3.5 Tunnel SAW record

[CySlyde]

wow.. after finishing reading that I wish I had kept up from the beginning...

just as a comment, i know this was solved, but for those of you who mentioned a radius was a fix to a bad design.. wouldn't stumble blocks be a fix to a poor design too?

also would there be any benifit to using composits over wood in the building of a SAW tunnel?

maybe this thread should be renamed to tunnel design theory and practice

 

[izitbrokeyet?]

Yo Cy,

One of my tunnel designs had stumble blocks added to get rid of a tripping habbit. No doubt, I added them to fix a design related problem I was having. The stumble blocks I added were a crutch to compensate for lack of frontal area in the sponson.

The best tunnel hull I have ever driven (the Magnum) has stumble blocks incorporated into the design. I suspect they are there are not there to correct a problem; More so, I think they are there to capitalize on the Bernoulli Principal which makes it stick it to the water in the turns. That boat turns on rails

I guess what I’m saying is that the stumble blocks are a legitimate feature that can be there to fix a problem, or as a planned part of the tunnels’ design.

Regarding Composites Vs. Wood:

My current thinking is that with modern motors, the power is there to go plenty fast. My strive for a light boat has resulted in one thing ……lots of fly-offs and lots of repair. In my own mind I blame this on the aerodynamic lift associated with higher speeds. After lots of tries, I have not found a way to moderate the tunnel lift (faster boat=more tunnel lift) If I decide to go saw again, I’ll shoot for a stout 5.5 -6.0 lb hull with very little dead rise and lots of power.

 

[Geraghty]

Kevin,

I can see your light has gone on.You have figured it out.

When you combine the blocks with Bernoulli,now you have a boat that anybody can set-up and turn with speed.All steering inputs are linear and predictable and the boat won't do anything stupid.

Now you can loosen up the boat set-up and start to drive with the throttle.Thats when it gets real fun.

Rod Geraghty

 

[Grimracer]

Yo Cy,One of my tunnel designs had stumble blocks added to get rid of a tripping habbit. No doubt, I added them to fix a design related problem I was having. The stumble blocks I added were a crutch to compensate for lack of frontal area in the sponson.

The best tunnel hull I have ever driven (the Magnum) has stumble blocks incorporated into the design. I suspect they are there are not there to correct a problem; More so, I think they are there to capitalize on the Bernoulli Principal which makes it stick it to the water in the turns. That boat turns on rails

I guess what I’m saying is that the stumble blocks are a legitimate feature that can be there to fix a problem, or as a planned part of the tunnels’ design.

Regarding Composites Vs. Wood:

My current thinking is that with modern motors, the power is there to go plenty fast. My strive for a light boat has resulted in one thing ……lots of fly-offs and lots of repair. In my own mind I blame this on the aerodynamic lift associated with higher speeds. After lots of tries, I have not found a way to moderate the tunnel lift (faster boat=more tunnel lift) If I decide to go saw again, I’ll shoot for a stout 5.5 -6.0 lb hull with very little dead rise and lots of power.

Isit,

I doubt that stumble block were added way back when to help the boat grab in the corner as you have such mentioned. More so back in the early days the boats would turn with a turn fin but as dead rise begin to increase to get rid of the turn fin (lifting little guy) a new problem can in to play.. “suck under”.. (I have no name for this maybe Rod can help here)..LOL..

Suck under (or whatever you call it) is ugly Bernoulli waving the flag saying “Im back”.. or as it is, the boat over steering or even stuffing as it goes around the corner.. however cant angle has a bit to do with this too..

The stumble block is there to control the turning depth of the front of the boat, only allowing so much sponson in the water as the boat turns. Does Bernoulli come in to play.. heck yea.. Just round off the edges of the stumble blocks and go play boats..

Skip a round stone for me MR. Bernoulli..

Rod is really the master at this stuff..

I leand…larend….learned all I does no from Mr G, and, mister pond the water dyno.. :blink:

ROCK ON

Grim

 

[CySlyde]

I wasn't talking about using the composites to make the boat lighter. sorry didn't mean to mislead you, I was just wondering if there was an advantage structually (sp) of using a composit over wood.

 

[Grimracer]

Next:

I have a lot of guys that are convinced that stumble blocks are causing there boats to blow off..

Hog wash Arnold.. It’s a poor design or poor set up or over powering mind to finger that causes a boat to blow off..(just to name a few of them)

O so apposite mr. tunnel boat racer. What happens as you pinch the air as it travels through the tunnel? O yea.. it speeds up…Hum.”thinking” then what…?

I think your catching on…

Grim

 

[Slideblues]

Cy, the way I think about it is the use of composites is to increase the density of the structure with out increasing the size or thickness. Woven fibers are more tear resistant and offer better shear strength than a grained wood.

Gene

 

[shoboat]

Gene,

I see now,when you are going 60+ MPH you need the SHEAR STRENGTH

and the TEAR RESISTANCE so the boat doesn't come apart :lol: :lol: :lol: .

Just a little humor Gene.

Thanks,

Mark Sholund

 

[Slideblues]

:lol: Hey Mark, yes thats a definite plus

Handy when you drive like I do,

He,He,

Gene

 

[Terry Keeley]

I wasn't talking about using the composites to make the boat lighter.  sorry didn't mean to mislead you, I was just wondering if there was an advantage structually (sp) of using a composit over wood.

Interesting thread, even for a "non O/B guy". :blink: Good to hear from you Tommy, maybe see ya this November!

I built a couple hydro tubs with CF 6 years ago and they still look good as new. The problem I had with that "naturally occuring cellulose product" was by the time I got a hull worked out it was all stress cracked and oil soaked. :unsure: With carbon you can build lighter than wood but end up much stronger and stiffer...

 

[Bob Kensill]

Mark

Are you going to the Flint record trials? Maybe you will have some props or pointers for me.

Bob

 

[shoboat]

Bob,

I do believe I will be down for that one, as a few of my BEST CUSTOMERS

will be there. What other props would you like me to bring if any?

Thanks,

Mark Sholund

 

[Bob Kensill]

Maybe one of those reworked h4 or a propshop 4213 that you were talking about.

 

[shoboat]

Bob,

Will do! Now back to work in the Prop Shop :lol: :lol: :lol:

Thanks,

Mark Sholund

 

[Bob Kensill]

I hate to show my hand (rpm) but I figure I need somewhere between 2.8 and 3.0 inches of pitch to get the job done.

 

[shoboat]

Bob,

With those numbers, here are your figures: Pitch 3.0" = 28,988 RPM at 70 MPH.

And Pitch 2.8" = 28,840 RPM at 65 MPH.

Those are some PRETTY STOUT numbers BOB! I'm sure with your setup that

will be attainable though. You will just need help from MOTHER NATURE.

Thanks,

Mark Sholund

 

[Bob Kensill]

Best rpm to date has been just a touch over 32,000. It just about makes your bones hurt.....lol.

 

[shoboat]

Bob,

If that is the case then 3.0" will be 77.30 MPH and 2.8" will be 72.10 MPH.

I would like to witness that kind of RPM in person. Even 30,000 RPM would

put up some impressive numbers: @2.8"= 67.60 MPH and @3.0"= 72.40MPH.

What is the record at? 60+MPH Right?

Thanks,

Mark Sholund

 

[TimD]

And Pitch 2.8" = 28,840 RPM at 65 MPH.

KB,

Are you reading this? Does that rpm figure sound familiar bud?

Tim.

 

[izitbrokeyet?]

yeppers