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Building Tips and technical articles. => Building techniques => Topic started by: Chris Wilson on September 04, 2012, 08:46:31 PM
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Just wondering who if any are using asymmetrically sized engine bearers with invert or upright engines with out thrust?
I have seen 1/2 x1/2" bearers used outboard and 3/8 x 1/2" used for inboard.
This allows an out thrust enabled engine to have far more material around the outboard bearer's bolt holes.
Kicking the rear of the engine inboard and keeping the prop driver centralized to allow for out thrust does seem problematical when using same sized bearers.
Thanks.
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If you use a 1/2 in. sq. mount on the right and a 3/8 x 1/2in. on the left that automatically puts in approximately 1/4 deg. of engine offset. Depends on the length of the nose and chord of the wing.
If you want more than 1 deg. or so and keep the engine centered about the only easy way to do it is build the mount as a crutch. Then carve the mounts with the offset needed to center the spinner. No matter what, one or more of the bolts will be fairly close to the edge of one or both mounts. Geometrically, there is no way to keep the glow plug centered on the fuse, the spinner centered, and have the engine offset.
You cone close by making the right wing slightly larger. This moves the center of drag to the right, functionally equivalent to engine offset. A lot of planes do this by using equal panel lengths an adding a bit extra wing tip weight and a flap that is slightly larger at the tip on the right panel.
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Guess I'm not understanding why it matters much if your spinner is offset some. Mine surely are but it is hardly noticable for say 1-1 1/2 degrees of engine offset. The nose is simply shaped to wherever the spinner falls. Just twist the engine a bit outboard by sanding or grinding on the mounts as required. I mount the spinner backplate on the engine with a ply nose ring double-sided taped on the backplate. Then build the nose out to the ring. Pull the engine then sand the nose blocks into the ring. Sure much easier than what I'm hearing here.
Dave
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What I like to do is to keep the spinner on the centerline of the fuselage. That means, that for whatever engine offset I use, normally about 1 degree but no more than 1 1/2 degrees, the engine is off the cente line and the motor mounts must be assymetric. The solution is simply use 1/2" thick maple that is up to 1/2" wide or more and cut the motor mounts accordingly. I am only suggesting that there is another way to do this.
Keith
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What I like to do is to keep the spinner on the centerline of the fuselage. That means, that for whatever engine offset I use, normally about 1 degree but no more than 1 1/2 degrees, the engine is off the cente line and the motor mounts must be assymetric. The solution is simply use 1/2" thick maple that is up to 1/2" wide or more and cut the motor mounts accordingly. I am only suggesting that there is another way to do this.Keith
Gee, didn't I read and was told that engine offset isn't used any more? Rudder offset also? I'm sure I did.
So, if it's not needed, and affermed by what has been offered as bonified information, why even bother?
Now I'm confused.
Charles
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It's an individual thing. Some do it and some don't. Just like the flat fin/rudder or airfoiled fin/rudder.
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Yes Keith there are sure more ways to skin the cat. Charles, Your rib about nobody using offsets-then don't look too close at some of those airplanes-it will burst your bubble! I've seen too many adjustable rudders. I'll say that I believe engine offset is more effective with far fewer trim problems than rudder offset but I do usually end up with just enough rudder offset to be sure it's not going the wrong way. I also believe in equal span wings for several reasons including NOT designing in more drag on the inboard wing panel. Some of my better flying ships have actually had the outboard panel 1/2 inch longer....
Dave
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Yes Keith there are sure more ways to skin the cat. Charles, Your rib about nobody using offsets-then don't look too close at some of those airplanes-it will burst your bubble! I've seen too many adjustable rudders. I'll say that I believe engine offset is more effective with far fewer trim problems than rudder offset but I do usually end up with just enough rudder offset to be sure it's not going the wrong way. I also believe in equal span wings for several reasons including NOT designing in more drag on the inboard wing panel. Some of my better flying ships have actually had the outboard panel 1/2 inch longer....Dave
Dave,
Are you saying to build a model that has an adjustible rudder? Otherwise to make a correction, if needed, you would have to cut and reglue the rudder.
I have a few things on the drawing board with one degree of engine offset and no rudder adjustments. I do have adjustible leadouts and the weight box.
I don't need to make mistakes.
Charles
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Yes Charles I sure would. I finally gave in on my team trials airplane from last year and put an adjustable rudder on. In that case it was to correct for a rudder that warped but just to have capability to adjust everything whether you actually do or not is golden.
Dave
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Dave,
Are you saying to build a model that has an adjustible rudder? Otherwise to make a correction, if needed, you would have to cut and reglue the rudder.
I have a few things on the drawing board with one degree of engine offset and no rudder adjustments. I do have adjustible leadouts and the weight box.
I don't need to make mistakes.
Charles
Charles,
Engine offset is sort of a matter of preference based on experience. Just like rudder offset, it can be overdone. which is not good. Some use engine offset and/or rudder offset for some right yaw just to make sure there is no left yaw trim problems which would be far worse than some small, probably undectable unfavorable right yaw.
Wow. Are you going all out to make a fully capable stunt ship? If you are, why not consider a Rabe rudder? Also, why not consider an ability to adjust the elevator/flap ratio.
By the way, apologies are still in order. What you did on that other forum, now erased, is kind of embarrasing. You did it. You cannot blame anybody else for your rather crude and immature actions.
KEITH TROSTLE
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Charles,
Engine offset is sort of a matter of preference based on experience. Just like rudder offset, it can be overdone. which is not good. Some use engine offset and/or rudder offset for some right yaw just to make sure there is no left yaw trim problems which would be far worse than some small, probably undectable unfavorable right yaw.
Wow. Are you going all out to make a fully capable stunt ship? If you are, why not consider a Rabe rudder? Also, why not consider an ability to adjust the elevator/flap ratio.
By the way, apologies are still in order. What you did on that other forum, now erased, is kind of embarrasing. You did it. You cannot blame anybody else for your rather crude and immature actions.
KEITH TROSTLE
Keith, don't think your going to get it.
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Charles,
Engine offset is sort of a matter of preference based on experience. Just like rudder offset, it can be overdone. which is not good. Some use engine offset and/or rudder offset for some right yaw just to make sure there is no left yaw trim problems which would be far worse than some small, probably undectable unfavorable right yaw.
Wow. Are you going all out to make a fully capable stunt ship? If you are, why not consider a Rabe rudder? Also, why not consider an ability to adjust the elevator/flap ratio.
By the way, apologies are still in order. What you did on that other forum, now erased, is kind of embarrasing. You did it. You cannot blame anybody else for your rather crude and immature actions.KEITH TROSTLE
Kieth,
Well, you started out nice, "play nice", then what happened? You had to bring up that Thread you and a few others ruined.
It was "you," as usual, who first made the remarks. Followed by others. You destroyed that modelers Thread.
I have a copy of that Thread and all comments that were made. Now why should I post your dirty laundry in this great Forum.
Robert told "everyone" to play nice or don't reply. If you can't muster up anything, just keep your finger off the button and don't reply to "anything" that has to do with Avaiojet. BTW. You are well known on both Forums.
Best advice I can give you.
Charles
P.S. Was it you who told me to use spell check?
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Charles,, for the record you are correct,, Mr. Trostle is very well known on both forums,, and very well respected as well,,
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Careful Mark, stating rational and truthful comments in response to one of Charles is apt to get you on the list and known as a "troll".
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Bill, I am one of the charter members on Charles' Troll list,
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So all this has gone down the toilet..........again.
And so quickly, I AM impressed!
Just for the record here -
Charles, you know me outside of this forum but I have to say that you have an irritating method combined question/statement that attracts the sharks.
I just wish that said well respected 'sharks' would skirt around the blood in the water for once and leave the topic alone.
(Kieth, no disrespect intended mate - its just that I hate seeing this turn into a three ring circus complete with clowns, and I include myself here - at times.)
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Gee, didn't I read and was told that engine offset isn't used any more? Rudder offset also? I'm sure I did.
So, if it's not needed, and affermed by what has been offered as bonified information, why even bother?
Now I'm confused.
Charles
Ok, I will have a shot at this.
Consider that even if the engines thrust line is perfectly aligned to be tangent to the flight circle you will have outhrust and most posts on this subject relate to angles added to that.
To have NO outthrust you must angle the thrustline inwards past the tangent and no body I know in stunt does this.
Speed guys do but they rely on their massive kph and whipping to keep the beast out there, we really don't have either of these luxuries.
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Ok, I will have a shot at this.
Consider that even if the engines thrust line is perfectly aligned to be tangent to the flight circle you will have outhrust and most posts on this subject relate to angles added to that.
To have NO outthrust you must angle the thrustline inwards past the tangent and no body I know in stunt does this.
Speed guys do but they rely on their massive kph and whipping to keep the beast out there, we really don't have either of these luxuries.
Hi Chris,
Good explanation; if I remember correctly, David Fitzgerald and maybe Brett Buck have tried a small amount of "in" thrust and I think that David does use some. On my Impacts I use zero thrust offset relative to the centerline of the fuselage & zero rudder offset with a 3/8" longer inboard wing. Works well on an Impact.
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Adjustable leadouts.
Wouldn't these alone add or subtract to the out thrust/in thrust? Certainly changes the in or out angle of the fuselage, to a great degree actually, especially if you have a range of 2" for leadout adjustment.
Appears so?
Charles
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Adjustable leadouts.
Wouldn't these alone add or subtract to the out thrust/in thrust? Certainly changes the in or out angle of the fuselage, to a great degree actually, especially if you have a range of 2" for leadout adjustment.
Appears so?
Charles
Yes it does appear so, but the lead out adjustment is more for keeping the model constant when the line length or weight (and consequently drag) changes.
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Kieth,
Well, you started out nice, "play nice", then what happened? You had to bring up that Thread you and a few others ruined.
It was "you," as usual, who first made the remarks. Followed by others. You destroyed that modelers Thread.
I have a copy of that Thread and all comments that were made. Now why should I post your dirty laundry in this great Forum.
Robert told "everyone" to play nice or don't reply. If you can't muster up anything, just keep your finger off the button and don't reply to "anything" that has to do with Avaiojet. BTW. You are well known on both Forums.
Best advice I can give you.
Charles
P.S. Was it you who told me to use spell check?
Danger, Will Robinson! Danger!
Dan