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Aug 25, 2004, 09:24 AM
Registered User
Thread OP

Corona CF boom breaking with boom strikes?


I have a corona with matt's carbon fiber tail boom and belt drive. I had a boom strike on a semi-hard landing and my cf boom snaped in two like it was made with balsa! I was below hover throttle and throttling down. The rest of the heli is perfectly fine. The only thing keeping the two parts together was the belt. I didn't have any protection other that 3-4 strips of black electrical tape, but I thought these cf booms were supposed to handle this better?

Is this normal? The Aluminum boom bends/dents and the cf boom snaps...same difference to me it it can't handle a hit.
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Aug 25, 2004, 09:34 AM
Destroyer of G-10
askman's Avatar
I use 3/8" ID silicone tubing to protect it. The CF is more likely to snap than aluminum from boom strike, but it is stronger. With tubing protector, I only broke one CF boom in long time. With Al boom, I would bend it on hard crashes beside the denting, which I do not have to worry with CF.

it is not indestructable.. titanium boom would be, but hard to find in size without custom order and weighs twice as much...
Aug 25, 2004, 11:18 AM
Registered User
Dr Honda's Avatar
what did you think would happen?? Carbon is stiff... but is very brittle. Put on the Sillicon hose... that will help.

sorry to hear about the boom strike though.
Aug 25, 2004, 11:39 AM
---------Speed!!---------
Carbon boom far out last the stock boom. But, it can be broken. It sure seems like it has a preference as far as what it will take. I have had them tolerate nearly unlimitted abuse. Then, from out of nowhere, it snaps on a relatively minor hit. If it is hit just right, it will snap.

Matt.................
Aug 25, 2004, 12:16 PM
luc
luc
I plant balsa sticks too
luc's Avatar
after around 200 flights with CF boom, and at least 30 various types of crashes, I only managed to break one (free fall from 50 ft).
On my previous VE, after 60 flights, I tore down close to 10....that gives you an idea of the strength of the carbon boom on the corona...
Aug 25, 2004, 12:20 PM
Gravity Tester
KnimRod's Avatar
In my experience, having boom supports seemed to agravate the CF boom breakage problem significantly because the boom assembly becomes very rigid. Putting some types of shielding on the CF boom seemed to agravate the problem too. Without the shielding, the blade seemed to get deflected off the boom somewhat while with the shielding, the blade appears to bite into the shielding with the boom taking all of the blade impact impact force in one area. I stopped using the CF booms because I spent more $$ replacing CF booms than I did replacing stock booms. The stock aluminum booms can be repaired some of the time too. I've had pretty good results with the balsa tie-wrapped to my boom. I haven't damaged a single boom with the balsa on it though I've gone through several pieces of balsa in some pretty good prangs.
Aug 25, 2004, 01:07 PM
Registered User
Thread OP
I guess my blade hit it at the perfect spot. Because when I took off the boom, I couldn't break it by hand. These things are very strong when general force is applied.

Maybe I'll try creating a downward angled horizontal fin like /\ to deflect the blades better or at least take the brunt of the impact.
Aug 25, 2004, 08:21 PM
Destroyer of G-10
askman's Avatar
I use heavy walled silicone tubing. I've had hits where it cut the silicone surface, but did nothing to the boom. it cost less than buck a foot from mcmaster-carr. and it adds lot of strength to the boom . 3/8" ID that has to be slipped on with soap and water. works well for me


Aug 25, 2004, 08:29 PM
Addicted to flight since 1944
rbrown3rd's Avatar
Sweet looking Coronas Askman. Is that an 8 cell pack on the one on the left? I have one coming in from Battlepack. I managed a hundred flights on one 7 cell pack. It is time for a second pack so I broke down and ordered one.
Aug 25, 2004, 09:08 PM
Registered User
barneyj's Avatar
I have Matt's CF boom. It's survived my worst crash ever. My friend(??) flew his plane into my Corona while I was 40 ~ 50 feet up. Where the Corona generally suffers fairly minor damage regardless of the crash, the tally for this one included:

Mega motor pulled mounting bolts through keel (motor ok)
keel snapped vertically in front of the big wire pass-through hole
Both blades cracked
bent main shaft
ESC tore through canopy and died
Futaba GY240 died
8 cell battery pack snapped at several solder joints
tail input pinion and crown gears smashed several teeth each
Main gear lost teeth
one tail rotor blade cracked
tail fin cracked

Matt's CF tail boom had a small nick where the blade struck it. It's amazingly tough.

I think it depends on where and how it's struck. Sort of like coconuts. Bear with me, I'm from Hawaii - everyone here knows this... After you husk a coconut, you end up with this cannonball looking thing. It's super tough. but if you tap it in the right spot, it splits in two. Why bust coconuts? Because the good stuff is inside...

OK, so I'm not completely serious about the coconut analogy, but I believe it does have a lot to do with how and where it was struck.

Aloha
Aug 25, 2004, 09:57 PM
Destroyer of G-10
askman's Avatar
that is the saft 3200s. I have 4 packs of them, because I cannot spend time waiting for it to charge between flight. too much demand on my time from the wife and kids. 100 flight on one pack is fairly amazing. I could not have done that.

anyway, CF boom is tough. Only time I broke it, is when I landed on the tail. I crashed hard yesterday, and I found out I cracked the main rotor hub. oh well. that is why I have two birds. I will get new hubs with 7mm shaft set anyway. First time I actually cracked the hub.... If matt does not come thorugh, I will be making my own aluminum hub....
Last edited by askman; Aug 26, 2004 at 12:32 AM.
Aug 26, 2004, 05:52 AM
Addicted to flight since 1944
rbrown3rd's Avatar
I can see the advantages in having two Coronas. I can't believe I am saying that. I must be hooked. Isn't there some kind of program to help Corona addicts?
Aug 26, 2004, 11:03 AM
luc
luc
I plant balsa sticks too
luc's Avatar
Well, I sold my second one, as it costs a bunch of money to keep 2 of these upgraded helis...I will concentrate on one now...
Aug 26, 2004, 11:15 AM
Addicted to flight since 1944
rbrown3rd's Avatar
Quote:
Originally Posted by luc
Well, I sold my second one, as it costs a bunch of money to keep 2 of these upgraded helis...I will concentrate on one now...
Oh good. There is hope for you then. I know I could not afford to maintain two of them.
Aug 26, 2004, 11:19 AM
Addicted to flight since 1944
rbrown3rd's Avatar
Quote:
Originally Posted by askman
I use heavy walled silicone tubing. I've had hits where it cut the silicone surface, but did nothing to the boom. it cost less than buck a foot from mcmaster-carr. and it adds lot of strength to the boom . 3/8" ID that has to be slipped on with soap and water. works well for me
Got a part number or a URL to the Mcmaster-Carr website? I never saw so much stuff. Can't find it.


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