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Author Topic: Big Job questions ???  (Read 950 times)
Allan Perret
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« on: May 05, 2012, 03:41:34 PM »

1..What is a good target weight for the Big Job ?

2..I've noticed the last couple of years that several have used 60+ size engines in them in place of the original's Fox59. 
    What was the weight and power characteristics of the Fox59, how does it compare to the modern 60 size engines.

3..For those that used the 60+ engines did it require a lot of tailweight for balance ?
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Allan Perret
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« Reply #1 on: May 06, 2012, 12:52:38 AM »

1..What is a good target weight for the Big Job ?

2..I've noticed the last couple of years that several have used 60+ size engines in them in place of the original's Fox59. 
    What was the weight and power characteristics of the Fox59, how does it compare to the modern 60 size engines.

3..For those that used the 60+ engines did it require a lot of tailweight for balance ?

Allen,

Maybe I can answer some of your questions.

By "modern" standards, the Bib Job is not a large airplane, though bigger than "most" OTS ships.  Area is about 570 sq in on a 54 inch span.  It is bigger than a Jamison, but not as large as the Humongous.  (These three aiirplanes represent some of the best in OTS designs currently being flown - my unbiased opinion.)  The original by the Naccarato's back in 1948 had the long shaft Fox 59.  Charlie Reeves (who finalized the plans published in Flying Models (as approved by Tony Naccarato and these plans are the basis for the RSM kit) has built several around 52 oz with the short shaft Fox 59.  He has won the Nats OTS event and placed well there and at VSC several times.  I have an engine very similar to the Double Star 54 in mine at 54 Oz.  It has also won the Nats OTS event and this year it won the VSC OTS event.

The Big Job has a very short nose.  It is critical to keep the weight out of the tail during consrtuction, though it is also important to keep the tail stiff.  I think it would be very difficult to build a nose heavy Big Job.  The problem is compounded because the nose/cowl shape almost dictates that either the long shaft Fox or engines with a shaft extension need to be used.   I have probably an extra 2 oz of weight in the front end of mine and I am using a shaft extension which moves the engine back, which has required more nose weight..  I do not know how much Charlie carries in his - maybe not so much because he can build light.  Because of the area, you should shoot for a weight of 50 to 52 oz for a nice performaing ship in the OTS pattern.  The airplane likes the power of the bigger engines.  My Big Job first flew with an OS 49 set up for Stunt by Tom Lay.  It workd OK, but the airplane really works better with the bigger engines.  The airplane would probably do OK with something like the ST 46, but it would be better with the ST 51 or even better with an old ST 60.  I think Windy Urtnowski has an ST 60 in his.

Charlie gets a lot out of his Fox 59's.  It makes a nice combination with the Big Job, but I will leave it to others to discuss how the Fox compares to other and "more modern" 60's.

Keith
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Allan Perret
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« Reply #2 on: May 06, 2012, 05:42:45 AM »

Thanks Keith for the reply.  The motor I was thinking of using in mine is a Stalker 51RE, weights 10.7 oz with the muffler.  The Stalkers have a longer than average dimension to the prop hub.  Its been a while since I put the engine on the plan, but I don't remember thinking an extension would be necessary.  What I do remember is that the muffler would stick out the back of the lower cowling.  If I wanted to have it completely enclosed I would have  extend the lower cowling an inch or so.  Would that modification cause an issue with being OTS legal ?
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« Reply #3 on: May 06, 2012, 09:27:28 AM »

i have had my big job for two years  it has a S/T 60 in it .after checking with Charlie i put the motor in the same place as the org 59 and made a spinner backplate with a built in spacer ,it flew right off the board .i have played with adding weights to the tail depending on where i was flying
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phil c
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« Reply #4 on: May 06, 2012, 08:09:43 PM »

Since nobody back then was thinking 50 years ahead, cut and try was often done on almost all the Old Timers.  The article on Don Still's Victory mentions using different nose lengths and tail lengths for different contests, and has some pictures.  The article on Hi Johnson's Stuka also specifically says to adjust the tail length, the tail area, and the nose to suit your engine and control preferences.  That would make it kind of hard to argue that if you had a heavier engine in a Stuka you couldn't extend the tail, and/or make it bigger, to get it to fly right.  The original builder did it.
« Last Edit: May 09, 2012, 05:06:15 PM by Paul Taylor » Logged

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« Reply #5 on: May 08, 2012, 05:39:09 AM »

I have removed my post as I can't prove it other thn my feeble memory.  Sorry folks but, I guess I am getting old. ZZZ
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We never really grow up, we only learn how to act in public.

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« Reply #6 on: May 09, 2012, 07:41:50 PM »

Since nobody back then was thinking 50 years ahead, cut and try was often done on almost all the Old Timers.  The article on Don Still's Victory mentions using different nose lengths and tail lengths for different contests, and has some pictures.  The article on Hi Johnson's Stuka also specifically says to adjust the tail length, the tail area, and the nose to suit your engine and control preferences.  That would make it kind of hard to argue that if you had a heavier engine in a Stuka you couldn't extend the tail, and/or make it bigger, to get it to fly right.  The original builder did it.

But there is only one design for the Big Job and only one nose length.  To suggest otherwise for the Big Job which is what this thread is about is wrong.

Keith
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