BIG4D

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I was recently given a Carl Goldberg Anniversary Addition Cub kit. The kit look to be complete, all parts seem to be there and in good shape. Parts bags are not open. The kit is old and had been stored in the original box for many years. All of the paperwork is also there.

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I am thinking I will build this kit. The instructions are calling for engine sizes between .40-.60 two stroke and .90 4 stroke.

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I am looking at using the Saito .82 4-stroke on the plane. Is this a good choice?

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The instructions talk about shortening the wings to make it a little more aerobatic, but I am a new pilot (learned last year) so I think I will leave the wings long and make it easier to fly. This will be my second plane. I have been (and still am) learning on a 25 year old Eagle 63.

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Is there anything I should know about this kit? Any tips or tricks that might make building easier? Any help would be appreciated. I have built kits before. I built the Eagle that I am flying now.

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One question in particular. The instructions say to use “Jet” to fuel proof the firewall. I remember using thinned 5 minute epoxy for this. Which is better?

What would you guys suggest for covering the plane with?

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Thanks.

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Dr1Driver

That Saito will be perfect for your Goldberg Cub. It will turn a big diameter/low pitch prop for gentle, scale-like flying characteristics.

Shortening the wings is called a Clipped-Wing Cub, and was pioneered by Hazel Sig when she wanted more aerobatics from her stock Cub. Built the wing full length at first. Later, you can easily remove the tips.

The only thing special you need to know about a Goldberg kit is it's a Goldberg kit. They are some of the easiest, most fun to build kits out there. The fuselage will go together with interlocking pieces, tape, and rubber bands, and will be almost fully assembled before you add the first drop of glue. Use thick CA on plywood, thin on balsa.

"Jet" is Goldberg's brand of CA. Any CA will work. You can use that or the epoxy. Both work well.

Covering MUST be a fabric-type, IMO. Solartex, Colortex, Worldtex, or any other heat-shrinkable covering with a fabric-type texture will look great on it. IMO, this stuff is easier to apply than the shiny plastic-types like Monokote.

Take your time, read the instructions completely and study the plans. Be sure you fully understand both before you pick up a piece of wood. If you need help, just ask.

Good luck with it!

dignlivn

I agree, the Saito 82 will be perfect.

Cubs can be a bear on the ground, full
size or model size. I also agree with using
Fabric to cover it. I like 21 century fabric
myself.

Bob

BIG4D

They can be a bear? Does that mean they are hard to handle on take-off and landing? If so, is it because it is a tail-dragger?

Our club field is a grass and pavement. Should I use the grass?

dignlivn

Yes, use some rudder on your take off roll.
Apply throttle slowly. It's just thier nature.

You will enjoy it


Bob

MinnFlyer

My Feedback: (4)

I am a HUGE advocate of building the "Clipped Wing" option on the Goldberg Cub!

Here is the story of the Airplane whose wing was too big....

Back in the 1920's they designed the Piper Cub. The idea behind this plane was that its designers envisioned that everyone in the country would someday own one, fly it to work, the grocery store, etc.

To make it affordable, they put a very small, inexpensive engine in it. In order for this tiny engine to get an airplane off the ground, they had to make the wing BIGGER THAN IT WOULD NORMALLY BE. So now, this little engine could get this airplane off the ground.

The problem was, it was under powered and that HUGE wing created a lot of adverse yaw.

By the 1930's, the dream of everyone owning one went away when they realized that very few people had runways in their backyard (Not to mention at their grocery stores), but a lot of pilots had them - and they were due for periodic overhauls. Some of these pilots realized that if they put a REAL engine on it, they could "Clip" the wing down to a NORMAL size and relieve some of the adverse yaw and other undesireable effects of that "Wing that is too big".

Unfortunately, now people think that Clipping the wing from the original design is making a radical modification to a good plane. In reality, the original wing was intentionally designed to be TOO BIG and the clipped wing is the correct size.

Now granted, some people have radically clipped wings on various aircraft, And some versions of Cubs have the wing clipped too much, but Goldberg got it right! The clipped version of the Goldberg Cub wing is the ideal size for that airplane.

Try it, you'll like it!


Read more: http://www.rcuniverse.com/forum/m_92...#ixzz0rmvnGDUG

Top_Gunn

My Feedback: (6)

I agree with Mike: it will be much easier to fly with a clipped wing. This is partly because of adverse yaw; with the full-length wing you'll need to use rudder as well as ailerons to turn. Also, the plane is a real floater, even with the clipped wing; it will be even harder to land with the full-length wing. My second plane was a clipped wing Goldberg Cub, and the field my club had then was somewhat cramped. I had to learn how to do slips in order to get it down unless I had a pretty strong headwind. I think that if it had had the full-length wing it would still be floating around up there somewhere.[8D]

heavy metal thunder

I have three CG Cubs, one has a old OS .60 four stroker, one has a Saito .65, and the third one has a old Enya .46 four stroker. The Cubs with the OS .60 and Saito .65 fly the Cub very well and has has the power to do mild aerobatic maneuvers, with a bit of reserve power. I fly the Cub with the Enya .46 4 stroker nearly WOT most of the time, to do loops and rolls I need to dive the plane first to gain some speed. The Cub with the Enya is the most fun because it requires me to play close attention to altitude and speed. A Saito .82 has more than enough power as a matter of fact I think it's over powered, but you can always throttle back.

Tarasdad

My Saito .80 used to reside in a Goldberg Cub. Full wing version wearing OD and invasion stripes. It was a sheer joy to fly at half throttle, and absolutely insane at full! I agree that it would probably handle a bit better with a clipped wing, especially if you want to do aerobatics. Ground handling really isn't that bad, just remember there's going to be quite a bit of torque from that engine and plan accordingly.

BIG4D

Thanks everyone.
I am seeing a general consensus that the clipped wing is what I should build.

I, too, thought the Saito 82 might be a little big, but the plans actually call for a 90 4-stroke! I actually have an old Enya 46 on my trainer right now. I had thoughts of putting a 40 2 stroke that I have on my trainer and putting the Enya 46 in the Cub. I don't want to fly around at full throttle all the time though, and with the 46 Enya being 1/2 the recommended size 4 stroke engine, I could see why you would have too.

Maybe building a second wing. That way I would have both the full size and the clipped version.
This will be a slow build so as I can take my time and build it correctly. I finished reading the instruction sheet from cover to cover last night.
I was thinking of starting a "Build Thread" while building. I like to read other threads like this. It is really cool to watch one being born!
I don't see a place to really post a "Build Tread" though.

One of the things it says to do is to build it on a table that you can stick the stick pins into to hold parts. What type of wood do you recommend for a table top? I tried sticking the pins into a peace of 1/2 plywood I has laying around, nothing doing, would just barely penetrate. Certainly not enough to hold anything.
Thanks for all the feedback so far. Can't wait to get it started. I will be using a fabric type covering for sure. My father recommended "Fabricote" but I can't find anything on it. I remember him using it way back when. Do they still make it? Was it made by Monokote?

MinnFlyer

My Feedback: (4)

Two thing:

First, although they say up to a 91 4-stroke, that manual was written many years ago when 4-strokes were not as powerful as they are now. You're 82 will be plenty!

Second, don't hesitate for a minute to build the clipped wing. It will still be a very gentle floater. As I said earlier, the BIG wing does NOT make the plane fly better or more gently, it only makes it more difficult to turn.

BIG4D

Thanks Minn.

On the engine. Makes a lot of sence. I have NO doubt that the 82 will be more than enough for me! The instructions do list a range for the 2-stroke, .40-.61, but it only lists the .90 for a 4-stroke, not a range of sizes. I love the sound of the bigger 4 strokes. Should be great!
Thanks for the advice! I am itchin' to get started!

dignlivn

I use foam insulation board 4x8 sheet
from lowes, around $10. That on top
of an interior door, works great for pinning
parts together.


Bob

MinnFlyer

My Feedback: (4)

I flew mine with an old Enya 61 4-stroke and it was a good match. I even flew it with floats.

BIG4D

Great sggestion Bob!! Thanks!

BIG4D

Here is another option I am looking at.
If I build it with the clipped wing, it stands to reason I might be able to get away with a smaller engine.
Do any of you have any experience with the ASP engines? They are considerably less expensive than the Saito.

Looks like there is a .61 then it jumps to a .91.

Would the ASP 4-stroke 61 power this Cub?

MinnFlyer

My Feedback: (4)

Personally, I think the ideal engine is the OS-70 (which is discontinued). I'm really not familiar with ASP

If you're thinking of buying new, take a look at the Thunder Tiger - F-75s or the Magnum XL 70 RFS

ARUP

No matter how you 'slice it' the Cub is a fun airplane! If you have access to a good 3-view, like one from Paul Matt, you can make some easy kit modifications for more scale realism. You can enhance the 'scaleness' of it by shortening the ailerons. Can't do much about their too narrow chord without a major wing structure overhaul. You can move some of the ribs around to scale locations. The stabilizer span is a little too long and can easily be modified. You could also build the stab in the same fashion as the SIG Cub is built (2 pc joined into fuse after covering) in order to be able to cover the rear fin/fuselage junction properly. It is very easy to add the 'clamshell' door to it. An internal elevator horn to pushrod is easy to do. The kit landing gear is a little weak and will gradually bend backwards and flare outwards. It's easy to make 'scale-like' rear struts to attach to the kit items. I've built 4 Goldeberg Cubs and my most recent is a J-2 version. It's in the 'bones' and will be covered in fabric, painted aluminum silver with dark blue trim. 1st (clipped) done like Hazel Sig's, 2nd in yellow on floats, 3rd and 4th (long) yellow. I'm also currently building a SIG 1/6 Cub converted to PA-12, L4 and J-4 Cub coupe. All of these Cubs will have 2 pc. plug in wings. I like Cubs a little! Good luck with yours!

dignlivn

You could pick up a used OS 70 here on RCU.


IMO, you get what you pay for in this hobby.

Bob

Tarasdad

An ideal 4-stroke for that Cub is in the .60 to .70 range. Plenty of power for mild aerobatics, very comfortable for just puttering around. As for a building board I highly recommend a sheet of Homasote if you can find it. Holds pins far better than foam, great choice when put on a hollow-core door. Whatever you choose for a pinning surface your building board has to ba absolutely FLAT for best results. Ahollow-core door works wonders.

Fasthobbys1

My Feedback: (11)

I have one with a Supertigre .61 2-stroke and it flies great. I run at half throttle most of the time with plenty in reserve.

southmountainbob

BIG4D:
I have this same kit awaiting it's turn on the build board. (two 2'x4' pieces of ceiling tile from your local building centre). I'll be watching this build with great interest. Ordered an Evolution .61 the other day. I'm wondering if this will be enough power to fly with floats. Anybody care to weigh in on this?
ARUP:
Is your Cub on floats clipped as well?

southmountainbob
Nova Scotia, Canada

cf6_mech

I bought a Goldberg Cub kit at a garage sale about 12 years ago and just started building it. I bought a Saito 82 for it. I really should have bought72 but they are the same wieght and I can always reduce power. I am building the clipped wing version. I was wondering if anyone has upgraded and bought a fiberglass cowl for their Cub?

BIG4D

Thanks for all of the replys. I am still considering engine options. I can tell you that I think that i have decided to go with something smaller than the Saito 82, it's just to big.
Right now I am thinking something in the .60 - .75 range.
I talked to the owner of a local hobbyshop here in OKC, and he told me the Saito would work and it would climb streight up with it! It would probobly even hover! LOL!! I hardly think a Cub like this was ment for 3D!!
So, I will be following your, and his advice and go with somethign in the range above. He also told me he would not recommend ASP. He said if I didn't want to spend the money on a Saito to go with a Thunder Tiger or the Magnum, so the search goes on for a power plant.

Mean while Ibuilt a table in what has be come my "hobby room". . Ibuilt it large so Iwould have plenty of room! it's about 8 ft long, by 3 foot deep. Should sufice. Top is nice 3/4 ply so it is nice and flat! Thanks for the advice Taradad, I hadn't thought about being flat being important. Ican sure see why it would be! Iwill try to find the Homasote. Can you tell me more about that?Ihave never heard of it. What about where I might look for it?

I think I will start a new thread when I start the build and link this one to it. If I can find sufficient backing I may start the project tomorrow!

The RCUcommunity here is great! You guys are very encouraging!!

On a side note today, I went to the field this afternoon and got some stick time in with my Eagle 63. It was the windiest I have flown in yet! When I got to the field and took my wing out of the cradle I built, my aileron servo was hanging by the torque rods!! Looked like the old plywood spacers (same age as plane) just seperated and failed. A little gap-filling CA and I was back going.
A gentleman showed up with a little plane that looked like these low wing modern day crop dusters (don't know the name). He had a little trouble with the engine but seemed to have it worked out. He taxied out and took off and it flew nice. After a while he circled back to the south end of the field and the next thing I know I hear "Dead Stick". I looked up and, boy, he was pretty far out. I though to myself "He's never going to make it." Sure enough it went down into some trees. We looked in waist tall grass and Poisen Ivy for more than an hour and a half and never found it . Ifelt really bad for the guy, this was his 3ed flight on it and it was his second plane. He soloed last spring. He says he is going out first thing in the morning to look again.
Our field is very close to a lake, and on the south end of our field is a Hobie sailing club and there was a lot of people there today. I am starting to think someone over there saw it go down and went and took it! Isure hope not, but these days you never know. A locating beeper would have been nice in this incident.

heavy metal thunder

Don't try it with a old Enya .46. I can get away with it because, I've had a lot of time flying Cubs of various sizes and engines. Plus I have 8 Cubs .25 to 1/4 scale size so if I lose one I'm not out. For the money a Magnum .70 is a good buy and good fit. I have one but it is installed in a .40 Spitfire, it does a decent job, I like the fuel economy with magnum .70. My favorite engine for the CB Cub is the old Saito .65. The clipped wing version flies a bit more like a sport airplane, for me I like the full wing version. For aerobatic type flying I'll bring out my Citabria or Decathalon.