Light RC Magnum Build Thread

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Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 11:12 am

First, I would like to thank Sam for getting me involved in the testing of the 33" Magnum Lite. It turned out to be fun for me, plus I could see how much work Sam goes through to make sure he has the best version of a plane available before he takes it to production.

Next, there are just about as many ways to build a plane as there are guys building them. The sequence of the build is not critical. I am retired, so I typically use several 10 - 20 minute build sessions in a day. I'll glue some parts together, then leave and do something else until the glue dries. This may not work for many of you. Just figure out what works and do it.

Last, I've found it is really helpful to have a pair of build tables. Mine were made from a single 2'x4' sheet of ½" particle board. I cut four 5½"x24" legs off one end, then split the remaining 24"x26" down the middle. The legs were simply glued onto the work surfaces. The only critical thing is the legs have to be identical heights.

Let's get started:
Attachments
Magnum.JPG
Finished product. Mine weighs about 6½ ounces with 2S 450mah LiPO battery.
Foamie tables.JPG
Build tables. You will see the benefit of having these later.
Horizontal pieces.JPG
Gather all horizontal pieces and have available.
Vertical pieces.JPG
Gather all vertical pieces and set aside.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 11:28 am

I like to start by gluing in the wing spars and the brace for the elevator. While the glue is curing, go ahead and glue the top fuselage parts together and the bottom fuselage parts together. In my preproduction version the wing spar slots were cut a little deep, leaving gaps in the foam on the top of the wing. This resulted in some Welders Glue oozing out and ending up on the top of my wing. Sam said he changed the depth of the slot, so this shouldn't be an issue. If your spar slots are a bit on the deep side, you may want to tape over them on the top of the wing to keep glue from oozing out.
Attachments
Main wing spar glued in.JPG
Glue the two wing halves together and apply glue to the 3mmx1mm main spar. Insert spar.
Main wing spar - weighed down.JPG
Weigh wing down to keep it flat while glue cures.
Wing subspars.JPG
Glue 3mx1mm subspars in place. Also glue fuselage and stabilizer pieces on at this time. Weigh everything down until the glue dries. There are also 1mm diameter supports that glue into the slots in the aileron counterbalances. Glue them in at this time.
Wing supspars - weighed down.JPG
Weigh everything down to keep it flat while the glue dries.
Stabilizer spar.JPG
Glue 3mmx1mm support in elevator.
Fuselage top and bottom parts joined.JPG
While the horizontal portion of the plane is drying, glue the top fuselage parts together and the bottom fuselage parts together.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 11:46 am

Some guys won't like my next step and think I am building out of order, but this is where my two tables come in handy. If you don't have the dual table setup, glue on the bottom of the fuselage and all carbon fiber bracing before attaching the top of the fuselage.

Once the glue has cured, turn the horizontal portion wings, stabilizer, fuselage) over so the top shows. Glue the top of the fuselage to the horizontal assembly. Support everything to keep the fuselage straight and 90° to the horizontal.

After the glue on the top of the fuselage cures, flip the total assembly over and glue on the fuselage bottom. Once again support the fuselage bottom to keep it straight and 90° to the horizontal assembly.

When you glue the fuselage together at the aft end, be sure to include a length of 3mmx1mm carbon fiber. This is a fuselage support and also doubles as your tail skid.
Attachments
Fuselage top glued on and trued-1.JPG
Triangles used to keep fuselage top 90° to horizontal assembly.
Fuselage top glued on and trued-2.JPG
Also use triangles to keep fuselage top straight.
Fuselage bottom glued on and trued-1.JPG
Also use triangles to keep fuselage bottom straight. Note tables are pushed together to keep fuselage top straight and 90° while fuselage bottom is glued in place.
Fuselage bottom glued on and trued-2.JPG
Triangles used to keep fuselage top 90° to horizontal assembly.
Tail skid.JPG
Tail skids goes all the way to the horizontal portion of the fuselage. Kind of hard to tell from this picture because I took it after everything was completed.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 12:09 pm

OK, this is the part of construction that many guys dislike - installing the carbon fiber bracing. This is all done with 1mm diameter CF. Note: Some of these photos are from my build. Some are from Dave McDDD's. I don't think either of us did the CF the way Sam recommends. Go to the Light RC web site and look at the construction manual for the latest in how to do the CF.

I like to use a large T-pin to poke the holes through the foam prior to inserting the CF. This makes a cleaner hole and prevents tearing of the foam.

Once I am satisfied I have the holes in the right location and the CF is the right length, I put about ¼" of the CF into the tip of the Welders Glue tube to get a small amount of glue on the rod, then insert. I keep the CF in the hole in the vertical section of the fuselage while doing this. The glue will get pulled into the hole when inserting the other end of the CF into the wing.

When gluing the tubes for the motor mount on, locate them so motor torque will push them up against the fuselage. I have several of Sam's planes. The motor was installed this way on all of them. I've never had an issue with the motor mount tubes coming loose. Also, if you have the tubes protrude about 1/16" forward of the motor inset, then you have a little material available for trimming the tubes to adjust side or downthrust as needed to suit your tastes.
Attachments
Use T pin to start holes for CF.JPG
Use T-pin to start holes for CF.
Fuselage CF-keep fuselage perpendicular.JPG
Use triangles to keep lower fuselage perpendicular to horizontal assembly while installing CF.
Fuselage CF bracing - McDDD-1.jpg
This is Dave's CF bracing, which is closer to correct than mine is. CF bracing ties into landing gear and wing spars, making a rigid structure.
Motor mount tubes-front.JPG
These tubes were actually mounted in the wrong place and had to be removed and redone. This photo really just shows which side of the foam to put the tubes. Also the motor goes into the inset. These tubes as shown are too long.
Motor mounted.JPG
Motor mounted and ready to go, except for the chipped prop which has been replaced.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 12:37 pm

Main landing gear struts are made out of 3mmx1mm carbon fiber and cross through the bottom section of the fuselage and glue into the wing right behind the front spar.
Also assemble wheel pants and decide whether you want to use wheels or not. There are two brackets that are folded and glued to the wheel pants. Landing gear struts go through the slots in the brackets. Make sure you can get the landing gear strut through the brackets before the glue sets. I test fit the supports on the pants and marked where the slots for the gear went. Then I cut a small slot between the two marks. I made sure to avoid getting glue where the supports went through.
Sam includes optional foam wheels in the kit. Dave McDDD made plastic skids by heat shrinking soda bottle plastic over 2¼" diameter disks then cut to length and glued onto the wheel portion of the pant.
Attachments
Landing gear front.JPG
I pretty much guessed at the strut length and location of attachment. Mine were 7" long. They passed through the fuselage at the bottom stripe. Sam now includes slots in the fuselage and wing where the CF is supposed to attach.
Landing gear side.JPG
I swept my gear forward ¼". This was way too much. The pre-cut slots will give the proper angle on the landing gear.
Wheel pants and supports.JPG
The supports are mirror images. They are folded at the score lines and glued into the slot in the wheel pant. The higher slot on the support goes on the inside of the pant (closer to the fuselage).
Wheel pant supports glued on.JPG
Supports glued into place. Let glue cure before installing onto landing gear legs.
Wheel pant mounted.JPG
Wheel pant mounted.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 12:53 pm

Pretty much all that is left is to install the optional SFGs (side force generators) and radio.

All servos were glued on with hot melt glue. The nice things about using this type of glue are quickness and if you need to replace a servo later, it can be loosened by putting a little denatured alcohol on the glue joint.

Aileron servos are surface mounted below the wing with the servo arm protruding through a pre-cut slot in the wing. The control horns are on the top of the aileron. Pushrod is pretty much a straight shot of 1mm CF with a Z bend at each bend.

If you use Z bends, be careful to shield the foam from heat when shrinking the heat shrink tubing that holds the Z bend to the CF pushrod. I typically use a wet paper towel for this.

I mounted the elevator servo below the wing in a slot in the vertical portion of the lower fuselage. The servo arm protrudes through the horizontal fuselage. The elevator control horn is on the top of the elevator. There are three pushrod guides included for the elevator pushrod. These are evenly spaced between the servo arm and control horn. I think my pushrod was about 12" long, so my guides were 4" apart.
Attachments
Aileron servo.JPG
Aileron servo hot glued in place. Position so servo arm is centered in the slot and stays in the slot thoughout its entire range of throw.
Aileron pushrod.JPG
Pushrod is basically a straight shot to the control horn with a Z bend at each end.
Elevator servo.JPG
Elevator servo was mounted near the center of the aileron in a slot cut into the vertical section of the fuselage. The servo arm protrudes through a slot in the horizontal section of the fuselage.
Elevator pushrod and guides.JPG
Elevator pushrod with front two guides. Position the guides to keep the pushrod as straight as possible.
Elevator horn and guides.JPG
Elevator horn is on top of the elevator.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 1:12 pm

Rudder servo and SFGs were next.

Rudder servo was surface glued to the side of the fuselage. I considered locating it so the servo arm would come through the vertical portion of the fuselage. It turned out I would have had to add a servo extension to mount it this way, so I just surface mounted it.

SFGs were mounted just far enough inboard on the wing to avoid interfering with the bevel for the aileron hinge line. Sam includes a 4" square of foam in the kit. This is to be used as a square - to help align parts. I pinned it to the wing about 8" from the fuselage. The back edge of the foam was right on the main spar. The SFGs were glued on right next to the 4" foam square. The larger one was closer to the fuselage.

I used hot glue to glue both the receiver and ESC to the vertical portion of the fuselage, below the wing. My battery slides into a slot at the main spar above the wing. CG is right at the back spar.
Attachments
Rudder servo.JPG
Rudder servo surface glued to vertical fuselage just in front of elevator servo
Rudder control horn.JPG
Note - rudder control horn goes on the smooth side of the rudder, not the side bevelled for the hinge line.
Wing side force generators.JPG
SFG installation. I used a small drop of Welders where contact was made with the wing leading edge and the very end of the SFG, top and bottom.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 3:01 pm

Really nice build thread Bob! :nw:

I also really like your split building table. That's a great idea! :tu:
:hover: McDDD #415

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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 5:50 pm

Thanks Dave.

I forgot two other points:
All of my assembly was with Welders Glue. I used just over half of a tube.
My build went pretty quickly. I received my kit on a Tuesday around noon. I flew it Wednesday evening.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 5:53 pm

Very cool. Great idea on the little tables. I'm very particular in my builds and that would be a great way to resolve the squareness issues I fight.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 02, 2015 11:18 pm

I'm hoping a guy I know is watching this and decides I need a pair of those tables!!!

Here are a couple pics of the intended carbon structure.
IMG_1267.JPG

IMG_1268.JPG

What we are looking for is to create a multi-triangle structure. A sort of leaning pyramid that eliminates the torsional flex epp allows.

I'm also supplying some parts that Bob didn't have with the prototype. They allow you to beef up the gear a little.
IMG_1274.JPG


Working on instructions now, should have them up tonight or tomorrow night.
http://lightrc.com/wp-content/uploads/2 ... -33-V1.pdf
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Re: Light RC Magnum Build Thread

PostPosted: Thu Apr 23, 2015 4:00 pm

Finally got a few min to paint mine.
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Re: Light RC Magnum Build Thread

PostPosted: Tue Nov 10, 2015 4:33 pm

Following your thread during the build of my Magnum Lite--thanks, Bob :) How are those Spektrum A2020's holding up? Any problem with stripping gears? Are they tougher than the DS35 Eflite servos? I ordered/have 8 of the Power HD DS44mg's at 6g each; was thinking of those on tail surfaces, but maybe something lighter on the 'rons.

Anyone try these Solar 3.7g servos? http://www.hobbypartz.com/33p-solarservo-d229.html A guy had them on a light Depron biplane at our indoor last weekend, but he's not a hardcore 3d'er...
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Re: Light RC Magnum Build Thread

PostPosted: Tue Nov 10, 2015 4:37 pm

I have posted about these before....
https://www.hobbyking.com/hobbyking/sto ... ouse_.html

Have them in a RebelZ lite and a TH crack Yak.
You won't be sorry you tried them if you do!
They perform very very well.
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Re: Light RC Magnum Build Thread

PostPosted: Tue Nov 10, 2015 4:56 pm

Thanks, jrjr. Wonder if those are the same as the Power HD's I mentioned? Pretty close in spec--always nice to find a cheap servo that works well, even though that may be an oxymoron lol
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Re: Light RC Magnum Build Thread

PostPosted: Tue Nov 10, 2015 5:35 pm

wyo69cowboy wrote:Thanks, jrjr. Wonder if those are the same as the Power HD's I mentioned? Pretty close in spec--always nice to find a cheap servo that works well, even though that may be an oxymoron lol

I don't think so. These are 5.5V max. What that does for you is for the standard esc's bec of 5.0-5.1 or so volt output, it puts you toward the top of the voltage range for these servos which gives the higher speed and torque that they have to offer. They can also be used for 1S stuff such as DLG's. My RebelZ lite is amazing with these servos. No issues as yet either.
Jack

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Re: Light RC Magnum Build Thread

PostPosted: Tue Nov 10, 2015 6:09 pm

wyo69cowboy wrote:Following your thread during the build of my Magnum Lite--thanks, Bob :) How are those Spektrum A2020's holding up? Any problem with stripping gears? Are they tougher than the DS35 Eflite servos? I ordered/have 8 of the Power HD DS44mg's at 6g each; was thinking of those on tail surfaces, but maybe something lighter on the 'rons.

Anyone try these Solar 3.7g servos? http://www.hobbypartz.com/33p-solarservo-d229.html A guy had them on a light Depron biplane at our indoor last weekend, but he's not a hardcore 3d'er...

I have the Spektrum A2020 servos in five airplanes. When I got them they were only $8 apiece (I know that's a lot of money for some on this site). They have held up fine, no stripped gears. The only issue is on my Laser I get some jitter. I've been flying that plane for a couple of years now, so the servos probably have in excess of 600 flights.

I should point out that my indoor planes are all on 2S. I typically don't fly any faster than I need to for the maneuver I'm doing. If someone likes zipping around at full speed with 3S, the A2020s may not hold up.

I'd buy more of them if I could find them for $8 again.
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Re: Light RC Magnum Build Thread

PostPosted: Mon Feb 29, 2016 2:47 am

Got my new RebelZ knocked out. Started on the magnum tonight. I sure hope these lipos don't go poof! :shock: :lol:
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Re: Light RC Magnum Build Thread

PostPosted: Thu Mar 03, 2016 5:03 am

Well it only took me five months but I managed to eek out another beautiful LightRC Magnum!

The kit was wonderful as usuall. The only vise I had with it was the servo slots were too narrow for a regular size 9gram servos And the slots for the fuse tabs were also too narrow. A couple skiffs with sand paper on the tabs fixed it but until then it was impossible to get them in. Probably just a fluke with this one kit, though, because every other LRC kit I've built has not had any parts fit problems.

Hovered it in the back yard for a moment with a fresh 500mah 35c 3s VH pack and the PowerUp 43gram 1100kv motor swinging gemfan 9/4.7 and it had very smooth power but not enough to pull this 35" bird through all I know its capable of so, like my RebelZ's, this too will get the SK3 2826 1240kv motor.

I can't wait to get this thing in the warm spring air and splatter my new YouTube channel with this sexy beast! :rockoncool:

Another big applause for Sam for his raw talent at bringing 3D lovers some wicked foamies! :clap:
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Re: Light RC Magnum Build Thread

PostPosted: Thu Mar 03, 2016 5:10 am

I have to point out that, at the angle in the pic you can really see how nicely the scheme comes all together from the fuse , seamlessly onto the wing. Sam really thought that through and does a fine job paint each part for such clean intersections like that!
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