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Old Jan 15, 2015, 08:29 PM
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Carl Goldberg Anniversary Cub any takers?

I have to admit I am little hesitant to post a building a project that has probably been done a bunch of time before; but posting a building thread tends to make the project move quickly. Hope someone follows. In the last two years I have attempted two float fly airplanes and both “looked” nice but neither was very fun to fly. My Sealane flying boat leaks water and quickly becomes tail heavy and very unstable. My VK Navajo was not engineered properly and could not come off the water. So this season I plan on having a tested design, yes a “Cub” on floats. First which Cub to build and secondly dedicated float flyer or convertible from ROG to floats?

First I have an existing power plant that I hope will fly a 1/5 model nicely, my OS Max 72 4 stroke. The two airplanes I considered was the Sig Anniversary Piper Cub or the Carl Goldberg Anniversary Piper Cub, booth 1/5 scale. I called around a little to see if someone I knew had one hanging around that they would sell me. No luck on that front, however my buddy Steve had a CG Anniversary float kit new in the box he was willing to sell. That sealed the deal I decided on the Carl Goldberg model. Even though it is less scale, has strip ailerons and slab sides, I felt it would build fast I was told that it is a decent and durable flier. I want a nice looking airplane with no hassles and I am not hung up on this being“Scale” perfection. Second choice was to make it a convertible model. This way I can finish the plane and fly it bit while I am constructing and finishing the floats.

Cruised around online and did not see a CG Cub for sale on the usual forums and people on EBay were bidding stuff up to full price plus shipping. Instead I ordered a brand new kit Sunday night from Omni Models $119 no shipping no tax 32 hours later the box arrived at my place of work. Let’s get started and hopefully finished!
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Old Jan 15, 2015, 08:41 PM
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I'm in!
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Old Jan 16, 2015, 01:00 AM
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nice start, I like starting with the tail first, just goes quick!

looks good!

I have an original GB Cub ARF! I got second hand, but looked brand new, and came with floats, although I have yet ta fly off floats yet! I do want ta try!

well be watching! ya just don't see anyone doing a standard Cub!
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Old Jan 16, 2015, 08:32 AM
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Nice start !

I had an OS .70 Surpass in my CG Cub. It was more than adequate. Your OS.72 should easily handle the added weight of the floats.

If you want scale detail, you could add barn door ailerons without too much extra work. I did it to mine.

Good luck on your build.
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Old Jan 16, 2015, 11:30 AM
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How we'll do the laser cut parts fit? I'm trying to decide if I want the laser cut kit or the older die cut.
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Old Jan 16, 2015, 05:22 PM
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My rambling thoughts

Hi guys nice to see some interest in the project. I will be posting some additional progress pictures from last night and today very soon. Now for corrections; I am actually using an OS 70 don’t know where I came up with 72? Memory not as good as it used to be, however as Tom mentioned that should fly things quite well. I really love my Surpass I am on my second set of bearings and the thing just keeps running. Have not even looked at the wing plans yet (shame on me) however barn doors might be lighter and look a little nicer. I have plenty of extra wood around the shop. Tom did you stick to the original plan outlines of the strips or modify the shape in some way?

Scigs 30 as for your question. In my opinion there is a little difference in the kit philosophy between Sig and CG. Sig kits are a little more elegant in there construction whereas CG kits slightly heavier and tend to use more plywood and less sticks. I have always been impressed with Sigs accuracy of the parts to plan outline. This probably because Sig uses CAD generated plans, and then cuts the parts off the CAD plans. In the case of the CG kit I am building in became clear, quite quickly that the kit is a modernized version of hand drafted plans. The laser cut parts do not exactly match the plans, however they fit together very well and that’s what really matters. The finished stab and elevator is at least 3/8 of an inch smaller than the plans outline but how critical is that? The CG kit is not a true scale kit but a standoff scale kit. The laser parts do assemble accurately and that is the measuring stick I would use.

On the CG plans there is a ¼ ply spacer on the front of the firewall. This is omitted on the newer kits and compensated for by using a carbon fiber filled extended engine mount that was not available when the kit was first manufactured. There are a number of other differences as well. The newer kit has CA hinges I don’t like those so I replaced them with the old CG plastic ones. I love those things, easy to install, tight hinge line and not messy to glue in and strong enough for a bird this size.

If you decided to go the Carl Goldberg route and, you have a bead on an older kit, and the price is attractive, then by all means pull the trigger. However from what I am seeing online, another older version just went off at auction on Ebay for $105.00. With $20.00 shipping you are now paying over full retail? I wanted to get to gluing sticks together so I ordered new from a local distributor, no tax. No shipping and in no time (30 hours) I am at the bench. Cheaper than Ebay would have been! Long story short you will not go WRONG with either choice but for my money I decided brand new kit, no water damage, no missing parts, no warped wood. Look forward to seeing which way you go, Post a thread
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Old Jan 16, 2015, 08:41 PM
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For semi-scale barn door ailerons just trim the supplied items to suit. Their chord won't be proper as that would entail moving the rear spars forward. I built one with scale length ailerons and it flew just fine. I have a build thread showing true scale changes for the wing over in the fuel scale forum. It is a GB Cub converted to a Taylor J-2 Cub.
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Old Jan 17, 2015, 03:36 AM
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]This post represents two nights work. the first evening was mostly sanding edges of die cut, router cut and laser cut parts. after I laminated all the sub assemblies I weighted everything down flat and let it rest overnight

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I started the next day by dry fitting the fuselage parts together. Right away I discovered the router cut parts were not seating correctly. I spent a couple of hours fussing over the fit of tabs and slots until I finally had the fuse dry fit together and ready to glue. This was a process even though the bulkheads were laser cut. Makes me think that the older die cut kits are even fussier

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Description: rest could not resist checking out the tail sitting on the fuse
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Description: Some more clamping and a couple of levels to check for twists.  the wing saddle and Stab platform both level time to glue.Name: SAM_1162.JPG
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After the fuse was glued at all of its bulkheads sides top and bottom I removed the tape clamps and rubber bands to reveal the basic skeleton. I finished up the evening by mounting the tail wheel bracket, cementing in the bulkhead extensions and adding the aft dowels that are the stringers. I found that the 18 inch dowels wee a tad short!. Fixed that by swapping them out for longer ones I had on hand.
I also used up all of the stab and elevator stock. The instructions call for using scrap to block the forward cabin and engine area. Luckily I had a piece of 1/4 by 3/4 inch on hand to bail myself out. I was pretty stingy with my cuts and I know there was no excess left.

Finished off by sheeting the nose sanding it flush and mixing a batch of epoxy to secure in the wing hold down blocks and landing gear plate. Good place to set it aside until tomorrow while the epoxy gets a good cure.

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Description: Adding bulkhead extensions to make the aft of cabin
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Description: front instrument panel cemented inName: SAM_1171.JPG
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Description: Landing gear plate tack glued in, I tried in the landing gear struts to make sure everything lined up.Name: SAM_1172.JPG
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Description: Front cabin area framing

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Description: This where laser cutting pays off these pieces have to wrap around instrument panel and firewall, those precut curves should wrap wellName: SAM_1176.JPG
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Description: Laser cut sheeting never ceases to amaze me.  I will save final sanding until sheeting dries out and I have renewed patience to produce an accurate shapeName: SAM_1177.JPG
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Description: Nice fit with epoxy fillet

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Description: Added epoxy to reinforce landing gear plateName: SAM_1180.JPG
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Description: Final view of aft cabin with dowels cemented in to create gentle curve
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Old Jan 17, 2015, 09:42 AM
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Quote:
Originally Posted by ARUP View Post
For semi-scale barn door ailerons just trim the supplied items to suit. Their chord won't be proper as that would entail moving the rear spars forward. .
This is what I did. It was simple, and provided a scale look.
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Old Jan 17, 2015, 10:51 AM
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My GAC has a lot of flight time on it and revealed one issue with the design that can more easily be fixed during construction.

The gear torsion arms fit into side slots and are held in place by the insertion hole in belly pan. When that hole enlarges due to wear and tear and any fuel soaking, the torsion arm can/will slide out of the groove. Glue a piece of 1/16 ply or 1/8 lite ply over the grooves to hold the torsion rods in place.

While they can be added later through F2, doing so is much harder.
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Old Jan 17, 2015, 11:28 AM
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Hmmm, I don't remember having fit issues with my die cut Goldberg a Cub I built back in the late 80s or early 90s, can't remember. Here is a picture of her.
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Old Jan 17, 2015, 07:44 PM
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Okay I get the picture on the ailerons, I have to admit that looks a lot better than the full strip. Not a hard mod at all! Since you did not mention any problem in aileron authority I assume it is not an issue. Thanks Tom, have to admit I am big fan of your build threads.

AA5BY, Great suggestion, by laminating a ply slab over the slotted landing gear doublers I will be building a box for the struts thereby limiting side to side slop that can round out and enlarge the bottom plate holes. I think I will dry fit the struts in again and glue the plate with them in place to assure they can slide in and out.

Scigs30 Nice model, nice covering no wrinkles or bubbles. I was not disparaging the old kits that are die cut, just experienced problems fitting the sharp tabs cut by the laser in to the rounded slots left behind by the CNC router that cut the slots in the fuse sides. My experience with die cut parts are that square tabs seem to flare out a little because of the rebound when wood is compressed by the stamping process. Us old guys are just used to fiddling with parts to make them fit right.

Spent the last 6 hours working on my bathroom remodel, I earned some shop time tonight.
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Old Jan 19, 2015, 06:21 PM
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The weekend progress

It’s a new day so I decided to shape the front cabin compartment sides and top. Sanding tool shows that I was able to reproduce correct contour.

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Description: Right side of Cabin sanded to shape

Earlier suggestion was to box in the landing gear struts. First I located the original die cut strut support outlines and traced out a second set on new scrap plywood. A quick trip to the bandsaw and then clamped the new braces in place with glue.

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Description: new braces glued and clamped in place

Up till now I have followed the instruction booklet to the letter, it’s time to start freelancing. I attached the Stab so I could shape the Fin fairing blocks to shape. The stab platform was level to the wing platform so I glued the stab on. An additional tail post was needed to square things up.

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Description: Stab attached and tailpost added

Dry fitted the fin and rudder; the laser cut fin matched the plan, but was a tad short of reaching the closest bulkhead. Repaired that problem and finished the fairing blocks.

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Description: Fin fairings cut and shaped and glued to the fin only

Next I cut and dry fit the front windshield and side cabin windows. If I strip off the protective plastic film from the acetate windows I always re-wrap them in Kimwipes tissues. I don’t know about you but I find brand new shiny acetate scratches very easily.

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Description: Left side windows trimmed and fitted

Next comes mounting the engine and cowl. I always find this step takes an
inordinately long time, with lots of tedious bolting and unbolting of engines and cowls. When a kit has an ABS part usually I quickly prepare to use it as a plug for making a fiberglass reproduction. The entire mold and layup process takes me a week. However the cowl supplied in the new kit was quite adequate uniformly thick and had no seams. Also to make a mold would have been challenging because of the slight negative angles around the lower oil cooler feature which would have had to have been removed. Again I took a breath, just a Sunday flyer its okay to use the supplied cowl. So forward we go with the stock cowl.

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Description: Stock cowl looks acceptable

The plans call for attaching cowl with 2 #2 wood screws. Well?, Wood screws in lite ply will be loose and wobbly before I even get around to covering, add a little oil exhaust fluid and vibration and the cowl will be cracked and wobbly in no time flat. Solution is rubber bottomed flat washers and threaded inserts

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Description: Cowl appears to mount nicely

Well I got the cowl mounted and it initially looked good, then the problems started. Engine had to be set back a bit for correct emergence. This interfered with the mounting hole and it became clear that the cowl was going to be cut back in a way that would cause cracking at the mounting hole.

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Description: Rear engine exhaust manifold interferes with fuselage side and is very close to original mounting hole

After mounting the engine I cut the cowl to fit. Modified the cowl by removing the thin stressed out area, and using two new repositioned mounting screws on the left side. Finished product looks good and every tool I own is on the work bench

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Description: Presto! Mischief managed
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Old Jan 19, 2015, 08:27 PM
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As per AA5BY, the torsion gear struts are a weak link. If you are building a dedicated float plane then no problem. If you are gonna do a bit of flying from terra firma then add a rear strut and fasten them together at the axle junction. Otherwise you'll be watching the gear slowly splay outward while the axles bend causing 'toe out'.
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Old Jan 20, 2015, 12:39 AM
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ARUP, I added ply plates to both sides boxing in the struts, but as I look in to the fuse I think I am going to put a put a solid maple strut from axel junction to axel junction that should brace things up. Thanks for the input it seems obvious, but I would not have thought of it on my own. Yes I am going to fly from the earth while I am making and glassing the floats
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