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Kris Flynn

Well-Known Member
Joined
Mar 11, 2002
Messages
4,335
free plans for anyone interested. Boat is 31" long.

Designed to laminate 3mm balsa to 1mm ply for keelson.

Cut the formers from 4mm balsa.

Only real change I would do is raise the rear tunnel depth 1-2mm

PDF Attached.

DWG Here

2nd design is my version of a Villain S1...where the Dragon started to take its current shape...there were many designs and builds before this, but this was a huge step forward, obviously because Mike was on a winner with his Villain S1!

31inch Dragon.pdf

29inch Dragon.pdf
 

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Thanks, very interesting. I've been working with a similar P limited design using a wider tunnel.

Lohring Miller

P1010234.JPG P1010236.JPG P1010235.JPG P1010237.JPG
 
I find it very odd that everyone is trying to re-invent the wheel and no one is working on aerodynamics. A big part of tunnels that has been completely overlooked. Oh well-play on--
 
Hi Tommy.

Are you willing to elaborate on what aspects you mean?

I have a different centet section profile and also width on my current M11 Dragons. I just wanted to re offer this set of free plans to anyone. I know it helped me in my early days of design.

I hope these plans inspire others to design their own.

Lohring.

How is that boat going for you? I remember you also changed the ride pad angles?

Build away Manuel...more the merrier!
 
The first issues were aerodynamic. The wide tunnel was to reduce the water drag with the limited power. At first it had too much lift so I lowered the angle of attack by reshaping the bottom to be parallel with the sponson edges. The transom flaps were ineffective so I removed them. The sponson angles, 17 degrees on the left and 20 degrees on the right worked well on the straights. The idea was to provide a deep vee effect in rough water. The boat then ran around the same speed as a 3.5 mod tunnel.

However, the left sponson buries in the turn in rough water. My first solution was to add a low angle section to the left sponson ahead of the recovery pad. This wasn't enough so I added a wider section to that area of the left sponson. See the pictures below. We'll see how that works. Any thoughts or suggestions?

Lohring Miller

P1010438.JPG P1010439.JPG
 
Lohring,

Are you sure its spinning out to the left and not to the right?

CG and ASP's

Where is your CG point from rear of sponsons?

What is the distance from your left ASP to the sponson surface?

What is the distance from your right ASP to the sponson surgace?

How wide are your ASP's?

Both the same width?

What is the distance from the rear edge of your ASP's to your CG mark on your hull?

Now the rocker.

On your setup board, if you lift the nose until the rear of the sponsons are perfectly flat, what is the distance from the sponson (tunnel edge) at the rear of your ASP's to the setup board?

How far from rear of hull are your sponsons flat before your rocker point starts?

Mark it.

From the start of your rocker point, how far to the rear of your ASP's?

Finally sponson twist.

What is your deadrise angle at rear of sponsons?

What is your deadrise angle at rear of ASP's?

Any (or all) of these are areas to look at when you have a tunnel spinning out in the turn. Tunnels are one of the hardest race boats to design and setup. Carl Van Houten and Tommy Lee are two of the masters of tunnel hull designs that many pattern their design after even today. As we Get better and stronger powerplants, better hydrodynamics and aerodynamics will push speeds even higher, hence the reason out of the box improvements in these areas like Carl's KARMA and TABOO designs, as well as Kris's Dragon designs, and from boaters/designers like yourself, are helping push these speeds even higher. I will watch for your feedback. Good luck with your new design.
 
As far as aerodynamics the cowl plays a big part in this also.I had two different cowl for the same boat to try and one cowl had more lift then the other.

Dave
 
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Lohring...if it were my hull and it was "dropping" the left sponson in rougher race water I would do similar to a htb360...I would make the ride pad wider (maybe 10mm or 3/8") for the front 40% of the boat. So similar to you but further back. Give what you have a try though!

Those stumble blocks are also pretty small. They make alot more difference than you might think with the turning. You could also try a slightly deeper (maybe 1/16" at a time) on the left side to see if it helps, or extend the block longer toward the front to provide more "support" for that side. When close 5mm makes a huge difference on location forward/back ;-)

My blocks are all 30mm wide for reference.
 
I have run my SAW 4s outboard with and without a cowl (dragon/vision) and habe not seen much of a difference in aero but more the extra weight in total and also forward of CoG
 
Hello Kris-I was just making a "blanket statement" that seems to me like everyone is trying to make a tunnel boat that looks fast &"zoomie" sitting on the table but making no progress on the water. This could be a controversial subject and some probably will not believe what I say but I don't care . I know what I have learned. I have no desire to get into a big discussion over this. (I'm too old) I do have access to wind tunnel data that was taken from a model of a full size boat and from what I know this is the only time this has been done. I do not own the data and I cannot and will not share the info on an open forum. However, all the aero principles that have been around for years and apply to airplanes, cars, trucks, etc. also apply to tunnel boats. There are no big secrets out there. I will share a couple of facts that may surprise you-maybe not. 1-a tunnel boat is not a good aero design. 2-the deck shape above the tunnel floor does absolutely nothing to affect performance, lift or anything. 3-you CAN NOT CREATE LIFT from the deck of a tunnel boat. 4-the cowling has no lifting capabilities and Kris as you have stated the boats work pretty good without them. Maybe a small increase in drag. A few things to think about.
 
Hello Kris-I was just making a "blanket statement" that seems to me like everyone is trying to make a tunnel boat that looks fast &"zoomie" sitting on the table but making no progress on the water. This could be a controversial subject and some probably will not believe what I say but I don't care . I know what I have learned. I have no desire to get into a big discussion over this. (I'm too old) I do have access to wind tunnel data that was taken from a model of a full size boat and from what I know this is the only time this has been done. I do not own the data and I cannot and will not share the info on an open forum. However, all the aero principles that have been around for years and apply to airplanes, cars, trucks, etc. also apply to tunnel boats. There are no big secrets out there. I will share a couple of facts that may surprise you-maybe not. 1-a tunnel boat is not a good aero design. 2-the deck shape above the tunnel floor does absolutely nothing to affect performance, lift or anything. 3-you CAN NOT CREATE LIFT from the deck of a tunnel boat. 4-the cowling has no lifting capabilities and Kris as you have stated the boats work pretty good without them. Maybe a small increase in drag. A few things to think about.
I have worked on tunnel hull aerodynamics for the past 20 years and it is what keeps me interested in the sport. I have learned many things about these persnickety little boats because I don't accept ANYTHING that I can't prove to myself. Yes I am hard headed. I have a wind tunnel that I test and prove all my boats on. It came with several variable surface texture settings and air speeds but I am not able to set them because they are randomly set by the guy who made it for me. The last tunnel boat design that I just recently finished is called the Taboo MR 300 (MR for Mike Rushing) This was the last project we worked on together before he passed. This boat challenged all my knowledge about boat design big time and I ended up spending 9 years in development (off and on) and 5 molds before I finally got what I originally set out to build. I learned a piece of the puzzle with each change I made. What I had originally set out to do by building the Taboo was to make a boat that was superior to the performance of the Lynx. This is why it took so long to accomplish. So far only two boats have come out of these new molds.

People who run my Lynx and who also know how to set them up correctly... will tell you that they can actually see the aerodynamics taking affect and working on their boats as they near the ends of the straights while driving them. You will never get this to happen unless you have a boat that is what I call neutral. Meaning the top and bottom of the boat are working together to the same degree "at a given speed". When you get to this magical point, you can push it faster than ever because everything is working together instead of one over powering the other as the speed increases. When I design a boat, I am all over it. Meaning, I am working it from all aspects of its shape, length, width, weight etc. leaving nothing out while trying to get the model to behave in a certain way. All of this effort only gets the initial prototype close to this point because believe me this is just step one of a long project when trying to tame a tunnel boat. The sleek resulting look of the boat is just what works best.

As Kris mentioned in his post about his cowling having little affect on his boat... When a boat is being controlled mostly by its hydrodynamic footprint, then aerodynamic changes may not have as much of an affect on the model and vice versa. This is not intended to be a slam to his model because the Dragon can run hammer down around the track and finish in some nasty water. We have been watching the performance of this boat and agree that at the end of the day, it is a good round track boat. When you get your model performing equally between these two effects (aerodynamically and hydro dynamically netural) is when you can really start to work on subtle changes that allow you to fine tune your model. This takes time and LOTS OF IT! You do not always make progress as it is easy to branch off into what you think is a "fix" to a problem only to learn later that you have been working on an "effect" the whole time and not the real root of a undesirable trait.

If you want to design, build and perfect a model tunnel boat, get ready to spend years doing it because if you throw one together and it is the best tunnel boat ever made in its class; you will not need to think that it will ever happen again. If it does, you would be better off using that kind of luck buying lottery tickets because take it from me, you will never make enough money from selling models to pay your bills.

But now to each his own. I'm not knocking anybodies designs or ideas. I think everybody should have their own ideas because that is what makes designing and building and racing tunnel boats fun.

See you at the time trials!

-Carl
 
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Hello Kris-I was just making a "blanket statement" that seems to me like everyone is trying to make a tunnel boat that looks fast &"zoomie" sitting on the table but making no progress on the water. This could be a controversial subject and some probably will not believe what I say but I don't care . I know what I have learned. I have no desire to get into a big discussion over this. (I'm too old) I do have access to wind tunnel data that was taken from a model of a full size boat and from what I know this is the only time this has been done. I do not own the data and I cannot and will not share the info on an open forum. However, all the aero principles that have been around for years and apply to airplanes, cars, trucks, etc. also apply to tunnel boats. There are no big secrets out there. I will share a couple of facts that may surprise you-maybe not. 1-a tunnel boat is not a good aero design. 2-the deck shape above the tunnel floor does absolutely nothing to affect performance, lift or anything. 3-you CAN NOT CREATE LIFT from the deck of a tunnel boat. 4-the cowling has no lifting capabilities and Kris as you have stated the boats work pretty good without them. Maybe a small increase in drag. A few things to think about.
Tommy,

This is great conversation feedback and hopefully you wont take this as a "big discussion", as there are a lot of smart people that follow these threads and this feedback or discussion is what helps create the ideas that make us all faster on the water. I looked over your information above and the wind tunnel data definitely helped in your Leecraft design to show CI or "lift coefficient". These numbers are calculated when you have air traveling at the same speed across the top and bottom surfaces and helps tremendously in helping you with designs to reduce drag. To help take tunnel boat designs to even higher levels, many are playing around with the phenomenon or result of utilizing both aerodynamics (can be recreated in a wind tunnel) and hydrodynamics (can only be reproduced as the boat travels across the water. This combined lift is created by the difference in fluid speeds of the speed between the upper and lower surfaces. This change in speed creates a change in pressure that generates lift. Many tunnel designers on IW have played around with this by moving the curvature on the top deck forward and aft. The faster the speed the more lift is created from this pressure and by moving this lift point, you can clearly see the effect it has in the tunnel hull from the start of the front stretch to the entrance of the turn, or in SAW from the start of the run to the end. The cowling, heck thats another conversation. Personally, I think using the cowling to direct the air flow over the deck has more of an effect on the tunnel performance than the actual cowling itself. These comments on Kris's thread are definitely great info for all of us to ponder. We may need to start a new thread altogether as this could get very interesting for sure.
 
My cowl on and off reference was for my SAW boat...I have not actually run my oval boat without a cowl (back to back).

I am not fussed where a discussion is done, as long as we are talking improvements and not just big noting ourselves, it will help everyone.

Have a look at the dates on my drawings...these designs are 12 years "old"
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I never hide from the fact that my design has evolved from a Villain S1 (see first post which is updated with my first evolution from a Villain). I have however done the changes I have because of on water testing and finding the need to go longer. The other stuff like sweep down on the sponsons was honestly for looks. I do however think the sweep down creates an interesting effect/shape/curve on the non-trip surface which helps? my design...or maybe it it just bullshit
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My M11 runs 24mm deep tunnel at transom and 28mm (30mm on some) at front of tunnel.

a 172mm wide tunnel at transom

Sponson tips 1.5mm higher

Any other questions, please ask.

Kris

(EDIT: ADDED extra information)
 
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Kris-I was just trying to answer your question but as you can see it gets off track with b.s. very quick. Ron-sorry buddy but you are way off on this one.1-I did not have aero info when I built the first 4-5 designs of my production boats-didn't have a clue. What I stated in my post are proven aerodynamic facts. 2. Once again, YOU CAN NOT CREATE DECK LIFT on a tunnel boat. There are 2- major reasons for this and apparently you do not know what they are. I answered Kris's question and now you guys can cuss and discuss this as long as you want. If some of these ideas that people are trying makes you sleep better at night then that is great. Go for it!!!
 
Hi,

would be good if Jerry Dunlap can contact Jay Selby . He wrote a very good artikel about aerodynamics of tunnelhull in RC-Modeler mag. Most influence about lift was the design of the tunnel it selve.see pic. .How to accelerate or to slow the airflow will rise presure or reduce it . I have test some of Jays design rules and they have all worked as he wrote. With this i would never place a wedge inside the tunnel . I have allways ad such wedge on the sponson at the front . For super high conering i also used turnfins , position after the c.g. . I have run a Prather 20 size tunnel in the Naviga F1 class and reached best time 12,2 seconds . The current record was in this class 11.1 second ,but this was with a full submerged propeller monohull that was spezial for F1 made. My tunnel run with a K&B lower ,a Octura 1250 with big cupping , prop. This tunnel run left and right hand corners as well with no spin out.

Little draw: at nr.1. the airflow will slow and the pressure rise and the result if lift the boat at this position.

Happy Amps Christian

IMG_2339.PNG
 
Kris-I was just trying to answer your question but as you can see it gets off track with b.s. very quick. Ron-sorry buddy but you are way off on this one.1-I did not have aero info when I built the first 4-5 designs of my production boats-didn't have a clue. What I stated in my post are proven aerodynamic facts. 2. Once again, YOU CAN NOT CREATE DECK LIFT on a tunnel boat. There are 2- major reasons for this and apparently you do not know what they are. I answered Kris's question and now you guys can cuss and discuss this as long as you want. If some of these ideas that people are trying makes you sleep better at night then that is great. Go for it!!!
Hey Tommy, no apologies required. Different opinions are a good thing. I think most of us have been told many times "this wont work", or "that doesnt work". It usually makes us even more determined, even if sometimes it may be deemed as BS. Happy Boating!!!
 
Guys,

Continuing the feedback on tunnel design, there are several articles available that can help with CG, sponson, and deck/cowling designs. Here is one in particular that has really helped me over the years. It is geared around F1 but applies even more to our models given the higher speed to size ratios.

Tunnel Hull Design Lift and Weight

The hull weight (including engine, driver, fuel, accessories, payloads, etc.) must be EXACTLY equaled by the lift forces generated. This is true for any boat (or aeroplane, too) in stable flight. The tunnel hull must however always be in 'stable flight', and so this balance is especially critical. Too much lift and we take-off like an aeroplane - too little and we have more "down" than we have "up", and this can be a distressing event for a planing craft!

There is lift generated in two ways. The planing sponson bottoms create 'hydrodynamic' or water-lift (lift due to forces on and reactions with, the water surface). Aerodynamic lift is generated by the relative air flow over the tunnel and deck surfaces or "wing" (lift due to forces on and reactions with the air, itself). This aerodynamic lift is affected by several factors, just like a wing on an airplane. (thickness, camber, angle of attack, etc.). The additional influence is that of the "wing" being in what is called "ground-effect". With an airplane, it is experienced when the craft flies close to the ground during landing and takeoff. With a tunnel boat, it is experienced all of the time, due to the "wing's" proximity to the water surface. The effects are complex, but generally, lift is enhanced due to the "ground effect".

There are additional sources of lift in the tunnel hull rig, such as the slight lift generated by surface piercing propellers, for example, but the contributions of forces like these to the whole force 'picture', are smaller, and beyond this article.

It is important to note that the relative significance of these forces changes as the speed of the hull increases.
 
My second article in the High Speed Boat Design series shows how lift in ground effect works. I spent a little time on how it applies to tunnels. The first part is in the October 2016 Propwash, the second is in the April 2017 issue, and the third on planing will be in the latest issue. All are under news at NAMBA.com

Lohring Miller
 
If.. the deck can not create lift does it also then not create drag................. not sure.. hum...

Not looking for an answer.. just pondering the question.

Grim
 
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