Any fellow hydro design enthusiasts out there?

[drbyrne55]

Always interesting to chat design.

With a tunnel in CSH, remember you have to measure your 3/4" min prop shaft height from the lowest planing surface even if it were on the chine like some Euro designs. Airtraps can be something like 7/8" wide and not be considered a planing surface if they serve the purpose of trapping air.

The 3/4" rule in CSH seems to have started a design shift. Some current designs were better suited for the rule. I am seeing design tweaks out there and expect to see more this year... and the trend will not be narrowing the boats. It comes down to water drag vs air drag, set up and pumping a Yamato, or maybe newly designed props.

Changing boat design and set up is very time consuming. Our OSY team spent the entire 2008 season trying to figure out an optimal safe OSY400 set up with turn fin tuning the big time burner but significant advancement. We spent each 2010 pre-nationals race testing one different CSH "change/variable" and finally found a fairly "raceable" compromise. We figure we are 70% complete but further testing needed with turn fin and "engine set up". If you do a you tube search you can find some very good CSH's running and can compare their running characteristics. Some are virtually the same boat but look how different they run.

Video1 lane 4 to 1; B/H, MRC, MJR, McCourtney..... lane 12 Oberto

http://www.youtube.com/watch?v=i5QXL...eature=related

Video2 B/H and Runnecraft out front here

http://www.youtube.com/watch?v=oPBI3tDyzmI

Smokin Joe in his older B/H and 102 .... Smokin the key word. Probably safe to say Joe is the only one in the country seeing 70 MPH racing CSH.

[mdaspit]

turn fin tuning the big time burner but significant advancement.

Wow, so many questions here, so I'll go at it one at a time.

Do I understand this correctly?

Tuning the turn fin has taken you the most time, and has given you significant result?

[Sonny]

A great discussion, good thread. Bill Nailed it. Well spoken. While we are on the topic of aircraft technology the new A10 airbus features a "Dimple tape" or what is basically golf ball dimples placed strategically around the exterior of the plane. Rumor is...the reason that a golf ball fly's straight is because or the turbulence caused by these dimples. Has anyone tried this? anyone willing to share?

[blueskyracer]

A great discussion, good thread. Bill Nailed it. Well spoken. While we are on the topic of aircraft technology the new A10 airbus features a "Dimple tape" or what is basically golf ball dimples placed strategically around the exterior of the plane. Rumor is...the reason that a golf ball fly's straight is because or the turbulence caused by these dimples. Has anyone tried this? anyone willing to share?

I know there is a thread around here about dimpling the bottom and I will keep looking for it. I remember it talked also about graphite bottom and all kinds of stuff but it all had to do with running surfaces. Folks all said it was the way to go but I have yet to see one with a dimpled bottom unless it was the onset of wood rot!!

[sam]

Sonny you should call Big Dave Augustine about the golf ball dimples. When he was doing patent research, a major client of theirs was a golf ball maker. Dave knows more about golf balls than just about anyone on the planet.

[Sonny]

Wow, so many questions here, so I'll go at it one at a time.

Do I understand this correctly?

Tuning the turn fin has taken you the most time, and has given you significant result?

We saw some pretty good improvement with some turn fin work also. Too thick, too thin, too much, not enough...The key statement that Brian made was turn fin vs engine setup. Get greedy with the setup and stingy with the fin because you don't want to drag it down the straightaway and you could catch yourself a life altering accident. That's what got me. I entered the corner with the fin out of the water and had to overturn to compensate. When that fin touched the water I got myself one hell of an education on the turn fin.

[Sonny]

Sonny you should call Big Dave Augustine about the golf ball dimples. When he was doing patent research, a major client of theirs was a golf ball maker. Dave knows more about golf balls than just about anyone on the planet.

Now there is a guy that I really enjoy. Dave lol Dave's a good egg. That's perfect I haven't talked to Dave in a while I should give him a call. Thanks Sam

[drbyrne55]

A great discussion, good thread. Bill Nailed it. Well spoken. While we are on the topic of aircraft technology the new A10 airbus features a "Dimple tape" or what is basically golf ball dimples placed strategically around the exterior of the plane. Rumor is...the reason that a golf ball fly's straight is because or the turbulence caused by these dimples. Has anyone tried this? anyone willing to share?

I think the tape is about $20,000 ??? a roll, they (3M I believe) did not want to sell me 20 feet.

We have 2 different turn fin set ups, basically under a mile or over a mile and has reduced lap times for us. "Drivability", John says. His ability to decipher "details" at 70mph and relate it to handling is quite amazing.

[ZUL8TR]

golf balls and drag .......

A great discussion, good thread. Bill Nailed it. Well spoken. While we are on the topic of aircraft technology the new A10 airbus features a "Dimple tape" or what is basically golf ball dimples placed strategically around the exterior of the plane. Rumor is...the reason that a golf ball fly's straight is because or the turbulence caused by these dimples. Has anyone tried this? anyone willing to share?

The dimples on the golf ball reduce the total drag and allows the ball to fly farther. The drag is reduced due to the turbulence created by the dimples that reduces the size of dead air (wake) behind the ball. Dimple designers shoot for the place on the drag (Cd) vs velocity (Reynolds #) curve where the Cd is the least. Note the plot in this article where the curves dip to a low point.

http://www.grc.nasa.gov/WWW/K-12/air...ragsphere.html

Recreating this reduced drag effect with dimples on a flat surface draged over water at an angle of attack is a totally different dynamic and I do not know of any research of dimpled surfaces on a flat surface at an angle of attach to the water. But some amount of roughness on the bottom would prove benificial as I have noticed on the hydro I ran. Much trial and error and time would be required to determine the results of all the variables.

[Aussie Steve]

Thread

I know there is a thread around here about dimpling the bottom and I will keep looking for it. I remember it talked also about graphite bottom and all kinds of stuff but it all had to do with running surfaces. Folks all said it was the way to go but I have yet to see one with a dimpled bottom unless it was the onset of wood rot!!

I believe it was covered in this one Mike .

http://www.hydroracer.net/forums/showthread.php?t=18557

[Fear the Duck]

With a wider boat, a wider tunnel is almost necessitated. With more trapped air, could a wide C Stock hydro overcome the increased drag? On that note, I'm not entirely familiar with the differences in handling caused by running shorter or longer air traps. Is it simply a trade-off of maneuverability and stability (short traps) for speed (long or full-length traps)?

[B Walker]

Wow, so many questions here, so I'll go at it one at a time.

Do I understand this correctly?

Tuning the turn fin has taken you the most time, and has given you significant result?

Yes. I did not know the Byrnes had spent so much time on them but I have a stack of failed side fins for my CSR over a foot high. I would put the design I have finally settled on up against anyones.

Tip: find the smallest fin that will do the job straight down and squared off (standard fin) measure that blade area below the bottom of the boat and make a variety of different shapes with the same blade area. Look at surfboard and waterski fins for inspiration.

You want the fin to gradually catch and not slam the boat down when engaged. But at the same time be able to use your body weight to pull it out of the water if you need to (finesse). It is a very fine line.

In my opinion the side fin is one of the most overlooked areas on a boat, yet can have significant impact on lap times.

BW

[mdaspit]

We saw some pretty good improvement with some turn fin work also. Too thick, too thin, too much, not enough...The key statement that Brian made was turn fin vs engine setup. Get greedy with the setup and stingy with the fin because you don't want to drag it .

What do you mean by a greedy engine set up?
I assume you mean more "radical", but what would be an example of that?

[blueskyracer]

All I am going to say is after last year, tunnel width and air trap depth play a major major part in how well you can keep the boat flying over the water. The right combination takes a lot of work right Byrne brothers but it does pay off.

[mdaspit]

You want the fin to gradually catch and not slam the boat down when engaged. But at the same time be able to use your body weight to pull it out of the water if you need to (finesse). It is a very fine line.

In my opinion the side fin is one of the most overlooked areas on a boat, yet can have significant impact on lap times.

BW

I had no idea, Use your body weight to pull it out of the water?
Can you tell me about that?