Bucker Jungmeister - First Scratch Build - Page 7 - RC Groups
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Oct 28, 2012, 10:01 PM
Registered User
vonJaerschky's Avatar
Pittsspecial has good advice. Nothing wrong with a second battery pack. This model can easily carry the extra ounce or two. The only thing I don't like about an extra battery is that generally it involved using an on/off switch, which is another failure point. Radio switches have always been a weak point in the chain. Of course adding a BEC is also adding a failure point, so pick your poison (or antidote, in this case!)
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Oct 28, 2012, 10:28 PM
What's 3D?
trumps's Avatar
i personally thing that the simpler the sytem the better, less joins, plugs, switches ect means less points for failure. a model running 4 servos should be easily powered by a decent quality switch type BEC.

Oct 29, 2012, 03:34 AM
eye4wings's Avatar
Having adopted the use of trim tabs on the larger control surfaces connected to act as servo assist to take load off the servos in the air I would be happy to use the existing ESC with the linear BEC. It has more capacity than average and so long as the servos you are using are not digital (I don't know the HS range) should be capable of working safely.

Having said that, much of my motivation for not replacing it for a new ESC would be the cost of units in that size.

The only rider I would add is that I would think you would be running at about 50 to 55A and not close to the 70A limit. If your static test is closer to the limit then maybe I would go for an ESC with switching BEC.

You'll have no trouble getting cooling air onto the ESC, but you may need to take a bit more care to ensure you have adequate outlet size (through the cockpit?) to ensure the flow of cooling air through the fuselage.
Last edited by eye4wings; Oct 29, 2012 at 03:41 AM.
Oct 29, 2012, 06:33 AM
Cut it twice, still too short
dglo's Avatar
I've already ordered the parkbec swiching bec. I plan on mounting both it and the esc on the sides of the motor mount box, there's plenty of room in the cowl behind the dummy radial. As the cowl is quite open at the rear there will be plenty of cooling air. But also as I understand it a switching bec doesn't reduce voltage through heat as a linear does, so that helps too.
Oct 29, 2012, 12:46 PM
eye4wings's Avatar
That is so dglo. And the heat produced in an integral linear ESC is often the reason for failure when running close to limit.
Oct 29, 2012, 01:43 PM
Right Rudder
PittSpecial's Avatar

To each their own....

Yes indeed, we all need to pick our setups based on what we all feel comfortable with.

As far as having Switches, I have lots of Traditional "GLOW SETUP" Switch harnesses that have worked flawlessly on my larger Glow-To-Electric conversions. The switch harness allows for you to work on any adjustments such as servo throw / travel etc.. without the need to have the potential of the Power System from being activated since it is completely Separate.

Again, I believe there are lots of Quality External BEC devices that one can use and very effectively, however, please do not exceed any parameters or this might happen (example):

lancairs_last_flight (0 min 54 sec)

Very Sad Results:

Happy Landings!
Nov 01, 2012, 08:09 PM
Cut it twice, still too short
dglo's Avatar
Been getting some odds and ends done. Made up a simple 1/8 ply motor mount box and got the motor mounted up. Then wrapped the motor in paper and tape so the dummy engine fits snug and figured out where the cowl needs to be. The four brass brackets were then JB welded to the cowl. The blue foam disc you see inside the cowl is to space the brackets from the rear edge of the cowl, which overlaps the firewall about a 1/4 inch.
Nov 01, 2012, 08:27 PM
Cut it twice, still too short
dglo's Avatar
Got the battery tray built, pretty straight forward there. Then figured in for a penny in for a pound. Frank made a fiberglass battery hatch and since I've done very little fiberglass work and need to make those very cool fenders, I might as well practice with the hatch. I think it came out pretty good, did it just the way Frank described in his thread. I was a little nervous about it coming off the packing tape but once I got a corner started it came right up.

One question though, even though the piece holds its shape well, it's pretty flexible, I was expecting it to be "stiffer". Is that pretty normal? Is it a matter of how many layers of cloth or the type of resin used? I used 4 layers of 2 oz cloth and Great Planes epoxy finishing resin.
Nov 02, 2012, 10:19 AM
Registered User
LesUyeda's Avatar
"Is that pretty normal? Is it a matter of how many layers of cloth or the type of resin used?"

Both. Seems like I used to use several layers of 6 oz. cloth, and epoxy resin.

Nov 02, 2012, 10:31 AM
Registered User
vonJaerschky's Avatar
Looks good! Mine is fairly flexible, too. But it isn't a structural part and does nothing but sit there, so it doesn't matter that it is flexible.
Nov 02, 2012, 05:17 PM
Registered User
2 oz cloth is pretty light weight, use what ya got, but biasing the layers so the weave is 45 degrees different from the previous layer adds a little more strength. Top layer being a lighter cloth like 2 oz or 0.75 oz helps reduce "imprinting" where the weave is visible. There are different weaves used for different properties with plain weave generally being cheapest. Satin weave being smoothest finish and better drapeability; conforming to curved surfaces. Sometimes the term like 4hs is used to tell you it is a harness satin weave with 4 cross threads for every straight thread...not quite the correct terms but, hopefully it conveys the concept.
Flexible isn't as brittle.
You can sand the underside and add a stiffening rib but I wouldn't; as anything that could be pushed into the lipo would destroy it or cause it to be damaged and thereby destroyed.
Nov 04, 2012, 02:06 PM
Cut it twice, still too short
dglo's Avatar
Thanks for the tips, and you're right, flexible is probably better for the hatch cover.

Got some paint work done. After sanding the cowl smooth, primer and white paint, had to figure out a way to mask the cowl bumps for painting red. Worked out well but it took a while to lay out the shape of the bumps on a sheet of plastic and trim and sand to the right shape. Pictures tell the story.

Each cowl bump gets trimmed with 1/16" striping tape but I don't know wether it is better to stripe it first then spray with polycrylic or spray it then stripe it, any suggestions? Already did a test piece and the striping tape is not affected by the poly.

Also got started on the LG fairings, the checkerboard is going much better than on the tail feathers, not sure why.

Nov 04, 2012, 07:07 PM
Registered User
Bill Smudge's Avatar
Doug your doing a great job on this one.

Enjoying your build thread build thread.

Nov 04, 2012, 08:20 PM
Right Rudder
PittSpecial's Avatar

Just a wonderful and skill work! It is turning out the best modeling work I have seen in a long time.

Thanks for the Painter's Blue tape trick! Oh, that template for the cowling are just perfect!

Nov 04, 2012, 09:55 PM
Registered User
Well, the easiest metod would be to mask a pinstripe of your base color, white, to be between the outer paint mask that protects your cowl white paint job. Then you seal the edges of your mask or burnish the edges of the mask down. Then you mist your red on building up evenly as some reds are fairly transparent. Then the masks come off for the overall cowl and pinstripe. Small pinstripes are very difficult on small models. Some times it is easier to take your pattern to a vinyl sign person for them to cut you a mask. That way you can carefully remove the bubble for the blister and the area for the red pinstripe. With alignment marks it is easier to place the mask. Once it is pressed down it works as well as frisket. Lower tack vinyl for paint masks is available, just not every sign shop will carry it. The regular stuff is likely to be too hard to remove without removing paint or worse.
Not a cheap route but easier.

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