80 MPH 21 hydro

[Grimracer]

Guys,
One more thing:

I see several discounting an idea because the gains are "minimal". Let's not forget that this thread is focused on the 21 class. The overal power at our disposal is minimal at best. Even though the output of the average 21 engine has nearly doubled in the last couple years, a 21 is still not a powerhouse by any stretch of the imagination.

Thanks. Brad.

Titan Racing Components

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Tubes are not going to be the answer to the boat being able to race at 80mph.. we all agree to this.. if I was going to go hunt down 80mph heat speeds this would be about 8 th on my list of 10 things to try.

Round is not a bad thing.. if you say that airfoil tubes will not dictate the pitch of the boat at speed i think you are mistaken. Between the two tubes on a 21 boat you could easily add 20+ square inches of lift/drag or whatever. get the boat out of shape and have that working against you...you have problems.. Note: A hydro(as we know it in its current forum) will get out of shape. My thoughts are all will.

Grim

 

[DJT]

Lets get rid of the rudder and steer with the sponsons, front would most likely work better than the rear.

 

[Dale0]

If you were to use two smaller tubes instead of one larger tube, the drag will be reduced more than half, and creat no more lift.

 

[Heartbeat]

If what Brad is saying is correct, Has anybody come up with a one tube design?

Just a thought

Mike

 

[izitbrokeyet?]

Thanks for a Great constructive post guys:

I don’t claim to know squat about riggers (probably never will :blink: ) but I do have experience in other types of systems that needed improvement. I’m thinking that there are two ways of going about it:

1.) Refinements in existing design

2.) “Out of the box” or paradigm shift changes

(Notwithstanding motor advancements) Given that small incremental advances will effectively add up to something significant.

The refinements in design would be items like the cleaning up the air behind the spoons/ shoes, boom tubes, tub etc.. And the paradigm shift would be steerable (sp) sponsons, aero turn fins.

Anyways…cool stuff

thanks again for another constructive post,

kb

 

[AWaddle322]

As some of you know i have always had a full sized boat. I recently got a new to me boat and a friend of mine has a boat just like mine (same year, same model, same manufacure) with one major difference mine has twins and his is a single. Just by chance we have both run our across the scales and mine with 1/2 tank of fuel weighs about the same as his with a full tank of fuel. Mine also has considerable lighter heads and intake and exhaust system (almost 800 pounds when you take it per motor and double it. I have 830 horspepwoer between the two motors and he has 500 horsepower with 1 motor.

With the boats close to equal in weight (72 pounds difference) and using the same prop (we used one of mine) and the lower units being geared the same. We also wierd a tachs direct and used them as hand held units to verify and validate this test. His boat is 9.3 mph faster at the same rpm (4700 rpm). Both test invoved each of us driving each othe boats and using the same gps for speed and we trimmed both for maximum speed. What this tell me is that maybe aerodynamics is not as important as hydrodynamics (you may be looking at the wrong side of the boat) as the only thing that is really different is that I have one extra drive and one extra prop in the water. Keep in mind that he has more horsepower and torque per prop but we are not extracting all we can from these motors at 4700 rpm with the same gear ratio and same prop. You would think that 2 props would reduce your slip factor but it does no due to the hyronamics of the extra drive and prop. Something also worth mentioning is we changed the weight of both boats (by adding people and for every 250 pounds we added we lost 0.1 mph.

Brad you stated that you did not feel that we could change hydro dynamics that we are using and i sum what agree but do believe there is things that could be inproved.

examples:

Strut- does it really have to be so much bigget than the size of the flexshaft?

rudder - some of the gas guys have gone to to knife blades. why do nitro guys use rudder that are up to 3/16 of an inch at the trailing edge? I saw Andy Brown try air rudder instead of a water rudder. I don't really rember the results but is fair to assume that we might have to make some changes to the aerodynamic part of the boat to make this work.

turn fins - in the real boats cats go as fast and turn as hard as hydro and they dont use a trun fin. How could this be incorporated. Also when you curl a turn fin you effectively make more of the leading edge make more contact with water. What would it take to make rigger turn as well with a smaller and littler turn fin?

water pick ups- there are very few boats that you don't see the water chocked of some how. why not make the hydro drag less by using smaller water pick ups.

ther is no doubt that hydro dynamics are much more important than areodynamics in my opinon. Next time you are your retrieve boat stick your hand in the water andtry to hold it there and then when you leave the pond stick your hand out the window and it will take considerable more strength to hold it the water.

The next major advance we will see in rigger racing will either come from motors

(fuel injection) or someone that takes the time to figure out what aerodynamic changes they have to make to have less hydro dynamic drag.

Brad one more thing to think about: Top speed has absolutly nothing to due with lap times and lap times is what wins races. Sometimes you have to slow down to go faster and this took me a long long long time to learn.

IT IS ALL A BALANCING ACT!!!!!!!!!!!!!!!!!!!!!!!!!!!

Allen Waddle

 

[Joe_Knesek]

Allen, I think you are on the right track. One thing I noticed this year is the baots that are running in the 70's are running smaller rudders and struts than we have on our boats. What I mean is they have less mass in the water because the blade is thinner and the strut is slimmer. Maybe reducing the hub diameter on the prop and going to a smaller drive dog would also help. The sponsons on my new boat have less wetted surface than my Extreme which was a 70 MPH boat.

Getting the motor to RPM is also key. All of the quick boats are turning a ton of R's. You can't expect a 20 motor to torque a boat around the pond.

 

[Brad Christy]

Allen,

It's not that I'm discounting the need for minimal hydrodynamic drag. It's just that I think a well designed outrigger is basically at minimal hydrodynamic drag already. Yes, we could go to a strut with a smaller cross section, but would it really do anything. Under normal running condition, it's well out of the water anyway. You mentioned a smaller turnfin. You also mentioned lap times. You wanting your cake and you want to eat it, too, eh? We both know what a good turnfin will do for an outriggers turn radius and speed through the turns. I'm pretty sure if Stu could minimize his turn fin without compromising the turning behavior, he already would have. As for the rudder and water pick-up, it has been shown that there is virtually no difference in performance between a rudder pick-up and a blade rudder with a "prop spray" water pick-up. The decreased drag awarded by the ultra thin blade is traded for drag created by the water blasting off the prop and hitting a brass tube positioned right in the prop stream. A thinner rudder is definitely a plus, and I am currently seeking a means to that end. News for this accomplishment (when it happens, if ever) will show up in the for sale section.

Personally, I think the key to an 80 MPH 21 hydro is in the balance of lift and downforce. When someone gets a boat set up to where it is at an absolute neutral position, it will run 80 if full heat race trim. Again, this is where the Crapshooter seem to shine. What I've seen, for the most part, are boat that is TOO stable (too much downforce) or too light (too much lift). Sometimes, there is a requirement transition, where a boat will need to shed some lift or downforce at a certain speed in order to go any faster. If this is where we are at, this barrier may stand for a while, or, like Mike Z says, maybe, it's time to step outside the box.

Most well built 21 riggers with "strong" engines are nearly at a 1:1 HP/lb ratio. If the full sized hydros (not the UL's) could do this, they would be racing a 200+MPH and they would all be outriggers, not airtrap hulls.

Thanks. Brad.

Titan Racing Components

 

[Ron Jefferson]

Although I appreciate the need for speed. I find it useless to focus solely on MPH. Running 80 in heat race trim with a .21 boat isn't a big deal if you're not concerned with it staying together or handling true race conditions we deal with each and every weekend.

If we want to mix both straightaway with oval racing it's going to take more than thinking out of the box. I myself have taken a different approach and have been more than satisfied with the results.

I've had my fair share of fast boats. Some good, some not, but only a few that I would consider spectacular. I want a boat that allows me to make mistakes. One that if you don't remember to poke out of the throttle at the end of the straight to make it go around the turn. It will still make it without barrel rolling and ripping off the pipe. Been there, done that.

I'm more interested in the complete package. One that's not only fast (not always the fastest) but can run in all conditions, turns and goes where ever you want it. One that can pull a move on someone that gives you a hole that knowone else can fill. One that you don't always have to be concerned about someone elses wake. A real champion fighter that can take a punch, I guess...

Don't get me wrong. I'm always searching for more speed. Setting the bar higher is always the challenge. Being able to beat the elements is reality.

And, don't give me that "8mph to make a legal pass" crap. That's only on the outside of a boat that's not upside down.

Ron

 

[Don Templeton]

Just a question but didn't I see pictures of Andy's record setting 120mph+ boat with four smaller tubes going to each sponson rather than two larger ones? Two back to back in the front and another two back to back in the rear. If so wouldn't that be a pretty good idea on a 20 boat also?

Don B)

 

[EatMyShortsRacing]

Hi Brad

Im not convinced that boats can or can not..maybe just at this point in time it could be a tough achievement. What is holding us back.

In my mind its hull design.. the current hydro designs have way out lived there design potential. Some refuse to see into the future and the design the next purpose built hull.. Lets lose the thought of what a "Hydro" looks like for a moment and focus on what we dont know.. This is what i do for a living and its not all that hard if you allow your mind to think this way.

Materials and motors are not the issue. None of these have much to do with heat racing speeds.. I mean by that that we know the faster we go the lighter and stronger the hull must be.. the motor must be strong and the pipe blaha blaha..

Its the hull design.. its the hull design..

Grim

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Hmmmmm how about in one other crucial area.... DRIVETRAIN?????? As long as you use a full length flex shaft how much power (and more specifically as a % of the total power available) is being lost in the drivetrain????

Mark I dont know if you had a good look at my 21 hydro last year at Detroit but if you did you know where I am going with this....

EMS Racing to go ahead sometimes you have to go back

 

[Don Templeton]

Are you saying you used a solid shaft direct drive or with a universal at the bottom? <_<

 

[TimD]

A solid shaft would be more efficient BUT it's all the other stuff needed with the solid shaft that causes headaches. Craig's boat uses a combination of flex, straight shaft and gear drive.... really unique

I'm curious to know what Grimracer is thinking about tub design - how about it Mike - whats on your mind?

This could be one of the most productive threads ever seen if it keeps going - good call Brad!

 

[TimD]

General question.

Are the current 21 riggers too small now dimensionally to be good allround heat racers? Do we need to start making them a little bit larger for different water conditions?

Tim.

 

[EatMyShortsRacing]

General question.Are the current 21 riggers too small now dimensionally to be good allround heat racers? Do we need to start making them a little bit larger for different water conditions?

Tim.

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Tim I remember when Tony R was making Stingers we built a 45 boat that was significantly faster than any of the other Stinger boats. Only one was built and it was ballistic (on its own)!!!! Never went into production because it couldnt win against the original Stinger 45. We staged 15 5 lap heats with 3 original 45s and this one new one. It never won a heat. The drive was shared between the four of us and the best it finished was 3rd. The fastest boat is not necessarily going to win the race.

2 problems we found:

More pace means less maneuverability - if someone left a gap underneath them in the corners it was invariably too late to take advantage of it because the boat would be out of position or going too fast to safely navigate that kind of gap. Always found ourselves on the outside of the course and usually out 3 deep because the more maneuverable boats nailed the start and hugged the first turn. Need a lot of pace to overcome a good boat on lane 1.

Also the driving had to be a lot smoother or this boat was over in a flash. The faster you go the less forgiving the boat will be.

Don,

Yes the stub shaft is about 9" long on a 1 degree angle with a 5" flex drive connecting to the gear drive (already lowered the drive point with the gear drive as well). Actually works out well because the engine also has an exhaust throttle so it all fits together nicely. Have ideas now for a new tub and lighter gear drive unit.

EMS Racing If its strange, I have it

 

[Watercadet]

The refinements in design would be items like the cleaning up the air behind the spoons/ shoes, boom tubes, tub etc.. And the paradigm shift would be steerable (sp) sponsons, aero turn fins.

That would be sweet KB! I can just see Outlaw wings on riggers

I have 830 horspepwoer between the two motors and he has 500 horsepower with 1 motor.With the boats close to equal in weight (72 pounds difference) and using the same prop (we used one of mine) and the lower units being geared the same.

Allan- why the heck would you use the same prop and Gear Ratios if you have 330 more HP??? That is an intersesting point that weight has an effect. I just can't see waisting all that power?

Adam

 

[AWaddle322]

Allan- why the heck would you use the same prop and Gear Ratios if you have 330 more HP??? That is an intersesting point that weight has an effect. I just can't see waisting all that power?

Adam

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When it was all said and done this was the best prop for my boat. My buddies boat couldn't turn this prop any faster than 4700 and i can turn them to about 5400. This is why we used 4700 rpm. And what this test was all about was trying to figure out the difference between singles and twins and the same boat. Twins have certain advantages (better ride in ruff water and easier docking , better handling at slow speed and a little extra piece of mind about getting home) and the singles has it advantages to (better fuel milage and faster top speed). The twin also has an advatage of a lot more acceleration.

The whole reason for this was to figure out how much haveing and extra drive and prop in the water actually hurt and to find out that 330 horsepower was not enough to overcome this. Even when he is proppoed his best and I am prooped my best I am still considerably slower (5 Mph) but I get there twice as fast.

The single engine boat chine walks badly making my boat kinda boring to drive if driving aboat in excess of 80 MPH can be boring.

Allen

 

[bzubee]

One of the changes the Fast electric guys have done is use music wire for the drive shaft, Octura even has a special part to adapt to the stub shaft. If you look at Submarine technology they worked with the propeller and other ways to streamline the hulls to pick up the speeds.

 

[Ron Zaker Jr]

Some really good stuff here,keep it coming.Here is a short story.My Dad was racing his 20 Hawk and cut inside bouy one and broke the outside sponson and carbon tubes clean off flush with the hull(second lap of the race). The boat finished the heat and was absolutely faster than ever(2-3 mph gain). He obviously could not let off,but this really makes you think "outside of the box". Some of the people on this board witnessed this,(Lambs Farm race) true story.

Ron Jr

 

[Tom v.d Brink]

faster than ever(2-3 mph gain

very interesting thoughts came up in my head reading this

but i just wanted to check one thing before i get into my maths

was it measured to be quicker or was the adrenalin flowing hard and

made the thought it was quicker?