DavidM":17xaqe8n said:
I am a little confused about the applicability of these three to a single outboard powered C-Dory:
1. Use of adjustable transom mounted trim tabs
2. Installation of a Permatrim which is a hydrofoil that mounts to the outboard.
3. Using the outboard's built in trim capability.
It seems that if the boat is has proper weight distribution fore and aft, then the outboard's trim capability should be able to dial the boat to match conditions.
If you have to move the outboard with its trim too much and you are losing thrust as a result then the Permatrim will enhance the outboard trim and let you get what you want without too much outboard trim.
It seems that adjustable trim tabs have no value on an outboard powered boat as the foregoing will do it much better.
Thoughts?
David
David M--I have been thru this--I bought my first C Dory 22 with a 90 hp Evinrude in 2002. My neighbor had a 22 at the time. I had neither trim tabs or a Permatrims. The boat was OK--but not what I expected for the "ride" and performance. My neighbor was adding trim tabs, so I became curious. Also in 2007 replaced that 22 with a 25 which had trim tabs--both kept on the West Coast. Because that boat had only the 130 Honda--(block same as the 115 hp) it was under powered--and so I added the Permatrim to help get the boat on a plane. It made a lot of difference in the ride.
The transom mounted trim tabs give balance right to left--and thus you can have a level ride. But they do not give enough "bow down" to push the boat thru the chop. By adding the Permatrims--the bow is pushed down, and the chop hits the "V" part of the hull, rather than flat part aft. The Permatrim increases the outboards ability to put the bow up or down.
Now, if you shift weight--lets say 100 feet of anchor chain--as one East Coast dealer did regularly--then the bow may be down too much when going down wind and waves--leading to dangerous bow steering and broach at the worse--poor handling at best. Granted the boats were first made more as day fishing boats--with a 70 hp outboard--and flat bottom with moderate rocker (up to 1987--when the V and some variable dead rise were added.
You will find that the "thrust" --which is important--pretty much aligns with the attitude of the motor--even with the trim tab--in fact in some cases it improves that part of the equation.
The trim tabs are side to side--For example, if Marie wants to go out of the cabin and sit on the starboard side of the cabin--and we are at a planing speed, she will tell me--and I will compensate to keep the boat level and ride comfortable, with the trim tabs.
If you don't have the tabs and Permatrim you are not getting the maximum out of your boat.