?)

What 'trim' levels are YOU experiencing or using for proper ride and performance?  Anything NEAR half way up?

Cheers  

Tim

Posted: August 09 2010 at 20:07 | IP Logged

FOLLOW UP ANSWER TO TRIM READINGS ON PRESTANCIA

After a couple of attempts I received a callback from Doral.  On my trim tab gauges I have three settings (lines) indicated.  One at 12 o'clock saying UP, another at 6 o'clock saying down, and then another line at approximately 4:30 p.m. saying nothing.  In a nutshell, my previous comment was questioning what the heck this '4:30 p.m' line meant - and how it differed from the boat manual's explanation, that the trim guages - for optimum performance and economy, should read 'half way' between fully up (12) and fully down (6).  (Or in other words '3 o'clock.')

The technician at Doral said that the manual was definately incorrect or unclear, and that I should NOT run the drives - certainly at any speed, at anywhere near 3 o'clock.  In fact, the 4:30 indicator line WAS CORRECT, and actually indicates an optimum or MAXIMUM tilt for the drives.  Anything OVER that would cause vibration, possible 'sucking' of air into the drives, and possible overheating.

So, that I guess answers my question.  He also clarified that ideally, I should be using the trim tabs on the throttle for proper boat (and bow) up/down attitude, and leave the hydrofoils or stabilizers at the stern for simply any port/starboard leaning or list, due to passengers, wieght distribution, etc.

I hope this clarifies YOUR trim tab readings and operation.

Tim

Posted: August 12 2010 at 13:30 | IP Logged

Hello Mike !

I think this is a fairly common problem - at times, with some boats.  I've read and have had a number of discussions regarding trim tabs and 'plaining'.  (Not sure if you've looked through some of the comments on the general "DORAL" forum, but I'm sure if you go through some of the previous PAGES of comments, you'll find them.)  A lot speak about always starting with the trims fully down, AND about proper 'loading' or dispersement of the wieght on the boat.

The President of one of the Doral groups in the States sent me a nice reply regarding this problem, and sent my questions to their fellow Prestancia owners.  His personal comments were:   I will share with you also my experiences in owning two Dorals, both a 2001 270SC (a little smaller than your boat) and a 2005 Intrigue (a little larger). What I have found to be true on both boats is that the drive trim indicators are grossly inaccurate, and change positions every time the drive(s) are removed for yearly service. What I do is the following:

Start with drive(s) fully down.
Add just a little "bow down" trim tab and throttle up to get onto plane more quickly. You may not need any trim tab to get onto plane.

Once I have reached cruising speed (about 30 MPH at 3500 RPM), add enough trim tab to prevent porpoising. Use sparingly. I trim the drive out just a little until I notice a slight increase in engine speed. Do this in small increments. Readjust throttles for the desired engine RPM and cruising speed.  If you trim out too far, you will get the vibration you mentioned. With the drives all the way in, some boats will transfer the drive vibration to the hull, some will not. My 270 did, but not the Intrigue.

I use just enough trim tab to prevent porpoising in a slight chop. Too much trim tab will make the boat wander (chine walk). As you increase trim tab and reduce RPM, you will notice a "rooster tail" forming behind the boat. You should probably not be seeing this in calm conditions. If you are, it might be an indication of too much trim tab. You should be getting more than 20 MPH at 3000 RPM assuming you have at least 5.0L V-8's. I suspect you have the drives too far up and the trim tabs too far down to compensate and they are fighting each other. Remember...trimming the drives up will raise the bow and lowering the tabs will lower the bow. Try lowering the drives to a "slightly out" position and use less trim tab; just enough to prevent porpoising.

Heading in to rougher seas, I increase the trim tab, pull the drives back in (all the way down) and reduce throttle to keep the boat on plane at a slower speed. I can keep my Intrigue up on plane at about 2600 RPM at 14 MPH. Never try this in a following sea as the bow will plow into the next wave. In following seas, let the bow come up so the boat takes the wave more squarely on the bottom.

Never rely on the drive trim indicators. Feel the boat.  Hope this helps."

I hope this helps you too.  Maybe there is another Monticello owner 'out there' who can respond to you?

Cheers

Tim