80 MPH 21 hydro

[Slideblues]

Tom, Since the last upgrade, I could not attach a pic any size till I did my comment to Glenn, I dumped a ton of my older pics using this method,

Or I guess you could open a album in the gallery,

Gene

 

[Ron Zaker Jr]

Hey guys, back to the part of the thread talking about streamlining the booms. Here are my best guesses, I know round booms are VERY draggy (is that a word?) and that changing their shape a little can cut down on their drag a lot. BUT I don't know how much the boom drag adds to the overall drag of the boat...I have to leave that to the guys with more sophisticated testing equipment than I have to figure out. My take on the pros VS cons is that they are easy to fix, don't make the boat do anything weird and may give another mph. Back in the mid 90's I figured out a way to streamline them that is simple and light (you know how anal I am about weight) and have done it on every SAW boat since.
I simply use a piece of balsa trailing edge stock (cut the width down so the thick part is the same as the dia of the booms) and thin heat shrink tubing like is used on battery packs and heil blades.

The fairings (I don't call them wings because they are not there to provide lift) are very easy to set where you want them. I set them straight, but even if they get moved they just set themselves in position when the boat gets moving fast enough. I have used tape to hold them in one position or another, but haven't really noticed they affect the boat to much.

I have four pictures that I will try to post to help show what I mean.

Glenn

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Glenn,

Mike Z is testing sponsons somewhat like the ones on your 12 boat,what does the outside look like ?Thanks

 

[Preston_Hall]

I have wondered about putting the engine on it's side but not for the purpose of stremlining the engine/pipe but streamlining the hull. I say this because I have never witnessed a streamlined cowl making any speed improvements.

If a rear exhaust engine is on it's side (for lower profile) and the tub is made wider to enclose the entire engine and pipe you could then make the profile of the top a consistant smooth shape. Look at the electrics for example. Now with everything enclosed you could get into aerodynamics with both the top and bottom of the tub.

 

[Don Templeton]

David Lee raced a lay down 60 boat at the Indy unlimited in the early 80s. It ran really well as I remember. I talked to someone that gets on this forum once in a while who has this boat today. He was at the Hydro Masters and I think he had a scale Budwizer boat. Cant remember his name.

 

[Ron Jefferson]

Here's some pics of an 80 mph heat raing .20 hydro. It's Orlics newest carbon fibre boat. Check out the transom (or lack of) and the way the strut runs through it. A bit of a nightmare to rig and fit a tank to but inovative I think. All rounded with no sharp edges except the ride surface on the fronts. Maybe some good ideas here. I believe the boat is somewhere in the low 3lb range.

Ron

https://www.intlwaters.com/gallery/thumbnails.php?album=59

 

[Don Templeton]

Well, now that my mind is totally mush from all the great thinking and designing and speculation on this post, I have made my decision. I don't want any part of SAW. Back to the nice running little heat racer with the hope that everyone else blows off. :lol: :lol: :lol:

Don

 

[TimD]

The lack of the flat transom was something I was hinting at in an earlier post. I was surprised to see the shape of the back of the sponsons tho'.

There also seems to have been a trend of making the tubs narrower in the last few years - what are peoples thoughts on this? How wide does the tub need to be to generate sufficient lift?

Tim.

 

[GTR]

Tim I also wondered about the narrow tubs because if thin enough they will contribute nothing to the equation and would just be along for the ride. Problem with all round surfaces is that you get prasitic drag as the air tumbles over the sides of the airfoil and causes turbulance along the edges. Better to have a sheer edge - this can be demonstrated by racing cars having edge strakes on the top corners of the gurads to keep the air travelling over rather than falling down the sides. Smooth and round is not always good. I would be surprised if for the tub low and wide is not better than tall and narrow - make the tub work for us. Maybe the riggers need to get wider like the Japanese ones and improve stability. Its a possibility that if you moved the sponsons further out you won't get the aero interacting between the tub and the sponsons. Forgot to say riggers operate in what is commonly referred to as ground effect so aero stability is very important both longitudanly (sp?) and laterally.

 

[F.Orlic]

Tim I also wondered about the narrow tubs because if thin enough they will contribute nothing to the equation and would just be along for the ride.  Problem with all round surfaces is that you get prasitic drag as the air tumbles over the sides of the airfoil and causes turbulance along the edges.  Better to have a sheer edge - this can be demonstrated by racing cars having edge strakes on the top corners of the gurads to keep the air travelling over rather than falling down the sides.  Smooth and round is not always good.  I would be surprised if for the tub low and wide is not better than tall and narrow - make the tub work for us.  Maybe the riggers need to get wider like the Japanese ones and improve stability.  Its a possibility that if you moved the sponsons further out you won't get the aero interacting between the tub and the sponsons.  Forgot to say riggers operate in what is commonly referred to as ground effect so aero stability is very important both longitudanly (sp?) and laterally.

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After designing many .20 riggers over the last 12 years here is few things I have learned. Rigger don't use or want to have any part of ground effect. Ground effect is evacuating the air from underneath, lowering the pressure and causing the vacuum which will in return make it tight. This is great stuff for cars but not for us. Very narrow tub are not good either. tub has to be wide enough to provide lift for most of the weight. Narrow tub would require wider sponsons, the problem with that is that you would provide lift at the lightest part of the boat, very hard to make it stable in race conditions. Wider tub and narower sponsons are better combo. Arne Holt designer of record setting electric boat is prime example what can be done with composite materials, for as long as people build boats with wood they will look very similar, the basic design derives from 70's with very little change. I have hard time believing that heat racing boat would run without outside sponson, however we might be placing it in a wrong place. Boats with only right sponsons have been used many times in a past for record runs mostly by Russian racers.

Can a .20 boat run 80 MPH in heat racing trim, my answer is yes, can it run 80 MPH for 6 laps or even 2-3 laps with other boats around my answer is no. Few guys (very, very few, easy to count on one hand) had boats running 80 + MPH in heat racing trim and they can tell you how hard is that. I have only seen two boats run over 70 MPH racing and they could run in lane 25 and still win just because everyone else runs low to mid 60's.

I have built 7 .21 carbon fibre boats about 7-8 years ago and I've expected to see other people getting into composites but it did not happen, that is the very first step towards higher performance. Composite materials will allow us shapes and design that can not be done with wood. Someone pointed out that carbon fibre boats are not any faster, I would not expect them to be any faster if they are same design as wood boats.

I'm sure we will see some very different ideas applied in near future, till than just keep impoving what you got.

Advanced Racing Tech

Frank orlic

 

[TimD]

Thanks Frank,

(very cool looking rigger by the way!)

The question that still needs to be addressed is "how wide does the tub need to be to provide sufficient lift at these higher target speeds?"

Tim.

 

[GTR]

Hi Frank

The ground effect I referred to was not the automotive 'ground effect' to which you refer - the evacuation of air from beneath a car. The ground effect I was refering to is aeronautical ground effect - as it effects helicopters, planes etc. It is the effect that displaced air has rebounding off a hard surface (ground/water) where an object travelling relative to this fixed surface will receive additional lift from the airflow under the object as it cannot dissipate as it would when airborne. This is a lift factor that could be designed in to tubs to allow the carriage of the weight of the boat so that more HP goes in to making it go forward faster.

Bornoulli operating on the sponsons, strut etc. ground effect operating on the tub. to get the right balance would be the challenge.

Sorry if I caused any confusion. To some extent this is how tunnels and traditional hydros are operating. It may be possible to apply some of this technology to a rigger. The use of composite materials would allow for more complex shapes to be realised with potential additional benefits. Problem with wood is essentially it allows for slab sided construction.

Another question that doesn't seem to have got much discussion here is the relative aspect ratios of length v width. There would have to be some scope for further development in this also.

Just trying to stimulate some discussion.

 

[P THOMAS]

" Arne Holt designer of record setting electric boat is prime example what can be done with composite materials, for as long as people build boats with wood they will look very similar"

Thanks for that info Frank, Where can we see examples of the Holt designs?

While thinking about the sport 40 boats. I too have came to the conclusion that they look the way they do is because they are built with wood.

The challenge is to think about what you want to do with a design that has lines and curved surfaces that would be hard to do with wood construction methods. Composite fabrication is only limited to your imagination, any shape is possible.

PHIL

 

[Ian Inverarity]

Phil,

Try here:

http://www.offshoreelectrics.com/

Near the bottom of the main page is a link to the pics and video. I presume this is the boat that Frank mentioned.

Note the width of the tub and aero shape. Also note the weight distribution relative to where the ride surfaces are. Very different to conventional riggers!

Ian.

 

[Ron Zaker Jr]

Frank,

AWESOME 20 boat man!!!! Looks great! How's does it turn?

Ron Jr

 

[MikeP]

Do you think that horizontal and vertical stabilizers in the rear can produce the same quality of ride as the rear sponsons provide?

MikeP

 

[Ron Zaker Jr]

Do you think that horizontal and vertical stabilizers in the rear can produce the same quality of ride as the rear sponsons provide?

MikeP

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Gary Preusse and I tested rear wings about ten years ago with very inconsistant results.Sometimes they "flew" with a good attitude and then the next run they would seem non functional.We were running tape on rears way back then and tested with and without the rears.We never really nailed down why the wings were so inconsistant.

Ron Jr

 

[TimD]

I was toying with the idea of some type of neutral wing at the back of the hull for the purpose of acting as a stabiliser if the front of the boat went above horizontal. Something like making the top skin of the tub wider than the tub sides (and thicker than the top skin obviously). Anyone tried this? Ron Jr?

 

[TomMoorehouse]

What about a center sponson as opposed to outside or traditional?

 

[Ian Inverarity]

I would think the ground effect of the relatively wide tub would be more effective for stabilising the tub than neutral wings.

Ian.

 

[Ron Zaker Jr]

I was toying with the idea of some type of  neutral wing at the back of the hull for the purpose of acting as a stabiliser if the front of the boat went above horizontal. Something like making the top skin of the tub wider than the tub sides (and thicker than the top skin obviously). Anyone tried this? Ron Jr?

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Tim,

I have not tried that,our wings resembled Top Fuel and Open wheel style and were mechanically adjustable. Your thought is very interesting.