Hollowed Out Cavity

[DNA RACING]

How did Flapjack perform?

it had some issues early on, but after that it was top 5 or so.

 

[MWDracing]

My unlimited car that ran against you in the March finals was hollowed out and unfilled. It did OK, if 2nd is OK. I used a slightly thicker type of Monokote. There was absolutely no vibration, but you have to have enough struts so it wont flex, and the shape must be right and heating it on is an art. I've tried several types of Monokote, and only one turned out right.

We won't tell them what the real difference was in your car Roger

Ian

My wild guess is wheels...

MWD

 

[OPARENNEN]

My unlimited car that ran against you in the March finals was hollowed out and unfilled. It did OK, if 2nd is OK. I used a slightly thicker type of Monokote. There was absolutely no vibration, but you have to have enough struts so it wont flex, and the shape must be right and heating it on is an art. I've tried several types of Monokote, and only one turned out right.

We won't tell them what the real difference was in your car Roger

Ian

My wild guess is wheels...

MWD

No Secret. I used GoatBoy's wheels. I have two sets, the second set was polished down to the point that the running surface was very pointed (Razor thin), the earlier set's running surface was maybe 1/64 of an inch thick. I RECENTLY ran tests with the same body and axles, including an older set of Jewkes wheels.
Results:
2nd set = zero (i.e. best)
1st set = 5/1000's slower on average
Jewkes = 1/100th slower on average

Go Goatboy's latest version

PS Incidently, in March Madness, I was using GB's earlier set, so in April, I should have better times (I HOPE), however, my test track is a plastic 32' track with a manual timer, which at best is unpredictable.

But back to the original point - Body was completely hollow, top to bottom, from forward weight pocket to front axle, covered by a certain type of Monokote (which you have to discover for yourselves) AND ABSOLUTELY NO VIBRATION! But includes iron on technique. Go Experiment.

 

[Ryanh]

Just out of curiosity how heavy "or light" are the hollowed bodies at the point of being ready to paint? Just trying to get a comparison to go by.

 

[Old Geeezer]

Mine are about .28 to .36 (glue,carbon fiber,wood) before paint. It is amazing how much various glues & chemicals weigh when building a composite car. I can get 4.25 oz. of 1/4" cube weight plus some tungsten putty in both the Unlimited & Eliminator class bodies. I am working on a new carbon shell design that will have no wood or fillers at all...... will see what happens it will be .17 oz and not require painting. The technology to do this is hard to scale to the size of these cars...... so it may not work. Not that it is not strong enough or will break apart, just that your fingers & eyes can't work with the materials at this scale.

 

[OPARENNEN]

Just out of curiosity how heavy "or light" are the hollowed bodies at the point of being ready to paint? Just trying to get a comparison to go by.

I weighed the various parts of two unfinished bodies, ready to finish except the noses had not been sanded to a point:
However, my bodies were both of DD4H's cherry pine. There are lighter grades of pine available, but I wanted more rigidity, plus DD's wood is easier to work with. One body was 3/16ths and the other 1/4 thick. Both were only frames, i.e. hollowed out.

Body unfilled with anything 1st body ='s .355 oz 2nd body ='s .345 oz
The balsa that I was considering to use as filler is .110 oz
The two pieces of Monokote (i.e. top and bottom) ='s .050 (i.e. .025 each)So a finished car with Mono top and bottom would be about .510 oz, or .460 w/o monokote, i.e. ready to paint.

I don't know yet how much sanding down the nose will reduce, but it will be very small. So that means that I can get about 4.5 ounces of weight in the car, or a bit more if I don't fill with balsa.

 

[Kinser Racing]

I'm starting to think I should hollow out my bodies. /images/boards/smilies/thumb.gif

 

[aircooled]

If fenders are used would that added weight reduce the amount of extra power able to use?

 

[Old Geeezer]

It depends on what the fenders are made out of, I just made a pair of carbon fiber fenders that weigh only .1 oz for the pair ( pain to make as it took over 15 hours of work.)

 

[Guest]

Ken,

Those are TRICK!! Excellent craftsmanship my friend. The builders over here just keeping raising the bar month after month with builds like this. Can't wait to see it run.

Ian

It depends on what the fenders are made out of, I just made a pair of carbon fiber fenders that weigh only .01 oz for the pair ( pain to make as it took over 15 hours of work.)

 

[Old Geeezer]

Thanks, Ian ...Actually I doubt if I will make any more as the time it takes is not worth the performace gain. I just wanted to see if it was possible and the team car seamed like a good way to try them.

 

[Chief]

[font="times new roman, times, serif"]Not to mention Old Geezer you are competing for bragging rights on the appearance of the car with me and my car and so far you are winning...Dadgum it anyway!!!

[/font]

 

[Old Geeezer]

Chief......that might have had just a little to do with it.

 

[Kinser Racing]

I couldn't agree more. Very nice!

Ken,

Those are TRICK!! Excellent craftsmanship my friend. The builders over here just keeping raising the bar month after month with builds like this. Can't wait to see it run.

Ian

It depends on what the fenders are made out of, I just made a pair of carbon fiber fenders that weigh only .01 oz for the pair ( pain to make as it took over 15 hours of work.)

 

[W racing]

Those fenders are awesome.

ANother benifit of the hollow body is that birch plywood is easier to paint than pinewood.

 

[Guest]

Spray the kicker on the balsa before you insert it into the cavity, then CA it around the edge only after you put it in the cavity. This way it won't soak all the CA into the balsa letting it bond with the pine on the edge. Are you covering just the top with birch?

This has got to be one of the coolest tricks. Zip Kicker before you glue!