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Old Jan 15, 2013, 09:44 AM
Slip the surly bonds...
Sopwith Mike's Avatar
Christchurch,England
Joined Aug 2004
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1.5 bass struts should be more than adequate at the weight you guys are building to. Maybe a direct comparison between a bass strut set and a balsa set with thin CF rod as reinforcement would be an idea? I don't think there would be much difference, but the CF rod ends are useful for attaching the UC to the fuz.

BTW, could you please point me at the motor/prop/SC/RX/servo set-up you are using? What for instance are UMX and UM? I have a 2oz biplane I'd like to get back into the air and the old 35mHz set-up I had was lost on the conversion to 2.4 gig. If it's any help I have the HK micro RX and 2 of their litle servos, but can't find an RX or SC with the same plug/socket arrangement.

Mike
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Old Jan 15, 2013, 10:15 AM
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glewis's Avatar
USA, FL, Tampa
Joined Jul 2002
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I'm on the fence on the strength of the bass struts. It's not so much the woods ability to withstand normal landing loads but the sideways shear and torque loads applied in a ground loop. Ground loops are common when landing these WWI models when I'm on the sticks... Well ground loops and noseovers too.

This is the stuff I refer to as the UM (ultra micro) equipment. UM is Parkzone's name for this line of small models.
The receiver and esc plus the rudder and elevator servos are all contained on the AR6400 receiver circuit board and is commonly referred to as a 'brick'.
The servos are a linear output arrangement instead of rotary as is customary. The motor is a coreless brushed motor that is 8.5mm in diameter and is contained in a gearbox. The prop shaft is threaded on the end making prop installation easy. The power comes from a single cell lipo 160mAh in capacity.

UMX is another Parkzone product name. I'm not real familiar with it, but I think it is the receiver with integrated brushless ESC. This unit does not contain any on board servos. Is power comes from a 2 cell battery. More power, but as is always the case, more weight.
Hope this helps.

Glenn
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Old Jan 15, 2013, 06:47 PM
confused poet
HanksGB's Avatar
USA, CA, Orange
Joined Feb 2004
1,040 Posts
Glenn,

The AR6400BL is the gen 1 UMX brick that has a brushless esc and two long throw servos on the board. The unit out of the Mig 15 is just the ESC, RX, and AS3x gyro on one board.

Nice looking Camel. I'm following along.

Hank

p.s. I think UMX is for ultra Micro EXTREME! not that it matters much.
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Last edited by HanksGB; Jan 15, 2013 at 09:41 PM. Reason: Left out information
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Old Jan 15, 2013, 07:09 PM
Registered User
Norfolk, England
Joined Sep 2001
7,462 Posts
Mike,
If that's the Orange 415 receiver, leads are here http://www.ebay.co.uk/itm/3505672952...84.m1423.l2649
I need to change the plug on my ESC that goes with the HK 8 mm geared motor and change the battery socket to suit Parkzone style cells. Hopefully that, along with 1.8 gram servos that fit the receiver, will do quite nicely for some 18" models I have lined up.

Pete
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Old Jan 15, 2013, 07:23 PM
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glewis's Avatar
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Pete, you planning on single cell operation?
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Old Jan 15, 2013, 09:56 PM
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USA, FL, Tampa
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I piled the complete unsanded airframe on the scale today. This included the wheels without tires, the receiver, motor and gearbox, the landing gear assembly and pushrods. All that's missing are the tires, prop, struts and covering.Weight is 33 grams so far, not too bad.

Glenn
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Old Jan 16, 2013, 12:15 AM
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Norfolk, England
Joined Sep 2001
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Glenn,
Yes mate, that was the general idea. Also makes the Vapor/Cub/Champ brick viable alternatives.

Pete
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Old Jan 16, 2013, 06:45 AM
Slip the surly bonds...
Sopwith Mike's Avatar
Christchurch,England
Joined Aug 2004
2,393 Posts
Quote:
Originally Posted by glewis View Post
I'm on the fence on the strength of the bass struts. It's not so much the woods ability to withstand normal landing loads but the sideways shear and torque loads applied in a ground loop. Ground loops are common when landing these WWI models when I'm on the sticks... Well ground loops and noseovers too. Glenn
Thanks for the gen on the micro gear Glen and Peter.

If you are concerned about shear loads on the UC, you could do worse than my solution, which is to incorporate scale rigging into the UC (strong thread is fine at these sizes) which absobs any sideways loads on landing.

I insert household pins into the ends of the basswood UC legs and snip them off about 4mm from the leg. These are used to locate the legs into the fuz, and into the cross strut which carries the axle. The rigging is held on these pins also. A dab of cyano holds it all in place.

I developed this method in response to my landing technique
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Old Jan 16, 2013, 07:16 AM
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glewis's Avatar
USA, FL, Tampa
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Pete, what you said makes me feel a lot better about my power choice. I was thinking the 8.5mm motor might not have enough 'poop' for a model this size. I'll be quite pleased if it will loop from level and am OK with it needing a bit of a dive to gain some speed first.

Mike, rigging, brilliant! I saw the rigging on the 3 view and it never dawned on me to use the landing gear rigging too.
My thinking now is a length of 1.5mm carbon glued to the leading edge of the front struts. The rod will extend into the fuselage into a small block to pin it in place. I'm hoping that will be adequate for a 2.5 oz model.

Glenn
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Old Jan 19, 2013, 07:56 AM
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glewis's Avatar
USA, FL, Tampa
Joined Jul 2002
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Progress report.
The graphics to print onto the tissue are almost done. I must have 15 hours into it now and finally have something that fits the fuselage. The wing graphics are ready too. Still have to resize the tail graphics to fit.

I could have just covered and painted the thing by now, but I always want to try something new. It's the challenge that keeps this interesting for this old engineer.

This method is new to me and I see a few areas that have me puzzled.
Maybe you guys have some suggestions.

As we all know the ink is not waterproof. So how do I attach the tissue with a water based glue, then water shrink the tissue?
My plan is to give the glue stick another try. My previous attempts at using glue stick were not successful. The tissue kept coming loose in the Florida humidity. This might have been caused by not sealing the tissue down with a top coat. The tissue that failed was on a foam model so I couldn't seal it down with dope like on a balsa frame.
Will the penetration of thinned dope through the tissue to the framework waterproof the glue?

The other thing is waterproofing the ink.
In the past I have used Krylon clear to seal tissue and decal graphics. Seems to me once I 'waterproof' the tissue, how will it shrink? Should I use alcohol to 'wet' it and maybe it will shrink some? Seems like the water will just sit on the surface and do nothing.

Once the tissue is tight I plan on using thinned Minwax lacquer for the 'dope' .
Anyone know if this is compatible with the Krylon clear?
Maybe I should 'waterproof' the tissue with Minwax lacquer spray instead?

Plan is to experiment with the tail first. That way if things go horribly wrong it's not such a big deal to make a new one.

Glenn
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Old Jan 21, 2013, 04:33 AM
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gupi's Avatar
Vienna, Austria
Joined Jul 2010
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Glenn, you can shrink the tissue with dope instead of water. That's how i always do it.
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Old Jan 21, 2013, 11:54 AM
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glewis's Avatar
USA, FL, Tampa
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I was planning on using a glue stick to attach the printed tissue and coat with Minwax lacquer on this model. That's three new (to me) techniques on the same model.
Maybe I should stick to trying one new technique per model and use dope instead. I'm running low on Aerogloss dope and have yet to find a suitable substitute. I'm hoping Minwax is the answer, it is available locally and is inexpensive.
I hope to start the printed tissue covering experiments soon.

Glenn
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Old Jan 21, 2013, 06:07 PM
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Cant wait to see the printed tissue, good luck with it Glenn!
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Old Jan 21, 2013, 07:42 PM
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glewis's Avatar
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Thanks man.
I just did a test print of the tail graphics, It is now sized correctly and is ready to print onto tissue. I won't get to it tonight though, it's getting too late for me now.

Glenn
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Old Jan 22, 2013, 03:42 AM
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Norfolk, England
Joined Sep 2001
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Glenn,
Last time I used printed tissue covering I briefly passed the parts through the steam from a kettle. It seems to dampen them enough to shrink without damaging the printing. It worked sufficiently well for my wings to start doing propeller blade impressions. Far more shrink than I'd expected, so I hadn't pinned anything down.
IIRC, I used glue stick to attach the tissue - Pritt extra strong.

I must stress that throughout the process you need to avoid getting any visible wetness on the tissue. Keep to the very edge of the steam and make quick passes until the tissue just starts to sag while still appearing dry.
Although I use an Epson printer, the ink was very cheap after market stuff from Ebay. Less than 10 ($15) for 3 full sets. Not even vaguely water resistant.

One method I saw, and tried, for sealing printed tissue (on a foam model) was to use the spray fixative artists use for pastel drawings. Although the model was a disaster, the technique seems to work well. 3 or 4 light coats gave it a nice doped type sheen.

Pete
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