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Author Topic: aerodynamics "bump" behind helmet on leathers  (Read 43998 times)
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xpertmachinist
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« on: June 12, 2015, 09:51:32 AM »

I have a question about aerodynamics on the back, that is sewn into the leathers.

At what point is a aerodynamic hump considered "aerodynamic performance", and or is it more for Safety to keep the riders head stable on a "naked" bike?

Kym's custom leathers are being made now and should we have a a bump or no bump?

nothing in the rulebook that I could see

cheers
xpertmachinist
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SPARKY
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« Reply #1 on: June 12, 2015, 11:14:45 AM »

7.C.2  only in partial streamliner
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« Reply #2 on: June 12, 2015, 12:01:07 PM »

Thank you for the fast reply

shawn
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donpearsall
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« Reply #3 on: June 12, 2015, 12:33:55 PM »

Sparky must be referring to some other rule book. Section 7 refers to the engine. I have looked at this year's rule book and there is no reference to the hump on the suit, just that the open class does not permit streamlining. You can email the question to the AMA Rules Committee at tech@bonnevillespeedtrials.com.

I have seen the hump on several riders, but don't know what class they were in.

Don
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xpertmachinist
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« Reply #4 on: June 12, 2015, 02:37:33 PM »

Thank you Don,

I thought I had the wrong rule book. Have sent off a email with this question.

Have opted to not have a hump put into the leathers, too much coin invested to have to use a seam ripper to take out when attempting to pass Inspection.

cheers,
shawn
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« Reply #5 on: June 12, 2015, 05:19:52 PM »

SPARKY is correct, page 127 in 2015 SCTA rule book.

Bill
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« Reply #6 on: June 12, 2015, 05:33:25 PM »

SCTA? What's that? The question was for BMST.

Don
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« Reply #7 on: June 12, 2015, 06:20:26 PM »

 smiley
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« Reply #8 on: June 12, 2015, 06:50:46 PM »

Since you are having a suit made, why don't you opt to have the hump removable with Velcro, zipper, snaps, etc? You will have the option of riding with it or not.
Don
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« Reply #9 on: June 12, 2015, 07:19:39 PM »

I would go with a zipper.
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« Reply #10 on: June 13, 2015, 04:29:01 AM »

I've got a hump sewn onto the back of my Z Custom leathers.  It is "removable" - sorta.  There's a zipper along the top - the dished inward portion where the back of my neck/head would touch it, and opening the zipper allows the "stuffing" to be removed.

Or so was the theory.  When the stuffing is taken out the remaining leather is stiff enough that it maintains shape anyway.  Tech suggested (what - an inspector "suggesting" something?) that if I wanted to run in a class where said hump is NOT allowed -- I'd have to somehow tape it down flat to the surface of the back.  Yeah - like that stiff leather could be mashed down enough to get through said inspector's approval process.  So - I simply ran in a class where there was no restriction on the humpitudity of the suit.

This comment is made with the intent of letting you know what happened to me under SCTA/USFRA rules.  I know the question was BMST-intended, but since I had the forum opened I thought I'd comment.
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Jon E. Wennerberg
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xpertmachinist
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« Reply #11 on: June 13, 2015, 03:47:18 PM »

I really appreciate the insight into this question.

We decided to have no bump at all; if ever we feel that it is needed we can make something work.

Thanks for everyone's two cent. Every bit was good even if coming from a different perspective.

Shawn & Kym
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« Reply #12 on: June 13, 2015, 05:20:26 PM »

Slim,

humpitudity ?
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xpertmachinist
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« Reply #13 on: June 15, 2015, 09:14:07 AM »

I understood Humpitudity perfectly well. It is a rare word in racing circles, and can be used to also explain a small rise point in the tarmac in the drivers line, the amount of clearance needed inside a cockpit for elbows, helmets and other clearance issues , and points that protrude from racing leathers; although I had only have heard it used with women leathers in a similar topic to refer to other fitting issues.  grin

Thanks again
shawn
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« Reply #14 on: June 16, 2015, 08:05:27 AM »

Joe:

I guess in your neck of the woods the word would be "humposity".  sorry for the cornfusion, but I sometimes forget to take into account that there are folks on this Forum that are from New York.
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Jon E. Wennerberg
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