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Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

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Old 01-09-2013, 06:22 AM
  #1
i3dm
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Default Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

Hello guys,

im building an Xtreme Jets F-18C kit. the elevators come with what appears to be an aluminum shaft, and the bushings inside the fuse for this shaft to rotate in are brass.
Stock bushings hav the ID a bit too big, creating slop in the entire elevator, and i would like to fix this.

How would you guys recommend fixing this matter ? the difference between OD of the rod and ID of the bushings is small, so an adapter tube is out of the question.

please express your thoughts.
thanks.
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Old 01-09-2013, 06:28 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

Mine had no slop. Ask them for replacements.
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Old 01-09-2013, 06:42 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

its an old kit. i dont think its valid for anything but ill try.

would still love to fix it myself.
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Old 01-09-2013, 07:44 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

If you can get the bushings out, & know someone with a lathe, you could get new ones made quite easily.
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Old 01-09-2013, 07:52 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods


Quote:
ORIGINAL: Jim Cattanach

If you can get the bushings out, & know someone with a lathe, you could get new ones made quite easily.
thats one option i thought of. perhaps make new bushings out of Delrin and not brass ?
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Old 01-10-2013, 04:36 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

Black Delrin is an excellent bearing material for this type of application.

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Old 01-10-2013, 11:34 PM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

It appears that you have the 1st generation system for the flying stab. Although they do work they were inherently weak. Even if you improve the brass bushing size/fit you will still have a lot of servo to control surface slop due to a very flimsy wooden servo mount on those first generation kits. The later versions of that aircraft came with a combination ball bearing supported stab receiver and aluminum servo mount that was far superior in strength and eliminated the geometry slop completely. I suggest contacting the factory to purchase the upgraded stab units. I had a friend that did this and the conversion was not difficult and the results were fabulous. The other major modification I highly suggest is tieing in the former that is most rear the main hatch to the top of the fuse and the vertical stabs(in the early versions this former only contacts the bottom and sides of the inner fuselage and not the top). Otherwise the vertical stabs will be very flimsy at the root where they connect to the fuselage.
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Old 01-11-2013, 02:36 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

I had the same issue when I built my Skymaster F/A-18C back in 2006 (I think it was purchased in 2003).

I ended up replacing the Skymaster elevators with aluminium servo arm units and elevators from JetLegend.

Please see the following link for details=> http://www.rcuniverse.com/forum/m_48...tm.htm#4824046

It took some effort, but it was worth it. I don’t have any slop in the elevators and the model aircraft is still being flown at our major jet meets.

Regards,
George
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Old 01-11-2013, 03:00 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods


Quote:
ORIGINAL: HotelSierra

It appears that you have the 1st generation system for the flying stab. Although they do work they were inherently weak. Even if you improve the brass bushing size/fit you will still have a lot of servo to control surface slop due to a very flimsy wooden servo mount on those first generation kits. The later versions of that aircraft came with a combination ball bearing supported stab receiver and aluminum servo mount that was far superior in strength and eliminated the geometry slop completely. I suggest contacting the factory to purchase the upgraded stab units. I had a friend that did this and the conversion was not difficult and the results were fabulous. The other major modification I highly suggest is tieing in the former that is most rear the main hatch to the top of the fuse and the vertical stabs(in the early versions this former only contacts the bottom and sides of the inner fuselage and not the top). Otherwise the vertical stabs will be very flimsy at the root where they connect to the fuselage.
can you please explain which former exactly ?
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Old 01-11-2013, 03:05 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

I have also contacted John to ask for current replacement parts.
does anyone have pics of the aluminum / ball bearing mechnism used on this model today ?
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Old 01-11-2013, 04:52 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

Hi Lior, some time ago I learned in RCU about using some thin CA in the stab pivot, (with the stab removed, of course) to get rid of the slop. It worked great in my old version SM F-18 wich I think is the same of yours.


Enrique
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Old 01-11-2013, 05:02 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

The guys have covered it well above with their comments. I did a similar thing on mine when I built it 6 years ago. I will take some pics tonight and post for you to see.
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Old 01-11-2013, 09:03 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods


Quote:
ORIGINAL: erbroens

Hi Lior, some time ago I learned in RCU about using some thin CA in the stab pivot, (with the stab removed, of course) to get rid of the slop. It worked great in my old version SM F-18 wich I think is the same of yours.


Enrique
we tried that but it doesnt seem to adhere to the aluminum very well.

John has already agreed to supply updated parts (aluminum mount + bearings) so i think this is probably the best solution.
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Old 01-11-2013, 09:06 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods


Quote:
ORIGINAL: Craig B.

The guys have covered it well above with their comments. I did a similar thing on mine when I built it 6 years ago. I will take some pics tonight and post for you to see.
with which mechnism ?
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Old 01-11-2013, 06:42 PM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

Hi Lior,

With the original mechanism supplied with the kit. Will get photos up for you in the next couple of hours. Check those elevator mounts very carefully! I pulled mine out with 2 fingers!! and then re-glued them and reinforced them as they ply wood was prone to flex and distort allowing for more elevator slop.

Regards,

Craig.
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Old 01-12-2013, 03:36 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods


Quote:
ORIGINAL: Craig B.

Hi Lior,

With the original mechanism supplied with the kit. Will get photos up for you in the next couple of hours. Check those elevator mounts very carefully! I pulled mine out with 2 fingers!! and then re-glued them and reinforced them as they ply wood was prone to flex and distort allowing for more elevator slop.

Regards,

Craig.
OK, im waiting for those pictures.
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Old 01-12-2013, 03:48 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

This is the only picture i got from John so far.

and he is asking for 68$ for EMS shipping (Yikes!) [X(]
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Old 01-12-2013, 04:45 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

The servo mount units available from JetLegend have ball bearings fitted on both sides of the control arm to firmly support the elevator.
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Old 01-12-2013, 05:20 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

Quote:
ORIGINAL: i3dm

This is the only picture i got from John so far.

and he is asking for 68$ for EMS shipping (Yikes!) [X(]
Hi,

i think send the bearings with mounts by EMS is little expensive, I suggest by air mail the shipping is Free, i will send these parts to you from Taiwan by airmail, but the delivery time is a month ,

Best Regards

Anton
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Old 01-12-2013, 07:54 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods


Quote:
ORIGINAL: i3dm

This is the only picture i got from John so far.

and he is asking for 68$ for EMS shipping (Yikes!) [X(]
Hi Lior

You asked to send the wooden former also inside the package.The freight includes those former also.One note is ISRAEL is the most expensive shipping destination even by EMS here.The relatively cheaper shipping is by airmail and shipping can be free for you if you don't mind the arrival time.

Best regards

John
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Old 01-12-2013, 08:52 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

Quote:
ORIGINAL: johnzqh


Quote:
ORIGINAL: i3dm

This is the only picture i got from John so far.

and he is asking for 68$ for EMS shipping (Yikes!) [X(]
Hi Lior

You asked to send the wooden former also inside the package.The freight includes those former also.One note is ISRAEL is the most expensive shipping destination even by EMS here.The relatively cheaper shipping is by airmail and shipping can be free for you if you don't mind the arrival time.

Best regards

John

Thank you John! that is a great offer - airmail is fine as long as it is registered with a tracking number.
but can you please post a pic of everything that is included (aluminum mounts, wooden former, bearings etc) ?

also can you confirm that the pivot shaft in the old model's elevators matches the bearings ?
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Old 01-12-2013, 10:21 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

Here you go Lior.....no matter what you need to stiffen up the plywood servo mount with some other woodwork. When I rigged up the servo, gave full up elevator and pushed the stab back the whole plywood support twisted allowing moe slop. These extra supports fixed the problem for me.....

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Old 01-12-2013, 11:59 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods


Quote:
ORIGINAL: Craig B.

Here you go Lior.....no matter what you need to stiffen up the plywood servo mount with some other woodwork. When I rigged up the servo, gave full up elevator and pushed the stab back the whole plywood support twisted allowing moe slop. These extra supports fixed the problem for me.....

Did you still use the bushings on the pivot shaft, or changed to ball bearings ?
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Old 01-13-2013, 03:13 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

I only used the original bushing and the original hardware Lior , BUT, I also lengthen then control horns used on all of my SKYMASTER jets. I make new horns out of 3mm aluminium that I bolt to the stock control arms. This allows me to lengthen the arms to the point that I almost double the length of the control arm and that goes a long way to reducing the slop in the system.
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Old 01-13-2013, 03:23 AM
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Default RE: Removing slop in Skymaster / Xtreme Jets F-18C elevator rods

Here is a pic of one such control horn extension...note that I added a locking nut on the ball link bolt after photo was taken...this was just a progress shot.
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