Sunsation Aggressor 25 tops 90
05-02-2002, 10:33 PM
#1
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Sunsation Aggressor 25 tops 90
Sorry - I've posted this same thing in a couple different areas of the Board - I know some only read certain sections.
First and foremost, a big thanks to all those who provided feedback after the first (dismal) water test. And a big thanks to Bruce – he ‘da man!
Background:
Boat: 2001 Sunsation Aggressor, 25’, 7’3” beam, 24 degree v-hull, delta pad. Guesstimate on the weight with ½ bag ‘o gas and 2-up is 4200#.
Motor: Bruce Dudley 572 tall deck Merlin, N/A, 8.8:1 cr, 680hp @ 5400 rpms, 670 ft-lbs @ 4600 rpms - an 89 octane motor.
Drive: (to be) IMCO SC, 1.34:1, std. length
First water test (Sunday, April 28th):
Done by Bruce. Flat water. Tried a 2” shortie Bravo o/d (1.50:1) with a 32P Bravo1. This hull has a known unhappy spot in the low 80’s. This was encountered at around 4600 rpms. Bruce was able to pull to 5100 rpms (with plenty of motor left), but the chine walk was wicked and did not significantly decrease after the low 80’s, as I understood it would. Bruce described the handling as such (the best I can recall): “Up to 75 mph, felt good. Near 80 mph it felt like the whole boat was out of the water, the ass-end was kicking to the side, then settling and catching, creating a viscous chine walk oscillation that didn’t improve significantly when trying to power through it. Extremely unsafe handling.”
2nd water test (Thursday, May 2nd):
Again, flat water. Temps only in the 50’s (you go Bruce!). Changed to a standard length Bravo with 1.36:1 ratio. Ran 3 different props: 27 Hydro Q-IV, 28 Bravo1, 29 Mirage+. Speed (GPS) and rpm’s below:
Prop rpms speed
Hydro 3600 55
Bravo1 3600 58
Mirage+ 3600 53(?)
Hydro 5500 91
Bravo1 5500 88.5
Mirage+ 5500 90
Overall, Bruce thought the boat felt best with the Hydro (which is what Sunsation had told us – we had a hard time believing this after the first test with the Bravo1 – if that prop was lifting the ass-end up, you would expect the Hydro to be even worse, right?). The high speed stability was much improved this time out. Can not say how much had to do with the lower x-dim and how much had to do with the fact that we were swinging smaller props at higher revs – my guess is they both had something to do with it - experience has tought me that there's usually a combination of 2 or more factors causing a "problem". Chine walking evident in the low 80’s, mild to moderate, but this time it decreased as speed increased. Only have tie-in hydraulic steering, but as many of you suggested, we will go all the way to the helm – should help “simplify” dealing with the bit of chine walk, minimizing steering over corrections.
There are still a bunch of smaller items that Bruce is going to work on b4 I can get behind the wheel. I look forward to learning how to drive this thing at speed. I understand it will not happen in a day – I’ve got plenty of vacation time built up!
A big thanks to Bruce – I couldn’t expect anything more – I’m truly impressed, and doing business with him has been excellent. Bruce is out of the St. Louis area. How did I find out about him? From the OSO Board! His e-mail address is [email protected] - he’s also the moderator of the OSO Technical Q&A area, though I don’t think he’s been on the Board for quite some time, since he’s been very busy. He can be reached at (314)-952-0861 (cell) or at (314)-731-3795. Just don’t bother him for another coupla weeks – I want my boat back!
Another update to follow once I’ve had a bit of seat time. Hope this info has been of some use for others who may be in a similar situation. It's been a learning experience for me, and even for Bruce a bit I think.
-Mark
Elkton, MD, 21921
[email protected]
First and foremost, a big thanks to all those who provided feedback after the first (dismal) water test. And a big thanks to Bruce – he ‘da man!
Background:
Boat: 2001 Sunsation Aggressor, 25’, 7’3” beam, 24 degree v-hull, delta pad. Guesstimate on the weight with ½ bag ‘o gas and 2-up is 4200#.
Motor: Bruce Dudley 572 tall deck Merlin, N/A, 8.8:1 cr, 680hp @ 5400 rpms, 670 ft-lbs @ 4600 rpms - an 89 octane motor.
Drive: (to be) IMCO SC, 1.34:1, std. length
First water test (Sunday, April 28th):
Done by Bruce. Flat water. Tried a 2” shortie Bravo o/d (1.50:1) with a 32P Bravo1. This hull has a known unhappy spot in the low 80’s. This was encountered at around 4600 rpms. Bruce was able to pull to 5100 rpms (with plenty of motor left), but the chine walk was wicked and did not significantly decrease after the low 80’s, as I understood it would. Bruce described the handling as such (the best I can recall): “Up to 75 mph, felt good. Near 80 mph it felt like the whole boat was out of the water, the ass-end was kicking to the side, then settling and catching, creating a viscous chine walk oscillation that didn’t improve significantly when trying to power through it. Extremely unsafe handling.”
2nd water test (Thursday, May 2nd):
Again, flat water. Temps only in the 50’s (you go Bruce!). Changed to a standard length Bravo with 1.36:1 ratio. Ran 3 different props: 27 Hydro Q-IV, 28 Bravo1, 29 Mirage+. Speed (GPS) and rpm’s below:
Prop rpms speed
Hydro 3600 55
Bravo1 3600 58
Mirage+ 3600 53(?)
Hydro 5500 91
Bravo1 5500 88.5
Mirage+ 5500 90
Overall, Bruce thought the boat felt best with the Hydro (which is what Sunsation had told us – we had a hard time believing this after the first test with the Bravo1 – if that prop was lifting the ass-end up, you would expect the Hydro to be even worse, right?). The high speed stability was much improved this time out. Can not say how much had to do with the lower x-dim and how much had to do with the fact that we were swinging smaller props at higher revs – my guess is they both had something to do with it - experience has tought me that there's usually a combination of 2 or more factors causing a "problem". Chine walking evident in the low 80’s, mild to moderate, but this time it decreased as speed increased. Only have tie-in hydraulic steering, but as many of you suggested, we will go all the way to the helm – should help “simplify” dealing with the bit of chine walk, minimizing steering over corrections.
There are still a bunch of smaller items that Bruce is going to work on b4 I can get behind the wheel. I look forward to learning how to drive this thing at speed. I understand it will not happen in a day – I’ve got plenty of vacation time built up!
A big thanks to Bruce – I couldn’t expect anything more – I’m truly impressed, and doing business with him has been excellent. Bruce is out of the St. Louis area. How did I find out about him? From the OSO Board! His e-mail address is [email protected] - he’s also the moderator of the OSO Technical Q&A area, though I don’t think he’s been on the Board for quite some time, since he’s been very busy. He can be reached at (314)-952-0861 (cell) or at (314)-731-3795. Just don’t bother him for another coupla weeks – I want my boat back!
Another update to follow once I’ve had a bit of seat time. Hope this info has been of some use for others who may be in a similar situation. It's been a learning experience for me, and even for Bruce a bit I think.
-Mark
Elkton, MD, 21921
[email protected]
Last edited by kook; 05-02-2002 at 10:43 PM.
enjoy and good luck 
Gold Member
