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Pulse 40 Tail shake

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Pulse 40 Tail shake

Old 09-28-2008, 10:43 PM
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sinjin90
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Default Pulse 40 Tail shake

I have had my pulse most of this year and with a O.S. 55 in it with 11x7 prop at full speed level flight i can see the elevator slab shake violently. Nothing loose, just there thin elevator doesnt seem to hold up to high speed. Anyone else have this problem and any solutions? Dont seem to be enough wood in rudder slab and elevator slab to use wire to link them together.
Old 09-28-2008, 11:59 PM
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smwave
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Default RE: Pulse 40 Tail shake

I've got a Pulse XT 60 but I haven't seen this issue. Is the shake coming from the servo or are you seeing it move while airborne? I'd check your reciever and make sure that your not getting chatter on the frequency your flying on. It could also be a loose connection. If the tail is loose you may need to put some extra stringers in it. I'm also using a hi-torque servo for all the control surfaces. (Futaba S-3010). I've been flying the Pulse all summer, and haven't seen any issues with the elevator.
Old 09-29-2008, 12:46 AM
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sinjin90
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Default RE: Pulse 40 Tail shake

While flying high speed, the whole elevator slab moves up/down. Its ok at slow speeds just when im doing high speed dives or runway passes shakes big time. I cant figure a way to fix it.
Old 09-29-2008, 01:52 AM
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Default RE: Pulse 40 Tail shake


ORIGINAL: sinjin90

While flying high speed, the whole elevator slab moves up/down. Its ok at slow speeds just when im doing high speed dives or runway passes shakes big time. I cant figure a way to fix it.

G'day Mate,
Easy to fix, don't fly at high speed, it was never designed for a 55, & is not stressed for high speed.
Old 09-29-2008, 08:08 AM
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Default RE: Pulse 40 Tail shake

do you hear any noise while you are seeing this? could it be a flutter?
Old 09-29-2008, 09:43 PM
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sinjin90
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Default RE: Pulse 40 Tail shake

yes, does make noise when it goes by, what causes flutter?
Old 09-29-2008, 10:27 PM
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jrbmoto
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Default RE: Pulse 40 Tail shake

You have a serious problem on your hands. You need to slow that plane down, what size prop are you running? Flutter will ALWAYS lead to catistrogphic structural failure! The stress on the wood structure and its glue joints will eventually cause them to break apart. Not to mention the stress on the gears in your elevator servo. To answer your question, flutter can be caused by many different things. Sloppy control links, too much gap between your control surfaces (you should always seal the gaps with covering material) but usually its because of too much speed. Try a 12X6 prop, it will slow the plane down a bit and also give you better verticle performance and slower landing speeds

-Johnny-
Old 09-30-2008, 04:31 AM
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sinjin90
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Default RE: Pulse 40 Tail shake

Guess i might have to slow it down, but it looks so good tearing through the air. The elevator slab seems to wimpy made to me i would prefer a solid slab of wood. Might come down to makeing a solid wood one and replaceing theres.
Thanks guys for the imput.
Old 09-30-2008, 03:48 PM
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Default RE: Pulse 40 Tail shake

sinjin90, there are ways to cure flutter. Check out this thread in the Beginners section:

http://www.rcuniverse.com/forum/m_7996322/tm.htm

Bruce
Old 10-01-2008, 12:40 AM
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Default RE: Pulse 40 Tail shake

I found that the noise mine makes is actually the vibration of the engine, shaking the wheels in the wheel pants....Coupled with the air rushing by the gear, it makes an awesome screaming sound on a fast dive. I notice a small amount of movement on mine, but I am using an OS 70 Surpass II with a 12x8 APC prop. Perfect power, almost unlimited vertical.
Old 10-01-2008, 12:50 PM
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Default RE: Pulse 40 Tail shake


ORIGINAL: sinjin90

Guess i might have to slow it down, but it looks so good tearing through the air. The elevator slab seems to wimpy made to me i would prefer a solid slab of wood. Might come down to makeing a solid wood one and replaceing theres.
Thanks guys for the imput.
That will not necessarily cure it.

It can on occasion actually exacerbate the problem.

It would be easier to stiffen the elevators by installing a CF strut ( something I do on all of my planes ) and then also stiffening the control surface with a small CF rod inserted lengthwise.

Tighten up all linkages and if possible move or enhance the point where the control horn contacts the surface... e.g. put something under the horn, to make the contact area larger.

Adjust the linkages for maximum mechanical advantage as well.

All of this will act to deaden any harmonics that occur in flight...

Of course your best bet is to slow the plane down, by utilizing a lower PITCH but larger diameter prop.



Old 10-01-2008, 05:55 PM
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sinjin90
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Default RE: Pulse 40 Tail shake

good info, would like to stiffen up the whole elevator slab but since there is little wood there i think will be hard to do. Would like a strut system to go to the rudder and bottome of the fuse but dont see enough wood to tap into. Will keep working on it.
Old 10-01-2008, 06:36 PM
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Default RE: Pulse 40 Tail shake

You can cut two CF rods to an appropriate strut size.

I position the strut to where it will end up, allowing for about 1/8" overlap on either side.

I press it into the wood to make where it will end up.

I then use a dremel tool with a cylindrical bit to cut out a bit of balsa where the strut will go. The dremel is held at the same angle the CF rod will end up.

Once done, a bit of 6 minute epoxy goes into the resulting hole/cavity and I slide the strut in place.

Quite easy to do even when there is not a lot of depth to work with... I put struts on my Mini Pulse as well.


You can also take a brass rod and cut an angle into one side with a grinding/cutting wheel.

Once done put the rod on a drill and carefully guide it in with the drill going, laterally to add additional stiffening. Epoxy a CF rod in place.

I've done this to control surfaces too to help stiffen them. Easy and quick to do. It adds almost no weight.


Old 10-01-2008, 11:18 PM
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sinjin90
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Default RE: Pulse 40 Tail shake

I like that idea, opjose. Will look into doing that.
Old 10-02-2008, 12:53 AM
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Default RE: Pulse 40 Tail shake

Here's a typical CF strut install.

I used a thick CF rod I had on hand on this .60 sized Extra 300S.



Tailwheel and assembly cost a whopping $2.00 here : [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXLLB9&P=7]Click me![/link]
Old 10-02-2008, 11:40 AM
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sinjin90
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Default RE: Pulse 40 Tail shake

Nice pic opjose, Going to hobby store now will pick up some rod, also is that a o-ring around your clevis?
Old 10-04-2008, 10:45 PM
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Default RE: Pulse 40 Tail shake

A friend had the stab rip off of his XT 40 in a high speed dive...with obvious disasterous results.

IMO an easy fix would be to peel the covering off of the bottom of the stab and sheet it with 1/32 ply.
I did that on my H9 P-40 and it helped a lot.
Old 10-05-2008, 12:38 AM
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Default RE: Pulse 40 Tail shake

Putting in a strut does not require removing any covering, and adds more stiffness.
Old 10-06-2008, 04:08 PM
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sinjin90
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Default RE: Pulse 40 Tail shake

i bought some rod now to just sit down and do it. Darn mini Blade is fun to fly around the house, hard to get any work done.
Old 10-06-2008, 05:53 PM
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Default RE: Pulse 40 Tail shake


ORIGINAL: opjose

Putting in a strut does not require removing any covering, and adds more stiffness.

The strut will stiffen it against bending loads, but the sheeting will help much more as to twisting loads...tortional rigidity.

Either way, it's a good idea to try something to help the rather weak horiz. tail assembly.

Even on mine, with AXi 4120/14 elec. power, I can see it vibrating...although nowhere near as bad as my friends PNP version.
Old 10-08-2008, 11:41 AM
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Default RE: Pulse 40 Tail shake


ORIGINAL: proptop


The strut will stiffen it against bending loads, but the sheeting will help much more as to twisting loads...tortional rigidity.

Either way, it's a good idea to try something to help the rather weak horiz. tail assembly.
Yup, of course it also depends upon the thickness of the sheeting used.


The best combo would be to do both, but if you really need this much, you - MAY - be flying the plane a - BIT - outside it's intended flight regime..
Old 10-10-2008, 12:06 PM
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Default RE: Pulse 40 Tail shake

my question is, how fast is it moving? i have my pulse moving fast also, and i have no problems with it. could be somthing not put together right in the body of the plane, possible. of course i had somthing that fell on the elavator and i had to peel back the covering and reinforce it, so i guess that could also be why i have no problem
Old 10-10-2008, 08:42 PM
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Default RE: Pulse 40 Tail shake

Each airplane is just a little different...like the wood used during construction of one might be relatively hard balsa...while the wood of another's might be softer and therefore less rigid. Luck of the draw you might say?

Another thing we have figured out is to re-shrink the covering periodically...keep it tight and that will help. Use an iron, and make sure the covering is stuck to all of the structure to tie them all together.

Over the years, I have test flown many planes, and have had several horizontal stab (complete ) failures...usually because of "punky" or "pithy" balsa...which is very light and almost spongy. A few years ago there was a rash of stab failures on the early H9 P-51's, and Hellcats, and a few of the Seagull products...among others.

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