A topic to think about

[Grimracer]

Lets ponder for a moment.

Ground effect... I suspect Colander Effect "could" come in to play with the top deck as well as lift and drag... I dont "think" the deck is working in "ground effect".. well necessarily ... However.. when the boat is "in ground effect" the lift and drag of the boat likely become critical to controlling the "flight" (flight is a tricky word here as it suggests "airborne"). We have said.. look at that boat "fly" but mean it never left the ground. We use "blow off" for our flight... (I know this well.. LOL)

Point is this.. the top deck does not operate in "ground effect" it merely attempts to control the "stability of the boat".. In saying this.. i dont feel an exotic shape is necessary to control this.. simple parabolas are likely a good "starting point".

Round on top.. sharp on the bottom.. as its most BASIC need. Pointy BAD.. round GOOD.. Mongo says so!

I "Dijest".. no really.. just had lunch!

back at it...........

Grim

I suspect... Kris.. the reason your boat went so fast after you narrowed up the riding surface is you minimized Colander Effect..(we can talk about that some time) Remember.. water has about 800 times more drag then air.. water first.. air second!

 

[Carl Van Houten]

Yes, heavily loaded planes that are too heavy to "fly" can actually get off the ground due to ground effects and crash into the trees at the end of the runway if the forward speed is not increased high enough past that point to lift the plane out of ground effect and into the zone of air that is above the height of the ground effect.

So even though our theoretical overloaded plane managed to leave the ground and travel the length of the runway it really was not able to actually "fly" the weight it was carrying. Leaving the ground is not technically "flying" just because the wheels are no longer toughing the ground.

The ground effect of a typical tunnel boat is about as high as the boat is wide so if you get high enough to completely break through the ground effect your boat is most likely doing back flips. LOL

Our tunnel boats never get out of ground effect.

 

[Grimracer]

Lord.. dont tell that to the Wright brothers!.. LOL

Grim

 

[Mike Makus]

Maybe a bit off topic but I have been trying to improve my TP2 areo dynamic package as it is still down 6 mph on a good day from my cookie cutter set up on my Dragon.

Or is it time to find a different hull to tinker with? TP2 with slimmer capsule area? Or maybe slimmer pickle forks to reduce cross section? What change were made on the TP3?
Thank you in advance

 

[Carl Van Houten]

The wright brothers? Those guys were VERY smart. Way ahead of anyone at that time. Have you ever looked into the design of their hand made wooden propellers? The efficiency of those first propellers they made was astounding! They lived in a house that was about 2 miles from where I was raised. The first flying school in the world was right here in Montgomery Alabama (Southern Boys of course) LOL

I would imagine that with their low powered heavy planes the ground effect was the first thing they learned. In fact the first few flights were probably nothing more than ground effect because if you remember they did not get that high off the ground on their first couple of flights.

 

[Kris Flynn]

Thank you for the "boat tail" explanation gents!

IMO the boat went faster as it was more settled...the hydro lift of the ride pads was too great so it would just tap dance and sometimes cause a crash if it got bad enough (i usually let off throttle before that).

Anyway, still happy to hear about or see your deck changes. I am assuming they were pretty drastic to make them handle so different.

 

[Grimracer]

Kris, here is a likely scenario.. the narrower pads ran higher out of the water.. I suspect this was likely the case.

Grim

 

[BobHorowitz]

I believe it's Coanda Effect.

 

[Grimracer]

Bob, I dont know how to make the little swoopy above the a...LOL.. but yes.. Coanda swoopy above the A) effect!

 

[BobHorowitz]

I think you need a Romanian typewriter.

 

[Brandon Atwell]

One thing me and Jr. looked at awhile back in some older hull design books, in addition to being narrower, a sharper angle will achieve faster speeds over a longer distance. So it looks like your angle changed drastically with the additions (reductions?) on the bottom as well.
Flatter sponsons will speed up quicker, higher angles will achieve a faster speed over a longer period of time. Hence why the JAE design is so successful on oval tries, the instantaneous punch off the corners the hull design allows. Hypothetically, a hydro design with some angle in the sponsons can achieve a better SAW speed if given enough room.

 

[Grimracer]

BA.. here is what I see with that.. dead rise is like.. dihedral. (Stability). the more of it you have the more stable your boat becomes.. hence the ability to run faster.. BUT.. when your stability comes from width and reduced "surface" above the water you don't need as much "dihedral". (hydro).. sure there is more to it then that..

Whats cool is we have hull types. There are limits (rules) with in those hull types.. without it.. this hobby would suck.

Day Hi to Dad, Uncle Tony and Jr for me...

Happy 2021

Grim

 

[Brandon Atwell]

BA.. here is what I see with that.. dead rise is like.. dihedral. (Stability). the more of it you have the more stable your boat becomes.. hence the ability to run faster.. BUT.. when your stability comes from width and reduced "surface" above the water you don't need as much "dihedral". (hydro).. sure there is more to it then that..

Whats cool is we have hull types. There are limits (rules) with in those hull types.. without it.. this hobby would suck.

Day Hi to Dad, Uncle Tony and Jr for me...

Happy 2021

Grim

Happy new year to you man! I’ll let them know you said hello, hope the world returns to somewhat normalcy this year and maybe we all can get together at a race site

 

[Steve White]

The wright brothers? Those guys were VERY smart. Way ahead of anyone at that time. Have you ever looked into the design of their hand made wooden propellers? The efficiency of those first propellers they made was astounding! They lived in a house that was about 2 miles from where I was raised. The first flying school in the world was right here in Montgomery Alabama (Southern Boys of course) LOL

I would imagine that with their low powered heavy planes the ground effect was the first thing they learned. In fact the first few flights were probably nothing more than ground effect because if you remember they did not get that high off the ground on their first couple of flights.

Wooden aircraft propellers. Takes me back to the late 60's and early 70's. A school friend had a neighbor that moved into the neighborhood 3 houses down from him. My buddy observed a fork lift used to unload machinery from the moving van and of course a 14/15 year old kid was curious and not afraid to ask questions. H. G. "Glen" Warren moved into the neighborhood. What a great guy and mentor he was to us.

He helped us with many projects for our mini-bikes to RC boat stuff. The man was brilliant, held many patents - which he had in a 3 ring notebook/folder. He designed the first machine to cut wooden aircraft propellers and said he designed the joystick for the P-51 Mustang. The flathead Briggs & Stratton engines on our mini-bikes had milled and fly cut relieved heads on them as well as diaphragm pumper carbs. My 5HP Lil Indian went undefeated at the neighborhood field drags.

Thank you much Mr. Warren, may you RIP.

Glen Warren

 

[Carl Van Houten]

Sounds like some great memories Glen. I worked for Hartzell Propeller here in Montgomery at one time. I mostly made 3d models of their turbo chargers. The prop division was in Ohio. Sometimes at lunch we would open the propeller files and look at how they constructed the models. There were some smoking smart engineers there for sure.

 

[Carl Van Houten]

Okay guys, let's ponder this.

You are going to the 2021 Outboard Tunnels Grand Nationals held in Wetumpka Alabama and you only have three boats to choose from. See attached 1,2 and 3. Pick the one you think you may have a chance to win that race with then explain why. Give a technical reason why you picked the one you did. I'm not going to comment I just want to see what you have to say.

The newest boat pictured is over 18 years old now. Are we making advancements in our sport or have we become stagnant? Where do you think the next big advancement in tnunnelboat design will come from?

 

[Steve White]

Okay guys, let's ponder this.

You are going to the 2021 Outboard Tunnels Grand Nationals held in Wetumpka Alabama and you only have three boats to choose from. See attached 1,2 and 3. Pick the one you think you may have a chance to win that race with then explain why. Give a technical reason why you picked the one you did. I'm not going to comment I just want to see what you have to say.

#3 simply because the overall execution of design is more sophisticated in terms of aerodynamics - don't know if they work or not - but, will give benefit of the doubt that a lot of R&D testing was employed to get that design to that point.

 

[Jeff whiddon]

I would run the the boat in the last pick. It has more dihedral and I know it helps with corner speed in race water as the boat seems to get better traction going thru the turns. In my opinion it seems to pull the inside sponson down making the boat corner better.

 

[Alan Elzer]

I'm enjoying this thinking pattern and all I put, causes I love my tunnels

 

[Kris Flynn]

Carl, we are talking aero here, yeah?

Those 3 hulls have MAJOR differences on the underside which FAR outweighed anything else.

Speaking of new boat designs, I would like to know what you improved on with the THOR design (over the Lynx and Taboo) and found in all the R&D you did prior to releasing them to know you were on a winner. Or was it more that you wanted a change and venture into the wood boat game?
Talking seriously here... have you produced a hull that has improved on your own masterpiece, the Lynx? Thats a tough one for sure! Credit can never be taken away for the advancements you made in RC tunnel boat racing with that beast.

I am still on the fence as to why you are trying to drive the aero game and say it is so important? Maybe for some designs that are heavily reliant on it, yes? I have never really sat and watched a lynx go round the track, so I cannot picture how it sets, corners and pops from a corner.

I am NOT saying it is not important...just wondering who got your knickers twisted in the first place about this lol

Hopefully none of that comes across in amy way negative...i know some jump to conclusions when they see what i write