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Old Nov 23, 2005, 01:51 PM
Horned one
zero-zero's Avatar
Vigo, Spain
Joined Sep 2004
759 Posts
Repair advice, please

Looks like my luck run out today. Cartwheeled my Fredy on landing and snapped the T-tail at the usual place. I'm not very experienced with glass repairs (although I know I will be, eventually ), but I would like to try to do the repair on the inside. Here's my plan, please share your comments:

1- take out rx and elevator servo (in the tail) to have easier access without wires.

2- sand the inside a bit to promote adhesion. Repair cracks with epoxy and microballoons.

3- seize the opportunity to apply a few pieces of carbon tow to the fuse boom to add strength (just because it's easier now without the tail).

4- Wrap a length of carbon tow into a tube about three inches long and tack inside one of the parts. Once properly positioned, wet with epoxy, put a sausage-shaped balloon inside (sticking out from the servo opening) and join both parts.

5- Hot glue a couple alignment braces on the outside. These can be pulled without leaving residue later.

6- Inflate balloon to press carbon into fuz walls.

7- pull out balloon (may have to lubricate? might as well use a condom. Yes - unused). reinstall radio gear and adjust CG.

Do you think this is a good approach? do I need glass also? how many layers of carbon / glass? adhesive epoxy or laminating epoxy for this? anything else I might be missing?

Here's the pics:
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Old Nov 23, 2005, 01:54 PM
Registered User
timmig's Avatar
Southern California
Joined Sep 2003
6,903 Posts
Sounds like a good plan! Just do it!!

Geez-- just repair it like you outlined! You can always build a new plane for Target's idea. Fix it and fly it!! KISS method. Once you repair it with the carbon and glass--it won't break there anymore. FWIW
T
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Last edited by timmig; Nov 23, 2005 at 09:52 PM.
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Old Nov 23, 2005, 02:09 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,672 Posts
I vote for elimination of the problem....

Extend the fuselage, and mount a vacuum bagged V-tail.
The plane will be lighter, you'll end up taking weight out of the nose, no doubt, due to the lack of servo in the tail...
And the stress point at the vertical neck will be eliminated...

T

PS! What servo is in there? a lighter servo would help keep the loads down. Just a thought.
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Old Nov 23, 2005, 02:45 PM
Horned one
zero-zero's Avatar
Vigo, Spain
Joined Sep 2004
759 Posts
Target, your plan has a couple shortcomings for me:

1- I would be avoiding the repair, and I want to build some experience.

2- It would require a vac bagging setup and the knowledge to use it right. I have neither right now, and frankly I'm not too keen on taking up yet another project where I would be working for my planes instead of the other way around as it should be.

Besides, the Ion is a T-tail, too, so I know I'll be doing this more than once. I'm not too keen on V-tails either - much prefer cross-tails.

So, any advice about how many layers, and do you think 3 inches of CF is enough?

PS: servo is already as small as I dare use. I can, however, move it a bit down and forward (less leverage) now that I have to pull it out anyway.
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Last edited by zero-zero; Nov 23, 2005 at 03:46 PM. Reason: typo
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Old Nov 23, 2005, 02:49 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,672 Posts
I like Kevlar for it's give over CF, but if that's all you can get, then use it. The only advice to your plan, is MAKE SURE NOT TO BUILD IN A STRESS POINT ! ! ! ! ! !
So, taper your repair pieces over a longer area, to spead the load.

What servo is in the tail?


Target
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Old Nov 23, 2005, 02:52 PM
Detail Freak
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Harbor City, CA
Joined Oct 2003
21,672 Posts
ZZ-

Check this out-

http://www.rcgroups.com/forums/showt...ilboom+repair+

This worked out really well, and hasn't budged since. Taper, taper, taper!

Good luck,
Target
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Old Nov 23, 2005, 03:11 PM
Crikey never leave beer behind
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Mt Annan Sydney Australia
Joined Dec 2003
23,379 Posts
I did type this once but it didnt post for some reason I like your repair scheme I would go with a layer of the same weight Kevlar and 1 layer of carbon failing that 2 layes of carbon but the Kevlar has the give you need. imho
SteveW
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Old Nov 23, 2005, 03:13 PM
Horned one
zero-zero's Avatar
Vigo, Spain
Joined Sep 2004
759 Posts
Ah, I remember that thread well. I'll keep the taper in mind.

Funny about your mentioning improved grip there. You'll see a pair of carefully shaped pieces of fine-grit sandpaper 3M 77'd under the wing saddle in mine. Works a treat.

Steve, thanks for your input. I'll call my supplier tomorrow, but I think they don't sell kevlar or carbon-kevlar cloth unless it's a very big order. I think 2x carbon will be ok?
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Old Nov 23, 2005, 03:36 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,672 Posts
ZZ- You need to just ask for a scrap (of Kevlar) from one of the F3F guys in your area, if there are any... All the guys I've asked for help have been extremely helpful....


3rd time's the charm: What elevator servo is in the tail fin???

Target
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Old Nov 23, 2005, 03:55 PM
Horned one
zero-zero's Avatar
Vigo, Spain
Joined Sep 2004
759 Posts
Sorry, Target, I kinda answered about the servo in post 4, but if you want brand and model, it's a Multiplex MS-X3. I'd like metal gear, but that's what came with the plane and has worked well so far.

About the F3F guys, the closest are probably about three hours from here. My usual slopes are really not suited for F3F birds, in fact most people fly combat wings and very few fly glass. There's the odd big scale bird, but I have not met another guy with a moldie on the slope yet.
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Old Nov 23, 2005, 04:01 PM
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Madrid, Spain
Joined Sep 2004
1,102 Posts
That post is amazing Target!
Z-Z, you should make just that way. It will be a perfect repair.
oh, btw, PM sent
Chets
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Old Nov 23, 2005, 04:09 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,672 Posts
I have a HS-55 in the T-tail of my Bandit hotliner, and NEVER had a problem.... They weigh next to nothing....

T
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Old Nov 23, 2005, 04:50 PM
Horned one
zero-zero's Avatar
Vigo, Spain
Joined Sep 2004
759 Posts
Targ, the HS-55 weighs 9 gr and has a torque of 1.1 kg. This Multiplex weighs 14 gr and has a torque of 1.8 kg. I have a couple of 55's, but they are scheduled for another plane. Do you think it's really worth it, considering that I can relocate this servo to the very bottom of the fin where it would have no leverage?
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Old Nov 23, 2005, 07:07 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,672 Posts
Beats me. Less weight back there is better, but if you are going to put it where it doesn't add stress to the neck then you'll probably be OK anyway.
Why cant the Mfg. figure these things out!?!

Do you have the servo torque calculator?
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Old Nov 23, 2005, 08:41 PM
Stay in it!!!!
Riverside, California, United States
Joined Aug 2004
5,050 Posts
I didnt read but the first two or three posts but, if it helps I have a Freddy V-tail in good shape I will donate if you choose to go with Targets plan.
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