Author Topic: APS body taper?  (Read 10942 times)

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Offline sofadriver

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APS body taper?
« on: November 16, 2014, 10:16:55 AM »
I know that if a streamlined shape tapers too quickly it will cause drag. I think I read 7 degrees of taper from centerline is about the optimum. Is that correct?
I've searched and can't find anything to confirm. If you can expand on this subject, I'd appreciate it
Mike in Tacoma

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Offline Sumner

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Re: APS body taper?
« Reply #1 on: November 16, 2014, 01:59:38 PM »
I know that if a streamlined shape tapers too quickly it will cause drag. I think I read 7 degrees of taper from centerline is about the optimum. Is that correct?
I've searched and can't find anything to confirm. If you can expand on this subject, I'd appreciate it

What I've read and what I used (a little under) for the rear of the lakester's body. 

I've also had it from someone I really trust on the subject that sometimes it is important to intentionally trip the air so that it reattaches but I've stayed away from trying to do that since I think now we are into needing a wind tunnel or Woody to make sure what we are doing is going to have the desired results,

Sumner

Offline Frank06

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Re:
« Reply #2 on: November 16, 2014, 03:36:30 PM »
Have a look over on ecomodder.com.
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Offline maj

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Re: APS body taper?
« Reply #3 on: November 16, 2014, 03:43:47 PM »
Can i ask why you removed the last fairing, i thought it looked like a very good starting point  ?

 have heard 7 deg also, but tend to use naca shapes as more info is available online esp for laminar flow or detach points


Offline 55chevr

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Re: APS body taper?
« Reply #4 on: November 16, 2014, 05:12:19 PM »
The racer with the best non wind tunnel designed  fairing is Tom Borcherdt "Koncretekid" ... a lot to be learned from his project.


http://www.landracing.com/forum/index.php/topic,9341.msg152684.html#msg152684


Offline sofadriver

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Re: APS body taper?
« Reply #5 on: November 16, 2014, 09:29:43 PM »
Can i ask why you removed the last fairing, i thought it looked like a very good starting point  ?

 have heard 7 deg also, but tend to use naca shapes as more info is available online esp for laminar flow or detach points


It was indeed a good starting point and a lot was learned. Mostly I learned that converting a fully functional road racing bike to an LSR bike  is not the way I need to go to accomplish my goals. I began to realize it halfway thru the first build. So after returning from BNI I decided to go all the way. I cut up the fairings to cement my commitment. A new chrome moly frame is being built and a great engine builder (and past BNI record holder) is on board and excited about the project. Height at top of riders helmet will be 32" and width of 20" giving a total frontal area similar to the Buddfab streamliner.
 I've seen pics of Koncretekid's beautiful bike. I'm taking the whole concept a few steps further. However, our color choice will remain the same since I've still got a half gallon of Rustoleum Safety Yellow paint and some rollers left!  :-D

 Seems to me that the "optimum" 7 degrees might depend on airspeed with more taper allowable at lower speeds (I'm not shooting for 200mph here). Any thoughts?

 Sum........who's Woody?
Mike in Tacoma

"aww, what the hell - let's just do it".............

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Offline wobblywalrus

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Re: APS body taper?
« Reply #6 on: November 16, 2014, 10:24:00 PM »
The book "The Racing Motorcycle" Volume 1, by John Bradley has quite a bit about bike streamlining.  He recommends no more than 10 degrees included angle to the rear of the point of maximum cross section.  I am not sure if this is the angle between one side and centerline, or both sides together.  The 7 degree maximum taper you are planning to use seems to be reasonable. 

Offline donpearsall

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Re: APS body taper?
« Reply #7 on: November 16, 2014, 10:30:24 PM »
Michael,
Take aerodynamic lessons from nature (actually hyrodynamic). The sailfish is the fastest fish in the world, so trying to duplicate that shape is one way to get good aero. I know you are constrained by width and length, but perhaps getting the fairing to emulate the shape as much as possible would not be a bad way to go ( I don't think you need the sail or bill).

Don
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Offline Sumner

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Re: APS body taper?
« Reply #8 on: November 16, 2014, 11:58:21 PM »
Michael,
Take aerodynamic lessons from nature (actually hyrodynamic). The sailfish is the fastest fish in the world, so trying to duplicate that shape is one way to get good aero. I know you are constrained by width and length, but perhaps getting the fairing to emulate the shape as much as possible would not be a bad way to go ( I don't think you need the sail or bill).

Don

If I remember right....



http://purplesagetradingpost.com/sumner/b-ville%20meets/2006%20BUB-4.html

... Dennis said that for the BUB liner he was inspired by the salmon but maybe it was another fish or no fish at all  :-),

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Offline fredvance

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Re: APS body taper?
« Reply #9 on: November 17, 2014, 03:04:39 PM »
I believe that Sam Wheelers streamliner used the Salmon.
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Offline WOODY@DDLLC

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Re: APS body taper?
« Reply #10 on: November 17, 2014, 04:37:32 PM »
They all look fishy to me!  :-D The BUB-7 is a NACA profile from the top and a salmon from the side. Denis likes to say, "The BUB-7 has a very low Coho-efficient of drag!"  :cheers:
http://en.wikipedia.org/wiki/Coho_salmon
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Offline Vinsky

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Re: APS body taper?
« Reply #11 on: November 17, 2014, 05:12:31 PM »
John

Offline Stainless1

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Re: APS body taper?
« Reply #12 on: November 17, 2014, 08:49:05 PM »
I believe that Sam Wheelers streamliner used the Salmon.

I was guessing sardine based on the driver compartment size  :-D
 :cheers:
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Offline sofadriver

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Re: APS body taper?
« Reply #13 on: November 17, 2014, 09:45:01 PM »
I believe that Sam Wheelers streamliner used the Salmon.

Yep. There's a metal salmon on the wall of my shop for inspiration!  :-)

How's the healing coming along, Don?
Mike in Tacoma

"aww, what the hell - let's just do it".............

Bike #833
100cc A/G, A/F and APS/G (in 2019)

Offline wobblywalrus

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Re: APS body taper?
« Reply #14 on: November 17, 2014, 10:44:24 PM »
My Triumph is fully partially streamlined as per FIM rules with a tail that sticks 7 inches back from the tire.  The wheelbase is three inches longer than standard.  I am 5'-11" tall and sorta wide in the shoulders.  It was not possible to get 7 degrees of taper behind the widest point and to have a reasonably narrow tail end.

The nose was made as blunt and rounded as practical so the wide part was as far forward as I could get it.  This allowed for a longer tail taper. The sides gradually transition back at an increasing taper rate with the greatest taper, 10%, being right near the tail end.  I figure, what the heck, it is too much taper but it is doubtful the air would be attached at the tail that far back, anyhow.  Along the sides and forward part of the tail the taper rate is less than 7 percent.

The idea is, it is impossible to get correct taper everywhere on the tail of a short bike.  The excess taper is put towards the back where it does the least harm.

Look at the pix on the DLRA website.  Note Brett DeStoop's Suzuki water buffalo.  That is a good starting point.