HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 03, 2013, 04:06 PM
Always more to Xplore
SoaringDude's Avatar
near Sacramento, CA
Joined Aug 2010
737 Posts
Tuan, have you measured the servo current that would be continuously drawn at elev neutral with your spring choice? If I understand the setup you're proposing, with constant spring pressure comes constant servo current.

Chris B.
SoaringDude is online now Find More Posts by SoaringDude
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 03, 2013, 04:13 PM
Thermal Wrangler
DrFragnasty's Avatar
Launceston Tasmania
Joined Mar 2004
2,053 Posts
Kudos for trying it Tuan; it should work well and liberate a bit more weight.

Chris A.
DrFragnasty is offline Find More Posts by DrFragnasty
Reply With Quote
Old Jan 03, 2013, 05:39 PM
Daryl Perkins's Avatar
United States, VA, Falls Church
Joined Mar 2007
1,335 Posts
Tuan

They said the Wright Brothers were crazy too. I enjoy designing stuff and going outside the box to gain an advantage. You go, boy!!!

Best of luck!
Daryl Perkins is offline Find More Posts by Daryl Perkins
Reply With Quote
Old Jan 03, 2013, 07:22 PM
Registered User
San Diego
Joined Aug 2004
2,064 Posts
Quote:
Originally Posted by SoaringDude View Post
Tuan, have you measured the servo current that would be continuously drawn at elev neutral with your spring choice? If I understand the setup you're proposing, with constant spring pressure comes constant servo current.

Chris B.
This can be addressed by a second spring at the servo to balance the load of the spring at the bell crank.

Tom
Kiesling is online now Find More Posts by Kiesling
Reply With Quote
Old Jan 03, 2013, 07:39 PM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
3,174 Posts
Quote:
Originally Posted by Kiesling View Post
What if the pull cord breaks? Probably not likely, but something to think about.

I also wonder about the flutter response of such a soft system.

I also wonder about the power of down input - especially at full down. It would suck to soften the down response when you push into the bucket before the zoom.

I know you're going to do it anyway but I'm still not sure what problem it will solve (the linkage on my Xplorer stabs is plenty tight).

Let us know how it goes!

Tom
I already though of that and have 2 separate kevlar threads in there for redundancy. They are same length and tied to the holes individually.

The "softness" I am not 100% sure, of but there's still 5 ounces of force when ele is full down. Down ele for the dip during launch is maybe 5 degrees but with the G's of the tail adding to the down force during this maneuver, I don't think there should be any problems.

Quote:
Originally Posted by SoaringDude View Post
Tuan, have you measured the servo current that would be continuously drawn at elev neutral with your spring choice? If I understand the setup you're proposing, with constant spring pressure comes constant servo current.

Chris B.
Roy suggested to use a counter spring at servo end and should be good to alleviate most of the pressure.

Quote:
Originally Posted by tewatson View Post
+100. This is a high-risk, very low-return modification (I would even argue that someone flying a properly set up stock plane and one with this setup could not feel a performance difference, in any way). In addition, most of the fields we fly in SoCal are surrounded by residential areas. I would hate to see a plane go in to one as a result of a quest to drop a few grams from an 1,800 gram airframe.

Tom
The only higher risk would be the spring malfunctioning. In this instance, I should still have control of the plane. The risk of both kevlar stings breaking would be less than that of the stab actuating rod coming apart.

Quote:
Originally Posted by target View Post
You will save more weight by simply ripping out the (IMO heavy-ish) stock pushrod housing and replacing the whole shooting match with some etched teflon tubing and a small-ish diameter CF rod (maybe .050"?)...
If you want to run a light spring also, then you will eliminate any possible (but likely improbable) double centering, and STILL have the capability of pushing with the linkage if the spring ever comes loose or breaks.

My 2 cents.

R,
Target
I thought about this when I redid the rudder pushrod in CF on one of the X's a couple years ago and actually ordered some pushrods in etched teflon from Kennedy composites, but was not 100% confident in the setup because of the difficulty in getting a good bond of housing to fuse and the .05" rod just seems fragile.
I might still go this route with the stock tubes, spring and kevlar string. The .05" rod with Hayes clevises weights 4.5 g and savings would then be about 8g.
Btw, the hollow rudder rod is only 7g with the L bend.
Tom[/QUOTE]


Quote:
Originally Posted by Daryl Perkins View Post
Tuan

They said the Wright Brothers were crazy too. I enjoy designing stuff and going outside the box to gain an advantage. You go, boy!!!

Best of luck!
Thanks for the encouragement DP.
I also thought about pull-pull for ele ( looping the down ele string around a carbon rod attched to the vertical's subspar) which would be an easy implement if the ballast area was not used. Perhaps still do pull-pull with spring and run all 3 strings ( 2 for pull up ele) in existing guide rod.

Maybe it will be all placebo, but removing almost an an ounce total from the fuses ends would be "a lot" for pitch and yaw inertia.
fnnwizard is offline Find More Posts by fnnwizard
Last edited by fnnwizard; Jan 03, 2013 at 07:50 PM.
Reply With Quote
Old Jan 03, 2013, 07:58 PM
Registered User
San Diego
Joined Aug 2004
2,064 Posts
Well, if you're going to do it, you should really remove the pushrod housing and splooge used to hold it in place. Otherwise you're leaving a lot of weight on the table (maybe a full 5 grams).

Tom
Kiesling is online now Find More Posts by Kiesling
Last edited by Kiesling; Jan 03, 2013 at 08:04 PM.
Reply With Quote
Old Jan 03, 2013, 10:55 PM
or F, J, K, or even TD
FLY F3B's Avatar
Joined Jun 2007
2,899 Posts
For pull pull you should simply tie the lines to the top and bottom of the belcrank at same distance from pivot as servo arm... Voila!

Mike
of course you'd have to flip the belcrank and make a new one that was meant to work like that, but hey, its a project to tinker with so...
FLY F3B is offline Find More Posts by FLY F3B
Last edited by FLY F3B; Jan 04, 2013 at 01:00 PM. Reason: Must state that I understood that the current belcrank would not work with my suggestion :)
Reply With Quote
Old Jan 04, 2013, 01:47 AM
Registered User
Tampere, Finland
Joined Oct 2009
140 Posts
What about using a guitar string for a pull line? I use 009 guitar string on my Dlg's, it withstands chafing better than kevlar.


Tommy
Tommy Wee is offline Find More Posts by Tommy Wee
Reply With Quote
Old Jan 04, 2013, 09:06 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
825 Posts
Quote:
Originally Posted by Tommy Wee View Post
What about using a guitar string for a pull line? I use 009 guitar string on my Dlg's, it withstands chafing better than kevlar.


Tommy
+1
And the added weight is less then a gram
roydor is offline Find More Posts by roydor
Reply With Quote
Old Jan 04, 2013, 01:59 PM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
3,174 Posts
Quote:
Originally Posted by FLY F3B View Post
For pull pull you should simply tie the lines to the top and bottom of the belcrank at same distance from pivot as servo arm... Voila!

Mike
of course you'd have to flip the belcrank and make a new one that was meant to work like that, but hey, its a project to tinker with so...
Not only that, but if you make a 180 style bellcrank there is not enough vertical room for the pull string to operate in any type of symmetric fashion.

For the X's style of pull, one end of the string is "free floating" and the one for down is "fixed" to a point. I have to figure the fixed point so that along the full travel the distance remains "close enough".

The servo end depends on if I have a fixed point or not (so that the string does not hit the ballast) and how far back the fixed point would be to determine if I need any type of "Ackerman" setup. The fixed point would be just a couple of guides the string would run inside of.

Here's a drawing I did to try and show in a more clear fashion. This is a crude drawing of the bellcrank and where the rear "pulley" (the blue cross) would be. Right now on my mockup it's just a pin back there for reference. What I am going to do is still use my spring, but initially have the down ele line un-tension enough so that the spring is doing all the down ele to test if the setup would work well and for how long.
In the drawing, red is center ele, green is up with magenta down ele.
fnnwizard is offline Find More Posts by fnnwizard
Last edited by fnnwizard; Jan 04, 2013 at 02:04 PM.
Reply With Quote
Old Jan 04, 2013, 02:22 PM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
3,174 Posts
Pictures to show pulley location for the down string, verifying close enough symmetric operation, etc.
fnnwizard is offline Find More Posts by fnnwizard
Reply With Quote
Old Jan 06, 2013, 09:50 PM
Flightcomp.com
ak79's Avatar
United States, CA, Torrance
Joined Apr 2006
1,585 Posts
I put some more stick time in on my 3.8 and I have to say that it is by far the nicest flying thermal sailplane I have ever piloted. CG at 123 and it feels awesome. I hope I can get my 3.5 to fly as good.
ak79 is offline Find More Posts by ak79
Site Sponsor
Reply With Quote
Old Jan 07, 2013, 12:05 AM
Thermal Wrangler
DrFragnasty's Avatar
Launceston Tasmania
Joined Mar 2004
2,053 Posts
Sounds good; can you expand on why it's the nicest you've flown ?
Chris (who's on the fence about getting a 3.5 or 3.8).
DrFragnasty is offline Find More Posts by DrFragnasty
Reply With Quote
Old Jan 07, 2013, 05:55 AM
PaulG
Newcastle, NSW Australia
Joined Dec 2004
294 Posts
maiden over

I just did the first few flights on my 3.8 X2. The weather with us today went from almost calm with a SE flow to strong E ( not sure, maybe 25 kph or more).
I just used some generic settings on it derived from my 4.0 X1. The first flights were a delight (apart from the launch, which took quite a bit of down elevator until it stopped stalling 1/2 way up the launch. Even with poor launches I was able to get my times and landings were very easy after I'd got the elevator compensation right. The plane had no bad tendencies and could be flown single stick (mode 2) most of the time. I played around with elevator/camber mix and camber on a slider. I came to the conclusion that both were good as long as the slider was used with sensitivity. Later on the wind got up and I started adding ballast. First 250 g, then 350g and finally 450g. The plane did not like the turbulent sea breeze with tiny rough thermals, I could not make my times. I changed to the Egida with 350g ballast and it was like chalk and cheese, the Egida ate the conditions and was as steady as a rock - still did not make my times but the plane as so controllable that I am sure if I had persevered I would have found enough lift to make time. By that time I had been at the field for 7 hrs, so decided I'd had enough. Horses for courses I think.
pigly is offline Find More Posts by pigly
Reply With Quote
Old Jan 07, 2013, 07:06 AM
Registered User
Sydney
Joined Mar 2005
80 Posts
Paul,
I've been flying the 3.8 x2's for around 9 months now and continue to be impressed. It does it all and at 1800g full strength is super light for our Aus conditions.

The biggest bonus is its legs especially when the wind gets up. Rarely do I need to use ballast (and if I do need to I've forgotten it), but when I have it doesnt change its feel. Like anything, there's no trade for stick time and learning your model. Pick one and it will do the job, X2, Egida or Aspire - but I have managed to convert the old man from the Aspire to the X2

fwiw Im still running the cg @ around 132 (no nose weight), it works. Tow hook all the way back. I've found the ideal camber setting to be around 5-6mm with elevater comp and done the dawn and dusk testing side by side comparisons to re-inforce it.

Chris, I have an order in for the X2 3.7 just to throw a spanner in the works!! With the larger centre section (bigger flap span) and smaller tips I think this might be my go to model. It will also give me all combo's to play with anyway. I like its geometry a little better too then the 3.8.

Cheers Matt
Lowey is offline Find More Posts by Lowey
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
New Product 0.9g Retracts Mk.II *NOW LASER CUT* Yellow Baron Scratchbuilt Indoor and Micro Models 2 May 29, 2012 04:38 AM
Wanted Hangar 9 Spitfire MK II 60 Parts cessnajfb Aircraft - Fuel - Airplanes (FS/W) 2 Mar 11, 2012 08:47 PM
Sold *Price Reduced* Saito FA-45 MK II sscherin Aircraft - Fuel - Engines and Accessories (FS/W) 1 Mar 11, 2012 12:06 PM
For Sale: Carl Goldberg Classic Falcon 56 mk II and Skylark 56 mk II kasra Aircraft - Fuel - Airplanes (FS/W) 2 Nov 22, 2004 03:35 AM