bentwings

While I'm into RC stuff... Ziroli 118 B-25 and a Z P-51 I'm also into racecars.

Nostalgia Top Fuel Funnycars to be exact.

Here is the question...we run a large flat rear spoiler roughly 65 inches wide by 12 inches high and angled back at about 45 deg. We are limited to spill plates from the base of the rear window to the top of the spoiler. In order to keep these straight in the direction of travel there is only a maximum of 40 inches between them. This means that the outer 12 1/2 inches on each side is just hanging out in the breeze....if you call 240+ mph a breeze. There is no rule regarding a spill plate on the very ends of the spoiler so do you think this would be worth while??? It is easy to fabricate this and may be slightly ugly but if it could provide more down force we certaily would try it.

There are many limits on engine size and equipment equavalent to "restrictor" racing so we are always looking for and edge. we have no access to windtunnel and I doubt anyone else does either...yet.

Hp is really not an issue even within the limits. We still can get loose of the top end so any extra down force is welcome.

We are already stretching the rules to the limit on the other allowed aerodynamics....side skirts, front spoiler, soft mounted body (squishes down to 0 ground clearance from 200 mph +), smoothed body lines and others.

The "big show" guys all run "dump truck" style spoilers with spill plates on the very ends so our thinking is that we can use something similar.

da Rock

Do what modelers often do. Try it out.

If you're talking about tip plates, they work. Your present foot long wings sticking out either side aren't doing you much good. Notice the front wing on F1 cars. They all have tip plates, don't they?

If you look at the side plates on the wings (roofs) of World of Outlaws dirt cars, what do you see? Advertising. So use that as camoflage for your plates if the only place you test is in the qualifying runs. Otherwise slap some naked ones on the car and do some test runs wherever you test. If you're pushed to try the plates where you go through inspections, then slap advertising on the plates to have a reason for them. Even your competitors might not think of aero.

Tip plates will definitely increase whatever forces those wings create. They'd be worth trying.

Be prepared for more than you expect however. You've basically got very low aspect ratio on those wings. That is not what usually works efficiently as a wing, and when stalled creates way more drag than anything else. I believe I'd have tried running without them suckers at least once way before now. I'd bet you don't get squat for downforce now but do get a bunch of drag as your car gets going. I'd bet running without and with tip plates both offer an opportunity for better top speeds. But if the downforce down the strip really is needed, even what you're getting now, the first test would be with plates. Going faster and without the downforce down the strip might not be easy to "trim" for.

Got any idea how much downforce the present rig is supposed to give you?

rmh

For the non racers - too much downforce up front can cause a "groundloop"
just like a car on icy road with rear drive - the rolling resistance up front, acts as the "pivot point".
This stuff is a tricky balance of correct down force up front -and rear downforce - a fueler which hooks up solidly at the wrong time goes airborne.

In a perfect world a computer wouldcontrol -perfectly the right amout of front downfoce.
The REALLY fast street racers run four wheel drive to keep traction/control correct .
over the counter cars now can hit -0-60 in under 3 seconds and 12 second quarter miles are common.
years back a 13 second street car was really quick

1320Fastback

I remember how excited I was when my 68 Mustang got into the high 13's

Now it's just a old slow classic!

Got a point with the F1 cars wings.
They are the most advanced form of racing and the aero packages they come up with are start of the art.

bentwings

This a nitro burning fuel drag racer. We have run 3.7 sec and 205 mph 1/8 mile without trying very hard. These motors make 2700-3000 hp and run 9500 rpm. It costs nearly $1000 a run with no broken parts.

So testing is very expensive. We typically would run a pass in competition without the device then make no changes and run with them. We have run 3 runs .03 sec apart many times so a test of one can be valid.

As for advertizing..we don't advertize without getting paid for it..period. So and tip plates will be bare for the tests.

This type of spoiler has been thru the wringer many times. Rip one off on a pass and you will have your hands full. I know the F! and outlaws look down on these cars but it is our type of racing and we have to play within our rules.

Lots of numbers have been kicked out on the real force these spoilers give. Back in the 70's when this style of Funnycars was first popular there was a windtunnel test done and it was reported that there was in excess of 1000 # down force due to the rear spoiler. the exact number was closlely guarded. As a result the limits today on this class of car. The headers produce more than this. If you drop a cylinder it affects handling and can cause the car to drift all over.

I just got a rendering of car and the new paint so I'll post a picture as soon as I can.

Thanks for the comments.

Our B-25 is very near completion...the FC is taking too much time. haha

combatpigg

My Feedback: (3)

Off topic, but about how much would it cost [on average] to run the same car on just methanol...?
There are transducers that could record the down force generated. I doubt they cost very much if you rig your own system from electronic supply house stock.
Just think about the power that gets diverted from going down the track into supplying down force. Take 1 step backwards for every 2 steps forward.

rmh

good 1/8 mile numbers!
You never do hook up, do you?

bentwings

The clutch hooks up at about the 1/8 mile and there is 5-10% slip at the tires from there on. There are clear tire marks all the way down.

We have an onboard computer/data logger, it cannot interact real time with the functioning of the car however by the rules. No traction control etc. Monitoring suspension would be difficult as there is no suspension. There are optical sensors to measure position but the tires grow rather dramatically so you would have to take this into consideration. We have a wireless real time down load which is one of my functions on the team. By the time the car gets back to the pits I have a full print out of what happened and a full overlay of the mechanical and fuel systems. I then enter the timeslip incrementals and plug them into the overlays. It's quite interesting. Sure wish we had this back in the old days. Reading sparkplugs and time slip was all we had. We don't even burn the plugs anymore unless something bad happens.

There is an alcohol class. Surprisingly they run slightly faster and quicker. They use much more streamlined bodies, far larger superchargers, and 3 speed transmissions plus they can have the "dump truck spoilers". Their cost to run is better than double ours. $10k for just the blower and it lasts only a few runs before it needs servicing. We have much more restrictive rules.

I ran the alcohol class back in the 70's when it was still fun. We ran 4.5's and 155 mph 1/8 mile times on what we call streetrod motors today. About 1350 hp. These cars would stay with the nitro cars for about 200 yards back then. Yes we had a spoiler too but smaller.

Today we use about 10 gal of alcohol a year to trim the nitro. We do start the car on alcohol but it runs so cold that the alum block doesn't get warm at all. Even after a full run on nitro the block and heads get only to about 170-180 deg. We have to pre heat the oil before a run too.

rmh

the costs for racing have gone outasight !
Everybody I know who runs out of street classes has a few sponsers
I was a drive it and race it guy years back-
The current hi tech stuf is really interesting but I just kinda watch -.
I think more fuel goes out the pipes than is burned on some of this stuff

bentwings

Here is the new car art work. All black, gold stripes with red outlines, ice blue lettering with a small amout of gold leaf.

Front spoiler is 2" off the ground ....min allowed
rear spoiler is level with the top of the car.....rule book
current spill plates base of rear window to top of spoiler.....tip plates unspecified....we will try and run them.
side skirts 2" above the ground behind the front wheel to 4 " off the ground at the rear wheel....rule book
minimum wheel well openings all around. Must appear stock...
vent window permitted with 1'" lip
rear quarter window permitted if fixed on original body style. (Cobra)
no vacuum holes permitted in the rear of the car...inside or outside.
Alll mounting screws are flat head stainless.
body is one piece fiberglass...weighed 80# raw and now weighs 110# with all mounting hardware, interior aluminum, front and rear latches, windshield, roof hatch, paint and dual parachutes......race ready.
426 cu in all alum hemi style motor, billit block and heads...no water passages, .750 lift 296 deg roller cam, mechanical fuel injection, supercharged, 90 % nitro fuel. 35 pounds boost, weighs 2300 rolling with driver. 2800 min hp. 9500 rpm.

thanks for the help

jester_s1

That's a sweet ride. How many runs can the engine make before it has to be rebuilt? I'm also curious what the differences are between this engine and the current top fuel engines if you have a minute to explain it.

combatpigg

My Feedback: (3)

Totally gorgeous..!
It is still recognizable as a Mustang.
I wish all Funny Cars were done the same way instead of looking like generic bars of soap.
Drag Racing in general has gotten too quick for me to watch. I'd rather just walk through the pits and take in all the craftsmanship and artistry.
I was happiest as a spectator when T/F and F/C were doing 7's..maybe high 6's in the early 1970's
I was also happiest when you could compete in a pro category without major corporate sponsorship..
In fact, I'd rather watch nostalgia drags, but those old clunkers do tend to oil down the track from time to time.....
I suppose the NHRA doesn't need to listen to old fogies like me if they keep raking in the dough.

bentwings

Thanks for the compliments. We are trying to make this as flashy as the cars were back in the 70's and run with the best of them. This is a spectator oriented operation so if you see use stop by and say hi. You will get the quarter tour. The truck and trailer are a showpiece worth seeing by themselves.

Ok I'll try to make it brief. We are pretty excited about this car and race team. There are 3 generations in the crew....me, my oldest son and grand son, plus a couple others. Probably unique in the Nostalgia Top Fuel ranks.

As for the motor. The block, heads, crank,rods,pistons, rocker arm assemblies, as well as smaller parts are all the same as the top fuel or "big show" as we call them. Cams are different, The fuel system, superchargers,and injector hats are different.

We are limited to a single magneto with points...similar to the 70's style
The supercharger is called a 6-71 but is all special and flows about like a 12-71 of the 70's
The blower can only be run 19.8 % overdrive. Even with this we still make 33-35 pounds of boost.
We can only use 1 fuel pump 21 gal per min certified flow.
This motor is 426 cu in where the "big show " guy all use 500 cu in 3/4" strokers. We are limited to 500 cu in but it is shaking out that 417-426 motors make more power. It's complicated. Lots of rpm. We have an even shorter stroke but larger bore motor in process.

The class Nostalgia Top Fuel funnycar is intended to represent the 70' funnycars. However the motors are up to date and while there are tribute cares such as this there are new names on these cars done by some of the younger guys.

The car my son and I built last year ran 5.90's and 240 mph on the lesser tracks in the midwest. Unfortunately the owner subscribed to the "used parts are ok" philosophy and 4 motors kicked and averge of 4 rods each out on 4 consecutive weeks. all 4 runs recorded 5.90's even with the rods hanging out at 1000 feet. The 5th week broke a rear end so it was a tough season. As a result the driver left the team and created this new team. We got good offers so we left too. Rats jumping the ship as we are told. haha

As for how many run between overhaul: difficult question
The motor is usually stripped to the block and crank each run. On a good day we just install the next set of rods and pistons in rotation....like pitchers in baseball. We call them "swinger" as they swing on a rack of 8.
We will run 5 runs and toss the rod bolts
10 runs and toss the rods
any pistons that survive 10 runs will be tossed
The crank goes in the trash at 20 runs
Bearings generally last a week end but are replaced as necessary. We check them every run.
Clutch parts are replaced as necessary. Generally the 3 discs last 5-10 runs and floaters about the same. the titanium flywheel and pressure plate may last a season but we have a new spare complete clutch.
The blower is checked each week and serviced as needed but it will get sent to the mfg for any major work. We have a new spare $9500.
the trans usually only requires clutch discs about 10-15 runs otherwise is pretty bulletproof. we adjust it each run.
The current rear end is "big show" and will last the season. A ring and pinion is $1350. We have a new one on order.
We use a dry sump oil system with 20 qts of oil. It's changed each run and sent to the recycle tank in the truck shop.
The motor uses about 13 gallons of nitro per run. 90% is pretty standard for our tune up.
Tires last about 10-12 runs. We have 3 sets ready to go. It takes a while to get tires so we have to stay on top of them, ordering them ahead of time.

Monday of the first day home the truck and trailer go into the truck shop for any service and refitting. Restock the coolers and refrigerator, dump the black water and fill the water tanks etc. wash and clean etc.

I have an Excell program to help with logistics on this stuff.
You can see why it takes 4-5 guys to operate these cars. There is a lot to do to turn one around in 45 minutes.

Now if you kick the rods out it is a different story. We have a complete spare motor that we can change in about an hour if need be.

Hope this answers the questions.

Sorry for filling the RC pages with hotrod stuff.
I'm working on the Z-B-25 scale exhaust system. You would think that with all the automotive equipment available it would be easy to make this up. haha. I lack a good bender for thinwalled tubing. I have a friend who has a metal working shop that is helping create a special bender so hopefully this will work out. I already have a system on the Z-P51 but my son wants me to re do it so I have more work. The bomber is almost ready to fly so I may just make a temporary straight pipe and get it going. I did repair a broken stainless steel pipe for one of the readers here a while back so I do do this occasionally. I have a brand new top of the line TIG welder so it's possible to do some delicate work like this.

jester_s1

Wow. I knew those nitro engines were high maintenance but didn't realize the engines were torn down that much in between each run. And to do it all in 45 minutes is amazing. Thanks for taking the time to explain all of that. And good luck on the B 25. I'll keep an eye out for pics when you're done.

bentwings

Here is my streetrod. I purchased a bare frame and fiberglass body then built the entire car myself except paint. I even have an industrial sewing machine that I used for the interior.
41 Willys, 350 sbc 6071 blower, 2x 750 carbs, T-350 trans, 9"Ford rear end 3.5 gears

0-60 3.8 sec with street tires, thru the mufflers....put it in drive and step on it. Burns reg 87 gas 15-16 mpg. 18,000+ miles. driven rain or shine and sometimes in the snow. I have driven it at 5 deg F

combatpigg

My Feedback: (3)

Thankyou very much for that fascinating snap shot of what it takes to run a funny car in that class...!
The Willys is just too much....! I used to look through the Anderson Industries catalog and drool at some of the early F/G bodies they had for sale.

Lownverted

My Feedback: (4)

Great read....thanks for taking the time to explain all of that stuff. Fascinating.

Anyway, I would be very tempted to try placing some VG's at the roof/window break. (if it's legal). You are likely making some lift there and losing some downforce from the spoiler due to separation. That coupled with the side plates should help out.

Cheers
Red

BMatthews

Could the "spill plates" be relocated to rise up off the side of the body and thus become end plates? I'm thinking that the spill plates would be the ONLY plates and that they would connect more or less to the body along the top of the orange trim stripe or just a little above. Would the rules allow that?

I'm thinking that if the spill plates were out further like this that they would scoop in some of the side air and push it into the inner area.

Another possible thought is that there's still quite a kink where the roof transitions to the rear window. A turbulator strip a few inches ahead of the roof to rear window trasition may well aid in getting a smoother flow into the dip of the window area and avoid much of the turbulent bubble masking out some of the downforce spoiler.

Much of how all this would work is based on rather WAG's about how the air is flowing over the car. If you can't get any wind tunnel time to test this you can do your own by using the old wool tuft and camera solution. Basically you tape tufts of wool over one side of the car and tape small "keychain" cameras on short stands to the other side that will film the tufts during a run. You then activate all 8 or 10(?) cameras before a launch, do the run then go back to the shop and load 'em all into the laptop to view. You then try something such as the turbulator strip and film the results on the next run. If you're running the car anyway you may as well get more than one use out of the cost of the runs. And if you can't actually arrange for any wind tunnel time for testing then tuft testing becomes a valid option.

Hint, like with any system that is being measured you have to make sure that the very act of measuring or introducing measurement means does not affect the results. For tufting an area the tufts alone can and would provide a skin turbulation effect so simply adding tufts ahead of the point where any laminar flow is occuring the results will be swayed. So you'll find that you need to do the tests in patches and learn about a particular area before moving on to the next downstream area of the car. But done in suitable stages you'll obtain a good feel for the areas of smooth and turbulet flow. Knowing this you can modify and test again with more tuft tests.

Another good option would be to mount the body to the frame with fixtures which have load sensors in them and record the readings during a run. By knowing the up or down loads at the body attachment points you can infer the amount of downforce being obtained, possibly any areas of low pressure above and high below and the effect of any modifications you're doing. If it's one of the bodies where it hinges off the front or back and attaches at the opposite end load sensorts at those points would be a good start. In addtion skin tension sensors located on the inside surface of the body would register any flexing inwards or outwards of the body during a run. Inwards implies a higher pressure outside than in and is good as it contributes to downforce. Any sensing of outward flexing on the horisontal surfaces implies higher pressure inside than out and implies some amount of upward lift for that area. Obviously the less lift and more down you have the better.

bentwings

rats...I just spent an hour writing a report and reply and the server dropped me. Sorry I'll have to respond tomorrow.

Here is the final rendering drawing. we like it

Thanks for the interest.

BMatthews

I've had that happen all too often with RCU. You'll find that using a "Post Reply" instead of the "Fast Reply" is less likely to have that happen. Or to be sure cut n' paste your reply from Notepad or similar into the editor window.

kenh3497

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Very nice car!!!

Ken

Sport_Pilot

I felt the same way when my 55 Chevy went into the 12's.

bentwings

A short update..
The body will be delayed a week or so...painter miscalculaied...haha
The aluminum or "tin" as we call it will be back from anodizing Monday.
The chassis should be back from the powdercoater Tues or Wed.
I'm currently building the fuel tank and oil tank.
Today my son and I tackled the rear end. It is a huge piece. we are changing ratio from 4.10 to 4.30. It was supposed to be a simple disassemble and reassemble. However the best laid plans........ turns out after tring the special tool for the pinion nut removal failed that brute force of a 3/4 in air wrench also failed so we put the model airplane technology to work. Instead of a Dermel tool we got after the nut with a cut off grinder. We cut almost a quarter of the nut off and still coud not get it to turn. finally a good amount og heat and the 3/4 air wrench got it moving. We were successful in not damaging the pinion so it survives as a spare part. I imagin a nedd pinion nut is inthe $100 range.

We also were contracted this week for a big race this summer. Called "The Night of Fire" It's at Cedar Falls Ia. Great program...jets, dragsters, us the funnycars, old time prostocks and "Bennie the Bomb"( blows himself up in spactacular ways) plus huge fireworks. I'll put more infor up as it comes in.

We still are looking at May 5th for the first runs. Byron Dragway near Rockford Ill.

Mean time I have my streetrod out cruising in the fine spring weather. tomorrow is the Sat breakfast and cruise.

Also did a little work on my other son's Z-B-25 exhaust system. We are going to try a borrowed bender for the tubing. He is also building a pair of Ultra Sport 1000's for his OS 1.08's.

BMatthews

Guys, as much fun as this is and as interesting it is I have to remind you all that this is a MODEL AIRPLANE AERODYNAMICS forum. I don't mind discussions wandering to the aerodynamics of other vehicle types be they models or full size. But let's keep things focused on the aerodynamics rather than getting into blow by blow painting and assembly side trips.

Sorry to put a damper on things but we need to keep it a little more focused or by the rules I'll be forced to close the thread.

bentwings

I was hoping we would not stray too far so if it is ok those interested can PM me and it can go off line.

thanks