Carbon fiber stretch tail boom for protos 500?

[flint723]

Anyone know if these are available anywhere? I see msh makes a carbon fiber non stretch boom. I did find this on ebay:

http://www.ebay.com/itm/2pcs-17MM-OD...item337e3f3162

It's the correct size, 17mm, but the stretch boom measures 506mm.... It might actually work anyway being 6mm shorter if I just make the slots not quite as deep on the front of the boom so it won't slide in as far. I'm not sure I want to pay that much though.

Any ideas?

Also does anyone know if the non stretch cf boom is actually lighter than then aluminum one?

[scott s]

My experience with carbon booms is that they resonate badly and amplify vibrations badly !! Unless you can get one with an aluminum core I would avoid them like the plauge LOL!

[Dr. M]

1) it'll be difficult for you to accurately cut the slots in the tube ends, even if you have a lathe, or CNC machine. nearly impossible without proper equipment. Don't think you can just dremel those slots.
2) Unless properly grounded, you'll have electrical storms around your boom from all the static. And it's really hard to reliably ground CF.

Otherwise, I've had good results with CF booms on my 450, but bigger machines are hit and miss. For some it'll work, while for others they'll create vibes, resonances, ESD issues, and COG/ balance problems.

[flint723]

What I was planning to do was build a double fence on my drill press that I can slide the tube in between, then use a carbide end mill in the drill press, and just slide the tube in between the fences to cut the slots.

Vibs/resonance should not be much of an issue for me since I run pretty low head speed (1800-2200). But ESD could definitely be a problem.

But I suspect it probably isn't worth the hassle/cost for the minimal/unknown weight savings. I was just kind of testing the idea out.

Still, if someone wanted to give it a try with me, I would be happy to buy those ones on ebay, cut the slots and holes, and mail one of them to you for $17. If no takers, then I will just scrap the idea, as its not worth $30 to me.

[scott s]

Originally Posted by flint723

What I was planning to do was build a double fence on my drill press that I can slide the tube in between, then use a carbide end mill in the drill press, and just slide the tube in between the fences to cut the slots.

Vibs/resonance should not be much of an issue for me since I run pretty low head speed (1800-2200). But ESD could definitely be a problem.

But I suspect it probably isn't worth the hassle/cost for the minimal/unknown weight savings. I was just kind of testing the idea out.

Still, if someone wanted to give it a try with me, I would be happy to buy those ones on ebay, cut the slots and holes, and mail one of them to you for $17. If no takers, then I will just scrap the idea, as its not worth $30 to me.

Actualy I have found that low headspeed is worse than high headspeed with carbon booms. Both extruded type and the pretty woven bi directional types (expensive) I have tried them on all sorts of helis and have come to the conclusion that they are simply not worth the money or aggravation from vibes and believe me they can be disaterously BAD!. There will be a wide rpm range that will just vibrate the tail and whole heli like you won't believe. As I stated the aluminum wraped in woven carbon seems to eliminate this but these are hard to come by. Just not worth it IMO.

[flint723]

All right I will listen to the voices of experience and not try it for myself

Thanks guys.

[Dr. M]

Originally Posted by flint723

All right I will listen to the voices of experience and not try it for myself

Thanks guys.

Actually, I'd encourage you to try it. Just because it's difficult and a few problems are anticipated doesn't mean you need to stop. In fact, the only way to improve the hobby is for people to try new stuff, in spite of others claiming it can't be done, or wouldn't work.

Now you are aware of the possible issues, so you can take measures to prevent them. You seem to have a solid plan regarding cutting the slots (remember to use a vacuum to suck up the carbon dust, which is really dangerous). All that's left is for you to give it a try and see if it works. So, in the spirit of advancing the hobby and the Protos, I look forward to reading about your results

[Aleusius]

Hi,

I just love my streched Carbon fiber tail boom.

I got it from here:

http://www.goodluckbuy.com/17mm15mm-...00mm-long.html

Caren

[crickr1]

Originally Posted by Aleusius

Hi,

I just love my streched Carbon fiber tail boom.

I got it from here:

http://www.goodluckbuy.com/17mm15mm-...00mm-long.html

Caren

Like the TDR style landing gear, Did you make yourself or buy?

[Aleusius]

sorry, the landing gear it is a 100% self made...

[solex227]

Originally Posted by Aleusius

sorry, the landing gear it is a 100% self made...

Nice work!!

[Dr. M]

Originally Posted by solex227

Nice work!!

+1 sweet skidz

[Aleusius]

thanks...

[crickr1]

Originally Posted by Aleusius

sorry, the landing gear it is a 100% self made...

No need for apology , Very nice job

[flint723]

So I couldn't resist the temptation and I bought the cf tubes on ebay (from china). They arrived without damage. Sadly they are heavier than the stock aluminum ones. They weigh 37.9g for a 500mm stick and the stock stretch boom (506mm) weighs 34.4g. I went ahead and made it anyway, because I have no other use for 17mm cf tube. I clamped some square tubing to my drill press and made a jig I could slide the tubes in. Luckily, I had a carbide end mill that was exactly the right size. I cut the slots and drilled the hole (also with the end mill). The cf tube is ~5mm shorter than the stock boom so I just made the slots shorter. I installed the boom, scratched off the resin under the servo mount and put the grounding wire on. Checked resistance from tail case end of the boom to motor mount, 0 resistance. I did a test with no mains and there was no odd behavior or resonance so I took it out for a test flight. It worked flawlessly.

In summary, there was no benefit other than the CF boom is much stronger than the stock aluminum boom (if that is even a benefit). It has 1mm wall thickness vs the stock boom's ~0.5mm.

On a somewhat related topic, I recently tried a CF boom on my 450 pro (which had a known tail vib problem). It was terrible, resonance so bad the boom supports were a blur. I put the stock boom back on and it was fine.

[rossk]

nice work on the experiment, I think being stronger is not that bigger advantage, mainly in a crash, I would want the boom to bend before the the clamps/frame gets damaged.

PS. in your signature, should that be a 3226-900kv, not 2226-900kv?

[flint723]

I don't think it's an advantage really either, I'll probably stick the stock boom back on when I feel like it. I did notice the stock boom I took off had a slight curve to it... Not sure how that happened, it's never been crashed or even landed hard. No signs of belt rubbing inside it though, maybe it was that way from the factory.

Yeah it's supposed to be 3226, thanks for pointing that out ;o.

[Dr. M]

Awesome job! Thanks for showing us the process and results. Now, go show off to those guys who were telling you it's too hard, or it won't work...

[Aleusius]

Hi Flint,

very nice job!

I think the Carbon tube has some advantages:

No need to adjust the belt on different temperatures.

no vibrations, very solid!

very very resistible on crashes! Changing the tube is always lots of work.

Since I changed the tail boom I head 4 Crashes with no relation on the Carbon tube! even on my last one, when the Protos break in two half.



So keep the carbon tail tube!!!

Caren

[flint723]

Yeah now that you mention it, I had noticed that the belt tension seemed to get looser when flying outside in <30°F temps with the stock boom. I was thinking it was the belt itself, never thought of the aluminum boom shrinking.

And ouch, that crash must have been a good one! Good thing a frame is only $16 (here) right?