gambling/experimenting

[Sonic Boom]

After exhausting the internet on what a shortened keel, lift rails and lift strakes would do on a series 2 46HP without finding the answer, we took the boat to Wanchese, NC and let the professionals have at it. Sharing the results in case anyone else gets a notion or curious about doing the same. The baseline numbers were 1750-1800 rpm was 20 knots where we cruised most of the time. On the pins was usually in the 27 knots range at 2100 RPM which we never run at. In full disclosure, these engines were detuned to 2300 RPM no load speed in leu of the normal 2500 RPM no load speed.

Yesterday we finally splashed her and noticed a 2 knot increase almost across the board. 1750-1800 was about 22-23 knots and on the pins was 30 knots. However, the real gain was the boat runs more level now without the nose high attitude and the rooster tail behind the boat is almost gone. The engine temps dropped at least a needle width, lower EGT and less noise. She will even cruise in the 1500-1600 RPM range at 17 knots now easing along. Wide open RPM increase 150 to 2250 and 2260 RPM due to unloading the engines.
View attachment 76879View attachment 76879
Hope this helps someone else looking for the same info.

 

[Timeless72]

In the words of the A Team...

Any other pics of the lift rails?

 

[Cricket]

Thanks for posting, really enjoy looking at these types of projects, would love to see additional photos of the strakes. Also, how did you, or the yard, determine size and where to place them? Been thinking about strakes and sort of stumped where to put them, etc.

 

[edward]

A lot of experienced talent and craftsmen in Wanchese.

 

[Cricket]

Sonic Boom, did Vern's son do the work?

 

[whoover]

I understand wanting gains in performance and economy, do you think you will loose dock handling with less keel and did anything change in regards to running on plane with less keel and running surface.

Walt Hoover

 

[madhatter1]

I understand wanting gains in performance and economy, do you think you will loose dock handling with less keel and did anything change in regards to running on plane with less keel and running surface.

Walt Hoover

That is the factory cut down keel for the HP. I’m more concerned with the perishable seafood sitting outside.

 

[bostonhatteras]

I'll second Cricket's thoughts on where to place the strakes and otherwise see more pics overall of the process. Looks like you decided to not do any lifting rails. Id imagine the strakes were done with a template and are entirely of thickened epoxy. As for cutting the keel, this has been in my mind for years. The process is just like any other fiberglass repair really. Making sure the inners of the keel being fully dry are a big concern. The opportunity for a keel mount transducer pocket is right there when doing that mod. Looks great and impressive results.

 

[rsmith]

They add the blisters around the shaft log too?

 

[Sonic Boom]

Will try to answer everyone's questions here:
Blue Devil Boat works did the job and determined where and how to fabricate everything, they also modified another Hatteras this year prior to ours and have a lot of experience doing these projects. Great guys to work with!

The lift strakes up front are closed cell foam glassed to the hull and then faired, this was done to eliminate hull suction.

The lift rails were put under the hull and made from wood and glassed over so we could haul out without lift blocks, they ran the rails up to the factory portion of the rails so it's a seamless design now. The hull doesn't "slap" with this design like the bolt on rails

About six inches was cut from the keel (even though this was already the shorter series 2 keel) at the deepest point at Blue Devil's recommendation, I'm glad they did this as a pile of water drained out of the keel and the factory foam when then did this. The waterline sits higher now now after losing the weight of the keel water

As for performance/stability, there's still plenty of keel remaining acting as a large third rudder and I haven't found any downside to this work yet.

I believe the blisters around the shafts are a factory HP modification?

The boxes of shrimp were getting warm in a hurry!

 

[rsmith]

Curious why you would detune the engines by limiting the no load speed. I believe the 8/92 for the entire 46 HP run was 650hp. Later in the 88 and up 52 they boosted them to 735 but all the 650h0 versions in the Hatts and Ocean Yachts seemed to hold up ok

 

[Sonic Boom]

Curious why you would detune the engines by limiting the no load speed. I believe the 8/92 for the entire 46 HP run was 650hp. Later in the 88 and up 52 they boosted them to 735 but all the 650h0 versions in the Hatts and Ocean Yachts seemed to hold up ok

You are correct, these are the 650 hp versions. The previous owner turned down the no load speed, he stated for longevity reasons and I never got motivated to turn them back up. Suppose If we wanted more speed we could but honestly would never run the engines that hard anyway so probably no point.

 

[31FlyCruzr]

Tim Powell had a 2017 thread, "Repowered Hatts Leaning" that has some good info related to making older hatts go faster, , congratulations on the improvement you gained, but older boats may also want to see what Tim found

Bill

 

[SKYCHENEY]

Put em back to original specs. You don't have to run them hard, but if you ever want that extra speed, it will be there.

 

[Sonic Boom]

Tim Powell had a 2017 thread, "Repowered Hatts Leaning" that has some good info related to making older hatts go faster, , congratulations on the improvement you gained, but older boats may also want to see what Tim found

Bill

Bill, that's a great thread! Ironically I could feel the hull suction Tim mentions even at 20 knots. The boat would make a sound then the surge forward when it broke the suction. It never leaned to the side though. The hull suction was the sole reason for adding forward lift strakes to get air under the hull. Seems rock solid now at 30 knots.

 

[Briankinley2004]

How did they avoid the keel tank when they cut her down?

 

[cww]

How did they avoid the keel tank when they cut her down?

They're called keel tanks but that's just a term carried over from commercial vessels, they aren't actually inside the keel. They're centerline in the space between the floorboards and the bottom of the hull.

 

[edward]

Will try to answer everyone's questions here:
Blue Devil Boat works did the job and determined where and how to fabricate everything, they also modified another Hatteras this year prior to ours and have a lot of experience doing these projects. Great guys to work with!

The lift strakes up front are closed cell foam glassed to the hull and then faired, this was done to eliminate hull suction.

The lift rails were put under the hull and made from wood and glassed over so we could haul out without lift blocks, they ran the rails up to the factory portion of the rails so it's a seamless design now. The hull doesn't "slap" with this design like the bolt on rails

About six inches was cut from the keel (even though this was already the shorter series 2 keel) at the deepest point at Blue Devil's recommendation, I'm glad they did this as a pile of water drained out of the keel and the factory foam when then did this. The waterline sits higher now now alosing the weight of the keel water

As for performance/stability, there's still plenty of keel remaining acting as a large third rudder and I haven't found any downside to this work yet.

I believe the blisters around the shafts are a factory HP modification?

The boxes of shrimp were getting warm in a hurry!

aWhere in Wanchese are you having the work done ?

 

[Sonic Boom]

How did they avoid the keel tank when they cut her down?

There was at least 8-10 inches between the bottom of the tank and the keel

 

[Briankinley2004]

There was at least 8-10 inches between the bottom of the tank and the keel

thanks. I plan on running a drill bit in mine on next haul out to see if water is trapped in it. I will use a 2” or so bit