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Too much thrust angle
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Is this too much thrust angle for a Super Sportster 40 MKII?
I had to put some washers on the right side to push the crankshaft and spinner to the center of the cowl ring. Please don't tell me there is too much. |
RE: Too much thrust angle
In the photos it looks like too much left thrust??? Ican't remember but Ithink the SS called for 2 degrees of right thrust. Ihave built a few but can't remember things like there thrust or CG anymore.
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RE: Too much thrust angle
How do I fix it? If I remove the washers from the right side of the mount the shaft and spinner won't be centered.
Will I have to cut the cowl ring and redo? Will if fly with the thrust the way it is? |
RE: Too much thrust angle
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Last photo shows left thrust I defiantly don’t have that in my plane maybe you can add some washers.</p></span> |
RE: Too much thrust angle
ORIGINAL: wzak29 Last photo shows left thrust I defiantly don’t have that in my plane maybe you can add some washers. |
RE: Too much thrust angle
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What is more important? Maybe rudder trim will solve the problem. maybe you can adj. the engine mount, move it over a little to center the engine.</p></span> |
RE: Too much thrust angle
Don't want the aggravation, would rather cut the cowl ring off and redo. Then you will get way ahead of me, more than you are :D
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RE: Too much thrust angle
ORIGINAL: shd3920 Don't want the aggravation, would rather cut the cowl ring off and redo. Then you will get way ahead of me, more than you are :D |
RE: Too much thrust angle
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Here it is without the washers on the right side of the mount.
Real serious problem, don't know how it came out this off. Please someone come up with an easy fix. The cowl ring can not be removed and redone it is all too solid. |
RE: Too much thrust angle
Easy fix, Remove the blind nuts from the back of the fire wall, take some dowel the size of the screw holes and with epoxy glue the dowels in then when set you can move the motor mount over to the left to compensate for the right thruse angle needed.
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RE: Too much thrust angle
Can't do. Too narrow a engine compartment. Both sides of the mount are already pressed against the sides.
Not an easy fix so I will have to cut the cowl off and add scrap wood to the left side to angle it to the right. But how much to angle it?????? |
RE: Too much thrust angle
Do you have a drumb sander or grinder on a dremmel??? Just a thought. How much thrust do you have when you remove the washers?? How far over to the left does the mount have to move before the crank is centered and does that give you any right thrust?? Is the fire wall already premade to give you a set thrust angle? Can you grind down the motor mount??
If you build a kit plane sometimes you have to think a little outside the box. On some kits the thrust angle is already set when you mount the fire wall into the fuse sides so you just have to center the crank by moving the mount/engine a bit to the left. Check your instructions and plans to see if this is already done for you. It doesn't hurt to trim down the motor mount of the inside of the cowl to get some room. |
RE: Too much thrust angle
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I guess the only fix would be to cut the cowl off at the red marks in the photo and add about 1/8" scrap to the left side at the blue mark. Then a whole bunch of scrap balsa around the cowl with alot of filler. Now all that will prob show through the covering.
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RE: Too much thrust angle
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ORIGINAL: Gray Beard Do you have a drumb sander or grinder on a dremmel??? Just a thought. How much thrust do you have when you remove the washers?? How far over to the left does the mount have to move before the crank is centered and does that give you any right thrust?? Is the fire wall already premade to give you a set thrust angle? Can you grind down the motor mount?? If you build a kit plane sometimes you have to think a little outside the box. On some kits the thrust angle is already set when you mount the fire wall into the fuse sides so you just have to center the crank by moving the mount/engine a bit to the left. Check your instructions and plans to see if this is already done for you. It doesn't hurt to trim down the motor mount of the inside of the cowl to get some room. |
RE: Too much thrust angle
It's difficult to tell the thrust line from the photos. If anything, it appears that the engine is shifted slightly to the left side of the fuselage (This is what you want anyway to add right thrust). If so, then a shim can be added to give the right thrust, but you will have to rework the fuselage to recenter the plywood ring to the spinner.
The best way to determine the thrust is to measure from a large prop tip to the tail from both sides when the prop is horizontal (make sure the prop is true by taking the first set of measurements, then turning the prop over half a turn.). If they call out right thrust, you want to have it. Otherwise the airplane will not track true when you pull into vertical. |
RE: Too much thrust angle
zero percent thrust needed according to the plans. The engine is straight now so I can not add any thrust by putting something behind the mount. The cowl is what is off so like I said the only fix is to cut the cowl and add 1/8" to the left, pushing the cowl to the right. But I have to do this without making the fuselage front crooked.
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RE: Too much thrust angle
Yeah, that's wrong, look at the spinner, in the photo, it clearly says for bolth top and side view, "0 Thrust", go back and remount the engine at 0 and 0, the best way to do this is with a robart meter, it has a crank shaft adapter on one clamp end, just zero the wing and the stab and check the engine, remove the wing and with the fuse on it's side, level and zero out the rudder and now check the engine, it should be at zero. Good luck, but trying to ignore this will cause a very poor flying plane that reacts strange as you add and remove power while flying. I even use my meter when gluing stabs and wing saddles in place, it helps to verify that the plane is straight and true. It's only 25 bucks or so but you'll never stop using it.
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RE: Too much thrust angle
The mount should have enough side play to re-center the engine.
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RE: Too much thrust angle
There is no slide play in the mounts, the sides of the mounts are already touching the inside of the compartment. And if I could slide the mount over it would move the centermarks of the mounts so they would no longer be centered.
It is not the mount that is crooked, as I stated the engine is straight, it is the cowl ring that is off-center. And by shifting the cowl 1/8" to the right should center it. That is what I will try. I really appreciate all the advice given here as I always do but I think I am confusing you all by making you think it is the mount/engine that is crooked. |
RE: Too much thrust angle
You just need togrind the mount on the side so you can slide the mount over to the left to center the crank!!
If you can't do that then just build another cowl!!! http://www.rcuniverse.com/forum/js/f.../msn/72_72.gif |
RE: Too much thrust angle
The issue here is that you moved the engine (by putting shims under the mount) to fit the cowl. This was your mistake. The cowl is supposed to be built to fit the engine. By this I mean that the engine needs to be properly mounted on the firewall. Planebuilder quotes the plans as mounting the engine at 0 degrees on both axis. So, this mean the engine mount should be flat on the firewall, and the engine mounted on the mount with the shaft inline with the centerline (thrust line) of the fuselage.
You have two choices. One, mount it the best you can and live with the cowl being "off center" with the engine. Two, cut of the cowl and rebuild it properly. My advice would be to cut the cowl off and rebuild it. By doing this you can take the time to verify that they engine is properly mounted on the fuselage. Ken |
RE: Too much thrust angle
Another alternative would be to buy a new motor mount and remount the engine.
Also, the sides of your 'cowl' look pretty thick. Is it possible to remove some of the material on the inside of the left side of the cowl. This would allow you to slide the motor mount to the left. HTH, EJ |
RE: Too much thrust angle
I understand now what you mean about moving the mount to the left to center the shaft. The problem I have with that is I need the center of the mounts to hold the nosegear. So by moving the mount to the left it will move the nosegear off center.
Is there a way to modify the mounts so that I can slide them to the left and perhaps drill new nosegear holes? |
RE: Too much thrust angle
No, you DO NOT move the mount. If the nosewheel is set on the centerline of the plane, this is where it's supposed be. If you move the engine or mount to fit your off center cowl you are going to put some very bad thrust angles into the plane, which will cause all kinds of problems flying. Like I said, you need to cut the cowl off and rebuild it properly. Or live with the cowl being off center.
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RE: Too much thrust angle
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Cowl is cut off and repair has started. Check out my build thread to follow the repair. Thank you Ken, I knew I could count on you. Thank you everyone else for your advice.
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