SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jun 23, 2014, 04:30 PM
Registered User
Joined Jun 2014
12 Posts
Help!
Broken Carbon Boom

Hi,

I really hope someone can help me, I am based in Germany at the moment and have really got into electric RC gliders.

I have just purchased: http://www.reichard.cz/modely/elektrovetrone/cumulus/ and had just finished building it and had just started balancing it before my first flight.

I had hooked it up to a fishing line on the centre of gravity and was working out how much weight and where I needed to put it. I worked it all out, got it balanced and decided to unhook it and add the weight.

Stupidly when I was unhooking it i had ahold of it with one hand about half way down the carbon tail boom, the weight of the nose with the battery, motor etc cause it to flex and crack right when my hand was holding it. (See Pic)



I was on the verge of having a full on tantrum

So now im sat with a 300 euro glider and have no idea how to fix it, please can someone help me and advise me how to. I have googled and found a lot on how to repair fibreglass, but nothing useful for carbon fibre.

Thankyou for any help!
toneeeee is offline Find More Posts by toneeeee
Reply With Quote
Sign up now
to remove ads between posts
Old Jun 23, 2014, 05:52 PM
Registered User
Joined Apr 2012
2,829 Posts
Hi, toneeeee, I think we have all done something similar. I'm not really an expert on repairing CF but just about any method one would use for fiberglass should work since it looks like a fairly clean break rather than being crushed or shattered. My personal favorite method to fix fiberglass is to make the repair with 30 minute epoxy which I thin with just a couple drops of rubbing alcohol so it really soaks in. I allow it to fully cure and then add external reinforcement. One can wrap the joint with glass cloth and thinned epoxy, add thin plywood splints, or both. It won't look terribly pretty but should get you back in the air.

Cheers!
peterlngh is offline Find More Posts by peterlngh
Reply With Quote
Old Jun 23, 2014, 06:35 PM
Registered User
Lenny970's Avatar
Greeley, Colorado, USA
Joined Feb 2000
2,911 Posts
It seems surprising that the boom would break just from the weight of the pod!
I would probably be inclined to use some CA to tack it back together, while making sure the boom was straight.
Then use some carbon tow and laminating epoxy to do an external structural repair.

I'd suggest that you post your question and picture in the Handlaunch forum.
That boom looks very similar to a typical DLG boom and I'm sure you'll find plenty of guys with experience repairing them in that forum.

Good luck,
Lenny
Lenny970 is offline Find More Posts by Lenny970
Reply With Quote
Old Jun 23, 2014, 07:39 PM
Registered User
Joined Apr 2012
2,829 Posts
Lenny has a good idea. Here's a thread that popped up. I think I like the idea of using several wooden sticks to make a plug that fits inside the boom and one could still add some external reinforcement.

http://www.rcgroups.com/forums/showthread.php?t=342435
peterlngh is offline Find More Posts by peterlngh
Reply With Quote
Old Jun 23, 2014, 10:17 PM
Registered User
United States, MA, Grafton
Joined May 2006
365 Posts
There was just an article on exactly this in Model Aviation, maybe last month. Basically: Tack it together with thick CA. Using a Dremel and a fairly narrow grinding wheel, grind several (as many as 12 depending on size of boom) longitudinal grooves along the fuselage, spaced around the circumference, spanning the crack. Do not grind all the way through, just deep enough to make a slight depression. Epoxy short lengths of carbon tow or strip into the grooves and blot off excess epoxy. Wrap with stretchy electrical tape until cured. Grind/sand smooth. Wrap with one layer of thin carbon cloth, epoxy, blot well, and wrap with tape again. Sand & paint.
tom1968 is offline Find More Posts by tom1968
Reply With Quote
Old Jun 23, 2014, 10:33 PM
Mesa AZ, it's a dry heat!
USA, AZ, Mesa
Joined Oct 2004
626 Posts
While tom1968 has good idea for a f/g boom, for a tube boom an internal tube of 2 or 3 inches in length that is a snug fit in the area of the break, epoxied in place, will make a stronger repair, and require less finishing.
I have used this method with good results.

Iain
rev.iain is offline Find More Posts by rev.iain
Reply With Quote
Old Jun 24, 2014, 03:55 AM
Registered User
Romania, Dolj, Craiova
Joined Sep 2007
15,410 Posts
You can find in EU, close to you with decent shipping, such booms from two sources:
http://www.topmodelcz.cz/index.php?d...u_eshop_id=672
http://clm-pro.com/accessories
renatoa is online now Find More Posts by renatoa
Reply With Quote
Old Jun 24, 2014, 04:37 AM
Registered User
Joined Jun 2014
12 Posts
Thanks for all the suggestions. I like the idea of adding a smaller diameter carbon tube to the inside, but not sure I have enough space to get it into the boom from the pod end. its an F5J glider so space is tight.

Also the idea of grinding lines and adding spars seems good, but the carbon tube is a little thin. So i think the only alternative left to me is to wrap it with glass or maybe some carbon tape and then epoxy or add spars on the outside and have an ugly glider.

Of course my other option is to buy another boom and replace it, but im not sure how easy it will be to remove all the currently epoxied parts, rudder and elevator mounts and push rod tubes etc...

If anyone else has any bright ideas which can stop me from crying like a big baby please post
toneeeee is offline Find More Posts by toneeeee
Reply With Quote
Old Jun 24, 2014, 05:20 AM
Registered User
martinh's Avatar
United Kingdom, England, Fleet
Joined Aug 2002
544 Posts
I'm gutted for you Toneeeee,

Check out this article from Tony at Sloperacer - Tony knows his stuff!

http://sloperacer.blogspot.co.uk/p/fu-fix-fixes.html

Scroll down for the boom repair part. May be some ideas for you there.

Good luck,

Martin
martinh is offline Find More Posts by martinh
Reply With Quote
Old Jun 24, 2014, 10:32 AM
Dean
A10FLYR's Avatar
USA, CO, Littleton
Joined Apr 2005
3,902 Posts
Tony does it right, use more layers of light weight glass/carbon on bias. I prefer to use a dart shaped piece of material starting with the narrow end on the boom. That way each layer tends to hide the edges of the previous layer.
A10FLYR is offline Find More Posts by A10FLYR
Reply With Quote
Old Jun 24, 2014, 11:19 AM
Fight On!
mario alvarez's Avatar
San Salvador, El Salvador
Joined May 2001
605 Posts
Why don't you reinforce it with a hollow carbon rod with an OD as the ID of the boom?
mario alvarez is offline Find More Posts by mario alvarez
Reply With Quote
Old Jun 24, 2014, 06:10 PM
Registered User
martinh's Avatar
United Kingdom, England, Fleet
Joined Aug 2002
544 Posts
Quote:
Originally Posted by mario alvarez View Post
Why don't you reinforce it with a hollow carbon rod with an OD as the ID of the boom?
Yes, this is the best way.

Then a layer or two of very light cloth and epoxy laminating resin on top.

Will be stronger than before and hardly noticeable.

Martin
martinh is offline Find More Posts by martinh
Reply With Quote
Old Jun 25, 2014, 03:27 PM
Registered User
Joined Jun 2014
12 Posts
Thanks for all the replies everyone! So I have got hold of some carbon tape and I have about 10 minutes ago wrapped it and glued it. Ive taken some pictures of the process I have done, its my first ever job like this and im sure I havent done a brilliant job, but lets hope its ok. Ill post the pics once done.
toneeeee is offline Find More Posts by toneeeee
Reply With Quote
Old Jun 25, 2014, 05:40 PM
Registered User
Lenny970's Avatar
Greeley, Colorado, USA
Joined Feb 2000
2,911 Posts
Quote:
Originally Posted by toneeeee View Post
Thanks for all the replies everyone! So I have got hold of some carbon tape and I have about 10 minutes ago wrapped it and glued it. Ive taken some pictures of the process I have done, its my first ever job like this and im sure I havent done a brilliant job, but lets hope its ok. Ill post the pics once done.
Great! You will learn by doing it and the next time will be easier.

Lenny
Lenny970 is offline Find More Posts by Lenny970
Reply With Quote
Old Jun 26, 2014, 04:25 AM
Tassie Electric, Heli, Glider
ChrisJ800's Avatar
Hobart, Australia
Joined Oct 2002
2,639 Posts
If you have an Archery shop nearby they are a good source of fiberglass and carbon tubes to make arrows! I passed a shop and bought a lot and found out the local hobby shops were buying them too and selling at inflated prices!
ChrisJ800 is online now Find More Posts by ChrisJ800
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold Quadframe Medium Weight hex with carbon booms acuralegendz Aircraft - Electric - Multirotor (FS/W) 0 Nov 09, 2013 11:14 AM
Mini-HowTo Tutorial: Wood/Carbon Hybrid Booms zpack Multirotor Talk 0 Sep 18, 2013 10:52 AM
How I fix broken carbon Boom treehog Hand Launch 3 Mar 06, 2005 04:52 PM
First broken carbon fiber boom rbrown3rd Electric Heli Talk 19 Feb 24, 2005 10:09 PM
Anyone good with carbon fiber? (Broken boom on Skywave - pic) Kodiak Flyer Parkflyers 1 Feb 06, 2003 05:17 PM