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Century Radikal E640 - Swift 16 NX
› SAB Carbon blades too long for HB Elite?
04-01-2005 10:37 AM  13 years agoPost 1
dajtw

rrNovice

London, UK

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Hi,

Anyone try these blades? I heard they were so good that I bought a pair for my Hummingbird Elite CP but first view was that it was somewhat longer than the stock wood blades and thought it _might_ just clip the tail rotor but hey, I thought the manufacturers would've thought about it. On running it though, it did indeed clip the rotor but thankfully things _look_ still intact. Thing is, the website where I bought it clearly says it is for the hummingbird CP or Hornet II. Specs are "SAB Symmetrical 255mm Ref: SAB370".

Now the question is, how on earth am I to fit these onto my hummer? I've heard about duct fans or something but I doubt this is the way? Any suggestions please? Much thanks in advance.

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04-01-2005 11:56 AM  13 years agoPost 2
growler

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Lisburn N.Ireland

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hi
im no expert but i was considering those blades as well.i have just got a hummer cp and i am finding that it is rubbish in the wind ,much worse than my fixed pitch.r the stock woodies at fault?do u have a direct drive tail on your cp?if not i think u will have to do this mod to run those bigger blades or extend ur tail boom.
hope this helps

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04-01-2005 06:22 PM  13 years agoPost 3
Tmaster

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TX

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You want more headspeed for the wind. Sense you guys have CP thats no problem; easiest way is to put a larger pinion on. Longer blades are not going to help. THey will just create more drag for the wind to grab, unless you get the headspeed up with the longer blades. Shortening the tail boom is better then making it longer for the same reasons. Shortening the flybar will give you a quicker responce for steering.
Heavier the heli the better too, try running a larger pack like 1200+ if your not already. Make sure your heli is balanced too.

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04-01-2005 09:40 PM  13 years agoPost 4
wilsonj

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Waikerie, South Australia

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Tmaster, I have to say your suggestions are only good if you are trying to combat wind.

Otherwise you want the heli as light as possible

Bigger disc will add stability

Longer boom will give more tail authority

Faster headspeed will actually increase twitchyness, as cyclic speed will increase.

dajtw,

you need to mount a direct drive tail. You will want this anyway, as the longer blades will create more torque, and the stock tail probably won't keep up.

I experimented breifly with extending the boom to get more authority. It did help, but its still not up to a shaft driven tail like on the pro. But it is still very good.

I have a tail kit that costs $30AUD, about $23USD that includes the motor, tail blade and new fin and mount. A friend makes them. I can email you a pic if you are interested, just PM me.

Regards
Jamie Wilson

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04-01-2005 10:03 PM  13 years agoPost 5
Tmaster

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TX

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Tmaster, I have to say your suggestions are only good if you are trying to combat wind.
yep!

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04-02-2005 06:13 AM  13 years agoPost 6
Rob_T

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..

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I just put some home made CF symmetric 255mm blades on my CP. They're tip weighted (I re-used the weights from a set of Century woodies) and weigh 20.8g each (a bit heavy...)

I really liked the result so I'd say go for it!

I have a direct drive tail (3x3 prop) and high authority tail motor, so there is no problem with chopping the tail blades off!

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04-04-2005 10:21 AM  13 years agoPost 7
dajtw

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London, UK

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Much thanks for all the comments. It seems that the suggested solution to my problem with 255mm carbon blades is to install a direct drive for teh tail rotor? Excuse my ignorance, but how would a direct drive be able to 'miss' the longer main rotors? I can see how the tail boom extension can resolve the issue as the tail rotor will be further away from the main rotor but how would a direct drive allow the tail rotor to avoid the main rotor?

For TMaster's info, I didn't really install the SAB carbons to combat wind problems but mainly because the CF blades are tougher than the wooden ones!! Flying inside a dinky flat is treacherous and I'm not keen on replacing those feeble and expensive wooden rotors every time it clips a door or something; my old hummer FP used to go around chipping the furniture which was (believe it or not) much more amenable!!

Thanks again all!

p.s. how easy is it for the shaft on the hummer CP to be bent? Looks solid enough but I do seem to note that the main head gear seems to be wobbly when spinning even when the blades are in-line. Just wondering if the shaft's busted... thanks!

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04-04-2005 10:29 AM  13 years agoPost 8
wilsonj

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Waikerie, South Australia

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The direct drive uses a much smaller GWS prop. 3020 or equiv.

Carbon blades will chip and break as easy as the wooden ones if you hit furniture!

Shaft bends easy on the hummer. But your wobble probably comes fromthe fact that the hole the shaft fits into in the head is sloppy. Allowing the head to teeter on the pin holding it on. On the PRO they have a collar at the bottom to fix this problem. Actually from memory the head was ok, but the masts are slightly undersized. I made a 3mm stainless mast and it was a much tigher fit.

Regards
Jamie Wilson

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04-04-2005 10:47 AM  13 years agoPost 9
dajtw

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London, UK

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Ahh, ok... I guess the direct drive tail is a must then..

Thanks muchly for the suggestion that the head/shaft fitting is faulty. I think your suggestion is probably more likely than my suspicion of a bent shaft as the wobbling is not definite all the time; I'd say there's wobble 80% of the time with maybe around 20% there's no wobble.

Not sure if it'll help but I've ordered the CNC head, anti rotation gear, CNC rotor holders and some other things to try get this thing working properly! Hopefully, the cnc head will give a tighter fit on the shaft.

Some carbon blades have chipped concrete flying outside which is why I have more faith in teh resiliance of cf blades than wood... Though I'd have thought cf blades should be more brittle... Am looking forward to seeing how the DD might perform At this rate I'm never going to have time to build the X400!!

Thanks!!!

p.s. given the shaft feels soooo solid, why do you say it bends easily? I'd have thought that to be the least likely to break?

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04-04-2005 01:53 PM  13 years agoPost 10
wilsonj

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Waikerie, South Australia

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Unfortunately it doesn't take much to bend them. And it only takes the slightest bend to case vibration.I've rolled oneon glass and only just been able to see the shaft was bent,but it was the cause of vibration. Trust me I have bent dozens.

If you ordered the alloy head for the PRO then you will get the collar. This will stop the head rocking and make for a smoother heli.

What motor are you using? If you have a brushless motor with no cogging then the auto hub will do little more than add weight. You are n't going to be autoing this heli too often, if at all. Especially and survive. Better off with keeping the heli light as possible, to get best performance.

Do a search for "CP hummer goes 3D" To see the power you can get from a light hummer.

Regards
Jamie Wilson

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04-06-2005 04:04 AM  13 years agoPost 11
dajtw

rrNovice

London, UK

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Wilsonj, thx for sharing the info. You're right, despite my disbelief, the shaft was indeed bent. Noticed it when motor ran with just the shaft sticking up and the wobble was most definitely noticeable. Can't believe a simple crash (drop to floor, head first) can bend that thick shaft!

Didn't go for the allow head for pro; just the metal head for the elite series; don't think we have anything for the pro model over here yet except maybe just the pro model itself! What's this collar? Is it simply so that it lodges the head unit up a bit more so it doesn't sit on the dodgy pin?

Took your advice and discarded the auto hub, installed dd for tail rotor and first flight using new parts had it crashing all over the place and have now busted the see-saw bit so waiting for parts again! I'm using the stock brushed motor at the moment, motor upgrade will wait till I get this thing successfully in the air under full control!! Like someone else mentioned before, the flybar ball links are extremely tight such that movement is less easy than my Hummer FP... any tips on loosening the ball links? Tried squeezing the ball links with no apparent change.

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04-06-2005 04:45 AM  13 years agoPost 12
wilsonj

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Waikerie, South Australia

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Yes, the collar simply keeps the head tighter on the main mast. Otherwise it teeters on the pin.

All the balls should allow easy movement. If they are tight it will dramatically reduce the stability.

I carefully squeezed the links while on the balls. Also rotate the link while doing this. All a bit fiddly, but it will help.

Good luck

Regards
Jamie Wilson

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Century Radikal E640 - Swift 16 NX
› SAB Carbon blades too long for HB Elite?
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