Carbon booms

[Rob43]

Guys - I've used carbon booms on other models, both were nitro. I have an X50 which I finally had a mild boom strike. It didn't severely damage the boom, but was enough that it dented the torque tube, so I had to replace it (went alum since it's my favorite beater).

My model has custom matte finish frames, and when I saw the Align matte finish boom, I had to have it.

Have any of you had problems with durability of the carbon wrapped Align booms?

[ticedoff8]

Durability? As in "does the carbon delaminate from the inner aluminum boom"? No, that has never happened to me.

I used the HN6097, but I stopped using them due the extra cost (4x the cost of the aluminum booms).
And, I was surprised that they are heavier than the aluminum.
So they are really about the "bling" factor

On my Raptor 90, the CF boom was 100% CF and lighter than the equivalent aluminum boom. But, also more expensive.

Hobbyking has 100% CF tailboom for the Trex 600 - and it is only $11 (2x the cost of the aluminum booms).
https://www.hobbyking.com/hobbyking/...s_HN6097_.html

Maybe it will work on the X50

[Rob43]

I meant for the 700N. I have a factory cf boom for the X50. Heard the boom is fragile and can fracture in flight near the boom block. That would be "unsettling".

[marc8090]

Don't use it! Fracturing behind the boom support clamp in flight is exactly what happened to one of mine. I don't, repeat DON'T have any audible hum since it is a known issue on the 700. That being said, I believe there is still a hidden resonance issue. I have switched to the aluminum boom. I like the bling of the carbon fiber, but not if it's going to cause a crash.

[Rob43]

Running the alum boom at the moment. I can hear an intermittent hum come and go. Always wondered where it might originate. Wonder if there is a way of attenuating it.

I am running KDE boom struts, the Align cross brace, and the tail pitch control is the KDE upgrade kit. Running the straight shaft with black gears out back with the V2 hub. 105 Cyclone tail blades. The machine seems extremely smooth and quiet to me, except for the low tone growl of the YS 91sr Long Stroke and Hatori muffler. Eventually going to upgrade to YS 91SRX Tareq or O.S. 105 HZ-R DRS.

[marc8090]

What tail ratio are you using? I believe that the ratios they have chosen are ones that create a resonance. All the issues started when they sped up the tails. There is an 89 page thread in the 700 electric section if you would like to do a little reading.

[Rob43]

Not sure. I have the black helical gears.

Edit: 104t auto-drive gear, 21t tail drive. 4.95:1

[DCflyer]

Originally Posted by marc8090

Don't use it! Fracturing behind the boom support clamp in flight is exactly what happened to one of mine. I don't, repeat DON'T have any audible hum since it is a known issue on the 700. That being said, I believe there is still a hidden resonance issue. I have switched to the aluminum boom. I like the bling of the carbon fiber, but not if it's going to cause a crash.

The resonance issue was due more to torque tube bearing placement and tail blades. In most cases, swapping from Aligns to Rail's fixed most people's tail hum.

In other cases, moving the torque tube bearings to an even greater offset position helped. I run 3 bearings in mine offset at different lengths to prevent a resonance stack.

Running the black gears out back also helps to strengthen the whole assembly as the tail shaft does not have a step down like the white gears do. This obviously requires you use the new and revised tail hub.

The carbon booms are proven stronger booms. I haven't seen nearly as many posts about them cracking at the tail case as I have on tail hum and tail shaft issues.

Rob, I have the same tail setup as far as gears go. Black 104T helical auto and 21T front drive. 4.95 ratio. This works well at 1900-2000rpm with 106 tail blades. If you run 115mm's you may be able to get away with the lower ratio that the electrics use. They run the 22T for a 4.73 ratio.

I actually tried out the 22T gear since I am gearing for 2050rpm, but once I installed it I took it right back out because the gear mesh as so tight. I guess I could have backed up my boom about 1mm, but i'll stick with the 21T for now.

I will say that I wish Align had gone with a larger diameter boom for their 700's. Most machines like the KDS and the Raptor E720 all use 20+mm booms which are very beefy.

Just make sure your boom supports and tail case bolts are nice and snug on the boom. Check these from time to time and retighten. I think the issue, on a nitro especially, is that they may loosen juuuust enough over time to allow the tiniest amount of back and forth play on the boom - eventually this will certainly cause this kind of failure.

[Rob43]

Thanks DC for your thoughts. Much appreciated. Also yours marc8090. It was good to consider the potential problems before experiencing them first hand!

I also took another parallel path as I enjoy messing with this stuff...

I found a carbon tube source.

http://www.ebay.com/itm/131285856782...%3AMEBIDX%3AIT

It's a 1000mm long section from which I can cut to fit, and slot and drill. It turns out to weigh slightly less than either the Align carbon boom (mine is 78g) or the alum boom, (95g). I weighed of these Align booms to know. The 1000mm tube is 98g. So, 785mm will come in around 77g. And it will be twice the wall thickness and 100% 3K carbon fiber. (If it gets here undamaged). I also happened to have a set of Rail 106's left over from another machine, so I fitted them on too. Also ordered the nifty KDE poly-lined boom clamp, and their support adapter fasteners. Make a nice little project some rainy Saturday at the bench.

For anyone interested in a DIY carbon boom, they offer other finishes too. I have a one-off set of frames which are very unique looking that are matte finish, so the prospect of a matching boom was interesting to me. I know it's nuts since the alum booms come in a pkg of two for about $9.

[Rob43]

I received the carbon tube this week. Looks as good as I hoped. I test fit the torque tube grommet to see if I'd have any trouble with it. It's a bit more snug than the fit with stock boom, but not a problem. The finish is very nice, and it's a heck of a stiff piece.

I will cut and slot it soon and fit it up. The stock matte carbon boom is still pretty nice, though. Just not likely as tough as the 100% CF tube.