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  • June 25, 2019, 06:55:37 PM

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Author Topic: 1/2a Pathfinder  (Read 1379 times)

Offline Steve White

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1/2a Pathfinder
« on: May 05, 2018, 06:31:51 PM »

I'm fixing up a used 1/2a Pathfinder for my grandson and would like to know how far back from the leading edge the CG is located and the allowable range. It weighs 15.75 oz and has about 1 1/4 oz of lead weight right behind the engine. The engine is a Tee Dee .051 with a master airscrew 5x3 3 blade prop, is this a good prop for this engine? I was planning on using .008 45' steel cables. Any advice would be greatly appreciated.

I don't have a manual for it and all I can find doing a search is, to build it to the plans and it will be ok. Right now it balances about 2 3/16", that seems kind of far back to me. Thanks.

Steve

Offline john e. holliday

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Re: 1/2a Pathfinder
« Reply #1 on: May 06, 2018, 05:33:46 PM »
Every body must be flying.  My general start is about 1/4th the way back from leading edge, maybe less.  nose heavy can be tolerated especially if he is just learning to fly.   That prop should work but I'm used to using 6-3 for 1/2A engines.   If it is a calm day those lines will work if you have enough wing tip weight.   Now I'll let the pros step in. D>K
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530

Have fun as I have and I am still breaking a record.

Offline Steve White

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Re: 1/2a Pathfinder
« Reply #2 on: May 07, 2018, 10:40:15 AM »

Hi John

Thanks for your reply. I decided to call Brodak and ask if they could help with the CG. They were very nice and very helpful, they pulled out a set of plans and measured them for me. It's 1 1/2" back from the leading edge. They said probably a 1/4" either way would be ok, so you were close. The chord of the wing including the ailerons is 7 1/8" at the halfway point of the wing, that would put the 25% that you said at a little over 1 3/4". Like I said though, it's about 2 3/16" right now, with about 1 1/2 oz of lead up front. It's very tail heavy, probably why he basically gave it to me.

I found a build thread on here that showed the build at various stages, on this one, the fuselage is hollowed out and braced from near the back of the wing, almost all the way to the end of the fuselage. The horz stab, elevator, fin and rudder are also hollowed out. This one is solid everywhere, probably why it's so tail heavy, along with the thick layer of paint he used. I'm thinking about drilling some holes and cutting it out as much as I can, brace it and use ultracoat or some stuff I got off ebay that's labeled as an alternate plastic film. I believe you mentioned you use it. Once it's heated, it's clear and can be painted over. It's supposed to be much stronger.

It doesn't have to be all the good looking now, as I expect some repairs as he progresses. I'll buy another kit and build it like the plans and have it ready for when this one is no more, LOL.

Steve

Offline john e. holliday

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Re: 1/2a Pathfinder
« Reply #3 on: May 10, 2018, 12:09:57 PM »
I have now finished and flown several planes using that mylar.   Putting it over the examining table paper it adds a lot of strength and is lighter than silk-span and dope.   As stated the stuff is cloudy until you put it on the plane and then goes clear.  Here is latest plane with monokote trim over it. H^^

It is called 'Lancet' built using Barry Baxter plans that Bob Mears now has. D>K
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530

Have fun as I have and I am still breaking a record.

Offline Paul Smith

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Re: 1/2a Pathfinder
« Reply #4 on: September 18, 2018, 06:13:53 AM »
I'm fixing up a used 1/2a Pathfinder for my grandson and would like to know how far back from the leading edge the CG is located and the allowable range. It weighs 15.75 oz and has about 1 1/4 oz of lead weight right behind the engine. The engine is a Tee Dee .051 with a master airscrew 5x3 3 blade prop, is this a good prop for this engine? I was planning on using .008 45' steel cables. Any advice would be greatly appreciated.

I don't have a manual for it and all I can find doing a search is, to build it to the plans and it will be ok. Right now it balances about 2 3/16", that seems kind of far back to me. Thanks.

Steve

Almost 16 ounces !!!  That's enough for a 15-size or even a 25-powered model.  Obviously, you put a heavy finish on this airplane.

In your position, my fix would be to extend the nose and have the engine and tank father forward, rather than add even more lead.  You have a lot of mass for even the best TeeDee engine.   Or maybe you could put an .09 or .12-size engine on it.
Paul Smith

Offline Dane Martin

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Re: 1/2a Pathfinder
« Reply #5 on: September 18, 2018, 07:40:09 AM »
Obviously, you put a heavy finish on this airplane.


Someone did, but not Steve as he indicated the plane was given to him.

Steve, any chance you can surgically remove the tail and just make a new set of stabilizers? I've had to do it a few times. Turns out to be a lot faster and easier than you might think.
« Last Edit: September 18, 2018, 07:56:54 AM by Dane Martin »

Offline Dane Martin

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Re: 1/2a Pathfinder
« Reply #6 on: September 18, 2018, 07:57:30 AM »
Pics

Offline Dave Hull

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Re: 1/2a Pathfinder
« Reply #7 on: September 19, 2018, 11:55:01 PM »
Danish,

Thanks for the motivational photos!

Were I in Steve's situation, I would try cutting the lightening holes in the stab and maybe elevators first and see how much weight he can get out. That is just Xacto knife and Dremel sanding drum work. If it helps enough, then recover it. (He said he was not all that worried about appearance.) If not, no loss before taking out the whole thing and replacing with a more lightly built item.

I've got a warped HS and elevators on the OPP "yellow 'pants." I think the SIG dope shrank and warped it. I contemplated replacing them as you suggested to Steve, but got sidetracked onto other repairs. Maybe the yellow 'pants will be next in line. Not sure how I keep the replacement from warping too, though. Maybe add some plasticizer.

McDivot


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