Rare Bear Anyone? Another question.

- T
- TX_QBALL
  
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posted
19 years ago

Thu, Dec 30, 2004 2:22 PM

My Bud has just about finished his RB and built to specs (per instructions) using all the stuff that came with it.

Tell you what: the thrust of the engine looks like "at least" 5 degrees of down thrust. The right thrust is slight and looks ok but the amount of down thrust looks bad as it's not even close to the center of the cowl hole. This cowl fits against a grove in the fuse so the cowl can't be moved too much. Just looks terrible. Anyone done this thing?? What did you do?? Shim the mount up??? Thanx

- S
- Steve
  
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posted
19 years ago

Fri, Dec 31, 2004 3:38 AM

snip

... the amount

I can't speak to this particular plane, but usually, when a firewall has built in right- or down-thrust, the engine mount is offset (left or high) to compensate and place the prop shaft at the opening of the cowl. Did the plane come with pre-drilled mounting holes for the engine mount? If not, it is highly likely that your bud missed the critial step of mounting the cowl and centering the prop with the engine bolted to the mount to determine the proper location for the mounting holes.

If the error is large enough, I'd just pull the mount and re-drill the holes in the right places. To fuel proof the old holes, you can just plug em with putty and epoxy over. If the new holes would have to be too close to the old holes (or partially IN the old holes) you might have to resort to plugging the old holes with pieces of dowl before you re-drill.

Here's hoping you can get to the back of the firewall. :P Good luck.

- J
- Jim Gill
  
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posted
19 years ago

Fri, Dec 31, 2004 10:09 AM

This does seem to be a design problem with the model. Just shim the motor mount to get the spinner in the centre of the cowl opening. Be prepared for the need to add down trim on the elevator for level flight, I needed most of the trim movement on the first flight. I found that the movements given are very sensitive and ended up on low rates set at 65% with 50% exponential on the test flight.

Jim Gill Dundee Model Aircraft Club

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