Rare bear 3 or 4 blades?

[jarrodeu]

For many years Rare Bear has had the 3 blade prop (I heard its from a P3 orion, correct me if I'm wrong) but this year are expirimenting with the 4 blade prop. I also heard that they are having problems with it. Have they decided which to use yet? Also Is there a relationship betheen the 4 blade prop and Critical Mass?
Jarrod

[Race5]

Re: Rare bear 3 or 4 blades?

The four blade prop is Rare Bear's. Critical Mass borrowed the prop from them to race last year since her prop was bent in the gear fold accident. They used the prop, in exchange for a carb that the Bear team needed since they did not have a good carb at the time. I don't know if the Bear is having problems with the four blade prop itself, however they are having problems with the ignition and carb again. The race fuel is eating the carbs up when it sits for so long. They'll get her going though, have faith!

Go Bear in '04

[Unregistered]

Re: Rare bear 3 or 4 blades?

The Champ Cars (Cart) run methanol. After running the engine on methanol, they purge the fuel system and engine after every run. It's purged with gasoline.

I never suspected this would be a problem with the racing fuel used in Air Racing.

Is there a problem switching back and fourth between racing fuel and avgas that would make this purge a problem?

Reever

[Race5]

Re: Rare bear 3 or 4 blades?

It would probably help, but maybe it's a plumbing nightmare? Of course I guess they could drain the main tank then run a little 110 through her. I dunno, but they are the experts, not me. I'm sure they are covering all their bases.

[AAFO_WSagar]

Re: Rare bear 3 or 4 blades?

Unless something has been discovered since I was there last week, the carb issue with the race fuel eating the diaphragms, was what happened last year.

This year, the crew replaced and/or had checked or repaired several items in the ignition system during the prop swap. There were some issues with the level of RPM drop during the mag checks.

As of last week on Sunday afternoon, the complete picture of what, exactly, is going on was not clear..

That said, the plan was to swap out the carb to a known good one to eleminate that as a possiblity in the diagnosis process..

Sharon and Lyle are working on an update that should bring us all up to date. It's a "story in progress" though so we may have to wait a few days while the crew finishes out the problem chasing.

Wayne

[Unregistered]

Re: Rare bear 3 or 4 blades?

The Champ Cars (Cart) run methanol. After running the engine on methanol, they purge the fuel system and engine after every run. It's purged with gasoline.

I never suspected this would be a problem with the racing fuel used in Air Racing.

Is there a problem switching back and fourth between racing fuel and avgas that would make this purge a problem?

Reever

The problem is the 165 Race Fuel is nasty, toxic stuff. That's why it works so good, but even if it's flushed with 110 LL after racing it seems to still take the flexibility out of the diaphragms a few months down the road.

DT