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djaflyact
Joined: 14 Oct 2013
Posts: 27
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 Posted: Fri Dec 06, 2013 8:03 am Post subject: Mod 78 News - Good and Bad |
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Well, I found the problem with interference with my right wing fit. I had forgotten (until I pulled the left wing out again) that I had a swelling fuel tank problem early on in the flying of the airplane. The brackets that hold the tank back worked great - in the area of the bracket, but in between the tank swelled until it rubbed on the aileron cross link between the CS08 arms. My solution at the time was to move one end of the cross link forward of the CS08. That allowed it to clear the tank, but that is now the reason I cannot get the right wing to fit. It has to go back to the original position.
I've got two choices: The cross link rubs the fuel tank or the I fly with only one wing.
Since there is no reasonable choice there, I think there are also now 2 possibilities: I move the fuel tank wall back or I bend the cross link bar to clear the swollen tank.
Right now, I only see the arcing of the cross link as the answer. If it is not straight, it will not be as strong in compression. I doubt the loads are very high, but there is the issue of jammed controls and the ability to provide force in a situation like that.
Would I make a contestant arc in the tube?
Would I make a joggle in each end so that most of the rod is straight?
Would I replace it with steel?
Would I fill it with something like epoxy to make it stronger?
Can the tank wall be pushed back? I can only imagine coating it with fiberglass or carbon cloth and some sort of hydraulic press holding it while it cures (I doubt this is possible).
Has anyone experienced this issue with the fuel tank?
Of course, the temperatures here have dropped to 0F at night, which is making progress more difficult. I am getting close, however.
Thanks,
Dave
A227
Mini U2
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alan.twigg775(at)gmail.co
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| Posted: Fri Dec 06, 2013 9:12 am Post subject: Mod 78 News - Good and Bad |
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Dave, mine is a new build and all is very tight back there with the modified Spar. I am fettling the right wing top surface at the moment but can see I will need to shave some material off the Aileron self connect, I believe I need to anyway to facilitate the main pin.
I have a borescope kit and will try to get pictures.
regards
Alan Twigg
Motorglider Mono
Kit 463 and getting closer.
On Fri, Dec 6, 2013 at 4:03 PM, djaflyact <djaflyact(at)gmail.com (djaflyact(at)gmail.com)> wrote:
[quote] --> Europa-List message posted by: "djaflyact" <djaflyact(at)gmail.com (djaflyact(at)gmail.com)>
Well, I found the problem with interference with my right wing fit. I had forgotten (until I pulled the left wing out again) that I had a swelling fuel tank problem early on in the flying of the airplane. The brackets that hold the tank back worked great - in the area of the bracket, but in between the tank swelled until it rubbed on the aileron cross link between the CS08 arms. My solution at the time was to move one end of the cross link forward of the CS08. That allowed it to clear the tank, but that is now the reason I cannot get the right wing to fit. It has to go back to the original position.
I've got two choices: The cross link rubs the fuel tank or the I fly with only one wing.
Since there is no reasonable choice there, I think there are also now 2 possibilities: I move the fuel tank wall back or I bend the cross link bar to clear the swollen tank.
Right now, I only see the arcing of the cross link as the answer. If it is not straight, it will not be as strong in compression. I doubt the loads are very high, but there is the issue of jammed controls and the ability to provide force in a situation like that.
Would I make a contestant arc in the tube?
Would I make a joggle in each end so that most of the rod is straight?
Would I replace it with steel?
Would I fill it with something like epoxy to make it stronger?
Can the tank wall be pushed back? I can only imagine coating it with fiberglass or carbon cloth and some sort of hydraulic press holding it while it cures (I doubt this is possible).
Has anyone experienced this issue with the fuel tank?
Of course, the temperatures here have dropped to 0F at night, which is making progress more difficult. I am getting close, however.
Thanks,
Dave
A227
Mini U2
Read this topic online here:
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Fri Dec 06, 2013 9:47 am Post subject: Mod 78 News - Good and Bad |
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Hi Dave
Can you just fly with one aileron? I saw a drunk farmers fly like that in both a Piper and Aeronca!
Bending aluminium is EZ, but since you have the ball end it will allow your kink to rock up and down. You may get away with it? Don't try bending in a vise, chance of kinking is far greater than if you drill a hole in a thick piece of wood, like work table or your basement stairs, of course a proper bender is best. Filling with sand can also help prevent kinking.
As far as rigidity and keeping things light, thin wall and large OD for a given weight gives you the most bang for your buck. In your case a smaller OD and thicker wall will give you a little more clearance with a slight weight penalty. 4130 is stronger than aluminium, you should even be able to go smaller in OD and if you weld it it can get away without heat treating, again with a slight weight penalty.
If your bow idea is not going to work, you could offset your mounting stud on the end of your tube to move forward the front edge of the smaller ID tube as far as you can, this would keep your tube straight.
I'm not at my aeroplane, but off the cuff a small OD very thick wall, perhaps even a solid piece of 4130 (see McMaster Carr too for 4130 in addition to ACS and Wicks) and a welded on piece of 4130 that is tapped to give you needed offset, then install in it a threaded stud (tack the far end to keep it from rotating) if you are close you could weld the stud directly to the 4130 and space the ball end slightly aft.
I would first rig wings without the pushrod to make sure you can rig. Then screw a piece of metal in place of the pushrod and determine what clearance you have to your spars. Soft aluminium rectangular bar from the hardware store comes to mind.
I am doing battle with making sure I can get my flaps to work post 78. I had my son (going to CMU for mechanical engineering) grind some numbers for me as far as the side force exerted when you put a bend in a tube. I used a 4 foot example with the bend occurring at the middle 2 foot point with a 100lb parallel force exerted on the two ends. May give you an idea:
http://www.europaowners.org/main.php?g2_itemId=394508
Ron Parigoris [quote][b]
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asarangan(at)gmail.com
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| Posted: Fri Dec 06, 2013 11:16 am Post subject: Mod 78 News - Good and Bad |
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I am not building mod78, but it sounds to me like a joggle may be
better than an arc. Instead of bending, you could weld the joints or
use elbow fittings. In any case, I would go with a thick wall tube. I
got some of these for linking my autopilot servos.
http://www.aircraftspruce.com/catalog/mepages/alumtube_6061t6.php
In any case, I can't envision any scenario where the aileron forces
are so strong as to bend a metal tube, unless your passenger is
fighting you at the controls 
Speaking of tank swelling, if your tank is currently dry, you may want
to take extra precautions when filling. Most tank failures have
occurred exactly in these instances. One option might be to fill it
slowly, over several days to allow the tank to slowly expand, before
putting much weight on its supports.
On Fri, Dec 6, 2013 at 11:03 AM, djaflyact <djaflyact(at)gmail.com> wrote:
| Quote: |
Well, I found the problem with interference with my right wing fit. I had forgotten (until I pulled the left wing out again) that I had a swelling fuel tank problem early on in the flying of the airplane. The brackets that hold the tank back worked great - in the area of the bracket, but in between the tank swelled until it rubbed on the aileron cross link between the CS08 arms. My solution at the time was to move one end of the cross link forward of the CS08. That allowed it to clear the tank, but that is now the reason I cannot get the right wing to fit. It has to go back to the original position.
I've got two choices: The cross link rubs the fuel tank or the I fly with only one wing.
Since there is no reasonable choice there, I think there are also now 2 possibilities: I move the fuel tank wall back or I bend the cross link bar to clear the swollen tank.
Right now, I only see the arcing of the cross link as the answer. If it is not straight, it will not be as strong in compression. I doubt the loads are very high, but there is the issue of jammed controls and the ability to provide force in a situation like that.
Would I make a contestant arc in the tube?
Would I make a joggle in each end so that most of the rod is straight?
Would I replace it with steel?
Would I fill it with something like epoxy to make it stronger?
Can the tank wall be pushed back? I can only imagine coating it with fiberglass or carbon cloth and some sort of hydraulic press holding it while it cures (I doubt this is possible).
Has anyone experienced this issue with the fuel tank?
Of course, the temperatures here have dropped to 0F at night, which is making progress more difficult. I am getting close, however.
Thanks,
Dave
A227
Mini U2
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=414977#414977
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budyerly(at)msn.com
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| Posted: Fri Dec 06, 2013 3:26 pm Post subject: Mod 78 News - Good and Bad |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> Dave,
I have not experienced your problem with the cross link rod rubbing the tank. Most probably your tank was installed a bit forward but it probably did swell as you indicate.
In 13 cockpit module builds I have always had 1/2 inch clearance and never had a tank rub even after 5 years of flying. Years ago I noticed a plane that came in with a rubbing rod but the tank was put in a bit askew and the aft bulkhead was pulled in 1/2 inch.
If the tank did not break its bond with the back wall or saddle then it is really bowing quite a bit. Armed with that bit of information and not wanting to replace the tank, can you build another tank bracket to ease the bulge back in the saddle area?
It is a nasty hole to work in for sure, and the modded spars really hog the room.
What I am thinking is a flat aluminum plate of stiff 6061T6 aluminimum 1/8 by say 3 inches and make a U shape around the spars and pushing up against the tank bulge.
Not being able to see your aircraft, this is a wild assed guess.
I had no problem clearing the bolt heads by countersinking and using AN 509 416R20 screws to replace the AN 4 bolts. Countersinking was done with a speacial tool we made. 30 minute job.
That said, it will be a game of inches for you for sure.
Borescope and time will tell what's happening I'm afraid.
Regards,
Bud Yerly
[quote] ---
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djaflyact
Joined: 14 Oct 2013
Posts: 27
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| Posted: Fri Dec 06, 2013 4:09 pm Post subject: Re: Mod 78 News - Good and Bad |
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Looking at it closer today, I discovered I had the offset brackets installed upside down. The support for the tank wall was not high enough. In addition, the CS08 brackets were farther than 3 inches from the seat back. I swear they were correct when I built it.
I was able to slightly modify the shape if CS08 (bend!) and now have the correct 3 inches. The rod can be straight and the only difficulty is now the swollen tank on one side preventing the offset bracket from fitting.
I'm planning to encourage the tank face to back up a bit while I slip the standoff bracket in place. I will warm it slightly as it is freezing right now. Maybe apply pressure over a period of time.
As insurance, I'll also replace the bolts that hold the rod ends at the top of CS08 with flush structural screws. I'm thinking that if the CS08 arm ever hits the spar, it would be better to hit a smooth surface , rather than bolt heads.
Thanks everyone for the input. This story keeps developing.
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