Plane is EXTREMELY Tail Heavy!
05-12-2018, 11:52 AM
#1
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Plane is EXTREMELY Tail Heavy!
I got a Great Planes Super Sportster 46 size low wing at a garage sale. It has an OS 46FX installed, all servos installed, and the battery is located beneath the fuel tank. Light weight Spektrum AR6210 receiver just behind the tank. No obvious things that might make it so tail heavy.
According to the manual I downloaded, the CG is 3-1/8" aft of the leading edge. In order to balance it there would require 14 ounces of weight just behind the firewall. That's an awful lot of lead! I doubt there's room for that much anyway.
Any suggestions (other than using a 61FX)?
Jack
According to the manual I downloaded, the CG is 3-1/8" aft of the leading edge. In order to balance it there would require 14 ounces of weight just behind the firewall. That's an awful lot of lead! I doubt there's room for that much anyway.
Any suggestions (other than using a 61FX)?
Jack
05-12-2018, 12:59 PM
#2
The first thing I would do is put on a HEAVY HUB.. and then any more weight you need to add should be as far forward as possible.. Also check to see there isn't some lead or something on the tail for some crazy reason.. Also some tail wheels are fairly heavy and you might be able to add a light foamie one instead.
Sometimes they just get built heavy !
Sometimes they just get built heavy !
05-12-2018, 08:19 PM
#3
I would be tempted to see if the engine could be moved forward, rather than adding weight...even if it meant making a new cowl or extending the fuselage to use the existing cowl. I can't see how it could be built with wood so heavy in the tail feathers that it would need that much lead up front to balance. what does the plane weigh, with engine mounted, right now ?.
05-16-2018, 02:16 PM
#4
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Got it balanced
I used the heavy brass "spinner" nut inside a 3" spinner. It balanced. It weighs 6 pounds and 1/2 ounce. I think the 46FX will fly it. If not, I'll use a 61FX.
05-17-2018, 05:11 AM
#5
6lbs-1/2oz. is fine for a .46, it should have no problem at all. I have yet to build a plane and have it come out at or even anywhere near what the kit or plans say it should weigh. for me it is so common that I have a feeling the weights listed are without engine, but they don't tell you that just to make their plan or kit look better. it seems that I always come out somewhere around the weight of the engine over what is advertised for the plane. I always try to "build to balance", eliminating the need for added weight. usually,.... I can come pretty close just by moving the engine ahead or back a bit without seriously affecting flight moments. the worst case I've ever had was my .46 size high wing coroplast trainer. it came out pretty tail heavy and I had no choice but to add a lump of lead to the nose. it now weighs 6lbs.-8oz. but it flies just fine with a 17.5 oz./ft wing load. I've noticed that a lot of the coro designs come out tail heavy. if you look closely at them, you'll notice that they look short coupled between wing and tail feathers and a little long nosed. I think the designers move the wing back on the prototype fuselage "after the fact", so to speak, to get the balance where it should be eliminating the need for adding large amounts of weight.
09-22-2018, 07:36 AM
#6
Cut holes through the vertical stab, rudder, horizontal stabilizer, a rear parts of the fuselage. Cover the holes with fabric, film, silk, silk-span, thin plastic, etc. Cut the holes in a way to preserve the structural integrity. Just a thought...
10-16-2018, 09:47 AM
#8
I have noticed several persons have tail heavy problems, many kits and plans were designed to use the older engines which were heavier than current engines so a builder should be cognizant of the situation and compensate for it during the building process. even redesign the empennage or suffer the consequences.
10-16-2018, 11:18 AM
#9
well, if the plan is that old, there should be no harm in weighting the nose to balance out close to the spec'd weight listed on the plan. the fact that a newer engine is lighter simply leaves room for balance adjustment (or a bigger engine, which can't hurt either).. if the tail can be built lighter so much the better, but just because the newer engine is lighter doesn't mean the plane has to weigh less.
10-17-2018, 03:49 AM
#11
AHHHH!!!!!! Not always LOL. Depends on what your trying to achieve. For many years I used a 1/4 scale Spacewalker as my loaner plane. One that was easy to fly, scale for those visitors who were into scale and nimble enough to do some decent aerobatics. After many many years of use it was damaged beyond repair so I was looking for something quick to replace it. The first batch of Piper Pawnee's (ARF) came out and low and behold the wing was almost identical so chances are the flying characteristics might be similar. I put the same OS .91 two stroke in and it did indeed fly much like the Spacewalker except on landing. The darn thing was so much lighter it was a bear to land in anything but a calm day not like the heavier but solid spacewalker. Moved the CofG and it made no difference so I noticed the wing tube was right on the CofG so I filled it with bismuth that melts at 165 degrees and it added 1 1/2 lbs. The difference was unbelievable that extra weight added nothing to the landing speed or took away from the agility but somehow smoothed out and stabilized the air frame in crosswind and gusty landing situations. It was now acceptable to use as my new loaner aircraft and has been for quite a few years now. Sometimes I have found that those with less experience who have trouble with landing some of the lightweight arfs in windy and crosswind situations can benefit with a bit of weight added to the CofG.
Last edited by Propworn; 10-17-2018 at 03:53 AM.
10-17-2018, 05:29 AM
#12
Banned
Do you build your planes as light as possible? Or do you aim for a certain wing loading zone?
I'm currently working on a Proctor Micro Antic. Plans call for it to weigh 8 ounces with a 36 inch wing or 5.75 ounce per sq foot wing loading. I have gliders heavier than that. So since I don't want a butterfly that flits around, I'm ignoring my normal weight practices and building it heavier to tolerate at least some wind.
And a higher wing loading Lands better. Sink is more predictable and it's less effected by small wind currents close to the ground. Yes, it will land faster too. But it's all a balancing act isn't it? And after all, isn't landing the one mandatory maneuver everyone must learn?
Last edited by Appowner; 10-17-2018 at 05:32 AM.
10-17-2018, 04:28 PM
#13
LOL App, ask the glider guys.......you crack me up!
Back in 1996 when I flew in the US Soaring team selection finals most top shelf sailplanes were 3 meter span and weighed around 70 to 80oz. My Synergy 3 that was my primary sailplane weighed 75oz empty. My backup which was somewhat a prototype that I called Synergy V was 70oz. During the contest we were launching with a slight downwind and had spotty lift. Virtually nobody was adding any ballast. I tried to during my second speed run but had two poor launches and did not log a run before working time expired. That zero really killed my score but I had fun none the less. Modern sailplanes are typically 3.4 meter to 4 meter span and average 60 to 70 oz. So over the past 25 years they have gotten larger and lighter. In heavy winds we do add ballast so in a round about way you are halfway correct. Ballast is added to retain the ability to travel out and down wind in search of lift. It has nothing to do with maintaining stability in the wind and will hinder when it comes to spot landings.
Back in 1996 when I flew in the US Soaring team selection finals most top shelf sailplanes were 3 meter span and weighed around 70 to 80oz. My Synergy 3 that was my primary sailplane weighed 75oz empty. My backup which was somewhat a prototype that I called Synergy V was 70oz. During the contest we were launching with a slight downwind and had spotty lift. Virtually nobody was adding any ballast. I tried to during my second speed run but had two poor launches and did not log a run before working time expired. That zero really killed my score but I had fun none the less. Modern sailplanes are typically 3.4 meter to 4 meter span and average 60 to 70 oz. So over the past 25 years they have gotten larger and lighter. In heavy winds we do add ballast so in a round about way you are halfway correct. Ballast is added to retain the ability to travel out and down wind in search of lift. It has nothing to do with maintaining stability in the wind and will hinder when it comes to spot landings.
10-17-2018, 04:50 PM
#15
Now, do I build as light as possible......YES. I will use a couple models as an example. First is a Lanier Laser 33%. The airplane has a 97" span and after a great deal of mods weighed just a tad over 15 lbs. Power was DA 50. The other airplane is my own design pattern airplane that weighs the allowed limit of 11 lbs and has 1,300 so in of combined wing area. A build thread can be found here on RCU in the pattern forum titled " Pattern Biplane ". Doing the math you will realize that both airplanes have quite light wing loading. Both fly exceptionally well. I will agree partially and say a heavier, poorly trimmed airplane will seem to be less disturbed by wind. More weight requires more energy to move so there we can agree to a point. Once disturbed it will also require more control input to correct. This is your statement falls apart. Imagine your airplane gets a gust and a wing dips. You haven't dialed in any aileron differential so when you input aileron you get roll, a pitch up and adverse yaw. The more wind the more control inputs that are mixed with some control cross coupling and you get into a pilot induced mess. Throw in the fact that most guys don't actually measure and adjust each ailerons throws to match and it gets even worse. Add in bad CG placement, thrust angles that aren't quite right and maybe even a throttle curve that brings the power on too quickly and you can end up with a hot mess in a hurry.
10-18-2018, 10:01 AM
#20
Gentlemen PLEASE! the problem is a Extremely tail heavy plane not how heavy a plane can get. you have diverted the subject matter and now personal feelings have entered the conversation.
many things spoken here does not assist in solving the original problem.
I for one would like to see a picture of the problem aircraft in and effort to assist Jack K resolve his problem. not personal history.
I can think of several reasons why tail heaviness occurs. LEE TAYLOR provided a good response.
many things spoken here does not assist in solving the original problem.
I for one would like to see a picture of the problem aircraft in and effort to assist Jack K resolve his problem. not personal history.
I can think of several reasons why tail heaviness occurs. LEE TAYLOR provided a good response.
10-19-2018, 05:09 AM
#22
Banned
For the OP. Bottom line is you must balance the plane to the CG in order to fly. Either add weight to the nose or remove it from the tail or a combination of both (preferable). How you do this is up to you. But remember, an ounce removed from the tail is probably worth 3-4 ounces added to the nose.
10-19-2018, 06:31 AM
#23
For the OP. Bottom line is you must balance the plane to the CG in order to fly. Either add weight to the nose or remove it from the tail or a combination of both (preferable). How you do this is up to you. But remember, an ounce removed from the tail is probably worth 3-4 ounces added to the nose.
Nice!!! We agree on something and it didn't hurt either one of us.
