---------------------------------------------------------- Kolb-List Digest Archive --- Total Messages Posted Tue 10/26/10: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 03:09 AM - thrust line (Ted Cowan) 2. 04:04 AM - Re: slingshot thrust line (Thom Riddle) 3. 07:46 AM - Re: Re: slingshot thrust line (Pat Ladd) 4. 07:48 AM - Re: Re: slingshot thrust line (Richard Girard) 5. 08:04 AM - Re: slingshot thrust line (Thom Riddle) 6. 09:35 AM - Re: Re: slingshot thrust line (Dana Hague) 7. 10:01 AM - Re: Re: slingshot thrust line (John Hauck) 8. 12:06 PM - Sling Shot engine shims (Richard Girard) 9. 04:39 PM - back to the drawing board (robert bean) 10. 05:01 PM - Re: back to the drawing board (william sullivan) 11. 06:33 PM - Re: Re: slingshot thrust line (Jack B. Hart) 12. 11:21 PM - Re: Re: slingshot thrust line () ________________________________ Message 1 _____________________________________ Time: 03:09:38 AM PST US From: "Ted Cowan" Subject: Kolb-List: thrust line I guess when I say it, it is BS but when someone else says it, particularly someone who DOESNT OWN OR FLY A SLINGSHOT, it is God's Truth. Do as you want with your little slingshots, I dont care. I offered the cure. One thing is a factory certain, the motor mounts on the slingshot were placed wrong. They were set as the ones on the other planes and not changed even though the factory KNOWS they are wrong. I have talked with them extensively and being as they dont offer the model any more, it is a mute subject. The wings on other models are set approx. 12 degrees and the slingshot is set at 9 degrees. do the math. do as you would like. I like easy cruise and economy with speed. Enough. Ted Cowan, slingshot, 912UL, zoom zoom. p.s. my cruise is 85 mph and burn 3 gals of gas per hour. can carry a 175 pounder in the back seat and I dont have to tug on the pole to do it. finished. ________________________________ Message 2 _____________________________________ Time: 04:04:10 AM PST US Subject: Kolb-List: Re: slingshot thrust line From: "Thom Riddle" Ted, You are correct regarding full power take-off. It becomes a handful quickly so I don't add full power until I'm airborne, and then only gradually. I guess I'll try a little at a time as others have suggested but will probably end up with about what you have. My concern is that the Jabiru mount is a steel pad virtually identical in size to the steel pad on the Kolb and is 2 or 3 inches square or perhaps larger. So it is not like the Rotax that have vertical bolts through the slightly flexible Lord mounts. It is steel to steel which means I will need tapered shims. The Lord mounts have horizontal bolts between the steel tubing Jabiru mount and the Jabiru engine which you can see clearly in one or two of Chris's photos, and in the attached photo from my SS. This is why it is not just a matter of simply inserting washers. If it was that simple it would have been done long ago. -------- Thom Riddle Buffalo, NY (9G0) Kolb Slingshot SS-021 Jabiru 2200A #1574 Tennessee Prop 64x32 Everyone is entitled to his own opinion, but not his own facts. Daniel Patrick Moynihan Read this topic online here: http://forums.matronics.com/viewtopic.php?p=317062#317062 Attachments: http://forums.matronics.com//files/jabiru_engine_rt_rear_cropped_196.jpg ________________________________ Message 3 _____________________________________ Time: 07:46:36 AM PST US From: "Pat Ladd" Subject: Re: Kolb-List: Re: slingshot thrust line <> When you are airborne is NOT when you need to apply full power. Back to basics. Were we not all taught to apply full power GRADUALLY and increase speed GRADUALLY?. If that is done then all the normal corrections of rudder and stick should take care of problems. Too much power too soon, before you have full control and the torque will get you. The phase when we are all vulnerable is when we are low so grab height as quickly as you can. That means full power BEFORE you leave the ground. Don`t we run full power checks to make sure that full power is available for take off? I am a comparative newbie on the Kolb compared to some of you but I flew my Challenger, with the same problem of a high mounted pusher for some while and the same applies Of course the Challenger with a tricycle gear didn`t have quite the same problems as a tail dragger How about cutting the Kolb boom down to get rid of the rear weight and convert to trike u/c. It was done with the Thruster, probably the most numerous type in the UK. When I had one in the early days it was a tail dragger but there are very few left now. New ones are built with a trike u/c and nearly all the old ones have converted. I am surprised that one of you, with the freedom which you have to Experiment hasn`t had a go at that. Now THAT aught to start a new thread Cheers Pat ________________________________ Message 4 _____________________________________ Time: 07:48:46 AM PST US Subject: Re: Kolb-List: Re: slingshot thrust line From: Richard Girard Thom, I don't have a Slingshot, but I do have a small machine shop. You dra w up the shims you need and I'll make them for the cost of material and mailing. If you're using AN3 bolts to attach the Jabby engine mount buying 16 new bolts shouldn't set you back more than $20 and neither will any shims. $40 seems awfully cheap to fix a problem and put your mind at ease. Rick Girard On Tue, Oct 26, 2010 at 6:01 AM, Thom Riddle wrote: > > Ted, > > You are correct regarding full power take-off. It becomes a handful quick ly > so I don't add full power until I'm airborne, and then only gradually. > > I guess I'll try a little at a time as others have suggested but will > probably end up with about what you have. My concern is that the Jabiru > mount is a steel pad virtually identical in size to the steel pad on the > Kolb and is 2 or 3 inches square or perhaps larger. So it is not like the > Rotax that have vertical bolts through the slightly flexible Lord mounts. It > is steel to steel which means I will need tapered shims. The Lord mounts > have horizontal bolts between the steel tubing Jabiru mount and the Jabir u > engine which you can see clearly in one or two of Chris's photos, and in the > attached photo from my SS. > > This is why it is not just a matter of simply inserting washers. If it wa s > that simple it would have been done long ago. > > -------- > Thom Riddle > Buffalo, NY (9G0) > Kolb Slingshot SS-021 > Jabiru 2200A #1574 > Tennessee Prop 64x32 > > > =93Everyone is entitled to his own opinion, but not his own facts.=94 > Daniel Patrick Moynihan > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=317062#317062 > > > Attachments: > > http://forums.matronics.com//files/jabiru_engine_rt_rear_cropped_196.jpg > > =========== =========== =========== =========== > > -- Zulu Delta Kolb Mk IIIC 582 Gray head 4.00 C gearbox 3 blade WD Thanks, Homer GBYM It is not bigotry to be certain we are right; but it is bigotry to be unabl e to imagine how we might possibly have gone wrong. - G.K. Chesterton ________________________________ Message 5 _____________________________________ Time: 08:04:09 AM PST US Subject: Kolb-List: Re: slingshot thrust line From: "Thom Riddle" Rick, Thanks a bunch for your offer. I will gladly take you up on it. I'll get the drawings to you as soon as I can. Have to take some dimensions first, probably not until the weekend. Thanks again. -------- Thom Riddle Buffalo, NY (9G0) Kolb Slingshot SS-021 Jabiru 2200A #1574 Tennessee Prop 64x32 Everyone is entitled to his own opinion, but not his own facts. Daniel Patrick Moynihan Read this topic online here: http://forums.matronics.com/viewtopic.php?p=317091#317091 ________________________________ Message 6 _____________________________________ Time: 09:35:11 AM PST US From: Dana Hague Subject: Re: Kolb-List: Re: slingshot thrust line At 10:44 AM 10/26/2010, Pat Ladd wrote: >How about cutting the Kolb boom down to get rid of the rear weight and >convert to trike u/c. It was done with the Thruster, probably the most >numerous type in the UK. When I had one in the early days it was a tail >dragger but there are very few left now. New ones are built with a trike >u/c and nearly all the old ones have converted. I am surprised that one of >you, with the freedom which you have to Experiment hasn`t had a go at that. Most of us prefer taildraggers... why take a perfectly good airplane and put a training wheel on it? :) -Dana do not archive -- Politicians and diapers have one thing in common. They should both be changed regularly, and for the same reason. ________________________________ Message 7 _____________________________________ Time: 10:01:45 AM PST US From: "John Hauck" Subject: Re: Kolb-List: Re: slingshot thrust line Gang: I feel like Dana. I like Kolbs the way Homer designed them. I have experience flying and demonstrating the first Sling Shot powered with a 582. I did not detect any adverse flight characteristics with it. Flew a TV videographer at Lakeland. Had fun wringing out the SS, low level through the cabbage palms and pastures south of Lakeland. There is a Kolb video clip with part of that flight on it on Youtube. I also have experience flying TNK's Rotax 912ULS SS. No perceived problems with it. I can not remember if there was any kind of modifications to the engine mounts. I think if there were, it would have been pretty obvious to me. I experimented with different thrust lines with my FS and my mkIII. Always going back to the factory recommended settings. When I take off in any model Kolb, I go full throttle immediately, but like any other aircraft, I don't jam the throttle forward. Kolbs are good aircraft. The only aircraft I fly. We have some pilots that seem to have problems flying them. Maybe they need more training and flight time. ;-) I am not saying that individuals that change the engine thrust line is wrong. Everyone is free to do as they wish with experimental aircraft. I am saying I could not find justification in my Kolbs to keep changes I made. Maybe I was doing it wrong. ;-( My own personal opinion. john h mkIII - 3,000.00+ hours airframe 912ULS - 440.00+ hours engine Most of us prefer taildraggers... why take a perfectly good airplane and put a training wheel on it? :) -Dana ________________________________ Message 8 _____________________________________ Time: 12:06:37 PM PST US Subject: Kolb-List: Sling Shot engine shims From: Richard Girard Thom, Ted, all, I went out to the hangar and measured up the Mk III and Firestar engine mounts to get some input for Autocad. I measure both at 9.5" between bolt centers fore to aft. Since I have to have a little material to hang on to while fly cutting the face of the shims I set thickness of the forward edge of the front shim at .125". Using Ted's suggestion that .875" (7/8") is the best height to correct the thrust line, I put the aft edge of the aft shim at 1.00". Connect the two lines and measure the angle and out pops 4 degrees on the button. Thom, based on your measure that your thrust line is currently 3.5 degrees up, shims based on these numbers would put your thrust line down (converging with the bottom of the wing by .5 degrees. Rick -- Zulu Delta Kolb Mk IIIC 582 Gray head 4.00 C gearbox 3 blade WD Thanks, Homer GBYM It is not bigotry to be certain we are right; but it is bigotry to be unable to imagine how we might possibly have gone wrong. - G.K. Chesterton ________________________________ Message 9 _____________________________________ Time: 04:39:43 PM PST US From: robert bean Subject: Kolb-List: back to the drawing board http://tinyurl.com/2uqvdvx ________________________________ Message 10 ____________________________________ Time: 05:01:45 PM PST US From: william sullivan Subject: Re: Kolb-List: back to the drawing board - Bob- I think you are right.- Bring him over here for a few EAA course s.- No worse than some of the stuff of 100 years ago. - ------------------------- --------------------- Bill Sulliv an --- On Tue, 10/26/10, robert bean wrote: From: robert bean Subject: Kolb-List: back to the drawing board http://tinyurl.com/2uqvdvx ________________________________ Message 11 ____________________________________ Time: 06:33:54 PM PST US From: "Jack B. Hart" Subject: Re: Kolb-List: Re: slingshot thrust line At 07:15 AM 10/25/10 -0700, you wrote: Thom, > The other problem with this that Chris alluded to is that the point and angle at which the thrust is acting is so far aft of the CG that it results in a significant nose down pitching moment when adding power, more so I believe than if the thrust was parallel to relative wind. > The nose down rotation due to the addition of power is caused by the thrust line (moment arm) passing above aircraft vertical cg. The higher the thrust line the greater the moment arm and the more the nose wants to go down. To compensate, one must apply stick back pressure to maintain constant level flight. This in turn applies additional load to the tail which must also be picked up by the wing. This effect is not influenced by the point of thrust application, pusher or tractor if the thrust line is parallel to the relative wind. If the thrust line is angles up to and above the relative wind. then point of application can have some effect. As above one would expect greater nose down effect as the thrust line is rotated upward for the pusher configuration as this again increases the moment arm relative to the vertical cg. Also if the thrust vector is not parallel to the relative wind, power factor will be present. One can detect this by making steep banks to the right and to the left. If power factor is present, the plane will bank much easier or feel more solid in one direction than the other. I added an attachment to help describe what is going on. It can be seen at: http://jackbhart.com/firefly/pf&thr.jpg Jack B. Hart FF004 Winchester, IN ________________________________ Message 12 ____________________________________ Time: 11:21:46 PM PST US From: Subject: Re: Kolb-List: Re: slingshot thrust line Yep ,got me why would you put a wheel on the front of a Thruster. Learned to fly in one of those . Did my first 100 hrs in one . Not many proplems with that wheel way out the back. It was a early one that was built for a 447 but was running a 503 so round outs tended to be a bit sudden. You could wheel it on sooo smooth you could hardly feel it was on the ground. My instructor hated that . Three point it he would say ,I did get good at that after a while. 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