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Post  Ken Cook Mon Nov 14, 2022 7:03 pm

Way back early on in this post, I mentioned of making a hole in the doubler. When I mentioned that you don't want the engine touching the fuse, I meant that only the lugs can touch. Don't let the ear on the bottom of the case touch the inboard doubler. It's also helpful to clearance the engine beams so that the case isn't in contact with the beams, just the lugs are. Drill a hole in the doubler and let that ear protrude out. Pay careful attention that none of the backplate screws are contacting your fuse in the motor mount area. Black oil is a result of aluminum, it vibrates, mixes with dirt and forms a lapping compound. Therefore, if you see black oil, it's usually a result of something coming loose like a muffler mount or engine mounting screws. I wouldn't remove those aluminum pads. Just remove your washers under the front lug. Leave them on as it offers the engine a better footprint and it doesn't squash into the wood.

           Just for the record, my advice is what works for me. I never use a 10" props on small sport models like Ringmasters and Flitestreaks or the Goldberg models. For the Ringmaster, I use the Master Airscrew 9.5x6. I find that it offers good rpm's and maintains a load on the Fox without overheating.

         On my Shoestring, I like the 9x6. I use this prop mainly on my Shoestring for two reasons. I race Foxberg and the 9 x 6  offers the speed I want without overheating from running lean so I can restart on pitstops. The 9x7 would be faster however, it's a bit much pitch and it really overheats the plane. For stunt or sport purposes where your not so lean it should work just fine. The Goldberg Shoestring has a design flaw in the wing. The Goldberg wing has it's two root ribs spaced approx 3/8" apart. This is where the problem occurs. the engine vibrations telegraphs down the fuse and resonates directly on this spot acting like a tuning fork. When we build them for racing, that area is filled in solid with a 1/2" center rib slotted for the bellcrank. Then the top and bottom sheeting gets fiberglassed . This insures that you don't lose engine power due to vibration issues.
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Post  Ken Cook Mon Nov 14, 2022 7:44 pm

I can only slightly see your tank. It appears to be a Brodak tank. Did you pressurize the tank prior to using it? When I say pressurize I mean doing so with a large 5 oz. syringe and underwater with all pipes capped and inflate it like your trying to pop it. If the tank even has a pin hole in any of the solder joints, it will cause the engine run to go lean and possibly vibrate as well. There's many issues as to why the engine vibrates. I can only offer some of the paths to take in trying to achieve resolution.

Brodak tanks in my experience are notorious for leaks and or pipes falling out of them. I never use them out of the package as I completely take them apart and resolder and replumb them. They use a crude method of making the tank and the solder is not of the best quality. If your not currently using a fuel filter such as a crap trap or a Dubro, I highly recommend doing so as this can break up air bubbles and this can steady the run of the engine as well.

When I have a engine vibrating, I pick it up off it's gear and while it's running and vibrating, I squeeze the tank to the fuse to see if it decreases or increases. Plastic r/c clunk tanks can immediately cure this phenomena. On some metal tanks, I've had to wrap the tanks with bubble wrap to stop the tank from shaking. When the fuel foams, it's going to cause the engine to run all over the map.

One thing myself and others in my club do is to use a spritz of the original Armor All in the fuel. A few spritzes in the gallon makes the fuel immediately stop foaming. Aside what many say about this practice, it works and it doesn't ruin plugs as I have seen claims of. My flying partner has been doing so for nearly 20 years and I know of very few that fly as much as he does. As a test in a small bottle, put some fuel in, shake it and watch the bubbles. Spray a spritz of Armor All in the fuel and shake it again and you will see no bubbles and it doesn't change a thing how the engine runs.

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Post  GallopingGhostler Mon Nov 14, 2022 7:50 pm

Is perhaps the black coming from?

https://fhsoils.com/red-max-faqs/
Red Max FAQs wrote:Why has my fuel turned black or why are some of the parts turning black? Are you using brass in any form, like a fuel clunk or tubing? Nitromethane reacts with brass over time, eventually turning it to powder.  It will turn the fuel black and degrade the performance.  Especially if you are running high nitro fuels, like Boat Racing fuels, use non-brass components.
That said, I don't know if that is specifically your problem, best if others pipe in.
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Post  Ken Cook Tue Nov 15, 2022 3:07 am

I see traces of the blackish oil around the engine lugs and washers. As I mentioned, placing washers under your engine lugs is a poor practice. It typically doesn't allow the engine to sit properly which in turn allows minute vibrations to occur. There's little to no need for engine offset as it can cause other issues. A Fox case is very weak. This can flex the case which can distort the case bushing on the crank. This in itself can cause engine run issues. It's very difficult to diagnose problems over the internet. I can only offer experiences I've dealt with and witnessed.

Vibrations also occur within the engine. This entails a entire new scenario of things to look at. Without taking the engine apart, I try and remedy most problems as I see them. I take the simple matters out of the equation and go from there. So the first and easiest is to balance the prop. Prior to balancing the prop, I like to reclock the prop exactly 180 deg and try again to see if any change occurs. Vibrations can really prove problematic and it can take multiple attempts to resolve.

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Post  Onelife Tue Nov 15, 2022 8:53 am

Thanks looks like I got my work cut out for me. First I will make sure that nub has enough room and the bottom of the engine isn’t touching fuse which I know it is and get a few new props thanks. And check the tank
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Post  Onelife Tue Nov 15, 2022 10:32 am

I opened up hole some and put a 9 1/2 6 MAS prop on and checked the tank , the tank had a leak. Haven’t tryed starting yet. S1 Ringmaster - Page 3 E7ec1f10

Thanks again
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Post  Onelife Sun Nov 20, 2022 12:21 pm

Ken Cook wrote:Way back early on in this post, I mentioned of making a hole in the doubler. When I mentioned that you don't want the engine touching the fuse, I meant that only the lugs can touch. Don't let the ear on the bottom of the case touch the inboard doubler. It's also helpful to clearance the engine beams so that the case isn't in contact with the beams, just the lugs are.  Drill a hole in the doubler and let that ear protrude out. Pay careful attention that none of the backplate screws are contacting your fuse in the motor mount area. Black oil is a result of aluminum, it vibrates, mixes with dirt and forms a lapping compound. Therefore, if you see black oil, it's usually a result of something coming loose like a muffler mount or engine mounting screws. I wouldn't remove those aluminum pads. Just remove your washers under the front lug. Leave them on as it offers the engine a better footprint and it doesn't squash into the wood.

           Just for the record, my advice is what works for me. I never use a 10" props on small sport models like Ringmasters and Flitestreaks or the Goldberg models. For the Ringmaster, I use the Master Airscrew 9.5x6. I find that it offers good rpm's and maintains a load on the Fox without overheating.

         On my Shoestring, I like the 9x6. I use this prop mainly on my Shoestring for two reasons. I race Foxberg and the 9 x 6  offers the speed I want without overheating from running lean so I can restart on pitstops. The 9x7 would be faster however, it's a bit much pitch and it really overheats the plane. For stunt or sport purposes where your not so lean it should work just fine. The Goldberg Shoestring has a design flaw in the wing. The Goldberg wing has it's two root ribs spaced approx 3/8" apart. This is where the problem occurs. the engine vibrations telegraphs down the fuse and resonates directly on this spot acting like a tuning fork. When we build them for racing, that area is filled in solid with a 1/2" center rib slotted for the bellcrank. Then the top and bottom sheeting gets fiberglassed . This insures that you don't lose engine power due to vibration issues.

Hey Ken
Starting another shoestring this one is a Goldberg kit. I’m going to reread your comment on the design flaw and see what I can do. I also used the template from the brodak kit to help lay a cord line hope it works. The way the punch out is now it looks a little off , like the wing is tilted up. Hopefully I will get this one a little better. Thanks S1 Ringmaster - Page 3 Image14
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Post  Ken Cook Sun Nov 20, 2022 6:57 pm

My current Shoestring is the Brodak version. I absolutely hate it. Everything about it in my opinion was poor. I didn't know this going into it. I had a unfortunate accident with my old Shoestring which I obtained through a friend. He obtained it from a British Spitfire pilot. I actually met him and that plane really took on a different meaning for my son and I. It was covered in silk and we picked every piece of it which painstakingly took hours to do. I recovered it in silk and refinished it. Yes, I could've built probably 2-3 others in the time it took me to repair and recover that plane.

The Brodak version uses a sheeted leading edge which is a real POS. Your supposed to try and use 1" pieces to bend. Pretty silly idea actually. So, I cut the entire front of the rib off and used my stock of 1" solid balsa leading edge stock and put the dadoes in it. The trailing edge was entirely too weak. I took the ribs and cut the back of them off as well and used aileron stock for a trailing edge. The wing is horrid as they use wide spars directly at the high point. This causes a speed bump as it's very difficult to radius the spar to match the airfoil. The floating bellcrank system is terrible as there's not enough room to even get your fingers in there. While the entire model appears to look like a Shoestring, it doesn't resemble a Goldberg kit in any way.
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Post  Onelife Sun Nov 20, 2022 7:14 pm

Ken Cook wrote:          My current Shoestring is the Brodak version. I absolutely hate it. Everything about it in my opinion was poor. I didn't know this going into it. I had a unfortunate accident with my old Shoestring which I obtained through a friend. He obtained it from a British Spitfire pilot. I actually met him and that plane really took on a different meaning for my son and I. It was covered in silk and we picked every piece of it which painstakingly took hours to do. I recovered it in silk and refinished it. Yes, I could've built probably 2-3 others in the time it took me to repair and recover that plane.

        The Brodak version uses a sheeted leading edge which is a real POS. Your supposed to try and use 1" pieces to bend. Pretty silly idea actually. So, I cut the entire front of the rib off and used my stock of 1" solid balsa leading edge stock and put the dadoes in it. The trailing edge was entirely too weak. I took the ribs and cut the back of them off as well and used aileron stock for a trailing edge. The wing is horrid as they use wide spars directly at the high point. This causes a speed bump as it's very difficult to radius the spar to match the airfoil. The floating bellcrank system is terrible as there's not enough room to even get your fingers in there. While the entire model appears to look like a Shoestring, it doesn't resemble a Goldberg kit in any way.

I agree 100% on the brodak kit I hated it. Like you mentioned 1/16 leading edge with a 1/4 kite spar. Lol it took me 2 hours to try and get the floating bellcrank in only to find out I had it upside down. The landing gear is a overkill. Yea I know the feeling.
I bought the scale model also. I did not start it yet being that I got 2 Goldberg SS and one Sterling RM.   take about buyers remorse on the scale SS. I really don’t know if I even want to attempt it would be willing to sell. I might be interested in selling the other Goldberg SS I don’t know yet. If you know of anyone let me know.
They took one of the classics (SS) and by trying to save a penny destroyed it

Just my 2cents.
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Post  Onelife Mon Nov 21, 2022 8:02 pm

If the stab is a heavy 5/16 out of square from front to back will it be a big problem? Front to back not square with the body
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Post  Ken Cook Tue Nov 22, 2022 2:33 pm

I've seen some really bad issues over the years. Funny how the problems I've seen always seemingly work. This is because it happened to someone else . If it was mine, it would never work. What I feel really hurts performance is when the stab is tilted. In general, when the stab is tilted the plane wants to roll to the high side. If you start trimming things to prevent this without fixing the immediate issue, it's like playing tug of war. The Ringmaster is a fairly successful model in which I'm sure thousands were screwed up along the way. Seeing that you know there's a issue, I would fly it as is unless it's causing problems.
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Post  GallopingGhostler Tue Nov 22, 2022 4:54 pm

In your case, I think you mean that the stabilizer hinge line is not perfectly perpendicular to the fuselage sides, but is slightly canted. S-1 hinge line is about 17 inches long. Then arc tangent of 5/16" : 17" is 1.05 gradians or 0.945 degrees. If you are measuring from the center of the stabilizer to tip, then double that.

IMO, yes, it is misaligned, but unless you want to take the time to cut and re-align, I'd test fly it on a relatively calm day. I am thinking that unless you are into contest flying your S-1 that probably the very slight misalignment would not have much effect on sport flying and stunts. The rudder and line guide placement has more of an effect for line tension.

Anyway, I'm not the one flying your creation, so YMMV (your mileage may vary). Very Happy
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Post  Onelife Tue Nov 22, 2022 5:40 pm

Lol thanks
Good answer sir , that was my plan, fly it and see.

And yes you are correct about the hinge line not  being perpendicular to the fuselage

If you can picture this the stabilizer is kicked back on the outbound side. I’m trying to square this up and get all the  dimensions using a metal 2 foot framing square.
Ever time I bang it agains the plane I have to sand another nick out.
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Post  Ken Cook Tue Nov 22, 2022 7:10 pm

If I'm picturing this correctly, your trying to hold the square to the side of the fuse?  Body of square along the fuse and tongue of square projecting out alongside of stab hinge line? I have a very lightweight aluminum rule. I triangulate the stab tips to the front doublers. Measure from tip of the stab on the angle to the very front of fuse and check the other side. Prior to wing assembly, I do the same with the fuse to the wing tips.
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Post  Onelife Tue Nov 22, 2022 7:59 pm

Thank you. Yes that’s how I am currently doing it. Your way is mush better a accurate for sure. It looked cockeyed after it was already set So then I took the square to it. I’m losing it in my old age. Maybe I just never had. But thanks
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Post  Onelife Thu Nov 24, 2022 1:28 pm

Where can I get the wing assembly for the Goldberg shoestring? Any one know?
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