Goldberg/Brodak Shoestring Wing

Joe Hello , I got the plane CG that needs some attention and have been wanting to get down from upstairs , What are the measurements of the wing cut out ? Eric

The answer is no. In fact, I find it to be a extremely poor design. A perfect way to ruin a classic. The entire wing was redesigned. The outline is the same but the leading edge is a sheeted 1" leading edge with no strength . They also used too wide of a spar on the high point of the wing which doesn't sand out well which leaves a speed bump on the high point. It also is very susceptible to horse starving when sanded due to the lightweight sheeting. Unfortunatley, I spent last weekend smashing and jumping on planes that I felt I was never going to use again and one of them with a perfectly good wing was a Shoestring. Do you have the leading edge stock? Do you have the trailing edge stock? Do you have the wingtips? These are the toughest to replicate. Ken

Ken Cook wrote:The answer is no. Unfortunatley, I spent last weekend smashing and jumping on planes that I felt I was never going to use again and one of them with a perfectly good wing was a Shoestring.? These are the toughest to replicate. Ken

Awe man......that sounds just cruel. Didn't want to eBay 'em or offer them up to others for the cost of shipping??  

I gathered that for an early 1950's design, very much Sterling S-1 Ringmaster like, probably flies similar to the Ringmaster. Over time, designers have found what works best, improved construction design as well as better and thicker airfoils.

Just like the Ringmaster, a few have revised for better building and flying. Not long ago, someone won or placed high in a large national CL contest with a Ringmaster. Goes to show that properly set up, the right pilot will make it perform.

Besides, not all us are competition minded. These are good sport designs. Back when they were selling in the 1950's to 1960's, they were decent performing machines, even with the cheaper quality kit wood and above all, affordable. Not all aim to fly picture perfect AMA patterns, it is the fun of flying that is more important, IMO.

George, many have used the Ringmaster in contests. Older designs of that era were handicapped as far as maneuverability. Too short of wingspan and thin airfoils were very typical. However, the Ringmaster while it also suffers the same fate, it can out perform pretty much all that was available back then. Another + was it's cost, they were cheap. Goldberg kits had a lot more engineering involved and the overall kit and instructions were superior to a Sterling kit. Sterling kits are just plain awful. The funny thing is the C-series Sterling kits offered  very clear and detailed instructions. Almost every Sterling kit builds nose heavy even using the lightest engine of the period. Many opted for no landing gear as this greatly assisted the flying ability. Not the case with a Goldberg Shoestring or Cosmic Wind or even the Buster. These planes are generally tail heavy requiring a bit of lead in the nose to calm down the twitchy flying. While both planes have identical wingspan, the Shoestring offers a thicker airfoil which just outright flies the plane better over the Ringmaster. The Shoestring offers a slight advantage having just a few more sq inches.
              What I did  notice is that the Shoestring can develop a case of BAD vibrations. This is due to the wing construction. The Shoestring has two ribs in the center spaced equally so that the fuse is directly over top of it. This void can transmit vibrations right back into the nose and leading edge of the plane. Making the center rib a solid 1/2" rib takes care of this problem and prevents leading edge and cheek cowling cracks.

Ken Cook wrote:What I did  notice is that the Shoestring can develop a case of BAD vibrations. This is due to the wing construction. The Shoestring has two ribs in the center spaced equally so that the fuse is directly over top of it. This void can transmit vibrations right back into the nose and leading edge of the plane. Making the center rib a solid 1/2" rib takes care of this problem and prevents leading edge and cheek cowling cracks.

Ken, regarding vibrations, for real shakers like the older Fox .35 stunt, I've gathered that this is why many prefer full body fuselages over profiles. They better dampen vibrations. However for me, I like profiles because they are so much easier to build. And yes, as you illustrate here, there are room for improvements to construction. But then, 66 years have past. As you pointed out, kits were cheap then. No doubt that a few compromises were made to keep kit prices down.

It amazes me how much the hobby industry provided much employment. Companies turned out kits in the thousands each week. Kind of reminds me of a song (words rephrased )

sung to Paul Revere and the Raiders 'Indian Reservation' wrote:They took our whole C-L generation
Locked us out of parks in our nation
Took away our ways of flight
Unmuffled engines and the circles so tight.

Took away our right to fly
And taught our children kit building was nigh
All the kits we made and sent
Are now a day's make from the Orient

Plane building people, plane building tribe
So proud to live, so proud to fly!

But maybe someday when they learn
Control Line building will return, will return,
will return, will return, will return!

akjgardner wrote:It’s been several. Years since I posted this , I am starting to get back into the hobby. I wonder if now somebody out there makes laser cut ribs for the Goldberg shoestring ? Any help would be appreciated.  Thanks

it just so happens that I have been asked to draw and laser cut a kit for the Shoestring Stunter... however, I have only found the plans that have the root and tip rib. I can draw in CAD and laser cut the parts but I would like to have scans of the actual ribs, etc. I also plan on cutting the 1/2" thick center rib, that is if I can get the originals. Even if someone has the original kit (unbuilt) and would be willing to trace the ribs, that would ensure accuracy. My goal was to resurrect these obsolete kits as close to original as possible and leave it to the big stores to make new and improved versions.

Locating a accurate solid leading edge is going to be the challenge. Regardless of rib accuracy, if the leading edge isn't the correct thickness, it's going to be problematic. These are very expensive nowadays not too mention far from being straight which caused the demise of them. Sig was a source but they're all but defunct nowadays. Midwest used to carry the 1" solid leading edges in bundles of 10. You were doing well if you managed 3 good straight ones. They were also a bit pricy. In addition, a lot of trailing edge stock is aileron stock which uses a right triangle vs a isosceles style triangle.

That being said, I think the best solution to this is to use the Brodak ribs which can be purchased in a rib kit and modify as needed. While the trailing edge on this wing utilizes two sheeted pieces a few things can be done to add tremendous strength. Substitute and rework the trail section of the rib using medium 1/8" by 2" . I preferred to build as is, I then cut off 1/2" of the trailing edge and glued a piece of spruce to the trailing edge and shaped to the rest of the wing. As for the front, I just used vertical grain shear webbing in between the rib bays.

With a search there is one Co. that have leading edge 3/4 and 1" for sale https://webstore.eliminator-rc.com/midwest-3-4x3-4x36-leading-edge-balsa that looks good . I have the plans i guess the plane is upstairs and still needs attention , Good to hear from you Joe !

Thanks for the info.  I am a BIG fan of the two-sheet pieces on LE as well as vertical webbing between spars (did the webbing on my Veco Brave resurrection) but my main goal here was to replicate the original.     Maybe that isn’t such a good idea after all give the scarcity of materials.  Yah, too bad about SIG.  I called them in November and got the heads up about the takeover (took the business back) and now relocating, getting out of the balsa retail biz and will outsource their kits overseas going forward.  Bummer .

[quote="Ken Cook" Unfortunately, I spent last weekend smashing and jumping on planes that I felt I was never going to use again and one of them with a perfectly good wing was a Shoestring. Ken[/quote]

Many years ago I was given a bunch of FF and C/L planes by a former WWII pilot/modeler One of these being a partially completed Berkeley Navion with an arrow hole in the fuselage. I realized very quickly that someone elses airplanes didn't have the same interest as my own. While I did fly a few of these (how about a double rotor autogyro) most of them sat unused. The rest of the airplanes languished in my old summer camp for a few years until I decided to renovate that building.

So most of the planes ended up in the campfire..

Wouldn't you know it several years later he got the modelling bug and asked for the Navion back...…..

It's been many years since then and for the likes of me I can't remember what I told him about his plane.

I even thinned the herd this past weekend. Three more to the can. I'm finishing a new Sterling Mustang and a Yak. My old Yak is next to go. Sad but they have a life expectancy and it exceeded it.

excuse the double post

akjgardner wrote:It’s been several. Years since I posted this , I am starting to get back into the hobby. I wonder if now somebody out there makes laser cut ribs for the Goldberg shoestring ? Any help would be appreciated.  Thanks

I just finished drawing out all the ribs for the Goldberg Shoestring Stunter as close to original as I could with only the paper plans with the root and tip rib.   Not sure if the original kit LE was 1” all the way out or if it tapered.   The smaller tip rib #9 would indicate that it did taper.  I can cut these out in 3/32 balsa.   I made the center rib a bit different based on suggestions… in that the center ribs are sandwiched together to form a 1/2” solid center rib.  3/16 - 1/8 - 3/16.  There was much agreement that the two parallel center ribs on original caused too much vibration.    The left rib has notches for the bell-crank platform tabs as does rib #2.  I prefer this over gluing additional supports.

Additionally, the original ribs had what appears to be 1/8” square tabs where it would sit in the horizontal notch of the Leading Edge.  I left the front of the rib in tact as I would prefer a vertical notch in the leading edge vs the long horizontal.  However,  I did burn the lines on the rib in the event the builder wanted to go original and easily cut with xacto knife.  





Let me know if you are interested in being my test subject.

Got the PM… (too new to reply. LOL).  Will be in touch, glad to be able to help…

Great news (at least I think so) a fellow from another group is sending me a complete original die-cut Goldberg Shoestring Stunter kit…. As a loaner. This will allow me to really get the actual measurements off each part so I can truly make an original copy and/or short kit. Been thinking about the leading edge… like mentioned, that 1” L.E. is expensive and although available, not always going to get a nice straight piece. I’m kicking around the idea of using multiple sticks to build up the leading edge. 1/8” x 1” x ??? Cut with width of the rib bays glued to another 1/8” x 1” x ??? To make the first 1/4” thick part of the L.E. But having the notches ready to accept the ribs (vs. having to saw notches into solid L.E. Material). Then glue/laminate in 1/8” increments until the desired depth is achieved. This will be straight as well as strong. Like I said, still kicking it around.

Received a complete original Carl Goldberg Shoestring Stunter from a fellow enthusiast… began taking measurements and drawing… got the number 1 rib nailed. I’d say in about a week I’ll have a nice short kit ready to go.

That looks really Good perfect fit ! Have you gave any more though about the leading edge ? Is it 1" or 3/4 " ? I have a shoestring that needs recovering and the bell crank mount repaired upstairs , but not been up there in a while .

@getback so I have drawn all the cutout parts to the kit on CAD and am in the process of cutting all of them. Had to wait on 3/32 balsa for the ribs (i think they were actually 5/64 thick originally) so for the leading edge, 1” is what came in the kit… with the 1/8” notches and the horizontal groove. The 1” L E is available still on the web (Forget off top of head where i saw it ) but probably will attempt to build one up… using 1/8” x 1” stock spacers glued to 1/4” x 3/4” stock then 1/4” x 1/2 for nose… then just shape it once all glued. If I laser cut the spacers, will be better than me trying to notch 1” L E stock with saw blade.

Something like this




I tackled the fuselage by using two 3/16 and one 1/8 balsa sheet laminated to make the 1/2” thick fuse… might even make it stronger/stiffer using 1/8” ply in middle or even the two 3/16 balsa with 1/16 ply on each outer side for strength.

That looks good ! The 1"x36" LE was about $9 a stick w/o shipping , site is a few frames back^^^ should work with the combination you have for the thickness and sand out , i know you need a special machine to cut the radius for LE . That's a good idea i think to reinforce the fuse by sandwiching A ply in there either inside or outside ,hard to say witch is stronger ? Talk later