Szolack withdrawing from Shootout Action
10-21-2016 | 08:28 AM
#161
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From: METRO BEACH, MICHIGAN
I have not been on OSO for a long time but the carnage of late is hard to ignore.
Tunnel boats are absolutely wings in that they create aerodynamic lift via a pressure differential between the upper and lower surfaces of the tunnel. Whilst an aircraft in free flight derives 2/3 of its lift from the upper suction part of the wing, a wing in extreme ground effect is the reciprocal. The suction portion of the wing produces the same quantum of suction lift as in free flight but the pressure side of the wing (by virtue of its proximity to ground (water)), produces vastly more lift. When combined with the effective increase in aspect ratio , GE lift is very efficient and that’s why aerodynamicists have been chasing this Holy Grail for over a century.
HOWEVER these poor chaps in the Skater are just the latest victims of GE’s dark side - The change in Cm (pitching moment) and centre of aerodynamic pressure (CP) when the wing (tunnel) starts to rise from the water and/or increase its angle of attack (AOA). In extreme GE, the CP is roughly 40-50% of the chord (subject to AOA, aspect ratio, section etc). Due to their ‘dirty’ upper side (cockpits etc) and very low aspect ratios, tunnel boats derive very little of their operating aerodynamic lift from the suction side of the wing (which acts at roughly 25% MAC). This explains why a tunnel boat’s CP is closer to the centre of area (i.e. 50% MAC) when in GE. However once the bow starts to rise, the CP moves towards the freestream point of 25% MAC and the nose down pitching moment decreases. Most tunnel boats have their lcg at roughly 70% of the chord, so once the bow starts to rise the CP moves further and further away from the lcg, and we all know what happens next. This is exasperated by the fact that at higher AOA's the tunnel starts to create vortex lift (same as Concorde) by virtue of its low aspect ratio. Therefore instead of stalling (as a conventional aerofoil would at a high AOA), it keeps on lifting and then (as mentioned in a previous post) pure drag takes over. If you look at the video of this most recent tragedy, the angular velocity is shockingly high. It shows just how out of balance the boat is (at this velocity) once it loses the stabilising support of the surface. Tunnel boats are partial aircraft with no means of aerodynamic control and negative aerodynamic stability (lcg is not even close to the CP once a perturbation which causes a bow up pitching moment occurs).
For those that have not been enlightened by Mr. Szolack’s astute decision, fly at high velocities at your own considerable risk,
ND1
Tunnel boats are absolutely wings in that they create aerodynamic lift via a pressure differential between the upper and lower surfaces of the tunnel. Whilst an aircraft in free flight derives 2/3 of its lift from the upper suction part of the wing, a wing in extreme ground effect is the reciprocal. The suction portion of the wing produces the same quantum of suction lift as in free flight but the pressure side of the wing (by virtue of its proximity to ground (water)), produces vastly more lift. When combined with the effective increase in aspect ratio , GE lift is very efficient and that’s why aerodynamicists have been chasing this Holy Grail for over a century.
HOWEVER these poor chaps in the Skater are just the latest victims of GE’s dark side - The change in Cm (pitching moment) and centre of aerodynamic pressure (CP) when the wing (tunnel) starts to rise from the water and/or increase its angle of attack (AOA). In extreme GE, the CP is roughly 40-50% of the chord (subject to AOA, aspect ratio, section etc). Due to their ‘dirty’ upper side (cockpits etc) and very low aspect ratios, tunnel boats derive very little of their operating aerodynamic lift from the suction side of the wing (which acts at roughly 25% MAC). This explains why a tunnel boat’s CP is closer to the centre of area (i.e. 50% MAC) when in GE. However once the bow starts to rise, the CP moves towards the freestream point of 25% MAC and the nose down pitching moment decreases. Most tunnel boats have their lcg at roughly 70% of the chord, so once the bow starts to rise the CP moves further and further away from the lcg, and we all know what happens next. This is exasperated by the fact that at higher AOA's the tunnel starts to create vortex lift (same as Concorde) by virtue of its low aspect ratio. Therefore instead of stalling (as a conventional aerofoil would at a high AOA), it keeps on lifting and then (as mentioned in a previous post) pure drag takes over. If you look at the video of this most recent tragedy, the angular velocity is shockingly high. It shows just how out of balance the boat is (at this velocity) once it loses the stabilising support of the surface. Tunnel boats are partial aircraft with no means of aerodynamic control and negative aerodynamic stability (lcg is not even close to the CP once a perturbation which causes a bow up pitching moment occurs).
For those that have not been enlightened by Mr. Szolack’s astute decision, fly at high velocities at your own considerable risk,
ND1
10-21-2016 | 08:44 AM
#162
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From: Plainville/Old Lyme, CT Boca Raton, FL
The simple fact is that cats are using lift, running at speeds that even a 747 will fly at, and basically the only thing touching the water is the prop with no way to control the flight of the boat. Overall its just a bad recipe.
Alot of us will be in Key West in a couple weeks admiring the new boats with their ultra modern paint, interior, electronics systems, new Merc turbo motors, etc.... But, if you take away all the paint, bling, fancy stereos, etc...., its bascially the same old fiberglass antiquated cat that cam out in the mid 80's with nothing done to accommodate the fact that they are basically airplanes that sit in the water.
I also think that most of the people on this thread agree that once the bow gets high enough, and starts to blow over, there's basically nothing that can be done. That is why an AHRS system would be needed and could catch the boat before the angle of attack gets to the point where a canard or spoiler system would not help.
Have any of you tried to hold a piece of plywood in the wind????? That is what a vertical cat is going against, and like i said, at that point its too late.
Alot of us will be in Key West in a couple weeks admiring the new boats with their ultra modern paint, interior, electronics systems, new Merc turbo motors, etc.... But, if you take away all the paint, bling, fancy stereos, etc...., its bascially the same old fiberglass antiquated cat that cam out in the mid 80's with nothing done to accommodate the fact that they are basically airplanes that sit in the water.
I also think that most of the people on this thread agree that once the bow gets high enough, and starts to blow over, there's basically nothing that can be done. That is why an AHRS system would be needed and could catch the boat before the angle of attack gets to the point where a canard or spoiler system would not help.
Have any of you tried to hold a piece of plywood in the wind????? That is what a vertical cat is going against, and like i said, at that point its too late.
Last edited by 302Sport; 10-21-2016 at 08:50 AM.
10-21-2016 | 09:59 AM
#163
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From: Traverse City, Michigan
I'm guessing the investment in testing for each hull design to establish a baseline aerodynamic profile will be significant. That and the costs to develop aircraft quality fly by wire controls should eliminate most owners due to design, testing and hardware cost. After all these are unique sport boats not fighter aircraft.
10-21-2016 | 10:35 AM
#164
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Joined: Jul 2006
Posts: 874
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From: Charleston, il
I have not been on OSO for a long time but the carnage of late is hard to ignore.
Tunnel boats are absolutely wings in that they create aerodynamic lift via a pressure differential between the upper and lower surfaces of the tunnel. Whilst an aircraft in free flight derives 2/3 of its lift from the upper suction part of the wing, a wing in extreme ground effect is the reciprocal. The suction portion of the wing produces the same quantum of suction lift as in free flight but the pressure side of the wing (by virtue of its proximity to ground (water)), produces vastly more lift. When combined with the effective increase in aspect ratio , GE lift is very efficient and that’s why aerodynamicists have been chasing this Holy Grail for over a century.
HOWEVER these poor chaps in the Skater are just the latest victims of GE’s dark side - The change in Cm (pitching moment) and centre of aerodynamic pressure (CP) when the wing (tunnel) starts to rise from the water and/or increase its angle of attack (AOA). In extreme GE, the CP is roughly 40-50% of the chord (subject to AOA, aspect ratio, section etc). Due to their ‘dirty’ upper side (cockpits etc) and very low aspect ratios, tunnel boats derive very little of their operating aerodynamic lift from the suction side of the wing (which acts at roughly 25% MAC). This explains why a tunnel boat’s CP is closer to the centre of area (i.e. 50% MAC) when in GE. However once the bow starts to rise, the CP moves towards the freestream point of 25% MAC and the nose down pitching moment decreases. Most tunnel boats have their lcg at roughly 70% of the chord, so once the bow starts to rise the CP moves further and further away from the lcg, and we all know what happens next. This is exasperated by the fact that at higher AOA's the tunnel starts to create vortex lift (same as Concorde) by virtue of its low aspect ratio. Therefore instead of stalling (as a conventional aerofoil would at a high AOA), it keeps on lifting and then (as mentioned in a previous post) pure drag takes over. If you look at the video of this most recent tragedy, the angular velocity is shockingly high. It shows just how out of balance the boat is (at this velocity) once it loses the stabilising support of the surface. Tunnel boats are partial aircraft with no means of aerodynamic control and negative aerodynamic stability (lcg is not even close to the CP once a perturbation which causes a bow up pitching moment occurs).
For those that have not been enlightened by Mr. Szolack’s astute decision, fly at high velocities at your own considerable risk,
ND1
Tunnel boats are absolutely wings in that they create aerodynamic lift via a pressure differential between the upper and lower surfaces of the tunnel. Whilst an aircraft in free flight derives 2/3 of its lift from the upper suction part of the wing, a wing in extreme ground effect is the reciprocal. The suction portion of the wing produces the same quantum of suction lift as in free flight but the pressure side of the wing (by virtue of its proximity to ground (water)), produces vastly more lift. When combined with the effective increase in aspect ratio , GE lift is very efficient and that’s why aerodynamicists have been chasing this Holy Grail for over a century.
HOWEVER these poor chaps in the Skater are just the latest victims of GE’s dark side - The change in Cm (pitching moment) and centre of aerodynamic pressure (CP) when the wing (tunnel) starts to rise from the water and/or increase its angle of attack (AOA). In extreme GE, the CP is roughly 40-50% of the chord (subject to AOA, aspect ratio, section etc). Due to their ‘dirty’ upper side (cockpits etc) and very low aspect ratios, tunnel boats derive very little of their operating aerodynamic lift from the suction side of the wing (which acts at roughly 25% MAC). This explains why a tunnel boat’s CP is closer to the centre of area (i.e. 50% MAC) when in GE. However once the bow starts to rise, the CP moves towards the freestream point of 25% MAC and the nose down pitching moment decreases. Most tunnel boats have their lcg at roughly 70% of the chord, so once the bow starts to rise the CP moves further and further away from the lcg, and we all know what happens next. This is exasperated by the fact that at higher AOA's the tunnel starts to create vortex lift (same as Concorde) by virtue of its low aspect ratio. Therefore instead of stalling (as a conventional aerofoil would at a high AOA), it keeps on lifting and then (as mentioned in a previous post) pure drag takes over. If you look at the video of this most recent tragedy, the angular velocity is shockingly high. It shows just how out of balance the boat is (at this velocity) once it loses the stabilising support of the surface. Tunnel boats are partial aircraft with no means of aerodynamic control and negative aerodynamic stability (lcg is not even close to the CP once a perturbation which causes a bow up pitching moment occurs).
For those that have not been enlightened by Mr. Szolack’s astute decision, fly at high velocities at your own considerable risk,
ND1
10-21-2016 | 12:42 PM
#166
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Posts: 3,869
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From: St. Pete Beach, FL
The 36' was relying on its angle of attack getting pushed up dangerously in order to increase the lift.
10-21-2016 | 01:23 PM
#167
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From: Overland Park, KS 87mm Loto
They had a issue with the props getting together, fixed that, then lost a turbine, tested it and said they were very impressed but never gave a speed. Then the shelved the project
10-21-2016 | 03:29 PM
#169
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I would like to hear Mr. Szolack tell us about this shootout run. This is very impressive.
I would like to hear his thoughts at around .15 seconds when they push the throttles down, then again at .30 when the boat seems to pack the tunnel completely.
It's incredible. And extremely fast. Those engines are singing, wonder what RPM's at WOT.
The one thing I notice is that the boat starts "galloping" at quite a fast speed... then once the tunnel is packed, it levels out and is hauling' ass...
https://www.youtube.com/watch?v=w7sbSIZKAIM
I would like to hear his thoughts at around .15 seconds when they push the throttles down, then again at .30 when the boat seems to pack the tunnel completely.
It's incredible. And extremely fast. Those engines are singing, wonder what RPM's at WOT.
The one thing I notice is that the boat starts "galloping" at quite a fast speed... then once the tunnel is packed, it levels out and is hauling' ass...
https://www.youtube.com/watch?v=w7sbSIZKAIM
Last edited by jusabum; 10-21-2016 at 03:32 PM.
10-21-2016 | 04:03 PM
#170
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Posts: 620
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From: Cincinnati ohio
I do not disagree with the design procedures of the boats that built back in the day and the way some are built today. Your point is a valid. Nor am I here to defend Skater but I ask all you this question.
1) How many times has any boat ran over 190mph? Not to mention being in the 36' size range.
2) Of all the runs over 190mph not counting the big Mystics or turbine boats how many other manufactures other than Skater have accomplished this? Gino's MTI did it and is the only other brand I am aware of.
I would bet if they left this boat set up to run 170mph or less it would not have went over. Jim had told me many times they wanted to break 200mph. To the best of my knowledge the time trials being run that day were not on a closed course and limited to a mile. It was a radar run for top speed. We all know the boat ran 194mph at LOTO in a mile course. Maybe they were looking to break 200mph and were well on there way before it went over.
Point is that if you take anything with a wing at those speeds it will fly at some point. There is a reason Nascar added restrictor plates, roof flaps etc. Indy car changed motors for less HP. NRHA shorten the length of the run. Reason being even with spoilers, and down force if the vehicle got out of shape it would lift and fly up in the air. You are also correct there were things that keep the bow down and make the boat safer. But just like they lose is fast. Add down force and maybe the boat only runs in the 180's? Cars have to deal with smooth pavement and only wind gusts on a track. Boats have many more variables no CAD design will help if you encounter something at those speeds that upset the running angle of wing. The dangers involved at those speeds will never be safe. Just my .02 cents.
1) How many times has any boat ran over 190mph? Not to mention being in the 36' size range.
2) Of all the runs over 190mph not counting the big Mystics or turbine boats how many other manufactures other than Skater have accomplished this? Gino's MTI did it and is the only other brand I am aware of.
I would bet if they left this boat set up to run 170mph or less it would not have went over. Jim had told me many times they wanted to break 200mph. To the best of my knowledge the time trials being run that day were not on a closed course and limited to a mile. It was a radar run for top speed. We all know the boat ran 194mph at LOTO in a mile course. Maybe they were looking to break 200mph and were well on there way before it went over.
Point is that if you take anything with a wing at those speeds it will fly at some point. There is a reason Nascar added restrictor plates, roof flaps etc. Indy car changed motors for less HP. NRHA shorten the length of the run. Reason being even with spoilers, and down force if the vehicle got out of shape it would lift and fly up in the air. You are also correct there were things that keep the bow down and make the boat safer. But just like they lose is fast. Add down force and maybe the boat only runs in the 180's? Cars have to deal with smooth pavement and only wind gusts on a track. Boats have many more variables no CAD design will help if you encounter something at those speeds that upset the running angle of wing. The dangers involved at those speeds will never be safe. Just my .02 cents.
