Repair on Pulsar 3.2 sailplane

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JohnOSullivan
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Repair on Pulsar 3.2 sailplane

Unread post by JohnOSullivan » Thu Oct 20, 2016 8:36 pm

I busted up my 3.2m Pulsar badly at Shearwater at the barbecue and am currently repairing it.
All wing panels were affected with trailing edge breaks and squished ribs. the fuselage nosecone was squished and the pod behind the wing was snapped. Left wing spar of outer panel was snapped. It looked like it was done for good.
However, bit by bit it is re-emerging.
Update on Pulsar 3.2 repair.
1) Finished fuselage repairs on nosecone and pod break
2) Repaired outer wing tips TE breaks and rib breaks (at least 6 breaks) ( now covered with fluorescent yellow)
3) Centre panel ribs reglued and ready for covering
4) Spar repair on left outer panel in progress. Drilled two 4 mm holes in wing joiner and put 4 mm carbon rods in to carry loads into outer panels. will wrap join areas with carbon to carry the load.
Looks like it will be back as good as new.
Just for fun, I added fluroscent yellow bands on wing covering the outer tip panel repairs.
Attachments
Wings and fuselage.JPG
Tip Root spar break repair.JPG
Fuselage repairs ready for painting.JPG
Fuselage repairs Kevlar.JPG
John
MAAC #5401 L
MACI (Ireland) IRL#26

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CF Av8or
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Re: Repair on Pulsar 3.2 sailplane

Unread post by CF Av8or » Thu Oct 20, 2016 9:34 pm

Great job, John! Glad to hear that it will fly yet again.

Vic

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AndrewS
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Re: Repair on Pulsar 3.2 sailplane

Unread post by AndrewS » Thu Oct 20, 2016 10:45 pm

Like the yellow, John. Now it'll be easier to tell them apart. :lol:
Great job on the repairs.
Any new ideas on what might have gone wrong?

Andrew
Andrew Smith,
HEFA 3
MAAC 76250

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JohnOSullivan
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Re: Repair on Pulsar 3.2 sailplane

Unread post by JohnOSullivan » Thu Oct 20, 2016 11:25 pm

The yellow band was so we can distinguish between our Pulsars.
I still cannot determine what caused the crash. The model climbed to about 75 to 100 ft and suddenly went into a vertical dive. No evidence of a turn to left or right, it was just as if it got a full down elevator. I throttled back immediately, but judging by the damage, it appears that the motor was running on impact. Never had any glitches in over 4 years + of flying.
The wing breakages were of trailing edges and rib fractures and the crunching of the fuselage indicating a vertical impact. Repairs were possible because of the high quality of the structure, which resulted in breakages at repairable points. The carbon trailing edge carbon strip (0,75mmX4.5mm) snapped in about six places and some ribs split longitudinally and were able to be re-glued without distorting the airfoil. The trailing edges were repairable by laminating the breaks with tapered 0.2 mm carbon cap strips on top and bottom of the trailing edge. Due to the slim fuselage, it was not possible to add Kevlar reinforcement inside the breaks, so 2.2 gm/sq metre Kevlar was wrapped externally around the breaks. The spar break was probably the hardest to make as it was a key structural component. With the substantial carbon wing joiner, I was able to drill two 4 mm holes and fit 4 mm carbon rods to extend past the joint break which spread the load past any point of possible failure.
I am sure that the finished model will be just as good as the original, but maybe an ounce or so heavier.
John
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JohnOSullivan
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Re: Repair on Pulsar 3.2 sailplane

Unread post by JohnOSullivan » Tue Oct 25, 2016 3:46 pm

Update on the Pulsar repair.
Everything's all back in shape (and hopefully strength). I'm happy with the results and repairs are hardly noticeable.
Just got to do some amperage and thrust checks on the motor and re-install. Still have not figured a cause for the crash so will have to proceed with caution on testing.
I was contemplating on changing to my Taranis radio before crash and maybe my Futaba got jealous and decided to teach me a lesson.
John
MAAC #5401 L
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AndrewS
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Re: Repair on Pulsar 3.2 sailplane

Unread post by AndrewS » Tue Oct 25, 2016 6:25 pm

Fingers crossed for the re-maiden, John
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trevor
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Re: Repair on Pulsar 3.2 sailplane

Unread post by trevor » Wed Oct 26, 2016 10:41 am

Looks great John. Good luck
what do you mean low rates and expo???

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JohnOSullivan
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Re: Repair on Pulsar 3.2 sailplane

Unread post by JohnOSullivan » Sat Jan 21, 2017 9:22 pm

Finally got to get the repaired Pulsar out today.
I discovered the cause of the crash. I had moderate down elevator trim coupled to the throttle (to prevent looping under power). Well the mix had got screwed uo and it was giving full down elevator on full throttle.
Today I was testing with 50% throttle and was working fine, but on full throttle it tucked its nose down, just as it did on the crash. Once this was realized, it flew quite normally and is now back to 100% of its original performance. Very happy with this. It's good to pinpoint the reason for the crash, otherwise each flight is a guessing game.
Now approaching 5 years flying it is as performing good as ever.

I have also been building a 2 metre lightweight sailplane fitting in with newly developed German rules for wooden airplanes and light Hi-starts.
The Mayfly is a redesign of my 1980's Minifex 2 metre sailplane with altered wing planform, extended fuselage and smaller tailplane and fin and more efficient wing sections.
I have one almost completed wing, one Sailplane fuselage and tail group and one electric fuselage and tail group completed and it looks good
Attachments
Mayfly 2 metre sailplane and electric
Mayfly 2 metre sailplane and electric
P1100126.JPG
John
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astroflyer
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Re: Repair on Pulsar 3.2 sailplane

Unread post by astroflyer » Sun Jan 22, 2017 9:21 am

Well done John! Sure is great when you realize what happened and can correct it. I'm stealing these two photos and your info for the February MAAC newsletter. Hope you don't mind.

I'm assuming you made the photo of your new build, who made the photo of you? Always like to give photo credits!

saboo
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Re: Repair on Pulsar 3.2 sailplane

Unread post by saboo » Mon Jan 23, 2017 12:04 pm

With the revised airfoil, is it a JOS2016 section or SDXXXX or SXXXX Michael Selig section or what?

Have you reduced the tail areas due to the longer tail moment arm or just to change the spiral stability?

The reasons for the change are often more informative than the fact of the change itself.
Nothing like the smell of electrons in the morning ;-)

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