Lift .
More lift>.> I received an e-mail asking me what I considered the best benefits or accomplishments with this exhaust system providing more room is an obvious benefit and quiet running one of the other accomplishments of this design.
But of all the things I have accomplished with this system most definitely needed lift that has been proven to be one of the benefits of this system as to hull performance. I first understood this back in the late 1990s doing a refit on a Bertram 43 'Stay Loos'e" with 6V92 Detroit's. Bertram sent the owner to us to fix several exhaust issues such as high back pressure and excessive exhaust noise and exhaust soot. After all the work had been done and we fix the back pressure & noise issues we understood one more benefit this exhaust had. At start- up testing the mechanics was running the engine under no load at the dock running the engines to the full throttle 2350 rpm.
One of the mechanics on the dock said that exhaust is lifting that boat out of the water and the fact was the boat was lifted out of the water a 3 to 4 inches and standing in the cockpit you could feel the feeling of some type of lift rocking back -and -forth from the boiling water coming from under the boat out of our two exhaust exit points
On sea trial that afternoon with the owner he said the boat was much faster getting on plane.
At the same time my company was doing a number of R&D projects on a number of Sea Ray hulls I was designing a hull performance system we were extending the tunnels but also using the bottom extension as an exhaust system and it was most definitely very quite. We did around 17 test hulls on Sea Ray from the 34' to the 65' the before and after testing was showing 15 to 20% better fuel efficiency and getting on plan was 50% faster. We knew this due to the before and after teasing we did at the time my thinking was most of the added performance was coming from just the tunnel extension and for sure the extension was doing much of the performance we were seeing .
But the 43 Bertram had no extension.
I few months later I once more experienced this lift on our first MTU exhaust project on the 60' Bertram the "Blue Heaven" on sea trail the captain remarked she is a lot faster coming out of the hold as we call it getting on top .
A year later in 2000 on the to sea trial of Odyssey the 105’ sportfish built by Broward Yachts she was our first big yacht applications her power at the time was the new MTU M-91 16V2000 engines she was built using our stringer system design. At sea trial Brian Howell head of MTU Southern District when we went to full throttle, he remarked could you feel that” he said it was as if she was lifted on to plane. It was on that sea trial I understood the 3rd benefit of this design faster planning speeds just getting on top faster it’s created by the exhaust burl out pressure pushing the hull upward. But once the hull reaches cruising speed most of this upward pressure is then redirected aft through the aft thrust’ Slot. The most benefit are the heavier FRP hulls such as Viking & Hatteras or semi displacement were needed left is always welcomed.
The exhaust going though the rear exhaust thrust slot resembled that of a water jet you could tell the exiting water that covered the exiting exhaust could clearly see was moving faster then the water coming off the hull bottom. So I knew the performance we were seeing on the 17 test hulls was a combination of the extension of the tunnels as well as the exhaust pressure now we knew the exhaust had something to do with it . And now with my latest design we have now found a way to use the exhaust and control it for even better performance using 100% the the engine power.
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