Re: Hydrofoil on sterndrive or not ?
Their a neat idea, but how much speed to they take away on top end? I thought that the main purpose for trim tabs was for leveling the boat, not so much for planing or to control porposing? I added a set to my old Grady White 24' to correct listing in cross currents and wind which they did well, but they were hydraulic trim tabs with a switch, gauge, pump and two rams. They worked great, but to much correction made a noticable change in my fuel usage. I often found myself dealing with some listing to conserve fuel, or moving passengers to one side to correct rather than just trimming it out. Mainly that was due to a lack of fuel capacity, but it still held 40 gallons. I could save as much as 3 gal/hr by not using the trim tabs. That boat had a V6 Mercruiser drive.
I considered trim tabs on my current boat but haven't really seen the need to go through the trouble to add them. My larger boats have always had them, but I never gave them too much thought on the smaller boats.
I have always added hydrafoils to all of my other outdrives, but that Grady White didn't have one and my current boat that I bought used doesn't have one. Other than being a bit slower getting on plane, I like the handling at higher speeds without the hydrafoil. Especially if I need to make a quick change of direction. Adding the hydrafoil to any boat I had also scrubbed about 4 mph off of it's top speed. My last boat came without one, and I added one to it, it helped in all ways other than top speed and quick turns, it actually made the boat hard to turn, it would skip and spin out if I pushed a hard banking turn, where as the problem didn't exist without it. I ended up only puttting it on if I was towing a skier, all other times I left it off.
I think what would happen as I banked into a faster turn, the one side of the hydrafoil would come out of the water and act as a ski of sorts sideways, the first time the boat broke loose was a total shock and on smooth water. I did a few tests and I lost almost all ability to make hard turns with it on. The first time it kicked out it spun me around 180 degrees at about 20 mph. It felt like spinning a car around and hitting a curb. Without it, the boat handled like a dream, it just had trouble getting up on top with a skier. I ended up leaving it off when I sold that boat. That was the only boat that I noticed such a negative change with one, but it was the first of that was used to pull a skier or just for fun and not for fishing. That boat never left smooth freshwater. The feeling that boat had with the hydrafoil on felt like the rear of the boat was loose on the water when you went to turn, it would dig in hard and let go and spin out, the resulting stop when the hydrafoil made contact again with the water was bone jarring. As the boat turned, the hydrafoil was actually riding up on top of the water due to it being now angled upward. When the boat lost speed, it would "dig in" and stop the spin abruptly. I had always added them to boats that were pretty much underpowered, so they were a big help getting on plane, but when I added that one to a boat that had more power, I think I was able to find a serious downside to them.
When I say turning at speed, I don't mean a sudden jerk of the wheel, it would happen on any sweeping turn at cruising speed. That particular one was a two piece Dolphin brand hydrafoil on an OMC drive. I can say whether or not my other boats would have had that problem, but they were all mostly fishing boats that rarely would achieve enough speed to be a problem.
I definitely like how adding a hydrafoil worked on my old bass boat with a 40 HP outboard on an aluminum hull. It helped that boat in every way exept top speed.
