There are several ways to get more speed out of a TI. If you understand how a 3point hydroplane works, ( I used to be a hydroplane racer), then you can by several means accomplish what you want to do.
First off you have to get the displacement hull out of the water, ( for that length max speed is around 8 mph with the hull flat in the water, ( like a ship). When exceeding around 8mph the power to go faster increases exponentially.
Another big factor is propellor pitch, and rpm, physics dictates the max speed, pretty much all trolling motors and small outboards are designed to provide max speed at around 6-7 mph, ( like a threaded nut running up a threaded shaft). You turn at a certain rpm, it will linearly move at a certain speed, ( there are prop pitch charts and calculators all over the net to calculate such things). We used many different methods to get higher speeds out of our TI’s.
Method 1: add giant sails to the boat. We had a 135 sq ft spinnaker, that was mounted on a bowsprit, that changed the angle of the sail so 1/3 of the energy was converted to lift. So if sailing in a strong downwind the bow lifts out of the water at least a foot, ( the sails on TI’s are mounted too far forward on the hull, and there is not enough floatation on the hull, so the bow dives, ( we have had several dangerous pitchpole events, so you need to be careful). Because the back of the boat being pointed, at higher speeds, over 9-10mph the entire rear of the boat goes completely underwater, for several reasons, at 9mph the rear mirage drive openings, and the scupper holes become drinking fountains, ( water shooting in), filling the rear passenger area waist deep in water, ( wife didn’t like that,lol). Plus any waves, the engines go under water, and quit, when starved for air. To remedy those problems we added a removable fiberglass/ foam hull mod to the back of the boat to convert the hull to a planing type hull, which also added 200lbs of additional flotation to the boat. We then plugged the rear scupper holes, and the rear mirage pocked with a contoured drive well plug. The scupper holes we added angled tubes at the bottom, so they created suction to drain at high speeds. Once these mods were made, using the lift of the spinnaker, and the planing rear mod, we could go downwind easily at 1 to 1 windspeed easily. But only downwind, so in 22mph downwind runs we could easily go over 20mph, with the bow 2ft in the air, and the rear planing, we could overcome the normal 3-4 ft waves associated with high winds. But you have to realize the boat was not designed for those conditions, everything has to be massively re-enforced to withstand the extreme forces. Very easy to rip the AMA’s off. When we added hydrofoils to the front, ( near the drivers seat) to lift the bow, ( following the 3 point hydroplane principles). We were able to sail at different points of sail, ( not just downwind with the spinnaker). The problem there is to actually get up on the foils, the power required is huge to get thru the transition. Even with our 30sq ft wing jib, and mainsail, in optimum conditions, ( on out boat optimum was with the wind around 20degrees off the bow upwind). So with our twin hybrid honda’s with special high pitch props, providing around 8mph momentum, plus 10-12mph natural wind, we had 18-20mph wind blowing. On our face, and across the sails. With the wing sail providing around 1/3 of it’s energy providing lift to the bow, to get the nose out of the water. Then the back half of the boat working as a planing hull, ( like a powerboat planes). Once you get on plane the horpower needed by the outboards goes down to around 1 hp from each outboard, so you can cruise at 10 -12 mph all day, getting around 60-80mpg from the motors, ( about a buck a day fuel cost), most of our outings were 2-3 hours, covering between 15 and 20 miles. Daily range was areound 100 miles, ( keep in mind the florida keay are huge, and we were mostly offshore, ( as offshore scuba diving was our main pastime). If it takes 4-5 hours to get 10 miles out to a dive site, it’s not worth going. And if the winds are over 7mph, the underwater visability goes to crap, and nobody wants to be out in 4 ft waves. So our criteria was if it takes longer than an hout to get to a dive site, it’s not worth going. Also in the keys we get instant storms almost daily, ( always un-forecasted). So for safety we have to be able to get back to safe harbor in under 30 minutes, ( hard and fast rule).
A long time ago we played with the hydrofoils, and me being a motorhead, I souped up the Honda’s with nitrox injection, and super high pitch props, ( 10” pitch props). To be able to get thru the transition, and get up on the foils. Once up on the foils, the sails in decent winds can maintain, ( similar to how a trifoiler works), but with just the tip of the back end planing on the water at speed. All that was more dargerous than can be imagined, and I had many dangerous spectacular crashes and pitchpoles, before abandoning the hydrofoil concept alltogether back in around 2012. And went to the hybrid outboards, wing sails, and widened hull,( 12ft wide), planing hull, etc, that I ran until 2018 when I had to throw in the towel for health reasons. Bottom line, doing foils is a total waste of time, and really dangerous, don’t bother, unless your trying to impress all you Trifoiler friends, ( lol). Lot’s of Trifoilers down here.
I had the time of my life, and great fun and reward for my efforts, and was out every single weekend having fun. The deal with my wife to buy the TI, back in 2010, is I promised to pedal the boat 15 miles a week as my exercise program after having a heart attack in feb 2010. We bought the boat in April 2010. First week it took 10 hrs of pedaling to get my promised 15 miles in, ( I think I was over sold on the boat capability, just a little).
Me being a retired design engineer with absolutely nothing else to do, I re-designed pretty much everything on the boat. By mid 2010 I was able to get my required 15 weekly peddling miles, ( I always peddled 90% of the time), done in around 3 hrs. By 2013 I could easily get my required 15 miles in and alway measured on a gps, and shown to wife when I got home. I was able to get my required weekly 15 mile recorded and logged in around an hour and a half to two hours. That continued until I had to give it up in 2018, ( result of a long ago broken back injury from a martial arts tournament, which handling the boat, made worse), until under doctors orders I had to give it all up. Bottom line…. Don’t bother trying to get much more out of the boat than it was designed for, just not worth the effort, and can be dangerous.
Just use the boat as designed, like 99% of all the other users who enjoy their boats just as they came form the factory, with a couple tweaks here and there, ( like a small suzuki 2.5 outboard), more for safety than anything else. FE
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