stunthanger.com
General control line discussion => Open Forum => Topic started by: Paul Taylor on July 02, 2016, 08:31:46 PM
-
Need a little trim help.
Was doing some trim flights today on a new plane.
I tried this three time and same thing.
First turn of the hour glass and a few feet into the up leg the plane seems to roll in and the lines get soft. Right after the turn. I have never experienced this on any other plane. Doing a little research I saw a thread that talked about "hinging" after a hard turn. Could this be what my plane is doing?
The thread spoke of the Fix might be too much tip weight or maybe move the lead outs. (What direction?)
It has .7oz of tip weight now.
Any help would be appreciated.
Thanks
Paul
-
A little more information please!
What kind of plane is it (how big), and what is the powerplant, and what are your lap times and line length.
Does it also do this in the first corner of the inside square loop?
Randy Cuberly
-
Need a little trim help.
Was doing some trim flights today on a new plane.
I tried this three time and same thing.
First turn of the hour glass and a few feet into the up leg the plane seems to roll in and the lines get soft. Right after the turn. I have never experienced this on any other plane. Doing a little research I saw a thread that talked about "hinging" after a hard turn. Could this be what my plane is doing?
The thread spoke of the Fix might be too much tip weight or maybe move the lead outs. (What direction?)
Just to clarify, you see the *top* of the airplane during/just after the turn?
Brett
-
It's the bottom of the plane. When it does it I bail to inverted flight.
Plane is a Vector 40. PA 40 UL on a pipe on 60ft lines. Running a 5.5 lap time. I did notice a little lightness on the lines in the top of the out sides around the 2 o'clock position. And now that you mention it I think it did it in the first turn of the inside squares. It made me thing to take it easy on the triangle and I flew a real odd egg shape so did not see it there.
I really banged the first turn of the hour glass and that is where it really showed it.
Thanks
Paul
-
Paul my first response is to say it's flap asymmetry. The inboard flap is overpowering the outboard. Try adding some area to the outboard flap. A narrow strip, say 3/32 to 1/8" full span stuck on the flap trailing edge or a tab about 3/4" x 4" put on as far out as you can will move you in the right direction.
Also if the leadouts were really too far back you might see this because the inboard wing is leading the outboard and will kick the leading wing hard when the flaps are deployed.
Dave
-
It's the bottom of the plane. When it does it I bail to inverted flight.
Plane is a Vector 40. PA 40 UL on a pipe on 60ft lines. Running a 5.5 lap time. I did notice a little lightness on the lines in the top of the out sides around the 2 o'clock position. And now that you mention it I think it did it in the first turn of the inside squares. It made me thing to take it easy on the triangle and I flew a real odd egg shape so did not see it there.
I really banged the first turn of the hour glass and that is where it really showed it.
Thanks
Paul
If you are seeing the bottom of the airplane first, it's rolling out, and not in. The hard control during the input probably makes the lines act like a spring and pulls the model in as a secondary action, and that is when the line tension gets soft? As to a cause, Dave is probably correct on the flap issue and line rake. Don't think I have ever seen or experienced anything like this. I have had my Primary Force do funny stuff a couple of times at the top of the hour glass on the third corner but not since I have put the current power plant on it. That might have been caused by forces that led Al Rabe to invent his rudder system for that very turn of the hour glass. Wish I could be more help but I would have to see the model in flight to guess any more. I would think that if it was a really chronic problem, you would see it in the first pull up for the wing over and any inside square maneuver, as has already been mentioned. Keep us posted on further findings and fixes.
Type at you later,
Dan McEntee
-
I agree pretty much with everything that's been said. I especially agree with Dave that it sounds like flap asemmetry. Outboard flap needs a tab. I would mention that 5.5 second laps is pretty slow if you're on 60 ft lines. something closer to 5 seconds would be more appropriate.
Lines being too far aft would accentuate that problem.
I would do whatever it takes to get the flap areas equal and set the lines at about 1/4 inch behind the CG, and speed up the airplane a bit to about 5.1 second laps. The greater speed will make trimming a bit easier also because the reactions will not be quite so violent. Part of what's happening could be the beginning of a stall because the slow speed plus violent corner can create an accelerated stall condition on the outboard wing.
Wish I could see the airplane fly. Trimming by remote location is frustrating! y1
Randy Cuberly
-
I am looking forward to see what Brett has to say. And Randy is on the right track also. There could be a combination of things that are showing the plane is out of trim.
Are your wings level during normal level flight. There could be an imbalance between the tip weight and a slight wing warp or slight flap misalignment (it does not take much to screw things up). First, 3/4 oz tip weight might not be enough. Yes, you might have 3/4 oz out there, but does it take 3/4 oz of weight on the inboard tip to balance the wings? If there is a slight amount of washin at the outboard tip, (outboard tip TE lower than the inboard tip TE), that outboard tip will tend to lift more in that first turn of your hourglass, causing loss of tension.
One thing to check - do you have equal tension when doing inside loop and outside loops. If not, then there is a combination wrong tip weight, wrong leadout position and/or assymetric TE between the left and right wing panels.
Also, it would be interesting to know if you have good line tension on the first outside corner of your square loops. That is a place where one expects to loose line tension because of gyroscopic precession. If you experience little or no change in line tension after that first outside corner, then I would suspect that the outboard tip TE is lower than the inboard tip which does not help you on the first turn of your hourglass. You can adjust by tweaking the flaps or even twist the wing using a heat gun. (Some use hot towels, but the heat gun is easier to control in that process.)
(my 2 cents)
Keith
-
Vector ARF has equal wing span and needs lot of tip weight. Vector kit has 3/4 -1" offset and does not need as much.
Ed
-
Thanks guys. Good info.
I have some things to try now.
It is a kit. I did change the wing tips a little.
Will keep you posted.
-
The Vector is a name-brand stunter, so I wouldn't expect sufficiently blatant flap asymmetry to cause these troubles. Are your flaps sealed?
-
The Vector is a name-brand stunter, so I wouldn't expect sufficiently blatant flap asymmetry to cause these troubles. Are your flaps sealed?
Thanks Howard.
No the flaps are not sealed. And not a tight fit either.
-
moved your leadouts forward - on all my vectors I had the leadouts as far as possible forward. if they were back - the plane hinged much like you are experiencing
-
Thanks Howard.
No the flaps are not sealed. And not a tight fit either.
Seal the flaps! "Not a tight fit" may actually help suppress the weirdness from unsealed flaps, but try them sealed anyway.
-
Lines are too short, lap time is too slow, and I'm wondering if the elevators are aligned to each other. Seal both flaps and elevator hingelines. What's the prop and launch rpm? ??? Steve
-
It's the bottom of the plane. When it does it I bail to inverted flight.
Plane is a Vector 40. PA 40 UL on a pipe on 60ft lines. Running a 5.5 lap time. I did notice a little lightness on the lines in the top of the out sides around the 2 o'clock position. And now that you mention it I think it did it in the first turn of the inside squares. It made me thing to take it easy on the triangle and I flew a real odd egg shape so did not see it there.
I really banged the first turn of the hour glass and that is where it really showed it.
Off-hand is seems a bit slow, but that will likely just make the problem easier to see, not cause it.
Obviously I think you should seal the hinge lines, but that may not solve the problem. What you seem to be describing is line whip, and you are seeing the second motion it takes after the corner. I think it is probably yawing nose-out due to the leadouts being set too far aft, and rolling inboard in the corner from inadequate tipweight, then after you straighten out, it yaws nose in and rolls out as the lines whip back in reaction to the corner. Carefully check what the yaw angle does during the corner, I suspect it will yaw out dramatically first, then back in at the time you noted. It may or may not roll in, because the yaw reaction will tend to obscure the lack of tip weight.
I suggest this. Observe the roll angle through the intersections of the round 8s (horizontal, vertical, and overhead). See which way it rolls through when you switch from inside to outside and outside to inside. Set the tipweight to minimize the roll change through the intersection. I would start adding it until was obviously rolling away from you in both loops (see the bottom on the insides and top on the outsides), then back off, so you know for sure that you have too much, then you can take it out in small bits (1/8 ounce at a time) until you get a minimum roll change through the intersection.
Then check the yaw angle in the corners. I expect you will see drastic outboard yaw on insides and almost nothing on outsides, or at least a lot less outboard yaw. Start moving the leadouts forward 1/8" at a time until the yaw reaction in the corners is minimized. As you do this, keep checking the roll angle change through the round intersections. I bet you will need to keep adding tip weight at you move the leadouts forward. At some point you will get a minimum reaction in roll AND minimum reaction in yaw. Assuming you have the rudder straight ahead, this will be the best you can do. Then you can adjust slightly around there and see if there is any improvement.
If you have rudder offset or rudder airfoil, your minimum yaw reaction will still be pretty large. At which point you should go put it dead straight ahead and adjustable (cut it off and refinish of necessary), put the leadouts where LINEII tells you to, and then do the same thing except changing the leadouts, you adjust the rudder in *tiny* increments to do the same thing.
I am not entirely sure that I understand the issue correctly from your description, but you are likely to get pretty close to right following the above procedure even if it's some other issue. It's more-or-less consistent with the Paul Walker flowchart and the "Functions of trim adjustments" thing I wrote. In any case, it does require careful observation of the roll and yaw angle while you are flying, which seems to be an ability that varies wildly from individual to individual. IF you need more experienced help, then it is always worth seeking it out.
Brett
-
Paul, check your tail weight & CG..
John
-
Paul.
Also 5.5 second lap times on 60 foot lines isnt exactly ripping through the air maybe fly faster.
-
Thanks guys for the feed back.
I down loaded Bob's program and ran the numbers. I moved the leadouts about 3/4 of an inch forward.
I had .7 oz of tip weight and pulled out .5. Thinking about adding it back.
Thoughts?
-
Thanks guys for the feed back.
I down loaded Bob's program and ran the numbers. I moved the leadouts about 3/4 of an inch forward.
I had .7 oz of tip weight and pulled out .5. Thinking about adding it back.
Thoughts?
Less than a quarter of an ounce of tip weight sounds too light -- and while too much tip weight is a little bit bad, too little tip weight is a disaster.
Put it back, then do what Brett said about flying and taking out tip weight as you go.
-
Thanks guys for the feed back.
I down loaded Bob's program and ran the numbers. I moved the leadouts about 3/4 of an inch forward.
I had .7 oz of tip weight and pulled out .5. Thinking about adding it back.
Thoughts?
PUT IT BACK! My theory suggests that it might be inadequate already, and you are making it through only because you are yawing the nose out in hard corners. If you remove the outboard yaw, then you will need adequate tipweight. Note also that the outboard yaw would normally cause a roll in the direction you would expect for excess tip weight, so the yaw effect may be fooling you into removing tip weight.
You many need to remove some later, but wait until you see what happens with your other huge adjustment.
As a check on your LINEIII math, I would expect the centerline of your leadouts to be about 3/4" or so behind the CG.
BTW, just talking about how much tip weight really doesn't tell us much. What would tell us something is if you note how much weight it takes on the inboard tip to counterbalance what you already have. Balance the plane in roll with temporary weight on the inboard tip and whatever you have in the outboard tip, then you know how much effective tip weight you have. It might be way off from the actual amount you entered because of variations in the wood weight and finish weight you may have built in, and the intentional asymmetry (like longer inboard wing, and the leadouts and leadout guide).
Brett
-
10-4.
Adding the weight back.
I hope to test it this week if the weather allows. T-Storms predicted most of the week.
Line III put it .5534 behind the CG.
500 wing area
46.5 span.
Wing tips are smaller. Shaped like a Mustang and tapers back.
I will try and see if I can tell you more about the tip weight. Stay tuned.
And thanks a bunch!!!
-
Ok went and put the .5 back in.
The added weight to the inboard to balance it out.
It took 1/4 oz to level it out.
(http://uploads.tapatalk-cdn.com/20160705/db0cb7710a86ce3cf13df3b427e23380.jpg)
Sent from my iPhone using Tapatalk
-
Ok went and put the .5 back in.
The added weight to the inboard to balance it out.
It took 1/4 oz to level it out.
Ah, so you really have 1/4 ounce of tip weight. Assuming you have 3/4" asymmetry, add another .5 ounces to the outboard tip. If it is equal span, add 1.5 ounces.
Brett
-
If you have a 5 ton stock R.C. muffler hanging of the inboard side at the front , particully a blunt front one , It could cause that sort of bother .
If its accerating out of the corner , the mass inboard can retard that sides progress . Plus its inboard weight - why it noses in crabwise .
Had a blunt muufler inboard thatd votice the inner wing thru stab , starting a yaw , downhill in hourglass & wingover ( nowhere else ) .
No Muffler or muffler Outboard , it didnt happen .
-
Brett- 1/2 in difference. So would that be 1oz?
@Matt - PA 40 on a pipe. No honking tube muffler hanging off the nose.
-
Brett- 1/2 in difference. So would that be 1oz?
@Matt - PA 40 on a pipe. No honking tube muffler hanging off the nose.
1/2 ounce more than it had when you counterbalanced it with 1/4 ounce. Shoot for a weight that will require a counterbalance of 3/4 ounce.
Brett
-
Gotcha. Will set it up tonight when I get home.
Stay tuned.
-
Ok. 1/2 oz added.
3/4 oz to balance it out.
Now we are in a holding pattern waiting on the weather.
Thanks guys for the help.
-
Ok went and put the .5 back in.
The added weight to the inboard to balance it out.
It took 1/4 oz to level it out.
Sent from my iPhone using Tapatalk
Why? I don't understand this move at all.
Just use outboard TW only. Add and subtract as needed.
-
Why? I don't understand this move at all.
Just use outboard TW only. Add and subtract as needed.
Better Duck, Doug! Brett'll come and get ya!
This is the means whereby Brett determines what the real amount of wing weight is as opposed to saying "I put in one oz of tip weight" (which means nothing in and of itself with respect to roll issues.) No matter how much lead is in the outboard weight box, the important number is the weight difference between the panels. He starts the process by stacking (not adhering) weight to the inboard wing at the same location as the tip weight receptacle in the outboard wing until the wings are "balanced." The non-adhering inboard weight has now done its job and is put back in the tool box. Subsequent guestimates on tip weight adjustments are then based in part on the wing asymmetry...or lack thereof...and the existing weight as determined by the test.
(Worth noting is that with a substantial wing asymmetry (All American, Sr and its ilk) it is entirely possible that a too much longer inboard wing may be "heavier" than the outboard...and may have to be in order to solve wing roll issues, with excessive asymmetry the fix to the issue at hand could even end up being adding board tip weight!)
Good luck at the Nats.
Ted
-
Why? I don't understand this move at all.
Just use outboard TW only. Add and subtract as needed.
The weight on the inboard is temporary, just stacked on there, just to see how far out of balance the rest of the airplane might be. More-or-less, he is determining the lateral balance of the airplane. He had added 3/4 ounce to the outboard tip but because the inboard wing (and leadouts, and whatever), the inboard was heavier, so he effectively only had 1/4 ounce. Once you do the measurement, you just remove the inboard weight. You don't fly the airplane with the inboard weights.
This is the only reliable way of determining where the lateral CG might be and only way to realistically compare tip weight from airplane to airplane.
Brett
-
Better Duck, Doug! Brett'll come and get ya!
This is the means whereby Brett determines what the real amount of wing weight is as opposed to saying "I put in one oz of tip weight" (which means nothing in and of itself with respect to roll issues.) No matter how much lead is in the outboard weight box, the important number is the weight difference between the panels. He starts the process by stacking (not adhering) weight to the inboard wing at the same location as the tip weight receptacle in the outboard wing until the wings are "balanced." The non-adhering inboard weight has now done its job and is put back in the tool box. Subsequent guestimates on tip weight adjustments are then based in part on the wing asymmetry...or lack thereof...and the existing weight as determined by the test.
Good luck at the Nats.
Ted
Aha,,,,, I see. All the while I am reading this it is making sense,,,but,,,I am thinking that knowing what the difference is doesn't really do anything you still have to add and subtract TW until it flys right for said setup. Then I read BBs post about comparing models using this method and it comes full circle.
I have been following this thread so I can see what the answer is... At first glance I think its a combination of lack of speed and incorrect TW and line position. With speed being a large factor. 60' at 5.5 is really slow, it wouldn't take much to throw the model around at that slow of a speed. But that is just my thoughts... I could be wrong, I usually am, just ask my wife.
-
Aha,,,,, I see. All the while I am reading this it is making sense,,,but,,,I am thinking that knowing what the difference is doesn't really do anything you still have to add and subtract TW until it flys right for said setup. Then I read BBs post about comparing models using this method and it comes full circle.
I have been following this thread so I can see what the answer is... At first glance I think its a combination of lack of speed and incorrect TW and line position. With speed being a large factor. 60' at 5.5 is really slow, it wouldn't take much to throw the model around at that slow of a speed. But that is just my thoughts... I could be wrong, I usually am, just ask my wife.
Hmmmmm I think that's what I said a couple of days ago...but then since I've never won the Nationals (and never will) no one listens!
Guess I'll just ignore questions in the future, and go trim some airplanes and practice! <= <= HB~>
Phhtttttttttttt...
Randy Cuberly
Don't mind me,.. just in a crappy mood!
-
snip
snip
With speed being a large factor. 60' at 5.5 is really slow, it wouldn't take much to throw the model around at that slow of a speed. But that is just my thoughts... I could be wrong, I usually am, just ask my wife.
I totally agree with that, Doug. One of the problems of stunt guys talking on line (to the world) is that a tyro can pick up a single item (such as 5.5 laps) and make it some sort of miracle road to success. As in this case, that is seldom (if ever) the case. The variables are stratospheric and solving as many as possible is the only road to the big bowling trophies...as you well know! The interactions between this "magic" secret and the next simply overwhelm the novice. It's why stuff even as dated as Wild Bills "....painless" series are still valuable tools.
Forums like Sparky's are great resources for guys (guys in the gender neutral all inclusive sense, of course) looking for answers but this is definitely a weak spot that can put the breaks on their progress very quickly. Wish I had an answer.
Ted
p.s. We should get Howard to write the ultimate stunt text. Trouble is we'd end up with a flying field full of nothing but Impacts in a variety of colors...sort of like a bowl of Jelly Beans. <= <=
-
Orange you call a variety?
-
Hmmmmm I think that's what I said a couple of days ago...but then since I've never won the Nationals (and never will) no one listens!
Guess I'll just ignore questions in the future, and go trim some airplanes and practice! <= <= HB~>
Phhtttttttttttt...
Randy Cuberly
Don't mind me,.. just in a crappy mood!
Yes I read where you said you thought it was slow and I was agreeing with you when I read it...
-
Here is an update.
After making the changes things seem a little better but the issue in still there after the turn on the up leg of the hour glass.
I am now going to remove the pipe and try a header muffler. My flying friends are thinking the vertical CG so will give it a try.
The red line is where the plane seems to want seem to bobble.
-
Here is an update.
After making the changes things seem a little better but the issue in still there after the turn on the up leg of the hour glass.
I am now going to remove the pipe and try a header muffler. My flying friends are thinking the vertical CG so will give it a try.
The red line is where the plane seems to want seem to bobble.
It is not a vertical CG issue, and even if it was, you are far better off with a vertical CG issue and good power control than less power control. I have managed to get through 40+ years of model airplane flying without considering the vertical CG in any significant way.
Did you go through the sequence I suggested above? It may take a dozen flights or more with small one-at-a-time changes. If the changes did not result in the effects described, there may be some other issue (like tail tilt or skew).
Brett
-
Orange you call a variety?
Good point, Howard. Technically orange is a varietal, thus the confusion.
Ted
-
It occurs to me after reading about 2.6K "what's wrong with my trim" threads that what we really need is a data table for inquirers to fill out with measurable and/or observable criteria related to flight performance, i.e.: Model design if a common type, (if an original design: wing area and aspect ratio, tail area as a percentage of wing area) weight, engine, prop, line length, lap times, CG location as %MAC (avg chord would suffice), lead out exit reference longitudinal CG, Honest pilot/builder experience/skill level; observed flight attitude upright and inverted (OB wing up/down, body attitude in level flight (nose up/down), how much of the outboard wheel is visible behind the inboard wheel in level flight...Oh, dear, I'm just getting started!
I could go on and on but, without these and other important parts of the puzzle, a tyro pilot is always going to get a variety of well meaning suggestions...many of which might not be appropriate if all the facts were known. Way to many of us tend to evaluate other pilot's trim problems based on "similar" flight responses we have experienced ourselves...the cause of which may or may not be germane to the questioner's issues. Easy to say but not so easy to come up with a way to be more creatively accurate in our attempts to help.
I think many of us are capable of providing excellent support for other fliers issues but, without a pretty comprehensive cataloging of configuration and assorted other performance variables the questioner is more likely than not going to have to flip a coin as to which of many suggestions to try next. Each time the coin fails to match the solution the result will be more rather than less frustration.
Maybe some more input on what such a "How can I fix my XXXX problem" question format should include.
-
Here is an update.
After making the changes things seem a little better but the issue in still there after the turn on the up leg of the hour glass.
I am now going to remove the pipe and try a header muffler. My flying friends are thinking the vertical CG so will give it a try.
The red line is where the plane seems to want seem to bobble.
We need to know what changes you made.
Did you get it going fast enough first? If you make alot of trim changes with it going too slow and then finally speed it up you will have to go through it all over again. Get your speed more like 5.0-5.1 for your line length then trim it out. Just a suggestion.
-
Maybe some more input
^^ yepper,, that right there^^^^
Out of Respect , Ted commented he felt his post was out of place and I had quoted it, so I am withdrawying it well except for that one comment,
-
Thanks guys for the help.
Yes I made the suggest changes above.
I went to shorter lines and got the lap times up. Line tension is good. I added the tip weight and moved the L/O forward 3/8 of an inch and sealed the hinge lines on both flaps and stab. It seems to turn good in both directions. Wings still level. This is a Vector 40 with the tips tapered a little different, but all it all it's a Vector 40. It is powered with a PA 40 UL on a pipe. 11.5x3.75 Bolly. Launching between 10900 and 11200 RPM.
-
Do you know how fast it is going now?
Is there anywhere else in the pattern that is giving you odd behavior? If so what?
-
I can't tell from the picture, but, are the elev and flap hinge lines parallel?
dg
-
Lap time is 5.5.
Ole Dad will double check but will check the lines.
-
Lap time is 5.5.
Ole Dad will double check but will check the lines.
lap times of 5.5 on less than 60 foot lines? that seems very slow to me, it could be stalling, does it do the same thing in the triangle?
-
Something just ain't right, as they say. I would think that launch RPM and that prop should net you less than 5.0 lap time. Check the pitch especially at the tips.
-
Lap time is 5.5.
Ole Dad will double check but will check the lines.
It was 5.5 on your post back on July 3rd. TURN THE NEEDLE IN!! or ADD PITCH!!!! :) :) :) :) :) And try again.
-
^^ yepper,, that right there^^^^
original deleted as not appropriate. Gotta apologize for the double post however.
Ted
-
Ok. It was last week. I will get a lap time next time out and report back.
What would be a good lap time with a vector on 58 ft lines clip to clip?
-
Ted sounds like maybe provide as much information about the setup as possible?
I wish I could tell you exactly what it feels like when it does its bobble. But almost feels like it loses line tension for a split second and rotates over on its back making me bail to inverted flight.
-
It was 5.5 on your post back on July 3rd. TURN THE NEEDLE IN!! or ADD PITCH!!!! :) :) :) :) :) And try again.
doug,
Just noted he advised he was launching at between 10.9K and 11.2K with a 3.75" pitch Bolly. I'm not an expert on Bolly's but fly with 3.6 to 3.75 regularly with Eather props launching at 10 to 10.2K and trundling around at 5.25/5.3 on 65 eyelet to eyelet. Sounds like something is happening to a K or 2 of revs after launch...especially on 60' of wire. I'm curious what the pipe length is! What do the Bolly guys have to say about pitch, launch revs and lap times?
Ted
-
Hey Ted
Pipe is @ 17inches.
-
I can't tell from the picture, but, are the elev and flap hinge lines parallel?
dg
Hey Dale
Spot on.
-
I have not done this, help fix a model on line, in a while and this is actually kind of fun dissecting the setup to find the issue. Having said that I have done some thinking about where we are.
A long time ago I ran some Bollys. I ran them on an OPS 40 and a PA 61. Both were piped setups. I had good success with them as well. Then I switched to Eathers. The one thing I did notice right away was the pitch on the Eathers was much lower than the pitch on the Bollys to get the same level of performance. That is certainly not saying one is better than the other it is simply saying they are different animals. Apples to Oranges so to speak.
I would venture to say, without having seen said plane fly, the rpm noted at release and speed in flight is telling us the prop is too flat. Add pitch. This will lower the rpm as it should due to increased load. The 17" pipe length will be right on the money. At this time the 17" pipe length is too short for these rpms. The chart says it should be around 16.75. The chart also says Bolly 11.75 x 4.25 cut to 11.5 is a good starting point for the 40. It does not specify 40UL though.
The drawing is very helpful. I looked at it several times and read your description of bailing inverted. That section of the hourglass is one of the more difficult sections of the pattern for the model. The corners past 90 degrees really bleed off alot of speed and the motor will need to "boost" to keep the model moving forward. Without enough boost the model will continue to bleed off and it will stall, air snaps off the wing and it bobbles, and then you bail out. Even if there is enough boost but there is not enough pitch it still wont make it. When the model does something hard enough to cause you to bail out of a maneuver I wouldn't call that a bobble as much as I would call it a stall or something to that effect. It's a stall.
In my view, take it for what its worth, you are still too slow and the reason you are too slow is not enough prop pitch. Line length is good. Taking off at those rpms and only getting 5.5 on a 40 sized model on 60' lines is telling you that you need more pitch. Pitch it up until you are getting 5.0-5.1. You can still de-pitch the tips a little and pull the pipe out to cut off any over boost you are getting anywhere else but the speed will be such that the model will fly through the tough places and move on.
There is a happy medium on flat prop pitch. I used to run Eather 4 blades at 3.5 at station 8 de-pitched to 3.2 at the tip, take off rpms were 10,500 PA 65. I have found pitches this flat are excellent wind props due to the disc acting like a huge brake on the front of the plane. It would boost like hell but hit a certain speed and just not go any faster no matter what. This is where it is very important to have enough base line speed to get through maneuvers as you are not gonna get it from the prop and the boost gets cut off from the pitch as well. It was quite a killer rig if I do say so myself. I had to move away from it when I started building heavier models, not by my choice. :(
-
I don't see the weight anywhere & I never won a contest but can tell you for sure a Vector on a PA .40 pipe, turning 10,900 RPM, 60 foot lines at 5.5 lap times should fall out of the sky, I doubt Paul Walker could get that setup to function. I dont know what your adgenda is but if you prop it up to a minimum of 5.0 you "might" get it to fly better It's stalling in a big way a blind man can see that.
John L.
-
Guys I really appreciate all the help. When I went to the shorter lines I am almost sure the laps times went to like 5.2. But it has been a week ago and my memory is getting shorter.
I hope to try it again this afternoon under this heat dome and if the rains hold off.
I will let you know lap time on 58ft lines.
I might try a few different props too.
Stay tuned.....
-
Guys I really appreciate all the help. When I went to the shorter lines I am almost sure the laps times went to like 5.2. But it has been a week ago and my memory is getting shorter.
I hope to try it again this afternoon under this heat dome and if the rains hold off.
I will let you know lap time on 58ft lines.
I might try a few different props too.
Stay tuned.....
In this setup shortening the lines to get the speed is not actually speeding it up using the motor and pitch. It will probably still show you this issue but maybe not as bad.
Think of it this way, when you were on 60' at 5.5 that would be around 6.0 on 65' for a 60 sized model. That is not a common speed for good performing stunt planes.
-
In this setup shortening the lines to get the speed is not actually speeding it up using the motor and pitch. It will probably still show you this issue but maybe not as bad.
Think of it this way, when you were on 60' at 5.5 that would be around 6.0 on 65' for a 60 sized model. That is not a common speed for good performing stunt planes.
Thanks Doug.
So more pitch. Less RPM?
-
Thanks Doug.
So more pitch. Less RPM?
Yep. But dont get crazy with it. Add little bits at a time and test.
-
Hey Ted
Pipe is @ 17inches.
Sounds way short, like maybe .75" - 1.5" short, per the (pinned) chart on the Engine Setup Forum . Is that per Randy Aero's recommendation? And is it measured correctly? :o Steve
-
Yep. But dont get crazy with it. Add little bits at a time and test.
Rootbeard,
Don't you have any other props to try???? Pick up an 11X5 or so and stick it on to see what happens. An important part of trimming an airplane for peak (or even adequate) performance is finding the right prop
Quick question: does the ship move crisply out of the launch and the engine then audibly drop revs to result in the 5.5 laps? (still having a hard time getting my head around ~11K on any prop resulting in 5.5 laps on only 60 feet of lines.
Ted
-
The prop's not on backwards is it?
-
The prop's not on backwards is it?
Aha! A rational analysis, Curare. Problem solved. Kidding, of course, but what we're talking about would certainly be the result of doing exactly that!
Good one!
-
Paul,
I am fully in agreement with everything Doug, Ted and Brett are telling you. I want you to think about something you said earlier in the thread. You said
" It made me thing to take it easy on the triangle and I flew a real odd egg shape so did not see it there.I really banged the first turn of the hour glass and that is where it really showed it."
The triangle was egg shaped because you were flying too slow. You need to select a speed that allows the model to perform properly. Not a speed that makes you feel comfortable.
IMHO you should NEVER "really bang it". Even through these really sharp manoeuvres you need to "fly" the model through with fast but smooth control input. If you have too much elevator travel/handle spacing you could very easily stall the model if you are over turning. Once turned the nose of the model is pointing in to the center of the circle such that if you dumped a lot of airspeed right at the corner the inboard wing (which is traveling slower and stalls first) and nose would drop to the inside of the circle for a moment and show you the bottom of the model (incipient spin - it is an airplane after all) and then given enough power the model would work its way back on course.
Second, I note in your drawing the angle you have portrayed for the first turn and suggest that if that is the angle you perceive you are turning then you are over turning the corner. You might be surprised how close to vertical you need to turn to keep this manoeuvre at the proper size and not get into trouble on the last corner. I would rather see you make both the triangle and the hourglass tall and narrow first, then gradually widen it out rather than the other way.
There is no question that you should not have shortened the lines. 62 feet at 5.0 would be more appropriate and allow more precise control.
I also have a Vector 40 ARC.
Just some thoughts.
Kim.
-
I'd do presicely what Ted told you to do.
-
Can someone take a video of you flying the Vector through the hourglass?
-
Thanks guys. Lots of good info here. And will review this on my next time out. I did not get to fly the last scheduled day and now we have rain predicted for the rest of the week. I'm helping propbuster (aka Ryan) move this weekend. For those that remember propbuster. 😊 So no flying for a week.
I will update after my next flight.
-
This is getting GOOD .
If you dont let on when you get it sorted , we can get at least another two pages more . ;) 8) S?P D>K
S?P H^^
-
But will we see the topic end before New Year's Eve? mw~ Steve
-
Ok I got out yesterday finally with my friend Arlan.
Line length was 58ft 7in. Add my long arm and wing it's over 60ft handle to center of the plane. Lap time was 4.8.
Launch was 11,100 rpm. Header muffler.
I did a few wing overs inside loops. I then tried the hour glass. I did not bang the corner. It felt a little better but still felt a slight bobble. I noticed another little bobble on the down leg about the same spot.
The engine then proceeds to go lean and it's just hang on for the next what seems 10 minutes.
I think my flying buddy gave me some great advice.
Don't bother trimming the plane until I fix my fuel problem.
Jump in here Arlan if I missed anything.
I am hanging the plane on the wall until I feel like changing out the tank. 😖
-
Two weeks ago when we were flying I was holding Paul's plane and wincing as he tweaked the needle to around 11,200. Steady 2 cycle.
It unloaded out of a 2 cycle to a wet 2 for a couple of laps then I watched while it screwed him into the ground for 10 minutes.
Frustrated, he decided to short tank it until he found a needle setting.
He went up next at 10,800 burbling 4/2. It was rich and weak at first but leaned out sooner and ran longer than I would have expected.
Watching him needle the engine, it appeared to me that the response was delayed. The 3rd flight went up at as close to 11,000
as he could get it. Again, it was good for a handful of laps and then it was off to the races.
I suggested to Paul that he go through the entire fuel system and find the air leak or obstruction.
Later on that day or week he sent me this picture which is worth more than all my words preceding.
(http://)
So yesterday Paul showed up with a header muffler in place of the pipe, over which I voiced my displeasure at his changing more than one thing at
a time. I forgave him and he fired it up. Same as last time, it won't hold a steady needle, but 4 cycles at a higher rpm. When I let go it was oscillating between 11,000 and 11,100. It unloaded into a steady 4 for about twelve or fifteen 4.8 second laps, breaking nicely when pulled into a wingover
and insides. After that it was, once again, off to the races.
I believe Paul still has a fuel delivery issue and that although he found an obstruction, he still very likely has an air leak somewhere or vent issue
with his tank.
I also pointed out that he was pulling an hourglass with a full load of fuel, and he should really stop trying to trim a plane that hasn't had a single
decent engine run, No two alike. I have not seen 2 maneuvers back to back to be able give much feedback to Paul, but the plane is straight and
the controls are smooth. I think that once he sorts out his engine runs that lead-out position and tip weight will be his issues.
I haven't flown Paul's plane and neither has Jim Lynch. The reason we both told him this particular plane could have vertical cg issues is because of something you can't see in the pictures. The landing gear isn't stock and is considerably taller. The pipe is slung underneath the fuselage.....Way underneath. It looks like a Navy plane with it's tailhook down. That wouldn't be the first thing I changed, but it would be in the back of my mind
until I got it trimmed.
I think we could get it sorted out next time out, but Paul wants to get some handle time between thunderstorms so he's pulling out an oldie
but a goodie to get tuned up for Paducah in 2(?) weeks.
-
Paul,
When you fuel your tank, do you have a filter going from the fuel jug to the tank? That's an awful lot of junk to be in the filter.
-
Two weeks ago when we were flying I was holding Paul's plane and wincing as he tweaked the needle to around 11,200. Steady 2 cycle.
It unloaded out of a 2 cycle to a wet 2 for a couple of laps then I watched while it screwed him into the ground for 10 minutes.
Frustrated, he decided to short tank it until he found a needle setting.
He went up next at 10,800 burbling 4/2. It was rich and weak at first but leaned out sooner and ran longer than I would have expected.
Watching him needle the engine, it appeared to me that the response was delayed. The 3rd flight went up at as close to 11,000
as he could get it. Again, it was good for a handful of laps and then it was off to the races.
I suggested to Paul that he go through the entire fuel system and find the air leak or obstruction.
Later on that day or week he sent me this picture which is worth more than all my words preceding.
If it needles on the ground but not in the air, and you are otherwise running stock parts with standard pipe lengths, I would suspect that there might be some crud in the tank. The crud lies on the bottom of the tank on the ground, then you take off and it slings itself up to the pickup.
Please run the engine in the stock piped configuration with standard settings, so you can remove that as a potential source of problems. It wouldn't hurt anything to ensure that everything is properly sealed (no gaskets, just flatten the surfaces with 240 grit sandpaper on a hard block, and silicone header sealant), but the overall engine setup can be straight off the instructions. It's not an experiment.
Matt is right, that is a lot of crud in the filter and it has to have come from the tank somehow. Since it's a takeapart filter, it could also be leaking air at the joint so seal that up properly, and check.
As before, the original problem is not a vertical CG issue. It wouldn't be a transient condition, if you could detect it at all (which you probably can't). Plus, I have flown quite a few Vector ARF flights with a PA40UL on a pipe with extended gear, in fact won two ARF-OFFs with a borrowed one, and it flew fine.
Brett
-
I've found and seen those screw together filters cause motor runs like you describe.
Get a Craptrap, they seem to be the best.
Make sure you put it around the right way with the finest filter facing forward.
They have 2 filters inside, the coarse one first then the fine one. I've never had a problem with these filters.
Don't quote me but I think they are made by Sullivan.
-
(http://stunthanger.com/smf/index.php?action=dlattach;topic=43692.0;attach=256635;image)
Ah Ha , looks like the FILTERS BACKWARS ! ( o.k. we've all done THAT before . >:( )
The Big Hand Points To , the Fuel Tank . Or the big hole . The SCREEN is on the Motor End .
With only the weeney ' V ' C'sunk resivoir , its full in moments . The odd one has NO c'sunk V , ands full in nano seconds , as its a 2 m.m. THING .
-
I've found and seen those screw together filters cause motor runs like you describe.
Get a Craptrap, they seem to be the best.
Make sure you put it around the right way with the finest filter facing forward.
They have 2 filters inside, the coarse one first then the fine one. I've never had a problem with these filters.
Don't quote me but I think they are made by Sullivan.
Crap traps work OK but I have had them leak as well. The two halves are pressed (glued?) together and over time I have had them break loose and leak. After de-greasing they can be re-glued.
The Great Planes filters are the ones that are screwed together with a rubber seal in between. The seal can flatten, tear, etc, and leak. But, I prefer something I can take apart for inspection and cleaning.
Yes, I think the Sullivan filter (not take apart) has a coarse mesh screen in line with a finer mesh screen. It is tubular shape, very narrow, fits in tight places but is longer.
-
Crap traps work OK but I have had them leak as well. The two halves are pressed (glued?) together and over time I have had them break loose and leak. After de-greasing they can be re-glued.
Crap traps are not two-piece items. The Sullivan filter IS the crap trap, and used to be named that.
The only filters I have seen that are glued together are the old little blue type (whose origin I never knew) and the giant aluminum DuBro. The latter could certainly fall apart, and I have that happen.
Brett
-
I have used the old Perfect filters, then I got the blue filters from RSM Dist. and various metal filters. All have worked well except one. I had to take small wrenches to make sure it was tight. All of them had to be cleaned after a flight or two on a new tank. The last tank was the worst on my Vagabond. Finally sat in the back yard running the engine with the wedge end of the tank down. I always try to make clean tanks, but this one gave me fits. I now have several runs on it with no needle change or rpm change until last few drops of fuel. And yes, make sure the big chamber is towards the tank.
-
I have used the old Perfect filters, then I got the blue filters from RSM Dist. and various metal filters. All have worked well except one. I had to take small wrenches to make sure it was tight.
Just making it tight might not be enough. Some screw-together filters have fiber washers that are porous. Leak check them under pressure and under water like a fuel tank, and they sometimes look like fish aerators no matter how tight you make them. You need a solid rubber washer of some sort, or seal it with silicone sealant.
Brett
-
I would guess that a heatgun applied to a leaky Sullivan "Crap Trap" would probably fix it. Probably best to flush out any fuel with an inert compound like H20, or just blow it out with compressed air before applying heat. y1 Steve
-
Thank everyone.
I am using a different filter. Arlan works in a lab and he uses lab type filters. He can provide the specs but anyway was using a brand new lab filter. i also use a filling station on my jug and its is filtered.
This time my guess is something inside the home made tank.
I'm going to put in a plastic clunk tank.
Right now as Arlan said I just want to get a flight where the engine is not running away.
After that I may attempt the pipe after its trimmed out.
Now to figure out how to mount a tank on a engine cruch.
-
You'll have to re-trim it when you go back to the pipe, due to CG, prop, launch rpm, etc., likely being different. I'd go with the pipe. After all these lean runs, you might want to pressure test the pipe for leaks. I've never done that, but I also haven't had but one lean run, about 4-5 years ago; same dog.
:-[ Steve
-
Crap traps are not two-piece items. The Sullivan filter IS the crap trap, and used to be named that.
The only filters I have seen that are glued together are the old little blue type (whose origin I never knew) and the giant aluminum DuBro. The latter could certainly fall apart, and I have that happen.
Brett
I was told the blue plastic filters were Crap Traps. I never knew the Sullivan was once called a Crap Trap. I have not seen any of the blue plastic filters in hobby shops anymore.
-
I see Eric at RSM Dist. doesn't show the blue filters anymore. I got mine years ago at VSC from Eric. I see he has the Crap Trap filters which I never liked as they took up so much space and were hard to clean. H^^
-
The little blue plastic filters come from Master Airscrew, IIRC. I'd never use them in a fuel deliver hose of any sort, but they are perfect for use as an air filter on the uniflow air inlet to keep out small bugs and seeds.
The Sullivan "Crap Trap" filter is a great filter. When it finally gets clogged up, put in a new one. They are not meant to be cleaned. If your plane doesn't have enough room for one, you didn't plan well enough. Mock-up the engine/tank/hoses/filter early in the build. H^^ Steve
-
The little blue plastic filters come from Master Airscrew, IIRC. I'd never use them in a fuel deliver hose of any sort, but they are perfect for use as an air filter on the uniflow air inlet to keep out small bugs and seeds.
The Sullivan "Crap Trap" filter is a great filter. When it finally gets clogged up, put in a new one. They are not meant to be cleaned. If your plane doesn't have enough room for one, you didn't plan well enough. Mock-up the engine/tank/hoses/filter early in the build. H^^ Steve
Master Airscrew does ring a bell, maybe I actually *did* know that at one point. They work fine as long as you seal the joint with silicone, plier-handle-dip, Flex-Seal, or some equivalent.
The Sullivan "Final Filter" (formerly known as the Sullivan Crap Trap) are the best from a filtering standpoint. I use those, or the little filters that Dave Shadel used to sell, which are the same diameter as the tubing. They don't filter nearly as well and can easily clog because they are so tiny, but they will literally fit anywhere you can get tubing.
I actually don't recall what is the my good airplane right now, one of those two. I only very get anything in any filter, mostly because I don't usually screw around with my fuel, just open it up and suck it out. Almost anything else people do (ketchup pumps, coffee filters (NOT recommended), decanting from can to can) seems to introduce crud.
Brett
-
I have been using the Fourmost filter. They fit in tight spots and seal good to the fuel tubing. They solved some fuel flow problems on my racing planes.
Al
http://www3.towerhobbies.com/cgi-bin/wti0001p?&P=SM&I=LXBNU8
Try a APC 11.5x4 prop, with 60' lines lap time should be 5.1. I use this on my Vector powerd by a LA 40 and it flies great even in the wind.
-
"Ketchup Pumps"? No wonder you had trouble. Must always use the mustard version. The epoxy version work well, too, available from Tapp Plastics. ;)
Seriously, they're all nylon, except for the spring, what could go wrong? I've got two filters in my outflow hose, and haven't changed them or cleaned them in years and years. Paul, Dan and Howard used them, with no problems, so I don't understand why y'all had all the drama. Paul and Howard used to remove their pump and store it in a ziplock bag, but I leave mine in all year, year after year, only removing it to add fresh fuel. This past weekend, I topped up with ex-Lee Uberbacher 10-11-11 fuel mixed by Howard Rush some years before Lee died, which was awhile ago. Worked fine. I use a plastic funnel that I store in a ziplock bag, if that shows any responsibility at all. Had the cowl off the dog sometime last year, too.
I think it's a fine idea to change/clean the fuel filter multiple times during the first couple of dozen flights with a new tank. y1 Steve
-
Thats Not a Blocked Filter . THIS is a Blocked Filter ! . :##and its the right way round ! S?P ( backs full of ?? & %^# )
in the DRY on Grass Fields the wind blown grass shards , Dust , etc . and I think thats the old armourall siliconing fuel .
Shards of all things & looks like copper paste . Maybe from the coal mines . %^@ :-\
Winter Damp and theres not so many airborne particles .But its chillier . ! ;D LL~