Plane doing something strange in hour glass

[Ted Fancher]

^^ yepper,, that right there^^^^

original deleted as not appropriate.  Gotta apologize for the double post however.

Ted

[Paul Taylor]

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?

[Paul Taylor]

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.

[Ted Fancher]

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

[Paul Taylor]

Hey Ted
Pipe is @ 17inches.

[Paul Taylor]

I can't tell from the picture, but, are the elev and flap hinge lines parallel?

dg

Hey Dale
Spot on.

[Doug Moon]

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.  

[John Leidle]

 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.

[Paul Taylor]

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.....   

[Doug Moon]

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.

[Paul Taylor]

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?

[Doug Moon]

Thanks Doug.
So more pitch. Less RPM?

Yep.  But dont get crazy with it.  Add little bits at a time and test. 

[Steve Helmick]

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?  Steve

[Ted Fancher]

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

[Curare]

The prop's not on backwards is it?

[Ted Fancher]

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!

[Kim Doherty]

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.

[John Leidle]

  I'd do presicely what Ted told you to do.

[Mike Ferguson]

Can someone take a video of you flying the Vector through the hourglass?

[Paul Taylor]

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.

[Air Ministry .]

This is getting GOOD .
If you dont let on when you get it sorted , we can get at least another two pages more .      

 

[Steve Helmick]

But will we see the topic end before New Year's Eve?  Steve

[Paul Taylor]

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. 😖

[Arlan McKee]

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.

 
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.

[Matt Colan]

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.

[Brett Buck]

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

[Russell Bond]

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.

[Air Ministry .]

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 .

[Jim Svitko]

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.

[Brett Buck]

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

[john e. holliday]

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.   

[Brett Buck]

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

[Steve Helmick]

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.  Steve   

[Paul Taylor]

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.

[Steve Helmick]

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

[Jim Svitko]

   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.

[john e. holliday]

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.

[Steve Helmick]

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.    Steve

[Brett Buck]

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.    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

[Al Ferraro]

 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.

[Steve Helmick]

"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.  Steve

[Air Ministry .]

Thats Not a Blocked Filter . THIS is a Blocked Filter ! . :##and its the right way round !  ( 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 . !