Air Dam Placement

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Tim Strange

Well-Known Member
Joined
Apr 13, 2009
Messages
402
I am finally going to put an air dam on my Gas Scale Coors Light. I've tried C/G, strut and prop adjustments to no luck in eliminating blow-overs.

I know there aren't a lot of Gas Scales out there...so 1/8 Scale input is very welcome.

The hull is an ML boatworks kit of the 8255 picklefork with no rear wing.

How for back is ideal to place the air dam?

Thanks, Tim
 
try a mcdonalds straw with radio box tape try it in different places under the boat see where it works best then u can put a more perminate dam in the right place
 
Place it about an inch back from the leading edge. us some material that is about 3/4" high. I found an airfoil off of a set of cruze wiper Blades for my Miss Houston.
 
Thanks Ron...I did plan to use tape at first. But a straw just isn't big enough. I think that the tunnel width is around 13" on this beastie and was thinking a taller dam would be in order.

Phil, I did remember asking about your Cruze wiper blade, but never found one. Didn't realize it was 3/4" high. I was thinking about 1/2"...but I guess if I use 3M double sided heavy duty tape with the Bosch blade I have it will be close. Also, I was thinking yours was back much farther than that.

Thanks for the input...
 
Thanks Ron...I did plan to use tape at first. But a straw just isn't big enough. I think that the tunnel width is around 13" on this beastie and was thinking a taller dam would be in order.

Phil, I did remember asking about your Cruze wiper blade, but never found one. Didn't realize it was 3/4" high. I was thinking about 1/2"...but I guess if I use 3M double sided heavy duty tape with the Bosch blade I have it will be close. Also, I was thinking yours was back much farther than that.

Thanks for the input...
The part I used was the hard plastic airfoil not the rubber blade, It only comes as new on the car, replacements dont have that airfoil. Any wiper blade should be good, tape one on and if it seems to work make it more permanent with some shoe goo. Using Rons idea is good too just find some larger, longer tube.
 
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an easy to find and use material is the plastic corner protectors for sheet rock. Any hardware store should have it. It is clear and can be cut to desired height with scissors.
 
Curious why the hull needs an air dam is it lifting off the water? I have an 1/8 scale of Mikes and it is rock soild with out an added air dam. Not familar with the gas hull so kinda shooting from the hip. The 1/8 scale has a air dam built in ? Just curious thats all Jerry
 
Curious why the hull needs an air dam is it lifting off the water? I have an 1/8 scale of Mikes and it is rock soild with out an added air dam. Not familar with the gas hull so kinda shooting from the hip. The 1/8 scale has a air dam built in ? Just curious thats all Jerry
Jerry,

What hull are you running that is solid, is it one of the Extreme kits from Mike?
 
No it is a 8255 but it is a 1/8 scale. It is rock soild mine you it is set up for FE but it is really fast and I never pull back on the throttle even though sometimes I should. Running a x452/3 DT . Turn Fin by Mr Tyndall. My guess 50 plus for speed.
 
Jerry, I am not sure what differences there are between the Gas Scale and 1/8 versions are. All I can say is that my hull (as well as Phil's Miss Houston) has the tunnel break located at the back of the sponsons which creates a pretty steep angle.

With Gas Scale, the hull is 20% larger but the engine and pipe is like 2.5 times the size and weight. The tunnel width is wider and they run around 10 Mph faster than 1/8 scale.
 
As per Phil's suggestion (still cant find the wiper part) I added 3/4" PVC corner molding. I used 3M exterior 2 sided tape to attach for now. If I don't like the position or the dam I can cut the tape with a razer blade or Goof-Off may soften it enough to remove it. If that doesn't work I can always use the universal solvent...60% Nitro.

When I find the position and size I want, I will attach it with some nylon bolts so it can sheer away and not take the bottom of the hull with it.

Testing tomorrow!

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Something else to try is to extend the air traps further aft. You pretty much spilling all the air right after the sponsons. By extending the trap to keep more air under the back of the boat and the boat will blow off level if you will. Kind of jsut hops out the water and settles back down.
 
Thanks Mike, I agree with what you said about extending the air traps farther back to keep the air under the back of the boat. My heavy boat certainly needs some air focused to the aft end to even things out. If I built the hull with the tunnel break back a bit further (and thus more air trap), more air would be forced back instead of spilling out.

I am currently working on a couple of new Gas Scale projects, and these will definitely have the break farther back and a lower AOA (angle of attack) in the tunnel area. However, this will come at the cost of a ... GULP ... bellypan...

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Jim, I am pretty sure the issue is not with the AOA of the sponsons. The boat is spilling out air like Mike H. said, and the result for my build is that it is pretty much a tail dragger. This certainly does change the AOA of the sponsons.

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I do want to add that this was my first scale build, so I take any responsibility for my issues. It certainly has held up to more than it's share of blow-overs... so at least I know that it is built solid. The hull does run rock solid during testing and most race conditions. Maybe it is just race gremlins...
 
The AOA of the bottom is where I'd start. I know Mike "Grimracer" Zaborowski told someone to modify a Dumas sport 20 Pak by moving the break aft from the sponson transoms by two frames to prevent the boat from blowing over as easily. This lowered the AOA from 10 degrees down to 5 and also resulted in air traps back to the approximate scale location and prevents dumping air at the back of the sponsons. He claimed they race them in that configuration at the club he races with.
 
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Thanks again for the input...Unfortunately I had a mishap during the race this past weekend. Apparently The left sponson ducked under a wake in a turn and the boat rolled over. The incident didn't look spectacular...just rolled over. I was really surprised that my cowling was pretty much destroyed and the motor had a cracked cylinder and the carb needles were bent.

I am not sure if the air dam created to much suction in the turn (it certainly did suck!) or maybe I should have taken some weight out to move the C/G back. The boat certainly looked to have a better ride attitude with the air dam.

Anyway, here are some pictures of the motor for your viewing pleasure...

BTW I am in the market for a new cylinder or a new or slightly used K30RZ...

Tim

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Yeah it hit hard! I came into the corner right after Wes and saw the trench that the Lobster cut in the water, but I wanted to stay close to the boueys thinking I could at least give him a run. Left sponson caught the wake and just rolled. I guess the cowling acted like a brake and it stopped right there at bouey 2. 60mph to zero instantly!

I am assuming (from the bent needles) that the impact was enough to crack the case instead of hydro-lock. The good news is that I don't need a screw driver to adjust the needles. I have levers now LOL.
 
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