GOT RUDDER?

[HBjet]

GasTurbine, on this test, what where the water conditions? Did you test the 40mph boat with the rudder first, and then without? Also, on the 120mph boat, what were the conditions, and how did you conduct this test? If it was at a drag racing event, what was the reaction, ET, and MPH of both passes?
I'm not saying you didn't do these tests, but I am saying just be removing the rudder you are not going to notice a difference in MPH. Now, like you posted, if you add a Large rudder to your 120mph boat there was a 4mph drop in speed. One question, why would you have a Large rudder on a boat like that anyway?
I'm not trying to start anything with you, I just think your results have another variable in the equation which you didn't account for and I don't want everyone thinking there rudder creates so much drag to where they would notice a difference in top speed if it was removed.
HBjet

[GasTurbine]

Originally posted by HBjet:
GasTurbine, on this test, what where the water conditions? Did you test the 40mph boat with the rudder first, and then without? Also, on the 120mph boat, what were the conditions, and how did you conduct this test? If it was at a drag racing event, what was the reaction, ET, and MPH of both passes?
I'm not saying you didn't do these tests, but I am saying just be removing the rudder you are not going to notice a difference in MPH. Now, like you posted, if you add a Large rudder to your 120mph boat there was a 4mph drop in speed. One question, why would you have a Large rudder on a boat like that anyway?
I'm not trying to start anything with you, I just think your results have another variable in the equation which you didn't account for and I don't want everyone thinking there rudder creates so much drag to where they would notice a difference in top speed if it was removed.
HBjet
Im not going to individualy list the hundreds of tests we have performed on jets boat from 1968.
And yes...top speed will be affected by the addition of a rudder. A GPS only confirms what we have known since the early 70s. We can put any size rudder we want, on any boat.
You dont want "everybody thinking"? Sorry if the truth hurts...but rudders do in fact create more drag, and affect top speed. How can you even argue it doesnt? Do you just think that you can stick anything into the water from your boat, and it wont slow it down? Tell us HB...if your sure a large rudder wont affect top end...where is the line drawn? Can I still go 150 if I leave my trailer attached to the bottom of the boat?

[propless]

To your question, do you experience steering loss of control.
I have a 27' controlled by a jet, quite unusal I'm starting to gather. I also recently put on a PD and found the steering well, unique, fun, and sometimes scary as hell at slow speeds when docking with twenty boats all around you at the same time.
My original system had a small rudder that somewhat helped, so I elected to go to the large rudder offered by PD because of the size of my boat. I'm back to having "some" control over this aircraft carrier in the docks. Was it worth it, yes. Did I notice any loss of speed, not at my max speed of 50 or something.
I feel several folks hit this note in your post, it takes experience with your boat to "feel" your way and gain confidence with the steering (or lack there of) at slow speed. My wife and 13 year old boy still spell their name in the water attempting to go straight.
Hey, this is all a part of having a blast!

[HBjet]

Originally posted by GasTurbine:
Sorry if the truth hurts...but rudders do in fact create more drag, and affect top speed. How can you even argue it doesnt? Do you just think that you can stick anything into the water from your boat, and it wont slow it down? Tell us HB...if your sure a large rudder wont affect top end...where is the line drawn? Can I still go 150 if I leave my trailer attached to the bottom of the boat?
I'm still wondering if your 40mph test was with the rudder on, and then off the boat. Seeing a 1 mph increase the second time around, also with less fuel on board....hmmm? was it really the rudder removed that gave that 1 mph increase?
Let me ask you this, can you feel a 1 mph increase by the seat of your pants?
I agree a rudder creates drag, but your not going to notice a difference. A trailer, yes. But something a half inch wide which is rounded in the front, come on!
So if your cruising at 30mph and you stick your hand in the water (finger deep), making a rudder, will your GPS show a decrease of 1mph? Will the boat start to turn left?
Do you think we should remove the fins from each side of the intake because we can get another 1-2 mph faster?
I understand you saw a difference, but what were the variables? Water conditions? Did you run a few tests with, and then with out, our just one weekend with, and then the next without? Different air temps will effect on your motors performance, maybe you went a little faster because of the temp outside?
Do you see what I'm getting at? I would like to know what type of boats you conducted these tests on, and water conditions? Thanks
HBjet
[This message has been edited by HBjet (edited June 05, 2002).]

[ChetCapoli]

Originally posted by GasTurbine:
Im not going to individualy list the hundreds of tests we have performed on jets boat from 1968.
Sounds like the guy has done his homework here HB....why question it? Sorry if your man told you different but like you said "what works for one wont necessarily work for another"
Chet

[HBjet]

Problem solved!
Here is a pic of GasTurbine's ride. Apparenty we are talking about 2 different types of Jet Boats.
http://home.columbus.rr.com/n8wct/mvc-915f.jpg
HBjet

[GasTurbine]

[QUOTE]Originally posted by HBjet:
I'm still wondering if your 40mph test was with the rudder on, and then off the boat. Seeing a 1 mph increase the second time around, also with less fuel on board....hmmm? was it really the rudder removed that gave that 1 mph increase?[b]
Our sets started using our salom course. We would make a few passes each way with the rudder on...then off. We would average our times and log them. We would then do the same test...this time with the rudder off...then on.
We would do these "sets" over many days. After ample data was recorded, we would consider that "test" complete. We then would repeat these "tests" on different boats.
[b]Let me ask you this, can you feel a 1 mph increase by the seat of your pants? [b]
Yes...as a (retired) salom skier, I can.
[b]I agree a rudder creates drag, but your not going to [b]notice a difference.[b]
Thats were your wrong. You see HB...the coefficient of drag is not linear. For example, if the "dragging" object robbed speed of say .03% @ 40 mph...the drag would increase to 8% @ 120 mph.
[b] A trailer, yes. But something a half inch wide which is rounded in the front, come on![b]
My dog can tell the difference in 4 mph at top speed. http://free.***boat.net/ubb/smile.gif
[b]So if your cruising at 30mph and you stick your hand in the water (finger deep), making a rudder, will your GPS show a decrease of 1mph?[b]
Probably not at the GPSR level, but you have in fact slowed the vessle.
[b] Will the boat start to turn left?[b]
Depends on where you stuck your finger in at.
[b]Do you think we should remove the fins from each side of the intake because we can get another 1-2 mph faster?[b]
We did research in that area too. Those fins make the pump more eficient, thus canceling any drag issues. We did find however that "loader" scoops help the pump at low speeds, but effected top end drasticly.
[b]I understand you saw a difference, but what were the variables? Water conditions? Did you run a few tests with, and then with out, our just one weekend with, and then the next without? Different air temps will effect on your motors performance, maybe you went a little faster because of the temp outside?[b]
See above. The *only* varible was the rudder.
[b]Do you see what I'm getting at? I would like to know what type of boats you conducted these tests on, and water conditions? Thanks[b]
Do you see what Im getting at? Your across the board statment that no one would notice any performance changes by removing a rudder is wrong.
The boats? Sheesh...the first was a 1968 19' Rogers with a High-Power Hemi/GM 6-71 blower/Berk AA...the last is a 2001 22' Rogers with a GM 454/dual Whipple blower/Berk AA.
While these two happen to be similar, we have had/tested no less 12 in between.

[GasTurbine]

Originally posted by HBjet:
Problem solved!
Here is a pic of GasTurbine's ride. Apparenty we are talking about 2 different types of Jet Boats.
HBjet
No sorry...Im talking about jet-drive boats...Berkeleys, Jacuzzis, etc.
In addition to the turbine boat, we currently have a Rogers 454/Berkeley and a Cheetah 460/Berkeley.
[This message has been edited by GasTurbine (edited June 06, 2002).]

[Unchained]

[QUOTE]Originally posted by GasTurbine:
We did find however that "loader" scoops help the pump at low speeds, but effected top end drasticly.
Gas Turbine, I'm not here to argue as it seems like you have done a great deal of research, but explain your statement above. How did the loader scoop affect the top end drastically? In your testing was the loader a large drag because it scooped more water then the pump could use?
Mark

[GasTurbine]

Originally posted by Unchained:
[QUOTE]Originally posted by GasTurbine:
We did find however that "loader" scoops help the pump at low speeds, but effected top end drasticly.
Gas Turbine, I'm not here to argue as it seems like you have done a great deal of research, but explain your statement above. How did the loader scoop affect the top end drastically? In your testing was the loader a large drag because it scooped more water then the pump could use?
Mark
It only came into play at speeds over 90 mph, so it wont concern most who arent into triple digits. Were not exactly sure why...we believe the scoop created a high-pressure "eddie" in front of it, and a partial vacuum behind it. This was enough to disrupt the intake "flow", if you will, towards the back of the grate.
In our Hemi, we noticed better mid range (30-90) performance/acceleration, and then it stated to slack off. Our top end was 122 without, and 116 with. And yes...testing was done in multiple, reversing passes...starting with, one day, and without on another.
So, to clarify my statement, I would recommend a loader to anybody not at triple digits. It seems the drag issue is moot, as the "loading" benifits (to performance) cancel the increased drag.
Did you know that even painting a hull can hurt top end as well?
Worm can #3 now open. http://free.***boat.net/ubb/smile.gif