Re: Is this a good prop selection?
Cobra & Ratfish;<br /><br />First let me ay that I appreciate you all allowing me to step in on this topic. What I am preaching may sound like a sales pitch and may sound like another way of looking at boat performance, and maybe a bit of both. Thank you for your tolerance!<br /><br />Please keep in mind that I was never on a track to invent a new concept in Trim Tabs, I simply wanted my 10' (9.9HP) inflatable to stay on plane at a lower more comfortable speed. From that point on it was a learning process, and a business. <br /><br />Here is what happens with an active Trim System. This is not theory it is the results of in use testing and tuning. It is not rocket science either!<br /><br />Start with the most efficient position for the prop - perpendicular to the surface of the water. Also as close to the center line of the boat as possible - ie high enough to push through the center of the boat but low enough to insure good prop bite ( no ventilation, no cavitation).<br /><br />Next look at boat balance - if the motor is mid ship (MasterCraft) the balance is good. The better the balance the faster the boat. <br /><br />Next the hull design comes into play but keep in mind that the boat hull is rigid (fixed). A fixed hull will perform best at its optimum predetermined design criteria. Sounds complicated but it is not. For example a barge is designed to handle heavy loads, and a ski boat is designed to pull skiers and go fast. <br /><br />So we have three important and basic factors in allowing the boat to perform at its peak: Power (thrust), Balance (boat position in the water), and Hull design.<br /><br />Without getting into any specific design here is what the trim tabs do for a boat. <br /><br />1) They will compensate for balance issues (ie: stern mounted motors - I/O or outboards) <br />2) They will change the Hull design to increase the efficiency over a broader range of use, and pay loads.<br />3) They allow the motor/prop to be positioned for the most forward thrust.<br /><br />With most I/O's and Outboards the prop is used to do more than its intended job (propel). <br /><br />Tilting (trimming) the prop in helps lift the stern and achieve plane easier, but it is a compromise to thrust (acceleration).<br /><br />Tilting the prop out helps lift the bow to lift more boat out of the water. This is a compromise between less wetted surface, and prop efficiency.<br /><br />Stern loaded boats tend to porpoise, and tilting the prop under (down) will help keep the bow down and reduce porpoising. <br /><br />Lastly, the boat is never running under the same conditions, and therefore the most efficient (sweet spot) speed is hard to achieve. <br /><br />If you accept the above, then this is the reason Smart Tabs will not only increase low end performance but also top end performance. This includes more speed and obviously more RPMs. You are not just looking for RPMs as if they do not come with more speed then there is no need to turn the engine faster (more) as that just uses more fuel.<br /><br />Smart Tabs are active! They continually adjust to the changing conditions of speed, water, load etc. This is a hull design modification!<br /><br />Smart Tabs are adjustable (fine tuning) to the individual characteristics of the boat. Further optimizing the efficiency.<br /><br />Smart Tabs help lift the boat, and control the ride (porpoising and chine walking and tracking) like a suspension system on a car.<br /><br />Now, we have taken these extra jobs away from the prop and allowing it to do (only) its intended job of propelling. Trimming the motor for the best prop bite (not attitude or ride control) produces more Speed and More RPM.s. <br /><br />Properly adjusted you should see 100 to 200 more RPMs and 2 to 4 MPH increase in speed.<br /><br />Now since we are not worried about Hole Shots (since Smart Tabs do not allow you to get into a hole) the acceleration will be better, but more importantly you may be able to increase the pitch of the prop, and achieve even more top speed. <br /><br />Lubedude posted some of his results on his bass boat. If I recall he went from 57 with no tabs to 59 with the tabs and cut his hole shot in half. He then changed to a 25 pitch prop from a 23 and now runs 62 to 63 MPH. This is typical!
