Fix crack in helicopter Bubble ?

[Seahawk]

Originally Posted by Arizona_928

There’s a lot of static displays around, maybe reach out for a trade on a non cracked bubble.

That was my first thought as well...but I have had no luck: Rainy day here in Maryland and my mowing extravaganza has been pushed.

That said: https://www.faa.gov/about/history/brief_history#origins

Trust me, I am not a fan of the FAA, especially when they opine about drones, but processes and standards in aviation are penultimate especially in certified aircraft.

Once again, I am willing to fly wingman on this.

[afterburn 549]

I am all for buying a canopy if I can find one, yes it is do for an annual that's why I am scrambling.
It was born in 1957 and I have all manuals .
There is a place in Ca that makes canopies for these, Bell47 and others.
I am just having a real hard time locating them.

Hiller says they are in business, but so far my experience with them has not been exciting.

[Seahawk]

Originally Posted by afterburn 549

I am all for buying a canopy if I can find one, yes it is do for an annual that's why I am scrambling.
It was born in 1957 and I have all manuals .
There is a place in Ca that makes canopies for these, Bell47 and others.
I am just having a real hard time locating them.

Let me know if I can help. Seriously. The guys I am dealing with said there is no way you'll get an Airworthiness Cert in the present condition and the repair options are interesting at best.

I hope Tim Hancock chimes in. I could be wrong.

Please let me know.

PM me and I'll get you my personal email. I love helicopters and want to see this work for you.

[pmax]

[RNajarian]

I would consider joining the Hiller Helicopter Community page on Facebook. A lot of owners like yourself who may have leads on the parts you need.

[Zeke]

Originally Posted by 908/930

I don't think you will need to drill if you can bond it properly, was the stress that caused the crack internal? With the #4 it will flow through just about any space like water but you need to be able to force it together to get the material to bond. How long is the crack and how thick is the material?

My experience is that if you can trace the crack with a needle and apply, the Weldon fuses the plastic, the tighter the crack the better. Of course without equipment gravity is all you have. You may have to do both sides to get the surface right. One trick is to use clear packing tape to trap the solvent. That's what it is. Look up the MSDS for Weldon-4.

I think I have at least thought of using silicone caulk as a dam and peeling it off after fusing. I don't remember but I know there is no tape that will resist the solvent.

I have then gone through what is essentially removing the orange peel from auto paint and polished with auto products, You know 3M is the best here.

My experience is with acrylic furniture. I usually make radial stress cracks disappear. Really aggressive compounding removes a lot of sins. IIRC, no more than 1000 RPM on a circular wool pad. And even then you have to keep moving or go back to sanding. New 220 wet or dry gets this going quickly and then progress to 600. I never found the need for 1000, 1500 or 2000 grit. The cutting compound seems like 320.

Cleaning the cracks before mending is a whole 'nother ball game.

One last tip that I'm not too used to is to use a small flame. Again, I'm not called on to do this often so other than edge annealing a new assembly, YMMV with the heat.

I've got a clear acrylic plant stand in the shop right now. I just got my Weldon. It doesn't last long even in the original container. I may try keeping this batch in the fridge or freezer. I have to research that. Doesn't work well with cyanoacrylate because of the moisture. Cyanoacrylate doesn't seem suitable for a lot of plastics.

[mistertate]

Originally Posted by 908/930

Do you happen to own a vacuum pump? Do you have a place to purchase a small piece of acrylic to practice on, any sign shops nearby?
.

Ding ding!
Vacuum forming acrylic isn’t rocket science. Sign shop can handle the dimensions

[Zeke]

The problem of making one's own aircraft parts might turn into trouble of some sort that I would not be the one to understand. I imagine words like FAA and insurance. I believe an "inspection" was mentioned. Do these various parts not have any identification? I know it's an old aircraft.

[unclebilly]

If you could pull it back into position so it it perfectly lined up, you could put mild release on one side and make up a perfect fibreglass patch from 5 layers of 1.5 oz mat and then do the same for the other side. Them you could sandwich the cracked come between the 2 perfectly contoured glass pieces.

You are dealing with a mess there.

[908/930]

Zeke, Have you tried Aluminium duct tape? I have not tried it but it should work.

If afterburn 549 is allowed to repair I was going to suggest using the thicker Weld-on#16, using aluminium duct tape on each side of the crack to protect the plastic and apply a bead and cover with duct tape to buy some time and pull it through the crack with vacuum. I have used weld-on #4 but I would usually dissolve some material in it to thicken it up. Most of it was to manufacture prototype QC imaging phantoms, and sometimes repair ones that were mishandled and placed down hard and cracked. These were about $20k+ to purchase, you would think people would be careful with them.

Good idea to read the MSDS, then get somebody else to do it. At very least wear goggles. I had a coworker splash his eyes with a product used to dissolve and bond nylon, fortunately there was an optometrist office near and they could quickly flush his eyes out.

[Zeke]

Yes, the silver mylar tape should work but again it's the adhesive that is the consideration. I learned the hard way that common cloth duct tape does not work whatsoever with epoxy. Actually I haven't tried any tapes with Weldon-4.

Contains Methylene Chloride (same as paint stripper) and Trichloroethylene. It is a solvent, not a glue or cement, but modelers will call it cement.

So in reality, not many tapes will stand up to it. But the tape is only intended to trap the flow. I would do a few tests.

[afterburn 549]

Whoa whoa!
Hooa $$$$$$
It turns out, that Walters helicopters can get these parts !!
My emergency is now perhaps over?
Thanks for the input and help.
I might try a glue job, but if it fails to pass the test I now have an" Advance to the rear plan !"
Yea!

[Seahawk]

These guys?

Fort Wolters Helicopters

Where are you located? I'd love to come see your helicopter.

Originally Posted by afterburn 549

Whoa whoa!
Hooa $$$$$$
It turns out, that Walters helicopters can get these parts !!
My emergency is now perhaps over?
Thanks for the input and help.
I might try a glue job, but if it fails to pass the test I now have an" Advance to the rear plan !"
Yea!

[dar636]

I didint see any pics of the cracks but in general helo bubble enclosures are repairable - check out section 3 on transparent plastics...

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43.13-1B_w-chg1.pdf

[afterburn 549]

Thank you Dar636