Experiment #1

[Mike Larson]

Hey guys! As a relative tunnel newbie ive followed this and previous theory posts with great interest, as, with this post, my question was gonna be what happens when the water pressure is increased on the spoon surface? (bournelli) ie, when a tunnelhull reaches speed..... anyway, we know now, its from atmospheric actions on the hull.... so, im gonna state my solution idea, open to judgement.... if, the faster the hull goes, the more the downforce on the stern, causing an eventual blow off, why could you guys not place, say, a 1 ounce tank, in the front of the boat, filling it with water from an auxiliary pick up, as you run, to try and rebalance the lifting effect of the atmospheric conditions? it could be regulated with a needle to not have the bottle too full too fast...... of course,all know the delicate balacing act tunnels can be, so... good luck to the diligent soul to try it... im not interested in saw, i eat the stuff up you guys write, so, keep at it, as, im waitin for the record to fall..... good luck

 

[Slideblues]

Thanks Rod,

Time to glue fingers to forehead and make sawdust :lol:

Gene

 

[waterbug]

Hey Rod

Thank's for the lesson !!!!! Sir !!!

"Geraghty's R/C Boat Instatute"

Sign up now !!!! For Fall Quarter !!!! Hurry limited space available !!!!

:lol: :lol: Keep it coming !!!!!!!!

 

[Lake S.P.O.R.T.]

The wood boat certainly has its place in speed record history, past and present. The fastest boats in the world are wood. Bob Wartinger, wood hydro powered by a V-8 outboard, 176 MPH. Ken Warby, jet powered wood hydro, 317 MPH. And only in recent years have designers produced laminates strong enough to build F-1 tunnel boats with. The best thing about fiberglass....THE SMELL!!!!!!!!

 

[Slideblues]

Grunts like "Tim tha Toolman" RRRrrrrrrrrrr, I love tha smell of MEK in tha morning :lol:

Gene

 

[Lake S.P.O.R.T.]

Nah!! It's the styrene that I like! I don't get careless with the MEKP. Thats bad stuff.

Seriously, I think Rod mentioned something about rounding the leading edge of the wing on a tunnel? Interesting. Maybe this reduces turbulence.

 

[Jerry Wyss]

Nah!! It's the styrene that I like! I don't get careless with the MEKP. Thats bad stuff.
Seriously, I think Rod mentioned something about rounding the leading edge of the wing on a tunnel? Interesting. Maybe this reduces turbulence.

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Yes, smoothing of airflow In an effort to keep (I guess) the "wing" section from

becoming a "control surface",,leading to a pressure differential at the top and bottom of "The Wing". I think I remember Rod saying that we probably won't

be going fast enough to be affected by aerodynamic "drag" but will be affected

by built-in aerodynamic control surfaces, such as "The Wing" , "The Cowl" and such. I would imagine that a tunnel could benefit from a "neutral" wing center

section and with the rounder leading edge the "angle of attack" of the boat can change (which it does constantly) somewhat without leading to a large "pressure

differential" or at least without leading to a "sudden drastic" differential

 

[VansRacing]

There's alot of "Drag",,funny there's much less on the concave side :blink: So we make our "Bling Bling Blocks" like a "ski-jump" :lol: kidding h34r:

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Jerry,

Seriously,try backing the spoon into the stream of water.

What does the spoon do?

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Yeah,,,Draws it in,,works just like "lift" on a aircraft wing,,,OR NOT!!

I do remember Jim Auguston ( remember Him?) making "wedges"

for "stumblin'" blocks about 10 - 12 years ago. :huh:

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All humor aside <_< ,I was trying to give to you what took me 4 years,15 to 20 boats and literally hundreds of trips to the pond to learn.It is all so simple once you understand it.

Much to my chagrin,I have finally realized that you can't get there from here without going through the process.Honestly,the spoon tells it all.

What you experienced with the spoon is the Bernoulli principle.Research it.

If you are still so inclined then go to work,experiment and really understand the principle and learn how to apply it.This is my last "post" on this subject,forever.

If you have a question or want to talk about it I will be glad to discuss it on the phone or face to face but not on this G.D. computer.

Last words......I "know" this to be true.The Bernoulli principle is the only design parameter that cannot be compromised and this applies to tunnels,hydros and monos."Anything" that touches the water can and will feel the effects of the Bernoulli principle.Remember I said "ANYTHING"!

Everything else lift,CG,length,width,tunnel depth,dihedral,prop placement etc,etc,etc can all be compromised depending on boat application.If you want a boat that does "nothing stupid" and is blister fast,Bernoulli cannot be compromised.

If you have a boat that spins out,hooks,nose steers,doesn't launch worth a sxxt,will not air out,turn well or won't turn left then Bernoulli has been compromised.

There isn't a fiberglass boat made that ain't a can of compromises.

I am positive that there is more out there to be learned and yet to be discovered.

I know of one little design item right now just waiting to be found.It absolutely solves one of the tunnel boats biggest faults.

Tommy Lee discovered this item in 1996 and its success can be traced right back to the spoon.Really neither Tommy or myself never really knew what he had until about 18 months ago and by that time Tommy was no longer able to go on.I no longer have the passion or desire to continue racing at the level I once attained so this item is just going to sit here in the bank until someone earns it.

I am positive that someday somebody really dedicated into tunnel testing and design will run across this find and believe me they will have earned it.They will have to really understand what makes a tunnel boat work before they will even recognize what they are trying to solve.Right now this tunnel boat fault is just mutually accepted as the nature of the beast.

I suspect before it is done this discovery will be the next quantum step in tunnel speeds.

[side note.....Mark Anderson and I introduced Jim Auguston to the wedges on the sponson fronts at the 2nd Kingdome scale race in 1989.Mark and I put them on his boat between heats so he could get the boat through the corner.I still talk to Jim on a regular basis.

I just talked to Jim a week ago.He is retired and doing great flying his ultralite,restoring a old shovelhead Harley and riding a Honda Goldwing.

I still have Jims Winston Eagle lobster S.A.W. boat here all repaired and ready to run. 8lbs-3oz. RTR with a Picco EXR .67]

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I hope you and Tommy find somebody to build this boat for you guys. I would be interested in seeing it come race in the Southeast. Make it in a 3.5cc first. That would be the ultimate test right there.

-Carl

 

[Jerry Wyss]

I was wondering why I was getting all the attention concerning "The Spoon",,,it hit

me at 4:06AM this morning ,,That's why my boat in my picture is lifting NAHH,

I'm going back to bed :lol:

later edit: the very top of that that cowel looks just like that spoon i put in the water stream <_<

 

[Ron Drake]

There's alot of "Drag",,funny there's much less on the concave side :blink: So we make our "Bling Bling Blocks" like a "ski-jump" :lol: kidding h34r:

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Jerry,

Seriously,try backing the spoon into the stream of water.

What does the spoon do?

80388[/snapback]

​

Yeah,,,Draws it in,,works just like "lift" on a aircraft wing,,,OR NOT!!

I do remember Jim Auguston ( remember Him?) making "wedges"

for "stumblin'" blocks about 10 - 12 years ago. :huh:

80415[/snapback]

​

All humor aside <_< ,I was trying to give to you what took me 4 years,15 to 20 boats and literally hundreds of trips to the pond to learn.It is all so simple once you understand it.

Much to my chagrin,I have finally realized that you can't get there from here without going through the process.Honestly,the spoon tells it all.

What you experienced with the spoon is the Bernoulli principle.Research it.

If you are still so inclined then go to work,experiment and really understand the principle and learn how to apply it.This is my last "post" on this subject,forever.

If you have a question or want to talk about it I will be glad to discuss it on the phone or face to face but not on this G.D. computer.

Last words......I "know" this to be true.The Bernoulli principle is the only design parameter that cannot be compromised and this applies to tunnels,hydros and monos."Anything" that touches the water can and will feel the effects of the Bernoulli principle.Remember I said "ANYTHING"!

Everything else lift,CG,length,width,tunnel depth,dihedral,prop placement etc,etc,etc can all be compromised depending on boat application.If you want a boat that does "nothing stupid" and is blister fast,Bernoulli cannot be compromised.

If you have a boat that spins out,hooks,nose steers,doesn't launch worth a sxxt,will not air out,turn well or won't turn left then Bernoulli has been compromised.

There isn't a fiberglass boat made that ain't a can of compromises.

I am positive that there is more out there to be learned and yet to be discovered.

I know of one little design item right now just waiting to be found.It absolutely solves one of the tunnel boats biggest faults.

Tommy Lee discovered this item in 1996 and its success can be traced right back to the spoon.Really neither Tommy or myself never really knew what he had until about 18 months ago and by that time Tommy was no longer able to go on.I no longer have the passion or desire to continue racing at the level I once attained so this item is just going to sit here in the bank until someone earns it.

I am positive that someday somebody really dedicated into tunnel testing and design will run across this find and believe me they will have earned it.They will have to really understand what makes a tunnel boat work before they will even recognize what they are trying to solve.Right now this tunnel boat fault is just mutually accepted as the nature of the beast.

I suspect before it is done this discovery will be the next quantum step in tunnel speeds.

[side note.....Mark Anderson and I introduced Jim Auguston to the wedges on the sponson fronts at the 2nd Kingdome scale race in 1989.Mark and I put them on his boat between heats so he could get the boat through the corner.I still talk to Jim on a regular basis.

I just talked to Jim a week ago.He is retired and doing great flying his ultralite,restoring a old shovelhead Harley and riding a Honda Goldwing.

I still have Jims Winston Eagle lobster S.A.W. boat here all repaired and ready to run. 8lbs-3oz. RTR with a Picco EXR .67]

80498[/snapback]

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I hope you and Tommy find somebody to build this boat for you guys. I would be interested in seeing it come race in the Southeast. Make it in a 3.5cc first. That would be the ultimate test right there.

-Carl

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I hope to run with you guys with this boat. Let me or carl know what raceyou guys will be at i would like to see. Thanks Ron Drake

 

[VansRacing]

Well- as I read this I have to say something and I don"t care who gets P---ed off. Most of you younger guys weren't around in the mid to late 70's when there were several tunnels for sale to the public but you cannot believe how slow they were, how bad they handled and how hard they were to drive. In the early 80's Rod Geraghty came upon the concept of what I will call the modern-era tunnel hull i,e- shorter flat running surfaces and front sponsons, yes I said sponsons because that is what they are not stumble blocks.(the ones stumbling are the people trying to run without them.) After a year of phone calls and sending photos and drawings back and forth Rod and I came up with the XT-460 which is by far the best tunnel to ever hit the water for the average boater. This boat has won more races and National Championships than all the other brands combined. And is still winning today after 20 years. However, this is not a commercial, the point is that there have been NO significant changes in 20 years. The Aerotech,Hopper,Tri-star,Villian,Lynx and 10 other models out there were all copies or should I say direct descendants of this boat. Yes there have been minor changes but all of these boats are built around the "Geraghty"concept. So the bottom line is LISTEN- Rod is trying to get builders to think about why the boats do what they do and how to change them. I have built at least 25 boats that no one ever saw in the water except me. Some worked and some didn't and that is how you get there. You have to want it bad enough to find it.

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I have had a few people question me about my boat designs since Tommy Lee wrote this artical. Some of my customers seem to think that my boats are copies of the Lee Craft boats. I stayed off this topic because it was getting a bit nasty but I do need to state these facts.

I have never molded, stretched or quartered a model boat of any kind and never will. All of my boats have been built from scratch starting with the Aerotech SR-40 that was built in the early 80's and first out on the market in 1986 all the way to the Lynx and Shaman 7.5cc that is currently being molded in my shop today.

I will say this about Tommy Lees boats, "in their day" they were the bench mark of tunnel hull design and it is true that my designs were inspired by what was the fastest boats anywhere to be found however, all of my boats are and always have been, original, scracth built models. All of us have learned from old designs and carried over the things we believed to work best into our new models.

This is the basis of this sport in every class. Yes, my boat does have "turn pads" to smooth out the bite in the turns. We owe thanks to guys like Tommy and Rod for developing things like that but, but there is much more than that going on with the competetive designs these days. For me, this sport is 100% learning.

I am not upset with Tommy. In fact, he is what inspired me to push my boats to their limit and I actually owe my success today to him as he always had a butt whipp'n waiting for me and anybody else who showed up at the track.

But, for the record, All my boats are of my own scratch built design and always have been.

Okay, enough of the serious stuff...Let's RACE!

Carl Van Houten,

 

[bzubee]

Rod glad to see your are back how are you feeling? Iam going after the Sport Tunnel Hull Records in April in Huntsville I'll be using the engine you set up for me. If weather is right I should be able to get the record since a few years back using a stock OS The boat was timed at 49.6 using a Stock 1450, witnessed by John, Gary and Tommy the engine was two staging on the stock muffler. Hope you can make it down for the Internats this year?

Take a serving spoon or tablespoon and hold loosely at the end of the handle with two fingers and back the rounded part of the spoon into a fast stream of running water out of your kitchen faucet.What does the spoon do when it hits the stream of water?

Turns out there isn't enough global space left to add the photo.If you understand the experiment then try it.If not be patient,I will try to post it later.

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[Geraghty]

Rod glad to see your are back how are you feeling? Iam going after the Sport Tunnel Hull Records in April in Huntsville I'll be using the engine you set up for me. If weather is right I should be able to get the record since a few years back using a stock OS The boat was timed at 49.6 using a Stock 1450, witnessed by John, Gary and Tommy the engine was two staging on the stock muffler. Hope you can make it down for the Internats this year?

Bill,

I am still on the mend but doing pretty dam well for an old fart.

50 MPH on a stock mufflered O.S. 3.5 outboard ain't to bad.Two staging is the answer.That motor should do that all day long if you loosen up the boat.I assume you got some set-up help from Tommy???

Good luck and crush that record!

I don't hold to much hope for the Internats this year.I have some other commitments but David Hall and I are looking pretty hard at 2006,in fact you might even see us at a SAW with our own 3.5 sport tunnel boat.

Later,Rod

 

[David Homer]

Just discovered this thread last night... must have re-read everything 5-6 times since...lol I've only built 2 tunnels (the original JD WOF hulls), but I've always been interested in design and trying to figure out how things work.

Back in the late 70's I had a fascination with Ed Fisher's canard designs. I read somewhere that "ground effects" were the key to the canard's performance. I tried to design my own hull based on my best interpretation of magazine pictures.. and I enlisted the help of a friend who was an aviation engineering student. He came up with a wing profile that included a concave surface on the underside just before the trailing edge. He explained something to the effect this would cause the rear of the boat to maintain a certain height. The boat was never completed, but I've always wondered if that concept would actually work.

Now to get to the tunnel project..lol... I believe we are still dealing with "ground effects" here. Remember how Indy cars were designed years ago? The underside of the side pods were upswept, creating a huge vaccum holding the car down. The same thing is happening to our models..

Reading all the posts here... to me things became a bit more obvious... Theres no mystery why Jerry's extra wide stumble blocks brought the bow down... The same principle we've been talking about is in action... Right behind those blocks, a low pressure area develops, bringing down the front end... Grim touched on this, and the phenonemon at the rear of the boat. Obviously the airflow needs to either be slowed down and/or interrupted somehow to help break that vaccum.

This has almost got me reaching for the drafting board (I was working on a WOF version of the Dunlap 27 at one time...) Let me run through my basic idea here, see if has some merit.

First off I think I would want my center section to generate no or very little lift from the top, make it a flat area to start with. Just have to make sure the deck is parallel to the water surface at full plane.. The stumble blocks would be designed just like hydro sponsons (3-4 degree angle of attack, flat surfaces, etc). I would further enhance this by creating like a mini-tunnel directly in back of the blocks. The amount of downforce generated could be adjusted by varying the height of that tunnel. At the rear of the boat, I think this could be treated in a couple of ways. Take the tunnel floor and gradually (maybe 1 or 2 degrees or so) slope it downward towards the rear. It might also be beneficial to work in that concave surface I talked about earlier right before the trailing edge.

Obviously this is a starting point and only experimentation would yield the desired results. Just seems to me if this worked, the tunnel could not blow off, and also eliminate the need to add weight to the front...

I'm also thinking of designing a 40 size mono on the same construction technique as the "Wild Thing". Haven't yet visualized in my mind how a mono can take fullest advantage of the Bernoulli principle, but I have a sneeking suspicion the Seaducer comes close...

 

[chriscarbon]

david,

i have done some tinkering with tunnels and i will give you my 2 cents. i built a jd wof 3.5 for a friend four or five years ago. i cut out patterns and when i was done they didn't match the plans perfectly. <_< when i was done the boat looked good. the bottom was per plans (the most important part) the boat worked very well. both parties were happy. i also made one for myself. we placed in almost every race we entered or at least one of us did. the top speed reached was with his boat at 50 mph and mine was close be hind that figure, but who placed higher depended more on who was on the clock and other fundamentals. this boat had a 17 degree bottom. the dunlap 27 has a 17 degree bottom also but rides a little flatter. last year i built a dunlap 30 it is the fastest tunnel that i have but i didn't get to check it on radar so far. it corners nice and has a 15 degree botton. my suggestion would be the 15 degree bottom. after you build the sponsons i would use double side tape in case you have to make an adjustment. you would hate to be 1 degree off on a experimental design and have to do the alternative. the rest of your design sounds neat too and don't forget how much nitro it takes to get every thing tuned in.

chris

 

[jayt]

The "concavity" Dave spoke of makes the hull profile an "S" wing, a design particularly effective when in ground effect. Too many model boat "designers" forget that our boats' tunnel floors are not airplane wings and they should not be shaped like conventional airplane wings. The boats operate in ground effect and the aerodynamics are somewhat different than "clear air" wings as found on airplanes. Dave's engineer friend "got it".

 

[VansRacing]

Jayt,

I agree. The task should always drive the design and shape of your model. A good designer must question accepted base line theory.

Carl,

 

[Propjockey]

HEY ROD G...GUESS WHAT! I tried your little "spoon experiment" .....with a twist. Try this. Hang two balloons from string about an inch apart. Now blow air between them. They go together, not apart. HHMMMMM!!!!!!

 

[Tuna]

I love this stuff!!

When is brain teaser #2 coming?

Charlie

 

[Geraghty]

HEY ROD G...GUESS WHAT! I tried your little "spoon experiment" .....with a twist. Try this. Hang two balloons from string about an inch apart. Now blow air between them. They go together, not apart. HHMMMMM!!!!!!

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Ain't that amazin'.

The same Bernoulli principle applies!