80 MPH 21 hydro

Guys,

Since everybody is convinced that a 21 hydro can't run 80+ MPH in heat race trim, I curious as to why not. Are the engines just not strong enough? Is it the props? Is it that the hulls, being so light, won't handle the speed? Or is it that the guys who HAVE done it (and it has been done, repeatedly) haven't told the rest of us how they did it?

If it is the engines, it is only a matter of time until it is commonplace. In the mid to late 70's the open hydro class SAW record was somewhere in the low 70's (this was before my time, so I'm not sure of the dates or exact speeds). Now it is over 120 MPH and the 45 hydros are in the racing in the high 80's.

Has the right prop not been designed yet? I think it has. If you do the math for an Octura 1650 or ABC 1718, the theoretical speed potential is well into the eighties. With the 1650 at 30K RPM, you're looking at nearly 90 MPH. Now, I know you have to account for pitch slip, but the faster a hydro is traveling, the more efficient a prop gets due to the virtual lact of hydrodynamic drag.

Is a 21 outrigger too light to stay on the water at these speeds? I can't see how this is logical, since the SAW record is nearly 100 MPH. I know that this boat will not heat race worth a darn in the configuration it set this record with. Still, it shows that the proper balance of lift and downforce CAN be achieved to let the boat break free of the water but not let loose and go hurling through the air.

I feel that this is not only possible, but not that difficult. Just because something has not yet been done (which is not the case in this instance), does not mean that it cannot be done. JFK once said that we would not only put a man on the moon, but it would be done "In our lifetime", and most laughed at even the possibility.

Can of worms? You bet. Let'm loose.........

Thanks. Brad.

Titan Racing Components

How about we tackle all boats heat racing at 70, first.. Didn't see that at the Internats.. Heat racing and finishing..

CHowarth said:

How about we tackle all boats heat racing at 70, first..  Didn't see that at the Internats.. Heat racing and finishing..

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The water conditions @ the Nats prohibited speeds. That pond was by far the roughest pond I've raced @ all year. Coupled with hot temps, it's just not a good way to make speed.

There aren't many boats of any size that race at a consistant 80mph much less a 21. Before I gone further, yeh I know many of you have been clocked going much faster. So have I. But are you racing at these speeds? Most aren't. I'm not. Be real.

So with that out of the way, the fast 21 guys have said all along that you only go as fast as you need to go. Not even the guys runinng in the high 70's can run 6 laps at that speed. Not in a real race, 5+ boats I guess with not all being top performers, just an average race. Most of the speedy winners are fast for a lap or two and the race is done for them. They just ease off the throttle and cruise for 4 to 5 laps.

Sure, there are 80mph 21's. And with that in mind, 50 years from now the heat race speeds may be well over 100mph. But not now. Boats are getting faster but for somebody to make such a leap as to go from heat race speeds of 60-70 to 80+ all-of-a-sudden is a little much to believe without seeing.

Brad,

I don't think I ever knocked your boats and if they run like the Warlok and Crapshooters then they are indeed fine boats. But when you start "boasting", for lack of a better word, then you are leading yourself to fill some big shoes.

Myself, I think it has been fun posting and reading all this 80mph 21 stuff.

I wonder if this post will break any records? :lol: :lol: :lol:

To all 20 Hydro racers,

Maybe we should tackle this as a group.Everyone has positive points from there boats and negative points that need to be improved on. Maybe take a look at the negative points holding back speed goals.

Aero ?

Weight ?

Drag ?

Construction materials ?

Just some ideas to talk about.

Ron Zaker Jr

Guys,

OH, good! I thought for sure I would get crucified for this thread. I'm glad it went the direction it did.

Preston,

I guess I didn't really state it this way, but I was really speaking of a boat that would run 80+ in full heat race trim. I think most guys are struggling to keep it over 70 during most heats because that's about as fast as it will run. If a boat will run over 80 on open water, then it will effortlessly race with five eually competitive boats at 70-75+, with plenty of throttle if/when it is needed. This is what I'm after.

BTW, I've never claimed to be running 80. I just think it IS possible with the right design/set-up. I can only HOPE that it is with one of my boats. Personally, from what I've seen in the 45 class and above, I think the Crapshooter methodology is what is going to get us there.

Ron,

What do you think is the most significant factor holding any hydro back? I would think it would be the same for any hydro, regardless of size, only more so the less power you have available to overcome it.

I think we've gotten about as much of the boat out of the water as possible without adding wings, a couple more channels and calling it a plane with a prop in the water. I was watching Stu's 45 boat at the Polar Bear race and noticed something rather interesting. Down the front stretch (the only place close enough to really see it), you could look at the water as it went by and see where the boat was actually flying, not planing. There were gaps in the propwake 40-50 feet long and the boat looked stable. The magic of the Crapshooter at work. Simply amazing.

As far as aerodynamic drag, the boom tubes have got to go. If you look at a wind tunnel model, the only way to make the air any dirtier behind a round cross-section is to put a blunt, flat surface facing the oncoming wind. If we turn it into a neutral airfoil, it suddenly cleans up and causes almost no drag. The antenna is also a major source of drag. Has anybody ever laid their antenna along the radio deck lid, or along the tub sides?

Construction materials have come a long way in the last few years. I'm sure there are other materials out there, but are they available for our application?. There are alot of guys using carbon fibre, but I don't see any significant difference in weight of the complete boat. Anyone who has gotten a new hull, be it a Crapshooter, Eagle, RoadRunner, whatever, knows that the tub weighs next to nothing, so even if you cut it's weight in half, you haven't gained (lost?) that much. Even if you do find a source of significant weight loss, have your really gained any real performance? I've seen a few 3 1/5 lb. 21 riggers that would not heat race worth a darn because they wouldn't stay on the water (and these were owned by some VERY competitive boaters). Marty Davis has always said that the ideal weight of a 21 hydro is 3 3/4 lbs. Maybe with perfect balance (lift/downforce, not weight), a much lighter boat may prove the direction to go.

Thanks. Brad.

Titan Racing Components

I think a limiting factor for heat racing is pipe design. It is soooooo critical on a 21. Good throttle response is usually sacrificed to pull a decent prop pitch at the rpm that 21's need to make power. Once you get off the throttle for whatever reason - you will struggle to get it back up on song again.

Anyone made a slipper clutch or stall converter yet?

I have often wondered if a .21 buggy clutch could be converted for marine use. And would it hold up, or do any good?

Did someone say Gear Drive?????

hehehehehe

EMS Racing geared 21 hydros a specialty

EatMyShortsRacing said:

Did someone say Gear Drive?????

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Been there - done that and seriously considering doing it again. Downside is very high CG(and I'd have to make a new tub to suit), added weight and more things in there to go wrong.

I still haven't seen that geared boat of yours Craig. Nationals?

Hi Guys

Not that I know much but -

gear drive won't be a CofG issue if the engine is layed over at say 45deg or lower. This had the added benefit of allowing the pipe to arch up over the centre of the tub (for those not using MACs).

the aero impact of sponson tubes is obvious but maybe they could be altered in angle to provide adjustable downforce trim. Could the tub be changed in shape to be more slippery?

the slipper clutch idea is fairly straight forward but whether it could cope with the load of a prop in water is a different issue. Now if you combined the slipper clutch with a geared drive advantage you might end up with the advantage of both.

just some ideas to toss around.

Gary,

you raised a few good points there. I would have never thought of the drag induced on the arial tube but you are right - it would be significant in the bigger picture.

I would think (but don't know it to be fact) that the hydrodynamic drag from the turnfin and rudder plus any "wet" running surface would be more significant than Aerodynamic drag. How do we reduce the drag from these areas??

I would also think that the flat transoms we run on the riggers is pretty poor in terms of aero.

Tim.

TimD said:

EatMyShortsRacing said:

Did someone say Gear Drive?????

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Been there - done that and seriously considering doing it again. Downside is very high CG(and I'd have to make a new tub to suit), added weight and more things in there to go wrong.

I still haven't seen that geared boat of yours Craig. Nationals?

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May have it for Mulwala..... got a couple of engines to try (just so happens I have a couple more 21s to play with (off Ebay no less!!!!) - A CMB greenhead and a Nova...)

Once I am happy with the engine I will be working on the lightweight geardrive and maybe even the MK3 Stinger 21GD. I think at least 1 Stinger 45 and a few Stinger 90s and maybe even a Twin 90 may be on the cards.

Brad Christy said:

Guys,
Since everybody is convinced that a 21 hydro can't run 80+ MPH in heat race trim, I curious as to why not.  Are the engines just not strong enough? Is it the props? Is it that the hulls, being so light, won't handle the speed? Or is it that the guys who HAVE done it (and it has been done, repeatedly) haven't told the rest of us how they did it?

If it is the engines, it is only a matter of time until it is commonplace. In the mid to late 70's  the open hydro class SAW record was somewhere in the low 70's (this was before my time, so I'm not sure of the dates or exact speeds). Now it is over 120 MPH and the 45 hydros are in the racing in the high 80's.

Has the right prop not been designed yet? I think it has. If you do the math for an Octura 1650 or ABC 1718, the theoretical speed potential is well into the eighties. With the 1650 at 30K RPM, you're looking at nearly 90 MPH. Now, I know you have to account for pitch slip, but the faster a hydro is traveling, the more efficient a prop gets due to the virtual lact of hydrodynamic drag.

Is a 21 outrigger too light to stay on the water at these speeds? I can't see how this is logical, since the SAW record is nearly 100 MPH. I know that this boat will not heat race worth a darn in the configuration it set this record with. Still, it shows that the proper balance of lift and downforce CAN be achieved to let the boat break free of the water but not let loose and go hurling through the air.

I feel that this is not only possible, but not that difficult. Just because something has not yet been done (which is not the case in this instance), does not mean that it cannot be done. JFK once said that we would not only put a man on the moon, but it would be done "In our lifetime", and most laughed at even the possibility.

Can of worms? You bet.    Let'm loose.........

Thanks. Brad.

Titan Racing Components

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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

Well we have a thread with responses instead of arguing,great first step.

Construction materials: I was thinking more along the lines of shape capabilities rather than weight reduction,but we all know lighter is better.

Flat transom being draggy? Please explain

Antenna laid down : makes sense.

Underwater drag: what can be done better?

Aero: Any aeronautical engineers on line here?

Grim,

You are right about thinking "outside the box" we do have the motors,pipes,

and PROPELLERS to go over 80 MPH,but some new ideas on design is what is

really holding us back I think. My spin on the"new design criteria" would be to

make a tub longer and lighter. If you look and racing sailboats a longer

waterline is much faster and more stable on the water. I think that the design

and the drag are the two real issues that we need to address in our new designs.

The aero drag is what is holding us back now I believe. So we will need a wind

tunnel and someone who is good with physics to give us a hand on drag

coefficients and some of the other technical jargon that we need to overcome.

Oh Yeah, By The Way, I have plenty of ABC H-7's that will go 80+ MPH in the

right design. :lol: :lol: :lol:

Anyone have access to a wind tunnel? I need some drag coefficients off my latest

design.

Just A Few Of My Ideas,

Mark Sholund

Need full-blown wing designs on the tub and on the spoons. Get the pipe INSIDE the boat.

The faster the boat goes the more lift it needs to produce, move the lift near the CG and presto a stable hull that can FLY and still not loose it composure.

Air dumps on the rear of the hull.

Look at the german SAW electric riggers... They figured out a neat way of moving the lift of the tub to where it is needed...

They used plates that are bolted to the front of the tub to move the spoons WAY forward on the hull. This inherently moves the lift vector of the tub closer to the center of the boat, which would in theory produce more stability.

The spoons also are very small and designed to reduce drag as much as possible.

The only way you are going to get to heat-race in the 80's is to be able to FLY over choppy water...

This means that the spoons must be small and that the prop should be deep enough to prevent a small ripple on the waters surface from causing a change in the boats attitude.

Narrow rear shows with multiple wetted zones (areas) might be able to accomplish this.

I also think that some type of gyro controlled front winglets may be used to increase the FLY performance when the water is not working to your advantage.

There was a thread a while back discussing the advantages of airfoil shaped boom tubes. Although nobody could prove the advantage in pratcice on a boat, an airfoil is 10x more efficient than a round tube. The guy actually had a test stand to measure the differences.

I assume that by gear drive you guys mean a 2 speed transmission. The cars are using a very clean method of 2 speed. It isn't heavy either. Just think what a 1:1 ratio increased to 1:1.1 would do.

I can't see a clutch being of benefit. By the time it stops slipping you are probbaly going to be out of the straights. The reason most can't get back on the prop is because they are using too big a prop in the first place. It took a while for it to sink into my head, but bigger isn't necessarily faster.

The biggest advantage will be in reducing drag. When that is done the current slippage of props will reduce resulting in more speed while using the same fuel, engine, pipe, prop, etc.

It does seem true that by observations of many, the Crapshooter comes the closest to floating. If this is the case then I would think that particular hull would be the starting point in trying to reduce aerodynamic drag. If the CS does float the best then it would seem that a football shaped tub is not the way to go as it will provide no lift. The general idea is that you are going to be passing through the air at a given speed and you must make the energy of the air do the work. Not the energy of the water on the sponson bottoms.

Speaking of a wind tunnel, it was told to me that these guys that just went into space strapped items to the front of a truck and went down the road and measured forces from there.

Speed,,, needs only a motor and Control. Aerodynamics and drag just get pushed further out the spectrum the bigger and badder the motor. We made a peroxide motor in University and it powered a kids converted Battery-powered jeep up to 160Mph on a lake-bed. Melted the tiresbut it got there. Just a thaught

http://www.vintagekarts.com/Rockets/mot-h2o2.jpg

Preston_Hall said:

There was a thread a while back discussing the advantages of airfoil shaped boom tubes. Although nobody could prove the advantage in pratcice on a boat, an airfoil is 10x more efficient than a round tube. The guy actually had a test stand to measure the differences.
I assume that by gear drive you guys mean a 2 speed transmission. The cars are using a very clean method of 2 speed. It isn't heavy either. Just think what a 1:1 ratio increased to 1:1.1 would do.

I can't see a clutch being of benefit. By the time it stops slipping you are probbaly going to be out of the straights. The reason most can't get back on the prop is because they are using too big a prop in the first place. It took a while for it to sink into my head, but bigger isn't necessarily faster.

The biggest advantage will be in reducing drag. When that is done the current slippage of props will reduce resulting in more speed while using the same fuel, engine, pipe, prop, etc.

It does seem true that by observations of many, the Crapshooter comes the closest to floating. If this is the case then I would think that particular hull would be the starting point in trying to reduce aerodynamic drag. If the CS does float the best then it would seem that a football shaped tub is not the way to go as it will provide no lift. The general idea is that you are going to be passing through the air at a given speed and you must make the energy of the air do the work. Not the energy of the water on the sponson bottoms.

Speaking of a wind tunnel, it was told to me that these guys that just went into space strapped items to the front of a truck and went down the road and measured forces from there.

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Agreed. But, for the most part our engines are at max. The horsepower isn't going to double and the materials won't hold up.

Control. We don't get nice flat lake beds. We get chop half the height of the boat itself.