LocostUSA.com

I have no clue on the down force numbers with the spoiler. The whole thing is a WAG (wild a** guess). More monkey see monkey do than any real engineering. However, some down force should be better than no down force at all with a car this light in the back end. The assembly with rear boot cover weighs about 6 lbs. Not too much of a weight penalty for the size of the thing. We approach speeds on a big open course (70-80 mph??) where any aero CAN play a part in traction. How much? Who knows without significant testing. At the very least it looks racy.

The spoiler significantly adds to the strength of the rather flimsy (and light) rear fenders, which was the main goal. I designed an angle close to what the other monkeys are doing in D mod. The total height of the fixed assembly is 6.5" and we are allowed a full 10" away from the body work as a maximum. I thought this might be a good compromise vs. drag because I hope to have fun on track nights at the local road course without worrying about large billboard size pieces with significant drag. The entire width of the spoiler fender to fender is 72". That is a lot of surface area. The end plates can go up to 100 sq. inches but mine are in the range of 50 sq.in. I intend to add a 3.5 inch adjustable spoiler extension and see if it makes a difference. Also toying with the idea of a diffuser under the back end. I understand this will generate more down force than the spoiler with significantly less drag. I think the flat bottom of the Locost with the natural kicked up rear frame lends itself well to a diffuser application. We are allowed a 24 inch total length diffuser per the Mod rules, which happens to fit the car exactly. More Origami.

.....Mark (Just another blacksmith car fabricator)

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Building a whole car from scratch is a 1,000 little tasks, done 1 task at a time, while thinking 10 tasks ahead, then redoing it anyway.
South Bend Region SCCA D-Modifed Class Autocross & Track-Day/TT. Chevrolet 1.4 L Turbo Ecotec Power


Link to my build log:
http://www.locostusa.com/forums/viewtopic.php?f=35&t=3356

Thank God for an honest answer! I kinda figured it was like that, but then ya never know when you'll come across some genius (or BS artist) that can 'splain it all. I had a 4" tall spoiler lip across the rear of my car's bodywork, but it was foam core like the body and the thickness didn't look right somehow. I'm probably going to go with (about) that same height when I do it in aluminum.

I build a flat floor on the main part of the chassis of the Slotus, and a big ol' Gonzo-sized diffuser out the back. Like you said, that upward angled chassis just seems to beg for a diffuser. I'll try to get a decent pic of it, but you can get an idea from this shot of James welding whilst folded up like a taco: It's probably not compliant with anybody's rules, I don't begin to know how well it will work, but it looks cool...

I did read up a bit on diffusers, and it seems the downforce generated is applied near the forward end of the diffuser. I started mine just under the nose of the diff. Everything else is flat.

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

Ahh yes, the Yoga welding position. I am in much better shape at this point in my build than when I started.

A can appreciate your comment on the "Internet Experts/Genius's" amongst us. I always figured "if it don't work I can always change it" engineering philosophy.

....Mark

_________________
Building a whole car from scratch is a 1,000 little tasks, done 1 task at a time, while thinking 10 tasks ahead, then redoing it anyway.
South Bend Region SCCA D-Modifed Class Autocross & Track-Day/TT. Chevrolet 1.4 L Turbo Ecotec Power


Link to my build log:
http://www.locostusa.com/forums/viewtopic.php?f=35&t=3356

Any reason none of the DM guys are running Gurney flaps on the spoilers?

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-Andrew
Build Log
Youtube

Only because Gurney lips are prohibited.

I could be blind - I didn't see it specifically prohibited.

Does it fall under the general "if its not specifically permitted its prohibited" clause?

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-Andrew
Build Log
Youtube

Andrew,

I don't know much about gurney flaps but they seem to be used more on wings. This spoiler is just a flat plate with separated flow and it isn't obvious to me how a flap, gurney or otherwise, is going to do much of anything special in this situation.

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Warren
Isuzu Pickup/SR20DE, +401 COLD frame
Build Log: viewtopic.php?f=35&t=11601

Rule 18.F.1 precludes "wickerbills". ( aka a Gurney lip )

Andrew,

SCCA rules prohibition aside, I had another thought on my earlier comment: Intuitively, I think the gurney style flap (fence, or whatever name you use) must change the apparent angle of attack and pitching moment on the foil. The car itself acts as a good, bad or indifferent very low aspect ratio airfoil (or terrible if a Locost?) and a spoiler like this is effectively a gurney flap for the car ... Adding a gurney flap to this spoiler will not likely change the aerodynamic pitching moment (or downforce) on the overall car. Given the stalled condition of the spoiler, I suppose adding a gurney flap to what is already effectively a gurney flap might simply increase drag (?). All of which s moot in this circumstance.

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Warren
Isuzu Pickup/SR20DE, +401 COLD frame
Build Log: viewtopic.php?f=35&t=11601

Doh! Thanks. I guess it would make too much sense for a motorsports governing body to use the common name in their rulebook (unless Dan Wickerbill beat Dan Gurney to the punch?)

All valid points Warren - I could have sworn I saw them used on spoilers before but chances are I'm confused and making it up.

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-Andrew
Build Log
Youtube

Andrew said:


I think where you've seen the little "wickers" added on is on the trailing edges of wings attached to racecars. I have a friend that has them on both the front and rear wings of his A-Mod car. I've never seen them on a "spoiler" per se.

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

Maybe you're thinking of gurney flaps frequently being used on the rear 'spoiler' (not just the wing) of prototype/sports racers, which operate under somewhat different aerodynamic conditions.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

I have the front motor mount fabricated and motor mounted at correct location. Time to fab the header. This took 6-1/2 hours just to get equal length 2"x 22.5" runners to fit and tack welded. I can get the header in and out without moving the motor. Just enough room for the rest of the exhaust system going back to clear the right rear tire at the turn down tip. Glad my motor only has two primary runners!

_________________
Building a whole car from scratch is a 1,000 little tasks, done 1 task at a time, while thinking 10 tasks ahead, then redoing it anyway.
South Bend Region SCCA D-Modifed Class Autocross & Track-Day/TT. Chevrolet 1.4 L Turbo Ecotec Power


Link to my build log:
http://www.locostusa.com/forums/viewtopic.php?f=35&t=3356

Yo, Loco!
Great lookin' headers, Bro! Good work, especially getting the equal lengths... Well done!

JDK

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

Thanks. This really tested my spatial skills!

_________________
Building a whole car from scratch is a 1,000 little tasks, done 1 task at a time, while thinking 10 tasks ahead, then redoing it anyway.
South Bend Region SCCA D-Modifed Class Autocross & Track-Day/TT. Chevrolet 1.4 L Turbo Ecotec Power


Link to my build log:
http://www.locostusa.com/forums/viewtopic.php?f=35&t=3356