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Author Topic: Hooley Stude hood bulge - question for Sumner  (Read 4867 times)
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tortoise
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« on: January 24, 2007, 03:39:58 PM »

In the Hot Rod article this month about wind tunnel testing, under "things that don't work", it says that beyond about 45 degrees, additional windshield rake generally doesn't reduce drag. The bulge I speak of apparently is an attempt to make the center part of the hood an effectively very highly raked windshield. Do you have any reason to think this feature reduces drag?

The reason I ask is not because I suspect that it increases drag, but because it moves the center of pressure way forward, counteracting all the effort you've made to move it back. I've seen a video that suggests a little extra stability might be useful for the car.

I am aware that it is absurdly presumptuous for a wannabe like me to ask you such a question.
« Last Edit: January 24, 2007, 03:55:48 PM by tortoise » Logged
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« Reply #1 on: January 24, 2007, 04:03:15 PM »

In the Hot Rod article this month about wind tunnel testing, under "things that don't work", it says that beyond about 45 degrees, additional windshield rake generally doesn't reduce drag. The bulge I speak of apparently is an attempt to make the center part of the hood an effectively very highly raked windshield. Do you have any reason to think this feature reduces drag?

The reason I ask is not because I suspect that it increases drag, but because it moves the center of pressure way forward, counteracting all the effort you've made to move it back. I've seen a video that suggests a little extra stability might be useful for the car.

I am aware that it is absurdly presumptuous for a wannabe like me to ask you such a question.

A good question and one I don't have a for sure answer for.  I was interested in the 45 deg. thing in the Hot Rod article.  Surprised me, but I guess it is kind of the teardrop shape thing where the blunt part at the front that is pushing thru the air is fine as long as the taper at the back is less, like the 6-7 degrees PorkPie mentions to allow the air to stay attached and fill in behind the car.

The main thing the hump is up there for is to clear the 871 blower.  I wanted at first to extend the air inlet snout all the way along the top of the hood and out in front of the car.  Then Tom brought up the center of pressure thing that you are talking about.  So a compromise was made to take it to where it is now.  And yes it does move the center of pressure forward.  That and the traction issue that resulted in the near spin last year on the second run resulted in the  800 lb. weight increase.  Before the spin we already were over 200 lbs. more than the year before in hopes of helping with the CP/CG that you mentioned.  It obviously wasn't enough  cry.  We will take another 300-400 lbs. with us this next year in case we need it.

Finally the scoop could have been a few inches lower and presented more of the top of the windshield in the middle to the air, but I still feel the shape we have is better than doing that.  It would be interesting to have the wind tunnel time and see for sure.

I think the car is pretty aero as it has run 241 on what I believe is less than 700 HP at the crank.  We have talked about the possibility of a new nose for 2008. A longer nose would help to move the CP back also and the longer wheelbase should also help.

So like I said most of this is gut feelings and no hard facts.

One last thing as I don't know what pictures you are looking at, but.....

     

In the first year 2004 we didn't have a blower and were running fuel....

     

Now of course we do have a blower and needed to modify the hood.

c ya,

Sum
« Last Edit: January 24, 2007, 04:11:28 PM by Sumner » Logged

Rick Byrnes
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« Reply #2 on: January 24, 2007, 04:12:21 PM »

Interesting topic.  I also thought that laying down the windshield would help, but my aero guru said when he saw mine, that it is about perfect shape.  Laying down will not help a thing on my car.  Seems now I have a second opinion.
Hello Doctor?
As if I'm in a position to change the canopy anyways.

Rick


* WF 9.jpg (66.94 KB, 720x540 - viewed 199 times.)
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Rick
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« Reply #3 on: January 24, 2007, 04:22:13 PM »

We have talked about the possibility of a new nose for 2008. A longer nose would help to move the CP back also and the longer wheelbase should also help.
This would also give you the opportunity to get rid of the headlights, at the cost of losing some of the "Studie-ness" of the cars appearance.

What's the box behind the blower?
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tortoise
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« Reply #4 on: January 24, 2007, 04:24:55 PM »

Interesting topic.  I also thought that laying down the windshield would help, but my aero guru said when he saw mine, that it is about perfect shape.  Laying down will not help a thing on my car.  Seems now I have a second opinion.
Hello Doctor?
As if I'm in a position to change the canopy anyways.

Rick
Porkpie has mentioned the importance of a larger radius at the intersection of hood and windshield.
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« Reply #5 on: January 25, 2007, 02:04:05 PM »



Porkpie has mentioned the importance of a larger radius at the intersection of hood and windshield.
[/quote]

Could you remind me when I wrote "of hood and windshield"  undecided

to get a larger radius in the intersection, if we talk from the same, of hood and windshield will create a problem thru the windshield......I fear in this comment is something mixed up.....

Please clarify this comment in which issue I wrote this. Something is not right.
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Pork Pie

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« Reply #6 on: January 25, 2007, 02:50:09 PM »

to get a larger radius in the intersection, if we talk from the same, of hood and windshield will create a problem thru the windshield......I fear in this comment is something mixed up.....

Please clarify this comment in which issue I wrote this. Something is not right.
Apologies, I must have been mistaken. I tried looking for it to no avail. Looking at the Mcbride & Moran car's canopy makes it very clear I'm wrong. Perhaps some good will come from my stupidity if you will amplify upon this "problem thru the windshield".
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« Reply #7 on: January 26, 2007, 12:19:52 AM »

Interesting topic.  I also thought that laying down the windshield would help, but my aero guru said when he saw mine, that it is about perfect shape.  Laying down will not help a thing on my car.  Seems now I have a second opinion.
Hello Doctor?
As if I'm in a position to change the canopy anyways.

Rick

Let's also not forget we are dealing with two different animals here.  With the car the front of the car and the hood directs a large frontal area of air towards a rather wide flat area, the windshield.  The majority of this air has to run up the windshield and over the car with very little spilling off to the sides.

In your case most of the air at the front of the car goes down the sides and what strikes the windshield, canopy in your case is mostly just the air directly in front of it and with the curved front on it most of the air is deflected off to the side.  Probably up at an angle along the sides.  So you probably have very little air going up the front of your canopy and over and along the top.  So the air that is going along the top is probably fairly clean air.

This all is my guess anyway  wink.

c ya,

Sum
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« Reply #8 on: January 26, 2007, 12:28:49 AM »

  I don't mind admitting that I don't know anything about aero. Could you tell me if the windshield to hood radius you are talking about is the one you see from the top view or from the side view.

  When I laid out my lakester I just tried to make the frontal area small and the transitions gradual. My canopy doesn't have a radius from the top view and has a very small angle transition hood to canopy. I haven't seen anything exactly like it. Did I do something really bad here? I'd like to hear some other opinions on mine. It has a page on Sum's site. You can you can click on the URL below and take a look if you will, The canopy shape will be the same after it is fitted with the windshield .    

  Thanks Harv
« Last Edit: January 26, 2007, 01:29:16 AM by hitz » Logged

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« Reply #9 on: January 26, 2007, 11:07:49 AM »

 I don't mind admitting that I don't know anything about aero. Could you tell me if the windshield to hood radius you are talking about is the one you see from the top view or from the side view.

  When I laid out my lakester I just tried to make the frontal area small and the transitions gradual. My canopy doesn't have a radius from the top view and has a very small angle transition hood to canopy. I haven't seen anything exactly like it. Did I do something really bad here? I'd like to hear some other opinions on mine. It has a page on Sum's site. You can you can click on the URL below and take a look if you will, The canopy shape will be the same after it is fitted with the windshield .    

  Thanks Harv

Hello Harv,

can you add a picture where the canopy is shown....with some more of the car :wink:the picture you add shows me only the windshield, if I can see also the body in front and behind the canopy I will give you an answer.

And you have not to apologize, to explain so things in words is sometimes though, especially when the guy is German.

And aerodynamic is really complex to explain.... grin

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« Reply #10 on: January 26, 2007, 11:26:56 AM »

 I don't mind admitting that I don't know anything about aero. Could you tell me if the windshield to hood radius you are talking about is the one you see from the top view or from the side view.

  When I laid out my lakester I just tried to make the frontal area small and the transitions gradual. My canopy doesn't have a radius from the top view and has a very small angle transition hood to canopy. I haven't seen anything exactly like it. Did I do something really bad here? I'd like to hear some other opinions on mine. It has a page on Sum's site. You can you can click on the URL below and take a look if you will, The canopy shape will be the same after it is fitted with the windshield .    

  Thanks Harv

Hello Harv,

can you add a picture where the canopy is shown....with some more of the car :wink:the picture you add shows me only the windshield, if I can see also the body in front and behind the canopy I will give you an answer.

And you have not to apologize, to explain so things in words is sometimes though, especially when the guy is German.

And aerodynamic is really complex to explain.... grin

PorkPie here are a couple pictures of Harv's lakester in case you didn't find these,

Sum

     

     
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« Reply #11 on: January 26, 2007, 01:13:57 PM »

Alright, shows me enough.

#1: on the top a big radius between windshield area and top of the roll cage. An aero advantage would be when the gap from the canopy are on the top of the roll cage behind the radius and not in or in front of the radius.

#2: a so angle is not necessary, especially it produce a visuality (view) problem - the view breaks inside the windshield. Another problem, the windshield is very long - which produce a extreme pressure on the (flat) windshield area - the most pressure goes directly on the flat windshield and did not flow around/along the windshield.

#3: this corners are acceptable but ist needs a lot of pretension - due to this pressure problem I wrote under #2 the corner will try to lift. Or you can make the hinges very close to the corner.


* body-4 mod.jpg (55.69 KB, 480x320 - viewed 199 times.)
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Pork Pie

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« Reply #12 on: January 26, 2007, 01:18:13 PM »

Interesting topic.  I also thought that laying down the windshield would help, but my aero guru said when he saw mine, that it is about perfect shape.  Laying down will not help a thing on my car.  Seems now I have a second opinion.
Hello Doctor?
As if I'm in a position to change the canopy anyways.

Rick

Rick, your canopy/windshield is fine, may be up to 5 degrees more would be still okay - and important, you get a right view out of the cockpit, without getting trouble with the sun, in the morning or late evening.
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« Reply #13 on: January 26, 2007, 02:30:59 PM »

Porkpie, thanks for your observations. I can see things now that didn't enter my mind. There is a steel tubing frame around the perimeter of the canopy and the front of the canopy tucks under the hood about 3/4" (20mm) so I believe it won't be able to lift.
   I will be able to radius the canopy at the junction to the body at the roll cage but not much with out a lot of work. The windshield is already cut but not formed so I will go ahead as planned but with thoughts of improvement later on. If there is view distortion, It will be sooner than later.

  Thanks again

  Harv
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« Reply #14 on: January 26, 2007, 02:35:42 PM »

Sum, 

  Thanks for posting the extra pictures for me.

  Johnny on the spot as usual.

  Harv

 
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