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Old Jan 09, 2009, 10:55 PM
a.k.a. Matt Nelson
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North Tustin, CA
Joined Oct 2008
1,752 Posts
Mount the B-900 tailboom

Attaching the tailboom to the fuse is quite simple, because all the critical alignment has already been done - we already got the vertical stab slot perpendicular to the wing. The fuse is basically a cargo bay - just glue it on.

First step is to glue in the bulkhead. The instructions don't specify exactly where to mount the bulkhead, but the illustrations indicate that it is just forward of the wing mount bay, so that's where I stuck it. It required a little bit of sanding - both around its perimeter to allow it to fit in the fuse, and also inside the hole, to allow the tailboom to fit easily. The hole in the bulkhead is off center - it goes closest to the bottom of the fuse. I simply glued it in with a light coat of 20min epoxy and let it cure.

To mount the boom to the bulkhead/fuse, I first attached the wings to the boom, since the wing-to-fuse relationship defines how far the tailboom needs to be inserted into the bulkhead. I smeared a little 20min epoxy around the front end of the boom and slid the whole works into the bulkhead.

20min epoxy gives plenty of working time, so I made sure the wing/boom assembly was comfortably fitted into the fuse, then glued the rear-most part of the fuse down to the tailboom with a couple drops of thin CA. The fuse will require a pinch to get it tight against the tailboom. This locks the tailboom/fuse geometry. After it set, I removed the wings, then dribbled a couple drops of thick CA down the boom to the rear-most part of the fuse to reinforce the joint from the other side.

Easy.

Next step: attach the tailfeathers.

-matt
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Old Jan 09, 2009, 11:31 PM
a.k.a. Matt Nelson
MattN's Avatar
North Tustin, CA
Joined Oct 2008
1,752 Posts
Mount the B-900 tail feathers

The first step in mounting the tail feathers is to prepare the horizontal stab mount. It's balsa, so I used the standard method of wrapping some sandpaper around the tailboom, then used that to sand the correct groove into the stab mount.

The next step is to attach the spring return for the elevator pull-spring system. The system used in the B-900 is a little "different" - you first drill a hole into the rear of the stab mount, then glue in a little coiled spring (see photo). The stab mount is then glued onto the stab with some medium CA. So far, so good, but then you have to bend the spring so that it will push the elevator surface upward. Bend a coiled spring. Ok, I'll try. As the attached photo indicates, I made a mess of it, but it seems to be doing its job. The little oval in the photo is a FRP bearing surface provided with the kit that is glued under the spring.

I honestly didn't know what to think about this spring method. It seems somewhat awkward to me, and I seriously considered skipping it altogether in favor of the staple-shaped music wire torsion spring method. But in the end, I figured "what the heck. let's just build it as provided." They seem to fly for Harry, so how bad could it be. I can always change springs later...

I first attached the vertical stab to the tailboom. It's the easiest to do. Slip it into the boom slot, get the control horn along side the boom and the hinge square to the boom, then drip some medium CA down the inside of the boom along the stab/boom lines of contact.

Then glue the horizontal stab onto the boom. This should be parallel to the wings, so I placed the assembled wing/fuse/boom assembly upside down on the workbench, then positioned the stab on the workbench directly under it's place on the boom. With both pieces laying on the bench, they are pretty much guaranteed to be parallel (unless your bench has some serious issues!). I dropped some medium CA on the stab mount, then rocked the tailboom down for a landing on the mount.

Both of these joints are reinforced with fiberglass. I figured I'd use CA to wet the glass, since it should be lighter than epoxy, and that's important for tails. My first attempt (on the vertical stab) was a mess. I positioned the glass, dropped some thick CA and squeegeed it out with a stick covered in wax paper. The thick CA gave me the working time I needed, but it turned out very rough and ugly. With that lesson learned, I tried a different method for the horizontal stab reinforcement. I cut the glass to length, hit it with a very fine mist of 3M-77, then positioned it on the joint. I got it all smoothed down tight to the surfaces, into crevices, etc. Then I hit it with a few drops of thin CA. Awesome. It immediately wetted the entire joint, and looked great. No hassle, no racing the clock, no ugly mess. The attached photo shows the dramatic difference.

The airframe is almost complete...

-matt
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Last edited by MattN; Jan 10, 2009 at 11:25 AM.
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Old Jan 09, 2009, 11:39 PM
a.k.a. Matt Nelson
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North Tustin, CA
Joined Oct 2008
1,752 Posts
Attaching throwing peg

This Binary-900 is my first DLG.

That said, I really don't have the experience to decide where to place the throwing peg. Paul Naton's DVD suggests cutting out a cardboard template and trying several positions out for size so you can find the best place. I did that, but all the locations I tried seemed kinda similar. In the end, I just put the peg in about the same location as the one in the photo in the instructions.

-matt
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Old Jan 09, 2009, 11:43 PM
a.k.a. Matt Nelson
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North Tustin, CA
Joined Oct 2008
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The finished Binary-900 Airframe

All that's left is installation of the radio gear! Good thing it's the weekend!

-matt
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Old Jan 10, 2009, 10:19 AM
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Yorba Linda Ca
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Beautiful model Matt, and thanks for posting your build log. I look forward to seeing how this model flies!


Wayne
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Old Jan 10, 2009, 11:04 AM
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Raleigh, NC
Joined Jan 2007
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Here's mine... I haven't started the build yet. I took photos of how well this plane was packed...
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Old Jan 10, 2009, 11:24 AM
a.k.a. Matt Nelson
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North Tustin, CA
Joined Oct 2008
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Quote:
Originally Posted by LittleG
Here's mine... I haven't started the build yet. I took photos of how well this plane was packed...
Looks like Peak Hobby has only one box size! I ordered a Binary-III and two Binary-900's (maximize my shipping dollars!). They shipped the Binary-III in a box the same size as yours, and the two B900's were simply added inside. They did a great job of tying down all the fuselages, booms and wings.
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Old Jan 11, 2009, 01:11 AM
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with the spring giving tension to the servo, would the binding cause the servo to be at load at all times? making the battery last less longer?
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Old Jan 11, 2009, 09:23 AM
a.k.a. Matt Nelson
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North Tustin, CA
Joined Oct 2008
1,752 Posts
Quote:
Originally Posted by Hoangsta
with the spring giving tension to the servo, would the binding cause the servo to be at load at all times? making the battery last less longer?
There's been a lot of discussion about that in these forums. Yes, it does put tension on the servo, so the servo has to continuously fight it. But in this case, it's really not too much of a battle, for two basic reasons:
  • The spring is really very weak. If you look at the first picture of me holding the stab mount, you can see that the spring is very small, and it simply doesn't push very hard on the elevator. This is OK, since the forces on the elevator are generally very small at the few millimeters of deflection they see. This is why the #1 concern for elevator servos is centering, not torque, holding power or speed. The spring is just strong enough to do it's job.
  • The gear train helps. The gearing between the motor and control horn is many-to-one, so the motor turn a LOT to get the horn to turn a few degrees. That helps this sort of control system. It is actually pretty hard to turn the control horn by grabbing it and turning, as you are trying to impart lots of turns on the motor. It tough to even overcome the friction in the gears - your biggest worry is stripping the gears rather than spinning the servo motor.

In fact, because of the two factors above, the servo holds with ease. This is easy to see when you turn off the power - the control surface stays put (with zero active effort by the servo). So the servo obviously isn't struggling.

If you search these forums for "pull-spring" you'll see lots of discussion. There are many ways to implement it (some very clever), and there are obviously lots of folks out there using pull-spring with no issues at all.

Actually, my biggest worry with this B900 is that once I install the servos, there won't be any way to adjust the control horns or pull lines on them. It's just too tight in the fuse to allow for access. So this will be a "install it and forget it" installation. I gotta get it right the first time!

-matt
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Old Jan 12, 2009, 01:04 AM
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Thanks for the explanation!! I think i understand how it works now. Just never had a model that required pull-spring setups. I usually just do pull pull setup with kevlar.
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Old Jan 20, 2009, 09:04 AM
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Component installation

Bump...

Have you installed the components in the B-900?

Quote:
Originally Posted by pivlrs
All that's left is installation of the radio gear! Good thing it's the weekend!

-matt
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Old Jan 20, 2009, 10:17 AM
a.k.a. Matt Nelson
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North Tustin, CA
Joined Oct 2008
1,752 Posts
Quote:
Originally Posted by LittleG
Bump...

Have you installed the components in the B-900?
NO, DANG IT! I've been away on business travel, and have had my weekends soaked up with other obligations. I'm hoping to get into the shop the next couple of evenings to get the gear installed.

Not all bad, tho. I've had time to ponder the best way to install the pull-pull/pull-spring control lines. The issue is that you need to drill holes through the bulkhead, then through the rear of the fuse for routing the lines. BUT, you don't want any more friction on them than necessary... So, how does one get all those holes placed/aligned to allow for a straight run of the lines? I've got some ideas, and will play with them next time I'm in the shop...

It really is frustrating! There's only a few hours of work left...

-m@
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Old Feb 02, 2009, 06:40 PM
Foamy Season is here! MX2#1
pitviper51's Avatar
Elizabethtown, Kentucky
Joined Nov 2005
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very nice looking lil glider, i found it on hobbyclub for more then mentioned above.. and really like it. looks fantasic to.. my ole alula is worn out and since the new ones are not out yet this looks like it could be a nice replacment. and looks like it would get much higher on tosses, for the similar wieght that it is.. tho i dought it will be as durable as the 'lula cant wait to hear how this goes, gonna search for videos
mike
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Old Feb 02, 2009, 07:01 PM
Foamy Season is here! MX2#1
pitviper51's Avatar
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ok, found the peak hobby site.. where are you guys ordering from? thanks.. i like the binary III but the 900 is sooo hot... i like what i see in the videos so far
mike
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Old Feb 02, 2009, 09:12 PM
a.k.a. Matt Nelson
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North Tustin, CA
Joined Oct 2008
1,752 Posts
Quote:
Originally Posted by pitviper51
ok, found the peak hobby site.. where are you guys ordering from? thanks.. i like the binary III but the 900 is sooo hot... i like what i see in the videos so far
mike
Ahem... read the first message in the tread! I purchased directly from Peak Hobby - they are extremely responsive, and I had the model in about a week. The only downside is that the shipping is a tad on the expensive side, so I bought three models at once. They all fit in the same box, so the shipping costs were less on a per-plane basis. I think it was about $55 for shipping.

-matt
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