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Goldberg Cub build, thoughts, gripes, insights etc.

Old 12-30-2014, 06:50 PM
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P-40 DRIVER
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Default Goldberg Cub build, thoughts, gripes, insights etc.

I built one of these 25 years ago; when I was new, to the hobby. I don't remember much about it; at this point, but we are going to do another one. Cub $110, Magnum 52 $110, Tower Hobbies, delivered to my door, was the start of this project. The Blue head Magnum's seem to have fixed the mixture needle issues they used to have and I had zero issues breaking it in on my test stand, 10% Powermaster Castor/syn blend and a Master Airscrew 12/6 prop. The kit is as you would expect, but is not quite up to the standard of the old kit, no real issues but more on that later. I will be updating all the control linkages as I can't stand torque rods and wood push rods. I'm shooting for under 6 pounds all up and can see no reason why I can't get there. This is going to a utility plane so most of the scale stuff will be left off. Futaba EX 2.4 radio, Hitec servos round it out. I will also pretty much be using Dubro hardware throughout, more because I just have a certain way I set up planes more then anything else. I'm suffering from no time or money these days, so I needed a plane that required little to build or fly but kept my interest. I have not flown in over 2 years, and have very little RC stuff left.
Old 12-30-2014, 07:17 PM
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The kit is not die cut like the original Goldberg kit. Some of it is router cut, most of it is laser cut. The parts do not match the plans very well, and there is a laughable note in the box about how paper expands and contracts. Some of this is off 1/4", so I think its just sloppy re kitting on GP's part. No matter, some minor adjustments and it goes together just fine. For the price I'm not complaining. The wood quality is just fine, one of the dowels looked like a banana though, but was easily replaced at Lowes, I used wood glue to put the fuselage together and CA on the wing. Plywood and CA just don't seem to get along very well, so it took patience, a lot clamps and tape, but we got fuselage put together without incident with Titebond. I think the trick here is tobe very generous with the glue. Run beads of glue along all the joints and push in with your finger. patience is the key because you can a few joints at a time and let dry.
Old 12-30-2014, 08:25 PM
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The clipped wing is built with no dihedral or washout. This should make the plane a little less stable and bit more fun to fly. I wish they had designed the wing with cap strips on the ribs, so the spars would not have been flush; but it came out fine, so that's just personal preference. I'm using a 2 servo setup in the wing instead of the torque rods; easy, and it is a better setup. The wing tips took a heat gun and a lot of pulling to get right. I did not fiberglass the center section, there are so many pieces joining the wing halves together it like overkill to me. I think you could use the wing as a baseball bat, its so overbuilt. Just a side note, Monokote used to come in 78 inch rolls but now they are 72 inch rolls for anybody whose is planning to use the layout on the plans for covering, 2 rolls are not quit going to make it, I think.
Old 12-30-2014, 08:39 PM
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The landing gear good and stout. I used lite weight 3.25" Dubro wheels to save weight, but also because the Dubro Cub wheels are not the correct size. A little on the big side. I used JB Weld to secure some number 10 washers as backers to the wheels and notched the landing gear wire so the wheel collars would not get loose. Blue Locktite finished the job. I may or may not use the spats when I get that far.
Old 12-30-2014, 11:30 PM
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P-40,
This is one of my favorite kits. The parts fit is not what it once was, but with a little work you will
have a nice flying plane. Here's a clipped wing with a Magnum 70. I added a window in the top
of the wing & some jury struts. Also some side stringers on the fuse.
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Old 12-31-2014, 05:02 AM
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Very nice looking plane, mine is going to be a bit simpler so I can get back into the air with minimum fuss, I can't stand ARFs so this seemed a simple and cheap way to do it. Next project will be a bit more involved.
Old 12-31-2014, 06:34 PM
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The Magnum 52 was mounted using a Great Plains mount, 40-70 size I believe. This is much easier then the supplied mount, and I had one. The throttle linkage is a Dubro 2-56 rod controlled by a Hitec micro servo. Don't use flex rods for this job, they change length as the temp changes and are sloppy to boot. Your throttle linkage needs to be every bit as precise as your control linkages. A Dubro 8 oz tank, fuel line and filters finish the setup. The tank is wrapped in foam and sitting on top of 2 dowels which run crosswise through the fuselage. It is held in place by 2 removable 2-56 rods running the same way. I see no reason to run a full size servo on the throttle with micros being as cheap the days. an ounce of weight saving's here and there does add up, so take it when you can get it. On a side note, Magnum mufflers don't hold up wel, so you might want to consider an OS.
Old 12-31-2014, 06:46 PM
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I only run OS F plugs, seem tobe as good anything out there and are easily obtained. I run 10% Powermaster caster/syn blend 18% oil, its never let me down and is fairly inexpensive in Texas. I also run a return loop to my gas can so I don't spill fuel, this requires some way to break the fuel line to the muffler to catch the overflow. I'm partial to the Master airscrew K props as they are very tough and look proper.
Old 01-01-2015, 02:15 AM
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Put a couple pictures on us there P-40.
Old 01-01-2015, 02:18 AM
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That's gonna be a nice flyer with that 52 on it. I've flown these planes with everything
from FP40 to a 90 four stroke. I like a 52 on the standard J3 and a 70 on the clipped-wing.
Old 01-01-2015, 04:27 AM
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Old 01-01-2015, 04:51 AM
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Here's a couple, been awhile since I did the upload thing. Iphone to email to computer to rcuniverse. I have lots of pictures, more to follow.
Old 01-01-2015, 05:54 AM
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As you can see by the photo of the plane that we are in various stages of finish, this because I'm working on systems at the moment. It is much easier to t do all your systems work before you cover the plane. So when I actually cover the fuselage, the radio, gas tank etc will already be in place. The other thing I have learned the hard way and still violate now and again is to make everything easy to access and removable if need be. This takes a bit of planning but will make your life easier in the long run. I have already violated this rule by putting my connections in my wing where I can't get to them without cutting the Monokote. On a side note, do your prep, repair at home. Working on your plane at the field; unless its something simple, is a bad idea. It usually leads to bad fixes and more problems. If your doing a lot of repairs at the field, you have not done your prep work at home which just costs you money in stupid crashes and wasted trips where you can't fly.
Old 01-01-2015, 07:21 AM
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You say that you are using a fuel that has Castor Oil in it for your 4 Cycle engine. I thought I read somewhere that Castor oil is not good for 4 cycles. I have been told that it will gum up the valves and lifters when the engine is stored as Castor oil will turn gum if stored for long periods of time. I also use the fuel you mentioned on my 2 cycles and just love it. I have never had an engine failure due to a lubrication failure and I always use after run oil in them. I have separate fuel for my 4 cycles that has no castor in it. As for your plane, they are good flyers. You will need throttle management and good rudder control for take offs as the plane will want to ground loop. Good Luck, Dave
Old 01-01-2015, 07:46 AM
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Never been an issue as far as I know. I heard the same thing about YS engines but was corrected by a pattern guy who used YS engines all the time. So far as I know, modern 2 cycle castor/syn glow fuel can be used in 2 or 4 cycle glow engines without issue. sometimes I bump the oil content up to 20% depending on application. I have heard people having more issues running straight syn oil actually. I'm sure both will work though. Castor oil will not break down; like syn, if you have a lean run and it also protects against rust better.
Old 01-01-2015, 10:16 AM
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Originally Posted by P-40 DRIVER View Post
Never been an issue as far as I know. I heard the same thing about YS engines but was corrected by a pattern guy who used YS engines all the time. So far as I know, modern 2 cycle castor/syn glow fuel can be used in 2 or 4 cycle glow engines without issue. sometimes I bump the oil content up to 20% depending on application. I have heard people having more issues running straight syn oil actually. I'm sure both will work though. Castor oil will not break down; like syn, if you have a lean run and it also protects against rust better.
Klotz bottle says not to use it as a storage/after run oil. Saito has off and on said to use or not use castor. . I use 5% of it with rest syn. of 20% oil in all including my YS F120. I have engines not run since the '50's that ran with castor oil and put away with no after run that turn over fine now with no rust.

Happy New Year to All.
Sincerely, Richard

Cub Brotherhood #187; Sig 1/4 (Koverall/dope), H9 100 inch (Gen 1) (Solartex/?), GB Anniv Cub (NIB)
Club Saito #635; Saito 56, 100, 120abc, 130T, 180
Kadet Brotherhood #96; Mk 1 Kadet, Kadet Junior,
Sig Kougar, Sig 1/4 Cub, Sig 1/4 Spacewalker II
Carl Goldberg Tiger Club Member # 81
YS F 120
Old 01-01-2015, 11:38 AM
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Old 01-01-2015, 11:46 AM
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Just got out of my freezing garage, I've been installing my 2-56 steel pushrods from Great Plains. These are cheaper then the Dubro ones and Just as good. I try to keep them as straight as possible. I'm using Dubro Easy Connectors with hex head tops and steel push on clips. They are a little tight tight so I'm going to need to ream the holes slightly on the horns. I also installed a Maxx Products switch with a voltage display, I had lying around as well. Still need to install the battery and a final sand on the fuselage before covering.
Old 01-01-2015, 12:27 PM
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Originally Posted by spaceworm View Post
Klotz bottle says not to use it as a storage/after run oil. Saito has off and on said to use or not use castor. . I use 5% of it with rest syn. of 20% oil in all including my YS F120. I have engines not run since the '50's that ran with castor oil and put away with no after run that turn over fine now with no rust.

Happy New Year to All.
Sincerely, Richard

Cub Brotherhood #187; Sig 1/4 (Koverall/dope), H9 100 inch (Gen 1) (Solartex/?), GB Anniv Cub (NIB)
Club Saito #635; Saito 56, 100, 120abc, 130T, 180
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Sig Kougar, Sig 1/4 Cub, Sig 1/4 Spacewalker II
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YS F 120
I agree, Castor oil is your friend, I'm not a big fan of after run oil due to it being mostly petroleum based which has ruined some Oring seals used in my OS carbs. I just my engines dry of fuel. I will pickle them in castor oil if I'm not going to use them for while.
Old 01-01-2015, 12:32 PM
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Originally Posted by P-40 DRIVER View Post
I agree, Castor oil is your friend, I'm not a big fan of after run oil due to it being mostly petroleum based which has ruined some Oring seals used in my OS carbs. I just my engines dry of fuel. I will pickle them in castor oil if I'm not going to use them for while.
After run, being petro. based as you say, will also destroy the silicone regulator and pump parts in YS engines.

Happy New Year to All.
Sincerely, Richard
Old 01-01-2015, 12:57 PM
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I ordered some new batteries for my transmitter and receiver the other day after much contemplation. I ended up with the Futaba 600 mil amp replacements which ended up being the best deal on Sanyo NiCds. The NiCad battery is still the least fussy most reliable battery option out there. I looked at LiFe, A123 LiFe, NiMH, and NiCds. they all have their pros and cons which I won't go into here. I really debated running 4 or 5 cells in this plane but decided to go 4 cell due to cost and weight. I take very good care of and monitor my batteries so the reliability is there and sanyo cells are the best out there. I also have run these packs before without issue.
Old 01-01-2015, 04:39 PM
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Let's say you like building from the kit 'to look like the picture on the box'. There is only one thing I would highly recommend. Add a rear leg to the gear as a minimum essentials modification. The gear as designed will gradually splay outwards and the wheels will 'toe out'! Those landing gear fairings will eventually get lost in flight. By doing this one modification you will solve two problems.
Old 01-01-2015, 05:21 PM
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Thanks for the heads up, I don't know if I'm going to bother with the covers or not. But I see your point and its a darn good idea and very easy to do. A triangular leg would work much better.
Old 01-01-2015, 05:30 PM
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1/8" music wire should do the trick, and I have the bender.
Old 01-02-2015, 05:05 AM
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As you can see, the plans and wood don't match very well. I used wood glue on this part. I don't like CA and may give it up completely. nasty stuff.
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