Boom Size and Cowling for 91/101 JAE

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NeilSharman

Well-Known Member
Joined
May 5, 2005
Messages
112
I received my 91/101 Truex Short kit from Joe but havent yet ordered the boom tubes.

I measure the holes in the tub and sponson frames are around 10.5mm? What size booms are you guys using?

Was thinking I should just open the holes and use the 1/2" solid booms? or would 3/8" be sufficient?

Also, where do I get a cowl for this kit?

Thanks in advance.
 
Depends on power?? I built one for an OPS 90 and used the 5/8" aluminum booms and for a 67 90 I run 1/2" aluminum booms. I made the cowls for these boats e-glass or carbon. The OPS 90 boat had a 5" tub so air ducts were added along the cowl for air.

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Neil

I am using 3/8 solid carbon rods for mine. Doc Turner has a nice cowling on his 90 JAE. Mark Bullard made the cowling for him. I believe Mark has a vacuum setup for making the cowling, his number is 256-303-6423.

Bill Hoch
 
Boom tubes, everybody uses them but...they are not very aerodynamic. Think about what is happening behind them when you increase the diameter.

-Carl
Whats happening behind them is the same no matter what the attitude of the boat is. Air foiled shaped things, even those with some amount of down force, will become neutral at some point or maybe lifting if the attitude changes enough. What about the effects of the boats varing speed on stationary airfoil shaped things?

JA
 
Boom tubes, everybody uses them but...they are not very aerodynamic. Think about what is happening behind them when you increase the diameter.

-Carl
Whats happening behind them is the same no matter what the attitude of the boat is. Air foiled shaped things, even those with some amount of down force, will become neutral at some point or maybe lifting if the attitude changes enough. What about the effects of the boats varing speed on stationary airfoil shaped things?

JA
It is the accepted evil of the rigger design for most. I have seen some trying the airfoil carbon tubes. I'm not sure how much they would actually help with speed or handling but they would have to be better than the aerodynamic nightmare seen in the photos. Your right, their surface area would add unwanted lift at some point of AOA to the model but by the time the nose gets up to that point, the area of the tub would become the real problem. I am sure this subject has been beaten to death at some point.
 
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at subsonic speeds it just does not play a large a role. parabolas and rounds are just fine at our speeds.

Can they be improved.. yes.. but the payback is just not that large.

Grim
 
at subsonic speeds it just does not play a large a role. parabolas and rounds are just fine at our speeds.

Can they be improved.. yes.. but the payback is just not that large.

Grim
I don't want to blow Neil's thread up so let's not get crazy here but I do want you to take a piece of boom tubing the same diameter and total length (both tube lengths combined) that you run on your hydro, hold it in the center and hang it out the window at 80 mph (let somebody else drive)
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and see how small of a role it plays. It is a lot more drag than you think. Is it worth improving? I did that and I thought DANG! This is a CRAZY amount of drag. Another thing to remember is that all of the INDY cars have gotten away from round tubes in their suspensions and spend stupid amounts of money designing aerodynamic tubes because it has been proven that it is worth the effort and money to do it.

Just for the record my hydro has round boom tubes on it too.
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Sorry Neil.

-Carl
 
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K & S Engineering has this to cover up carbon tubes.

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Carl,

If you want to look at the real drag problem

on most of our hydros look at the engine cowling?

Lots of drag there on most boats. We tried the teardrop

shaped boom tube cover from K&S and did not find it worth

it at all. Now when we played with cowl designs in a mock up

Wind tunnel you could not believe the drag. For top speeds

on a record boat this maybe important, but only if you are close

to the record speed already. For most this is not even worth spending

much time on. The set up and Propeller are the right areas to play in as

you well know.

Enjoy Testing This Weekend,

Mark Sholund
 
Carl,

If you want to look at the real drag problem

on most of our hydros look at the engine cowling?

Lots of drag there on most boats. We tried the teardrop

shaped boom tube cover from K&S and did not find it worth

it at all. Now when we played with cowl designs in a mock up

Wind tunnel you could not believe the drag. For top speeds

on a record boat this maybe important, but only if you are close

to the record speed already. For most this is not even worth spending

much time on. The set up and Propeller are the right areas to play in as

you well know.

Enjoy Testing This Weekend,

Mark Sholund
The round boom tubes are a just nasty drag element that everyone has to accept.

There are a few cowling contours being used that are obviously not very air flow friendly for sure. When you see things like this It makes you wonder if they are intentionally imparting loads onto the tub to tame some undesirable quirks out of their model?
 
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3/8 solid carbon rod from Goodwinds is all I use on a 101 outrigger with no problems at all,the performance is outstanding!! I use them on 45s also.

JRX
 
3/8 solid carbon rod from Goodwinds is all I use on a 101 outrigger with no problems at all,the performance is outstanding!! I use them on 45s also.

JRX
I think I can validate what Joel said regarding Goodwinds. I contacted them regarding physical properties on specific CF pieces and they responded quickly and efficiently.

Of note, they will also cut roundstock to exacting length without charge. Small company, HUGE customer care and support.

Thanks,

Tim
 
3/8 solid carbon rod from Goodwinds is all I use on a 101 outrigger with no problems at all,the performance is outstanding!! I use them on 45s also.

JRX
I think I can validate what Joel said regarding Goodwinds. I contacted them regarding physical properties on specific CF pieces and they responded quickly and efficiently.

Of note, they will also cut roundstock to exacting length without charge. Small company, HUGE customer care and support.

Thanks,

Tim
They are great! Goodwinds for me too!
 
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