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Tom v.d Brink

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Welcome Readers and fellow boat fanatics,

 

When starting high school I had no idea how interesting this hobby was going to be when a friend brought me to the lake the first time. I started with a little electric that was great fun. what was supposed to be just a hobby has become a big part of my life.

I thank a lot to all the very experienced boaters who shared their knowledge so freely on the web. it started as the listbot and has now become many forums which daily have good information for all boaters

from beginners level up to the more seasoned boaters.

In this blog I plan to give back to the web what it has given me when I needed knowledge and learned (and still learning) from the experience of others.

I plan to write some interesting articles about the aerodynamics of our model boats.

the topic will probably not suit a beginner level boater that much and I do advise every one who reads this to improve your basic knowledge first before you embark on the aerodynamic path.

In the articles I will give evidence to the improvements but also point out the sand traps along the way.

but first a bit of what I have done so far:

 

well in 2000 I started to be really interested in SAW running with my .45 outriggers and since then I looked at a lot of aspects of running a boat at high speeds.

in 2004 I had some help from a Dutch company specialized in simulation software who ran some cfd-analysis (computational fluid dynamics) on the cad models I presented them with. It would be an understatement to say that it was just interesting.

From what was learned by the simulation I build a boat that ran well but gave additional problems to the list of problems I was already facing.

that is why I build another boat taking a step back to the basics. this basic boat helped me learn again to get the simple things right and brought me an official back-to-back pass of 103.57mph.

The aerodynamically improved boat still holds my one-way record at 105mph.

So the step back has proven to me that it is necessary to get your basics right and then try to get that last bit from the aerodynamics. however it will show that at high speed a little change can make a big difference.

 

So what can be expected in the blog further?

well first of all feel free to ask a question and if I have any knowledge on the subject I will talk about it.

And second I will start with the basics as it is also a learning path for me to really write down the plain facts. by writing it down it forces me to think about it harder and understand it a bit better yet again.

and finally I hope it can be something that every one enjoys reading.

 

As a final word of caution I am not a aerodynamics expert. By trade I am a junior engineer working on strength and stress analysis (this is also a topic that can be nice to discus perhaps). My personal interest is fluid mechanics and in that context I will write here.

 

so next topic will be some results from the first basic study.

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Tom:

 

Very interesting analysis!

 

I have always been told that the sponson booms are a terrible aero penalty. I have seen people place airfoils on the tubes to make the tube drag less. One HUGE problem with this is that any incline in the hull makes these foils have a positive attack angle and thus an increasing attack angle as the boat continues to blow off. They increase the problem of blow off. Do you have any ideas of an efficient shape to reduce drag without this inclination problem?

 

Marty Davis

 

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One HUGE problem with this is that any incline in the hull makes these foils have a positive attack angle and thus an increasing attack angle as the boat continues to blow off. They increase the problem of blow off. Do you have any ideas of an efficient shape to reduce drag without this inclination problem?

 

Marty Davis

 

Marty,

 

very good question and a difficult one to. I try will go into the problem of inclination of the hull when aerodynamic advances are made however a real solution depends on the application. Any hull doing a nose up pitching motion will suffer from the increased surface area causing an increase in the force wanting to blow the hull over. Of course any foils or additional area would add to the problem as more surface area.

The ideal solution would be a self correcting system where the increased force would work towards pushing the hull back into its original ride attitude.

A few solutions reducing the blowover problem are

making the foils as small as possible giving less surface area and reducing surface area in the front of the cg will reduce the over turning force.

the Jag's team also showed a nice solution in their design with the whole tub beeing far back. making it act sort of like a wind indicator as the hull pitches up the largest surface area in the back will cause a correcting force and their vanes at the rear of the tub add to this effect.

 

I will talk a bit more on the effects of foils later as i am currently finishing up my next blog instalment on the boom tubes.

 

 

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