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Author Topic: Bladder tube diameters  (Read 1392 times)

Offline Keith Miller

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Bladder tube diameters
« on: September 20, 2020, 02:51:59 PM »
Hi All -
I'm about to dig in and build the Vintage Performance Airplanes Jr. Satan. They provide the option of metal or bladder tanks - I'm going bladder.

I fly for fun, not competition, and on my other ships (Barracuda, Wakkerman), I use the 1/4" latex tubing from Terminal Tackle. Unconstrained, it expands to 1.75" in diameter, but I don't know how big the bladder tubes are in those planes.

The tube provided by Vintage Performance is 1.25".

Here's my question:
Is it preferred to leave some room between the bladder and the tube so that the bladder can fully expand without being constrained by the tube?
Or is it safe to let the bladder expand fully and press against the walls of the tube?

If so, I've found some LT-316 tubing from Terminal Tackle that's 1/8" ID that expands to .95" fully filled. But that would make for a long skinny tank.

Thanks





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Online pmackenzie

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Re: Bladder tube diameters
« Reply #1 on: September 20, 2020, 03:00:28 PM »
I would say just let the bladder expand to fill the tube.
Mainly because pretty much every model I have ever had worked that way :)
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Online Paul Smith

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Re: Bladder tube diameters
« Reply #2 on: September 20, 2020, 03:18:27 PM »
If the tube is too small it will create "false pressure" when the fuel is forced into the bladder during filling.  Soon the fuel will be depleted to where the bladder is loose, and a drop in pressure will make the engine go lean.

So size the tube to where it is slightly snug, but not constrained.  If it takes extra effort to complete the fill, you are probably making false pressure.


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Offline Keith Miller

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Re: Bladder tube diameters
« Reply #3 on: September 20, 2020, 08:58:25 PM »
If the tube is too small it will create "false pressure" when the fuel is forced into the bladder during filling.  Soon the fuel will be depleted to where the bladder is loose, and a drop in pressure will make the engine go lean.

So size the tube to where it is slightly snug, but not constrained.  If it takes extra effort to complete the fill, you are probably making false pressure.

That's along the lines of what I was thinking. I imagine the most consistent pressure from the bladder would require it to be allowed to grow to it's full expanded shape.
So for this smaller wing (the Jr. Satan), I think I may go with latex tubing that will fit when fully filled.

Online Paul Smith

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Re: Bladder tube diameters
« Reply #4 on: September 21, 2020, 06:23:19 AM »
As seen on many winning models, including World Champions, it's better to let the compartment stick out than to risk false pressure.

Also, don't ignore pacifiers or pipette tops.  They are easier to make than tubing bladders and they have lower pressure, which makes it easier to needle the engine.
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Offline Keith Miller

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Re: Bladder tube diameters
« Reply #5 on: September 21, 2020, 07:20:46 PM »

Also, don't ignore pacifiers or pipette tops.  They are easier to make than tubing bladders and they have lower pressure, which makes it easier to needle the engine.

Can you provide a picture or an example? This is the first I've heard of using pipette bulbs for bladders.
And I just read somewhere that pacifiers provide higher pressure than the latex tubes.   ???


Offline dave siegler

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Re: Bladder tube diameters
« Reply #6 on: September 23, 2020, 07:42:30 AM »
So look at the wall thickness of the tubing.   

I have 1/32 for 1/2a, about 1/16 for mid midsized stuff and weak needles valves and around 1/8 for Fig bore and F2d engines that have real good needles.  Try some thinner walled tubng. 
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Offline Mike Greb

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Re: Bladder tube diameters
« Reply #7 on: September 25, 2020, 08:16:10 AM »
I have been having the same problem, I have Nemesis II models that have really inconsistent runs and go extremely lean and then die with a fair amount of fuel still in the bladder.  The bladder tube is a Estes bt55 rocket tube that is about 1 1/4 id and squished to a slightly oval shape in the model.

Offline Fredvon4

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Re: Bladder tube diameters
« Reply #8 on: September 25, 2020, 10:27:13 AM »
Bladders

WalMart Gerber Pacifiers are way too High pressure .....the old Binky round versions were good but I can not find them

I sent Bob Mears some pipette bulbs but never heard if they were any good or not....easy to Google search for lots of places to buy in bulk relatively inexpensive
this link is not best price but give you and idea about pipette bulb
https://www.ebay.com/itm/Rubber-Pipette-Filler-Bulb-Glass-Pipette-laboratory-Dropper-Cap-Accessories-ODUS/114238373767?hash=item1a99233f87:g:P64AAOSwbe1dbdCm

There is a product to cover the end of Caulk tubes called a Little Red Cap....or Kitty Condom
https://www.amazon.com/Little-Red-Cap-Contractor-Saving/dp/B000H5S8XY/ref=asc_df_B000H5S8XY/?tag=hyprod-20&linkCode=df0&hvadid=167152075853&hvpos=&hvnetw=g&hvrand=16657658065328609455&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9027425&hvtargid=pla-362715054847&psc=1

Texas timers has 1/2a size
http://www.texastimers.com/

Yaro combat stuff in Canada has bladders and materiel
http://aerohobby.ca/store/index.php?main_page=index&cPath=11

Lots of sources for clear Florescent tube covers in various diameters

https://www.google.com/search?q=safety+covers+for+fluorescent+lights&oq=safety+covers+for+florescent&aqs=chrome.1.69i57j0.21071j0j7&sourceid=chrome&ie=UTF-8

https://www.amazon.com/Yellow-Colored-Fluorescent-Safety-Sleeve/dp/B003WZJA2E

https://www.homedepot.com/p/Lithonia-Lighting-4-ft-Fluorescent-Tube-Protector-TGT8CL4-R24/100163152

https://lightbulbsurplus.com/fluorescent-tubes/tube-guard-sleeves/

Phil Cariter Core house web site seems off line but he will respond to PM here on Stunt Hanger

http://home.earthlink.net/~philcartier/index.html      link worked for me last week.....hummmmm
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Offline Keith Miller

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Re: Bladder tube diameters
« Reply #9 on: September 25, 2020, 02:54:59 PM »
Here's what I'm learning -
A 3/16" OD, 1/8" ID latex tube fills up to right around 4" long with about 1.8 oz of water (fuel). See the pic. The inflated diameter actually comes to about 1.1".
The clear bladder tube provided in the Jr. Satan kit is 1.2", so the bladder won't be constrained.
I measured/modeled a simulated tank so that the length is 3 1/4" long (to where the bubble necks down to the un-inflated diameter) (in CAD). /DV
At 3 1/4", it will fit in the 4" long kit tube, and the volume works out to just a tad over 1.5".
That works for me y1... Should get 4 mins on that with a stock 15 engine (LA/FP etc). <=

I previously bought the 3/16" OD latex tubing from Terminal Tackle, but they're gone.
I found another source - Jann's Netcraft; $6.35 for 5ft., a few several colors available.

And, of course, it took me 12 attempts to post the pics because, little did I know, but a 700 kB picture is actually GREATER than the 1000 kB limit. Reverse Polish Math - I get it.

Offline Keith Miller

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Re: Bladder tube diameters
« Reply #10 on: September 26, 2020, 04:26:05 PM »
Bladders

FredVon4, your post is an EXCELLENT reference list - thanks!!
 :D #^

Offline phil c

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Re: Bladder tube diameters + A Couple Notes
« Reply #11 on: October 03, 2020, 12:03:14 PM »
Keith- some good replies here.  In addition:
The bladder pressure depends on the i.d. of the compartment, the wall thickness of the bladder, whether it rests against the wall. and how it was trained.
F2D planes seem to mostly use a 1.5in(~38mm) tube about 3.5in usable length.  That will hold enough fuel for a 4+min. run and usually a bit under 2min. for Fast combat, depending on nitro content.  Mostly the bladder seems to be trained to blow up in the middle and fill towards the ends. It's important not to overfill it or you get the false pressure.  You can train it to blow up from the closed end.  Then it's important to make sure the closed end goes into the corner at the far end of the bladder tube.  Otherwise it may run into the end and give false pressure  or into the wall cutting capacity.  For F2D planes you need all the fuel you can get.  Chop up a Sullivan Crap Trap filter for the aluminum end pieces.  They make very short ends that don't take up too much space.

If you need to use a smaller 1.25in. tube it needs to be about 8in. long for Fast combat. 6.5in. or so works well for smaller engines in Speed Limit or similar events.  Cut a slot in the sheeting or foam so you can see what the bladder is doing.  In either case, lubricate the bladder with silicone grease.  Train it to blow up from the closed end.  You may need to pull on the fuel line to keep the bladder centered in the tube. HOLD onto the fuel line at the syringe unless you want a bath in fuel.(applies above too).  Always force the bladder to start a filling at the closed end before you put it in the plane for the first flight of the day.

Either method can be used with Half A if you scale down to 1/32in. wall bladder tubing- usually 3/16 or 1/4 i.d. and 1/32in. wall.  The bigger tubing will give a little lower pressure.  If you're buying ARF planes adjust the diameter and length to suit.

Another "gotcha"-  latex rubber, virtually the only thing available for flying, is very sensitive to saliva.  If you want to see a piece of rubber fuel go south lick the end to get it onto a fitting.  Within a couple of days it will start getting soft and sticky. IF it DOESN'T it isn't latex.  There are several alternatives including neoprene, Norprene, reddish silcone tubing(stronger), or clear/pigmented(not as strong).  Same happens if you get spit on a bladder.  When it starts to get sticky throw it away and get some silicone grease for lubing rubber(fuel line and bladders!)

Latex is also very sensitive to UV(ultraviolet) in direct sunlight.  Get tubing with a colored layer.  It helps block UV and it telegraphs failure when you start to see pinholes in the color layer.  After the first pinhole you may get another flight, after that you're on borrowed time.

McMaster-Carr has about 100 different varieties in multiple sizes.  Search for flexible tubing.

It's been awhile, but I ran about 50 pressure tests on various bladder set-ups.
The old Binky pacifier(Binky still advertises but I haven't test the current version) blew up to about 6psi.  It would hold over 4oz. of fuel in a large enough compartement.  The pressure dropped only slightly until the pacifier was under an inch diameter.  Not quite enough fuel for current Fast combat.

1/32in wall latex has about the same pressure.  The bladder tube should be slightly smaller(3/32 in+/-) to prevent the tubing from failing early.  Depending on the tubing, 3/4-1in., for 1/4in id x 1/32 wall.

1/4 x 1/16 wall latex blows up at around 20psi.  This requires a much finer control of fuel flow from the needle valve.  Fast combat is OK with the huge amount of fuel they suck with SuperTigre style brass/lock nut style construction.  For anything else the current best is an F2D nva.  Ones like the Fora have a very usable setting range on F2D, Speed Limit, even Half-A.
     OS stopped making the 1a remote needle valve.  It was for the early OS 10 and 15 engines, and later up to the 25's.  It has an adequately fine thread and a smaller overall size and is easy to confuse with the many other NVA's OS builds(tm).  If you can find them they offer more mounting options than F2D NVA's.  Some people prefer that, no problem.

1/4 x 3/32 tubing works in F2D.  It is very hard to blow up without using a 3/4in. pump.  A 1in veterinary often used takes a LOT of muscle.  The bladder give around 30psi.  That much pressure isn't really needed.  The 3/32 wall tubing is substantially longer lived than 1/16in. wall.

There are also some tricks to bladder construction and use I'll get to later, unless somebody else does it first.
« Last Edit: November 28, 2020, 09:31:09 AM by phil c »
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Offline Bob Mears

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Re: Bladder tube diameters
« Reply #12 on: October 05, 2020, 09:01:50 AM »
https://www.ebay.com/itm/174400163161

I sell fuel bulbs on ebay. They're good for nostalgia pacifier replacements. Keep them refrigerated until you use them, and they still don't have a long life, but they do work well and not crazy high pressure.
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