Captain Grog
09-28-2006, 12:19 PM
Looking for some suggestions from all you well versed designers out there.
Background info: I have a 40 foot Dorado Center Console, 12,500 lbs. The hull is basically a scaled down PT boat hull with a rounded trailing edge. Very interesting layout. Out house in the middle, bowling alley on one side, shuffle board court on the other. Bring thirty of your closest friends and their coolers. Small V-berth up front. Single Volvo 430 hp. 30% overdrive splitter box. Carbon fibre driveshafts to two 290 DP lower units. One engine, four props and 32 kts (without the 30 people) @ 2800 rpm with MAYBE a foot wake - the boat rides FLAT. The best part, I average 5.7 gph at 18 kts and 1000 mile range. At full throttle I can turn it around in its own length - or park it like a car in spaces a 30 footer wouldn't consider. What a dream.
Ready?
I was replacing the outdrives on the Center Console (and putting a coat of Awl Grip on her - boat ten years old - hull #1, when the better half made a decision that a real cabin with air, generator and creature comforts were more important than quick. The dogs need the A/C you know.
We found one sweet deal on a 40' Dorado Bluewater Workboat - the one with the Hardtop.
See: dorado-marine.com to get an idea what the boat looks like. I'll either post pictures here or I can be contacted at ggabert@ensercorp.com and I'll be happy to send them to you.
Dorado recessed the prop in a tunnel two feet wide at the rear and a foot vertical and tapering forward five feet to the keel on the Bluewater series. This loss of lift causes the bow of the boat to point at the moon unless the trim tabs are in the full down position - they're 9" x 18". You can't see over the bow without the tabs all the way down and yes, the helm seat is raised. Thought about going to a set of 12 x 42's but I don't think they will be enough. Underway, the prop wash looks like a jet drive blasting out the back. Max speed is 22 kts @26 gph. Cummins 480 hp straight six, 1.33:1 gearbox swinging a 21 x 22 cupped four blade at the rated 2600 rpm. Cruise at 18kts @15 gph, 2150 rpm. 15,000 lbs.
I had the opportunity to see a Pearson True North 33 or 38 close up last weekend on a lift in Boca Raton. The three foot hull extension effectively reversed the prop tunnel back to within a couple of inches of arc at the trailing edge. You'd be hard pressed to tell this was a tunnel drive from the stern at rest.
With this in mind, I thought about taking a two (or three) foot long pattern of the stern and under body of the hull in glass, reverse it and bolt it to the transom, effectively giving me a 2-3 foot hull extension - and also canting the nozzle downward some, thereby greatly reducing the nozzle opening at the stern. The trailing edge of this extension would be 2 inches lower than the plane of the hull and effectively forming a hook to eliminate the need for the trim tabs - I'll be moving them to the rear). Am I on the right track? Will this help the thrust and raise the stern so I'm not digging such a hole? The boat puts out a four foot wake and doesn't feel like its 'on top' unless its wide open -and I can't afford to run at that speed. I've already moved everything possible that's heavy to the bow - water tanks, gear, etc. I suppose I've been spoiled
Suggestions other than put a cabin on the center console that I'm required to sell? (MY preference!!!!)
Background info: I have a 40 foot Dorado Center Console, 12,500 lbs. The hull is basically a scaled down PT boat hull with a rounded trailing edge. Very interesting layout. Out house in the middle, bowling alley on one side, shuffle board court on the other. Bring thirty of your closest friends and their coolers. Small V-berth up front. Single Volvo 430 hp. 30% overdrive splitter box. Carbon fibre driveshafts to two 290 DP lower units. One engine, four props and 32 kts (without the 30 people) @ 2800 rpm with MAYBE a foot wake - the boat rides FLAT. The best part, I average 5.7 gph at 18 kts and 1000 mile range. At full throttle I can turn it around in its own length - or park it like a car in spaces a 30 footer wouldn't consider. What a dream.
Ready?
I was replacing the outdrives on the Center Console (and putting a coat of Awl Grip on her - boat ten years old - hull #1, when the better half made a decision that a real cabin with air, generator and creature comforts were more important than quick. The dogs need the A/C you know.
We found one sweet deal on a 40' Dorado Bluewater Workboat - the one with the Hardtop.
See: dorado-marine.com to get an idea what the boat looks like. I'll either post pictures here or I can be contacted at ggabert@ensercorp.com and I'll be happy to send them to you.
Dorado recessed the prop in a tunnel two feet wide at the rear and a foot vertical and tapering forward five feet to the keel on the Bluewater series. This loss of lift causes the bow of the boat to point at the moon unless the trim tabs are in the full down position - they're 9" x 18". You can't see over the bow without the tabs all the way down and yes, the helm seat is raised. Thought about going to a set of 12 x 42's but I don't think they will be enough. Underway, the prop wash looks like a jet drive blasting out the back. Max speed is 22 kts @26 gph. Cummins 480 hp straight six, 1.33:1 gearbox swinging a 21 x 22 cupped four blade at the rated 2600 rpm. Cruise at 18kts @15 gph, 2150 rpm. 15,000 lbs.
I had the opportunity to see a Pearson True North 33 or 38 close up last weekend on a lift in Boca Raton. The three foot hull extension effectively reversed the prop tunnel back to within a couple of inches of arc at the trailing edge. You'd be hard pressed to tell this was a tunnel drive from the stern at rest.
With this in mind, I thought about taking a two (or three) foot long pattern of the stern and under body of the hull in glass, reverse it and bolt it to the transom, effectively giving me a 2-3 foot hull extension - and also canting the nozzle downward some, thereby greatly reducing the nozzle opening at the stern. The trailing edge of this extension would be 2 inches lower than the plane of the hull and effectively forming a hook to eliminate the need for the trim tabs - I'll be moving them to the rear). Am I on the right track? Will this help the thrust and raise the stern so I'm not digging such a hole? The boat puts out a four foot wake and doesn't feel like its 'on top' unless its wide open -and I can't afford to run at that speed. I've already moved everything possible that's heavy to the bow - water tanks, gear, etc. I suppose I've been spoiled
Suggestions other than put a cabin on the center console that I'm required to sell? (MY preference!!!!)