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1/2A Boomerang

Old 11-12-2014, 08:04 PM
  #26  
MJD
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The bladders I've made generally have lots of unexpanded tubing between the filled part and the nipple where it attaches. So I think as long as I see a few diameters of free tubing either side it wouldn't be overfilled.. or am I deceiving myself?
Old 11-12-2014, 08:41 PM
  #27  
combatpigg
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It's impossible for me to...speculate. Your brand of tubing vs what I find locally. I couldn't even tell you the specifics about who makes mine or exactly what size it is. A trial run or two on the ground to witness the engine happily drink from the bladder without any intervention during the run is as close as you can get to simulating the real thing. Problem is, you can't simulate that first big gulp of air and the unloading.
I am happy to put 3/4 oz in a 1/8" I.D. bladder and try to find a rich enough setting. All of my 1/2 A videos are based on 3/4 oz loads of fuel and most of those runs are about 90 seconds or so.
Old 11-12-2014, 11:13 PM
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20-25cc is what I'd target also, The real question was related to the convenience of needle access. I'll solder a brass slot screw head to the needle stub I think, or if enough material, sleeve it with brass/solder, then Dremel cut a screwdriver slot. Then I'll be ready to tweak at every start-up.

Since I bought a used Phoenix earlier this fall, seems every aircraft I own may eventually inherit the name. Recently refitted the Sparrow Hawk .010 foamy with a TD .020, it's ready to go. The Profi racer is ready to go, the Demon .67, a few other things that all needed just a bit of attention and/or ambition to get back into the air. And look what crawled from the ashes this evening - the Squirt rises. And, with a burst of ambition late this evening, some impromptu facial surgery was made to accommodate and .05/.06 mount and a throttled VA MKII. It's another stupid light airframe like the Boomerang, don't recall weighing it but in the 10oz range I think. One ACE panel. Stubby little thing. It flew alright with a Sure Start, but I the engine was erratic in the air. The glide was smooth, flat and gentle - the wing loading is quite modest. The VA should perk it up a bit, and with throttle.. well all the better. I have a nice homemade Fuji clunk tank to feed it, holds about 20cc. Lots for this combo. If Saturday looks respectable (I daren't look) it may be a chilly 1/2A party at the airfield. And some shots of the Boomerang interior. The Rx switch is - presently - a 6" extension with Velcro to stick the connection to the fuse side, Works fine, I want to pull the wing every flight to check the bladder, and it takes about 10 seconds so who needs a switch,

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Old 11-12-2014, 11:18 PM
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Oh yuck. I think we could get one more thaw and temporary respite, but I'm not counting on much more than that.


Saturday, 15 November
Cloudy with 60 percent chance of flurries. Low minus 6 (22F). High plus 3 (38F).
Old 11-13-2014, 11:28 AM
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Snowflakes aren't as bad as rain. I don't really like bladders, but have had fairly good luck lately. The main thing I found is to make sure the bladder is not squeezed in the compartment, or it will go leaner as soon as it runs a bit of fuel through. I seem to have trouble getting to the needle valve or hemostats fast enough when I am alone. Sometimes it takes 4 or 5 tries running on a prime. I am getting older, but it is winter now too. Backplate pressure is ok as long as there are absolutely no air leaks. Starting with backplate pressure can flood it very easily, and could be a problem in a cowled motor if you can not pinch the line easily. You are likely aware of this I am sure. Have fun on Saturday. Wish I could watch. I think it is 4 hours.
Old 11-13-2014, 12:13 PM
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Yeah, long drive to listen to someone *****ing about the cold..
Old 11-17-2014, 11:00 AM
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Winter is pushing itself through the door here by force, last few days have not been good RC days, I put up an EF-1 Shoestring on Saturday, but that was in 15-20mph winds and -3C temps, and it slices through that fine and it slows the landings right down. But I don't fly 1/2A, especially test fly them in those conditions. Not worth the misery.

Maybe we'll get a break.

But the cool tihing is I ordered one each of the HobbyKing Smart LiPO's with a recent order, one 250mAh and one 500mAh. The 250mAh unit is 13.5 grams.. a single LiPO integrated with a step-up voltage regulator/battery charger board. The battery can be disconnected from the board for storage, and is reconnected for the day's flying. There is a shorting plug that is removed to turn it on. So I'm guessing that there is a miniscule idle current when the battery is connected but the shorting plug is installed, hence the recommendation to remove the plug if the unit is not used within two weeks. The 500 mAh is only a few grams more.

I might rip out the 300mAh LiPO and searte step up regulator for this. I'll use them elsewhere but I want to use the cool & more compact stuff on the Boomerang. I'll add pics tonight.
Old 11-21-2014, 10:07 PM
  #33  
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I experimented a bit this evening and came up with the right length of 1/8" latex for a 25cc bladder, this goes to a 1/8" barbed plastic tubing coupler, and a length of medium silicone to run through the firewall to the engine. The bladder part is housed in a balloon, the neck wrapped around the coupler and secured with a Dubro fuel line clip. A small square of velcro hook secures it to the velcro runner along the fuse belly interior. It is 100% ready to fly. Test glides went fine last weekend. Content with radio installation. Ran a few primes through engine in basement on the 4.1x4.5 toothpick prop. "hey, what the heck are you doing down there??" from the living room directly above. Hee hee.

So tomorrow is supposed to be a bit above freezing, but winds are forecast and rain int he afternoon. I'll pack the airplane to the hangar in case there is a window of opportunity sometime during the day.
Old 11-22-2014, 07:37 AM
  #34  
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I am at the point where they don't yell from upstairs when I run off a prime. Been doing that for over 35 years. I still get whining with fumes, and the one time the volume was up when I watched the pulse jet video.
Old 11-22-2014, 08:23 PM
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Today was total blech.. fog, wind, rain, anything you can make out of wind, water, cold and misery seems to be upon us. Hope tomorrow gives a little break, I wanna fly it, I wanna fly it...
Old 11-23-2014, 01:36 AM
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Sunday [today] looks promising and Wednesday looks even better.

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