Re: benefit of bolt on finns on motor
This is from another post but applicable!<br />I am assuming that your first goal is to get the boat on plane easier, and stay there at slower speeds. Any time you add more planing surface to the hull it will plane sooner. However, please understand that the surface area of the additon (trim tabs or hydrofoil) needs to be in proportion to the size of the boat. Small boat small tabs. Big boats ig tabs. In most cases the hydrofoils are not large enough to give the best results, although they will give some results, which may depend on the balance of the boat. If the boat is only a little out of balance then the hydrofoil will seem to be very effective, but if it is a good deal out of balance then the results will be less effective at slower speeds.<br /><br />More importantly the hydrofoil lifts the boat by the engine, and from the center. Lifting from the engine adds stress to the cavitation plate, motor mounts, and mounting hardware. Lifting the boat from the center creates port to starboard handling problems at higher speeds, especially on V bottom boats.<br /><br />Additionally any fixed trim device, (hydrofoils, fixed plates, hooks in the hull, etc) will provide some lift at slower speeds, but continue at an increasing rate to provide more and more lift as the boat speed increases(even after planing). This is why most hydrofoil users will say the low end performance is better but "they create drag" at higher speeds and slow the boat. I would like to agree and disagree with this "Drag issue".<br /><br />What realy happens is that the extra lift on the stern also rotates the bow down, and in this position the boat is not at an efficient running angle (too much boat in the water). If you have electric tilt trim on the motor, you adjust the trim to raise the bow. This means that you are using the prop to adjust the attitude of the boat. This is not the job of the propeller, it should be left alone to simply propell. If the prop is running through the water at an angle to lift provide lift to the bow ( insted of perpendicular to the water) the prop thrust is not at its max effeciency. Results - Slower boat, Waisted Fuel, Poor handling especially in turns.<br /><br />If the boat is drastically under power and has a top speed of less than 25 mph, you may not see some of these problems, since the excessive lift only occurs as the boat inceases in speed.<br /><br />The most effective thing you can do to increase the boats performance is to have a variable hull design, so that the changing conditions can be compensated for by a changing hull design. For example,if on Sat. you wish to ski, then change the boat into a ski boat, and on Sun. you wish to hall 5000 Lbs. of rocks over to the breakwall change the boat to a barge. A little bit radical, but adjustable tim tabs simply chang the hull design to make the boat perform better, over a larger variety of conditions. <br /><br />Nothing will do the job better. Given the size of your boat , your best solution is Smart Tabs (either ST980-40 or ST1290-60 depending on the Hp of the motor). Do a search on this site to see what others are saying about Smart Tabs.
