adding weight?
01-11-2012 | 09:12 AM
#51
Senior Member
RE: adding weight?
ORIGINAL: HighPlains
Sorting ribs by weight puts the heavier ribs in the center of the wing if constant chord, but even when tapered, you can balance a wing with careful selection of which panel each pair of ribs go to. Same with all the other pieces that go in the wing.
Sorting ribs by weight puts the heavier ribs in the center of the wing if constant chord, but even when tapered, you can balance a wing with careful selection of which panel each pair of ribs go to. Same with all the other pieces that go in the wing.
CL stunt pilots/builders/designers don't even think about this issue any more. It is done as a matter of course. They know more than anyone how a plane feels in the air. Heck they are connected to it
To the OP....are you confused yet with the answers to your truly simple question? If you are the experimental type, why not do the simplest thing first? Bolt on the weight, get the cg where it needs to be and fly the crate 50 flights. Then do some of the lightening suggestions several of us suggested, and fly the crate another 50 flights. Then report here
01-11-2012 | 09:16 AM
#52
RE: adding weight?
As a general rule of thumb I try not to add unnecessary weight to models, however sometimes functional additional weight from say a larger engine or heavier batteries can improve the way some models behave in certain conditions. For example my Goldberg Extra at 10.25 lbs with a gas engine grooves so much better than when it weighed 8.5 lbs. with a .90 size glow engine. But then the CG Extra is really a stand out from the crowd and almost a one of a kind well mannered flying aircraft.
Karol
Karol
01-11-2012 | 10:01 AM
#56
My Feedback: (29)
RE: adding weight?
More power fixes things too. Typical IMAC 35% airplane weighs 26-27 lbs and is powered with 100-120cc. Some would call this overpowered. The power helps drive strait lines. When I started flying pattern with electric setups I was used to the power to weight ratio of IMAC airplanes. As a result I found some areas of my setup were a little lax and had to pay more attention to details to get the airplane to feel locked in during uplines.
01-11-2012 | 10:06 AM
#57
RE: adding weight?
ORIGINAL: cfircav8r
When flying full scale I love a light snappy A/C, however when I am flying full IMC with passengers it is far more comfotable for them and far easier for me if I am closer to the max gross weight.
When flying full scale I love a light snappy A/C, however when I am flying full IMC with passengers it is far more comfotable for them and far easier for me if I am closer to the max gross weight.
Do full scale pilots have any control over the CG location, or do they have to fly in a different manner when that CG is way off the ideal location?
01-11-2012 | 10:10 AM
#59
RE: adding weight?
ORIGINAL: HighPlains
Finding lead is easy.
http://www.rotometals.com/Lead-Sheet-s/31.htm
A quick recap - There are two separate discussions going on, so reading comprehension is required.
1.) On the issue of an airplane being "two light", add weight and get back to us.
2.) Moving the wing back on the fuselage will balance the plane. Easy to do when it has a wing tube and simple mounting.
We return you back to your regular programming.
Finding lead is easy.
http://www.rotometals.com/Lead-Sheet-s/31.htm
Do you people not think? Weight is not his problem, balance is. Adding a pound of lead at the CG won't do a damn thing for him.
1.) On the issue of an airplane being "two light", add weight and get back to us.
2.) Moving the wing back on the fuselage will balance the plane. Easy to do when it has a wing tube and simple mounting.
We return you back to your regular programming.
Thanks for pointing that out.
01-11-2012 | 10:10 AM
#60
RE: adding weight?
Crazy nick your se will fly fine with the added weight so go fly and find out if you can shed some of that weight later by fine tuning your cog. If you are a sport flyer you may well be happy with the performance, but at 7 lbs without fuel it is not going to beunlimited vertical/hover machine (yes you can hover a extra).,
If you cant loose any of the weight and want more performancethen later when your flight skills/comfort with this model improve ditch the weight and evolution 46 engine and fit60 size engine, hover and unlimited vertical for sure.
I have a irvine 53 in mine, great combo.
If you cant loose any of the weight and want more performancethen later when your flight skills/comfort with this model improve ditch the weight and evolution 46 engine and fit60 size engine, hover and unlimited vertical for sure.
I have a irvine 53 in mine, great combo.
01-11-2012 | 10:17 AM
#61
RE: adding weight?
ORIGINAL: speedracerntrixie
[/quote]
At first I read this and thought what an over exaggerated example it is. But I thought about it more and the answer is a yes! A well set up and trimmed 2 lb airplane would fly better then a poorly set up and trimmed 2.5 lb airplane in a 15 knot wind. Again, the airplane sees wind as a change in airspeed. A poorly setup airplane will react to changes in airspeed so obviously it will react to wind. Ask yourself if your airplane's trim changes at all between 1/4 and full throttle. If the answer is yes then it is not trimmed correctly. Does it really matter? Not if you are happy with the overall performance.
[/quote]
Over exaggerated example? I would hazard a guess to say that there are a lot more pleple flying 2 pound park flyers than 11 pound pattern aircraft. Yes a 15 knot wind can affect an 11 pound pattern aircraft to the point of runining someone's competition flight. But that same wind can ruin a 2 pound flyer's entire day or week or month.
01-11-2012 | 10:18 AM
#62
Senior Member
My Feedback: (4)
RE: adding weight?
ORIGINAL: on_your_six
3 pounds??? I would have hung a larger engine on the nose. Something does not sound right.
3 pounds??? I would have hung a larger engine on the nose. Something does not sound right.
Look at a P-40. Notice how much of the nose is filled with engine on the full-scale version compared to a model. So it's really not unusual at all to have to add a lot of lead to the nose - especially when dealing with a scale model
01-11-2012 | 10:20 AM
#63
RE: adding weight?
ORIGINAL: rgburrill
Dumb, dumb. I did not get that is what he meant. You, and he, are correct, moving the wing back would move the required CG back.
Thanks for pointing that out.
Dumb, dumb. I did not get that is what he meant. You, and he, are correct, moving the wing back would move the required CG back.
Thanks for pointing that out.
That distance is the stability margin that every plane needs in order to be stable in pitch.
What the OP has now is a distance between the CG and CL that is smaller than ideal (more pitch control authority, but less pitch stability), zero (dangerously neutral) or negative (tail heavy or total instability condition).
01-11-2012 | 10:21 AM
#64
Banned
RE: adding weight?
<span style="color: #ff0000">Hi again HighPlains,
I do no wish to change the format of the posting so I think I can use red color to distinguish your text versus mine.
</span>
<span style="color: #ff0000">I have no objection to laugh at myself. I know my limitations and realize that "I do not know it all" thus the urge to keep studying and learning more. I am willing to admit that everyone else knows more than I do. For sure many in this forum do; even the odd one that wrote that Zor knows nothing and just repeat what others are writing. Any reader can makehis/her ownjudgment on that.
Things I avoid discussing in the forum ___people's characters, personalities, knowledge of others, politics, religions, sex. It is unfortunate that in many cases we cannot disagree with some individuals on a technical matter because they are offended if you do not fully agree with them. Offending is against the rules of the forum but being offended depends purely on the reader although the writer will be the one penalized. Does not that sound a bit illogical? IfI respond defending my characteror personality then I am the one penalized? It does not make sense. But then the writer may also have been a moderator with the capability of penalizing someone.
Considering the large number of readers that are not participants but read these forums to extend their knowledge and find help; should we let them be mislead by a fair amount of misleading information written in the forum?
Zor
</span>
I do no wish to change the format of the posting so I think I can use red color to distinguish your text versus mine.
</span>
ORIGINAL: HighPlains
Zor,
Two objects can weigh the same, but the force it takes to accelerate them to the same angular rotation varies based on the distribution of the weight. Think dumbbell, with the weight on the end vs same weight concentrated at the center. Low polar moment, though I guess being from Canada Polar might have a different meaning.
<span style="color: #ff0000">If you read back in this thread you will find that I already covered this subject when I referred to mass distribution in a model. my recent comment was to avoid putting my own words in your mouth
. Of course you are correct and I had already covered that very same subject.
</span>
Sorting ribs by weight puts the heavier ribs in the center of the wing if constant chord, but even when tapered, you can balance a wing with careful selection of which panel each pair of ribs go to. Same with all the other pieces that go in the wing.
<span style="color: #ff0000">I wonder how many understood what you implied by "balancing a wing". Thanks for your present explanation.
Considering the weight of the ribs in a wing vs the total wing weight, you are correct but the result is not going to be very significant. Your idea can be carried further by finding out which end of the spars is heavier to orientate the spar with the heavier end at the root of the wing. The same could be done for any sheeting. Again the result would not be very significant and doubtfully observable by even the expert fliers. </span>
Dirty Harry said it best - "a man's gotta know his limits"
Zor,
Two objects can weigh the same, but the force it takes to accelerate them to the same angular rotation varies based on the distribution of the weight. Think dumbbell, with the weight on the end vs same weight concentrated at the center. Low polar moment, though I guess being from Canada Polar might have a different meaning.
<span style="color: #ff0000">If you read back in this thread you will find that I already covered this subject when I referred to mass distribution in a model. my recent comment was to avoid putting my own words in your mouth
. Of course you are correct and I had already covered that very same subject. </span>
Sorting ribs by weight puts the heavier ribs in the center of the wing if constant chord, but even when tapered, you can balance a wing with careful selection of which panel each pair of ribs go to. Same with all the other pieces that go in the wing.
<span style="color: #ff0000">I wonder how many understood what you implied by "balancing a wing". Thanks for your present explanation.
Considering the weight of the ribs in a wing vs the total wing weight, you are correct but the result is not going to be very significant. Your idea can be carried further by finding out which end of the spars is heavier to orientate the spar with the heavier end at the root of the wing. The same could be done for any sheeting. Again the result would not be very significant and doubtfully observable by even the expert fliers. </span>
Probably a good indication that I am "one of those that frankly never will".
Things I avoid discussing in the forum ___people's characters, personalities, knowledge of others, politics, religions, sex. It is unfortunate that in many cases we cannot disagree with some individuals on a technical matter because they are offended if you do not fully agree with them. Offending is against the rules of the forum but being offended depends purely on the reader although the writer will be the one penalized. Does not that sound a bit illogical? IfI respond defending my characteror personality then I am the one penalized? It does not make sense. But then the writer may also have been a moderator with the capability of penalizing someone.
Considering the large number of readers that are not participants but read these forums to extend their knowledge and find help; should we let them be mislead by a fair amount of misleading information written in the forum?
Zor
</span>
01-11-2012 | 10:30 AM
#66
My Feedback: (211)
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From: Sun City,
AZ
RE: adding weight?
Crazy Nick....you have a good question there. Moving the engine forward and/or lightning the tail of your Sig will get you balanced without adding weight. No question, you can force a square peg through a round hole is you apply enough force....I don't recommend that method of building. I have seen way too many models where someone was too lazy to do the job right and took the easy way out, and just bolted on some weight instead of planning the distribution of weight from the start of the build. Result: Over time that added weight destroys the airframe with each landing and each G force applied, resulting in a shorter life of the airframe and in some rare cases airframe failure. With just a little planning you can dramatically limit or eliminate added nose weight in almost all models...with the exception of the really short coupled ones. Congratulations on building a light model without sacrificing the structural integrity of it...not always an easy balancing act to pull off.
01-11-2012 | 10:49 AM
#67
Banned
RE: adding weight?
ORIGINAL: speedracerntrixie
At first I read this and thought what an over exaggerated example it is. But I thought about it more and the answer is a yes! A well set up and trimmed 2 lb airplane would fly better then a poorly set up and trimmed 2.5 lb airplane in a 15 knot wind. Again, the airplane sees wind as a change in airspeed. A poorly setup airplane will react to changes in airspeed so obviously it will react to wind. <span style="color: #808000">Ask yourself if your airplane's trim changes at all between 1/4 and full throttle. If the answer is yes then it is not trimmed correctly.</span> Does it really matter? Not if you are happy with the overall performance.
So a correctly trimmed 2 pound electric park flyer will fly well in a 15 knot wind? I don't think so.
Icannot fully agree with the green colored highlighted above.
Just before take off the trim is set for normal climb.
On levellng in cruise the trim is reset for cruise.
On descent and approach to landing again the trim is reset for approach speed.
None of the above apply to a model flier just constantly executing changes in attitude (note att no alt).
Changes in trim with changes in power setting is normal and not an indication of not being trimmed correctly.
Zor
01-11-2012 | 11:06 AM
#68
Banned
RE: adding weight?
ORIGINAL: rgburrill
Dumb, dumb. I did not get that is what he meant. You, and he,are correct, moving the wing back would move the required CG back.
Thanks for pointing that out.
ORIGINAL: HighPlains
Finding lead is easy.
http://www.rotometals.com/Lead-Sheet-s/31.htm
A quick recap - There are two separate discussions going on, so reading comprehension is required.
1.) On the issue of an airplane being "two light", add weight and get back to us.
2.) Moving the wing back on the fuselage will balance the plane. Easy to do when it has a wing tube and simple mounting.
We return you back to your regular programming.
Finding lead is easy.
http://www.rotometals.com/Lead-Sheet-s/31.htm
Do you people not think? Weight is not his problem, balance is. Adding a pound of lead at the CG won't do a damn thing for him.
1.) On the issue of an airplane being "two light", add weight and get back to us.
2.) Moving the wing back on the fuselage will balance the plane. Easy to do when it has a wing tube and simple mounting.
We return you back to your regular programming.
Thanks for pointing that out.
Careful guys.
Moving the wing back will move the CG back in relation to the fuselage but it will move it forward in relation to the wing and that is what counts.
Imagine the wing is moved all the way just in front of the fin. Where is the CG then ?
Zor
01-11-2012 | 11:43 AM
#69
My Feedback: (-1)
RE: adding weight?
ORIGINAL: on_your_six
3 pounds??? I would have hung a larger engine on the nose. Something does not sound right.
3 pounds??? I would have hung a larger engine on the nose. Something does not sound right.
ORIGINAL: Edwin
I just added 3 lbs to a ziroli 77'' stearman. It was done with 1/4'' steel plate cut to cover the firewall. Worked perfect.
Edwin
I just added 3 lbs to a ziroli 77'' stearman. It was done with 1/4'' steel plate cut to cover the firewall. Worked perfect.
Edwin
Anyone that builds should know up front about the rotary fact and the plane will be tail heavy. I knew this and as light as the aft section of my Sukhoi was built it still required lead. By building the aft section light it didn't require a lot of lead but I still had to add some.
Nothing strange about it. the rotary engines are very heavy. Not everyone cn just afford to swap an engine either. I have a very good selection of engines, my G-62 may have done the trick on my Suk but it was just way too much over kill just to get the CG correct.
01-11-2012 | 11:47 AM
#70
My Feedback: (29)
RE: adding weight?
ORIGINAL: Zor
ORIGINAL: speedracerntrixie
At first I read this and thought what an over exaggerated example it is. But I thought about it more and the answer is a yes! A well set up and trimmed 2 lb airplane would fly better then a poorly set up and trimmed 2.5 lb airplane in a 15 knot wind. Again, the airplane sees wind as a change in airspeed. A poorly setup airplane will react to changes in airspeed so obviously it will react to wind. <span style="color: #808000">Ask yourself if your airplane's trim changes at all between 1/4 and full throttle. If the answer is yes then it is not trimmed correctly.</span> Does it really matter? Not if you are happy with the overall performance.
So a correctly trimmed 2 pound electric park flyer will fly well in a 15 knot wind? I don't think so.
Just before take off the trim is set for normal climb.
On levellng in cruise the trim is reset for cruise.
On descent and approach to landing again the trim is reset for approach speed.
None of the above apply to a model flier just constantly executing changes in attitude (note att no alt).
Changes in trim with changes in power setting is normal and not an indication of not being trimmed correctly.
Zor
[/quote]
Zor, for the most part you are correct. I am trying to keep the discussion in context. The airplane in question is a sport aerobatic airplane with a symmetrical airfoil and is fully capable of being trimmed to not have any pitch changes during most throttle settings. If we were talking about a trainer or maybe a warbird, the pitch change would be of benifit especially a trainer that would be set up to climb and self right in the event of a dive.
01-11-2012 | 12:14 PM
#71
Banned
RE: adding weight?
ORIGINAL: speedracerntrixie
Zor, for the most part you are correct. I am trying to keep the discussion in context. The airplane in question is a sport aerobatic airplane with a symmetrical airfoil and is fully capable of being trimmed to not have any pitch changes during most throttle settings. If we were talking about a trainer or maybe a warbird, the pitch change would be of benifit especially a trainer that would be set up to climb and self right in the event of a dive.
Zor, for the most part you are correct. I am trying to keep the discussion in context. The airplane in question is a sport aerobatic airplane with a symmetrical airfoil and is fully capable of being trimmed to not have any pitch changes during most throttle settings. If we were talking about a trainer or maybe a warbird, the pitch change would be of benifit especially a trainer that would be set up to climb and self right in the event of a dive.
It now makes the readers aware of your reasons.
Nothing wrong with your initial claim.
Zor
01-11-2012 | 04:09 PM
#72
RE: adding weight?
ORIGINAL: Lnewqban
Interesting!
Do full scale pilots have any control over the CG location, or do they have to fly in a different manner when that CG is way off the ideal location?
ORIGINAL: cfircav8r
When flying full scale I love a light snappy A/C, however when I am flying full IMC with passengers it is far more comfotable for them and far easier for me if I am closer to the max gross weight.
When flying full scale I love a light snappy A/C, however when I am flying full IMC with passengers it is far more comfotable for them and far easier for me if I am closer to the max gross weight.
Do full scale pilots have any control over the CG location, or do they have to fly in a different manner when that CG is way off the ideal location?
01-11-2012 | 06:48 PM
#73
Senior Member
Joined: Jul 2004
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From: Arkansas city,
KS
RE: adding weight?
The method i use is to add weight "if needed" to get the plane to the manufacturers recommend cg.... Then fly ....... Then either add or take away lead to get the plane to fly the way I like to fly !!!!!!! Once i'm satisfied it goes back to the shop and i measure the current cg and i try to move what i can to take away all or as much lead as i can. My point here is that I am flying the plane.... Not the designer. and yes i frequently go outside the manufacturers cg range. Light planes go vertical faster !!!!!!!!!!!!
01-11-2012 | 07:08 PM
#74
RE: adding weight?
Thanks, cfircav8r.
Again, very interesting to me.
During a time of my life, I was loading and unloading UPS planes at the local airport.
There was staff dedicated to perform calculations for us to relocate containers of the packages along the fuselage, just to keep the CG close to where it should be.
Again, very interesting to me.
During a time of my life, I was loading and unloading UPS planes at the local airport.
There was staff dedicated to perform calculations for us to relocate containers of the packages along the fuselage, just to keep the CG close to where it should be.
01-12-2012 | 03:10 AM
#75
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From: Palatine,
IL
RE: adding weight?
If you can afford it ,now that you know it will take 6 oz. buy a larger engine. Those something extras are capable of some nice aerobatics and it would be smart to be way into the positive as far as you thrust to weight ratio.
