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Author Topic: Al B's Big Cat  (Read 3743 times)
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Bredehoft
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« Reply #50 on: November 24, 2014, 04:25:51 PM »

Hi John,

1) - CG is roughly midpoint, maybe farther aft.  I have never done a TVo calculation on the Big Cat, but it seems to like a rearward CG

2) - I'd run about 1.5x to 2 x the motor peg length.

3) - yes 18g - 20g should get you a nice, light plane.

4) - cannot answer; I don't use dope.  I just spray a light coat of krylon and go.

5) - I never tried that on the 5 or so we have built.  Yes, the stab is in the way for a stooge bracket.  We got around this by either hand-stoogin or mounting the model upside down int he stooge (our stooge has a set of holes at the very top).

Down and Side thrust and plenty of it.  They like to climb right and (with the offset rudders) glide right.  If it spirals in, add tail weight - OR - check the prop freewheeling.

--george

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iflyhlg
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« Reply #51 on: November 24, 2014, 06:47:42 PM »

George, are you saying that the model turns to the right in power and glide even with the left rudder offset? Both of my models turn left in power and glide and I had to add a strip of tape to make a wash-in tab to keep the inboard tip up on the first one. The second model I reduce the rudder offset.
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jswain
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« Reply #52 on: November 24, 2014, 08:03:05 PM »

thank you George.
This info is exactly what i was hoping for.
I will try the krylon on a test frame/tissue sheet to see how that goes, i don't want a pretzel but would like a nice appearance too.
The model is now in progress, it's nice to build something for once that goes together 'relatively' quickly Roll Eyes .
take care, john s.
Hi John,

1) - CG is roughly midpoint, maybe farther aft.  I have never done a TVo calculation on the Big Cat, but it seems to like a rearward CG

2) - I'd run about 1.5x to 2 x the motor peg length.

3) - yes 18g - 20g should get you a nice, light plane.

4) - cannot answer; I don't use dope.  I just spray a light coat of krylon and go.

5) - I never tried that on the 5 or so we have built.  Yes, the stab is in the way for a stooge bracket.  We got around this by either hand-stoogin or mounting the model upside down int he stooge (our stooge has a set of holes at the very top).

Down and Side thrust and plenty of it.  They like to climb right and (with the offset rudders) glide right.  If it spirals in, add tail weight - OR - check the prop freewheeling.

--george


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Bredehoft
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« Reply #53 on: November 24, 2014, 09:19:05 PM »

George, are you saying that the model turns to the right in power and glide even with the left rudder offset? Both of my models turn left in power and glide and I had to add a strip of tape to make a wash-in tab to keep the inboard tip up on the first one. The second model I reduce the rudder offset.

No, that was quite a typo that I made - the plane glides LEFT unless you change the tail - my very large mistake!

--george
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« Reply #54 on: November 24, 2014, 09:28:00 PM »

So you are climbing to the right and then gliding left. I will have to put in a lot more right thrust.Thanks George.
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Bredehoft
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« Reply #55 on: November 24, 2014, 09:32:59 PM »

In our experience, if you are using full torque on 2 strands of 3/16" or even moderate torque on 4 strands of 1/8", the plane will torque left on takeoff.  Counter this with right and down - avoid straight-away flying under moderate power.  Flying a lightly-built Big Cat with 2 loops of 1/8" "can" be flown left-left.

--george
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« Reply #56 on: November 24, 2014, 09:35:40 PM »

Thanks, I will try it next time I go flying.
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« Reply #57 on: November 25, 2014, 02:04:53 PM »

George, I have been using two strands of .150 for my models which weigh 16 grams. 1/8  gives me a long weak climb and 3/16 was way too much. I have been flying left-left but will try the right thrust and go right-left per your directions. I love flying them. I am doing 90 sec plus in calm conditions.
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jswain
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« Reply #58 on: November 29, 2014, 11:34:14 PM »

big cat update...

i almost have all the major bare frame components assembled/built.

just need to cut out the fuse cross members all the same size and build up the two fuse sides tomorrow.

hopefully the big cat is flying by the end of next week, i think its 'do-able' if the weather doesn't turn super-windy (as its prone to do this time of year...) Grin

john s.



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Swarthog
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« Reply #59 on: November 30, 2014, 01:23:52 AM »

Mine really likes to go left/left.  So much so that I would use slightly less rudder built in next time. My experience has been when putting in lots of turns the torque will make your thrust adjustments very touchy. A fun plane that actually handles the wind pretty well. 
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dputt7
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« Reply #60 on: June 26, 2017, 01:13:19 AM »

Hi
      Could someone please tell me the fuselage length of the Big Cat, Ive blown up the fuselage plan to the correct width but it comes out at around 20" long. I cant print on legal size paper so I need a length to scale to.
                                                                                                                            regards Dave
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Bredehoft
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« Reply #61 on: June 26, 2017, 06:40:02 AM »

16.5" Wingspan, 14.75" fuse length.

a laser-cut short kit is available HERE

--george
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dputt7
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« Reply #62 on: June 26, 2017, 07:31:51 AM »

Thanks George
                      The laser cut kit sounds good but I've got a couple of days off and I need a new model for Indoor so I thought I would give it a go.
                                                   Thanks again,
                                                                        Dave
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dputt7
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« Reply #63 on: July 02, 2017, 06:23:38 AM »

         Just got my Big Cat finished, thought you might like to see it.
                                                                                                     Dave
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Bredehoft
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« Reply #64 on: July 02, 2017, 06:29:30 AM »

Looks great!

--george
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Hepcat
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« Reply #65 on: July 02, 2017, 08:37:20 AM »

There was some concern earlier on in the thread about the offset on the fins.  It looks to be about 1.5 degrees to me.  On that basis I reckon that flying in circles about 50 feet diameter the offset would not have much effect because the circular airflow relative to the model would be be passing evenly on both sides of the fin. By all means check my figures.  I know that at my age I do make silly mistakes doing sums.  There is no magic about the 50 feet but I think that would be the sort of figure you would expect with a model of this type.

John
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dputt7
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« Reply #66 on: July 02, 2017, 09:30:04 AM »

     John
             The offset on the plan I used is 5degs and as I intend to fly this indoors with a long slow motor and just a couple of degrees side thrust I would expect that this would be about right, though I base this only on experience and no theory what so ever.  I should get a chance to fly it next Saturday night so "the proof of the pudding will be in the eating"
                                                                                                                                                                                                             regards Dave
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dputt7
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« Reply #67 on: July 09, 2017, 05:12:51 AM »

  Had a chance top fly my Big Cat last night at Indoor.  It was a bit nose heavy so I took the easy way out and added a small piece of clay to the tail and then all it needed was a bit less downthrust. I just used a loop of .135" rubber and it put in flights of around a minute, quite a satisfying flyer.   It flew in left circles of around 25'-30', From an ROG the circles were slightly larger but as the power decreased it tightened up a bit.  If I get keen I may try a lighter prop or a bit more incidence in the tail plane so I can remove the clay.  Very pleased, it's a great flyer.
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