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2 Questions about Viper? - 10/19/2007 2:28 AM   
John Raymond


 

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Status: offline 		Where can I order a bubbless (Bladder) tank for a viper, and how do you mount it that it doesnt interfere with the aerlion servo?

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RE: 2 Questions about Viper? - 10/19/2007 2:55 AM   
scausey



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Status: offline 		John.

I would order from http://pspec.com and make it a 4oz. This way you put behind the first former and it will not be close to the servo. Just check your CG to make sure every thing is correct.

I know when I first checked the CG, it was nose heavy, that is why for the placement behind the first former, plus it keeps the fuel close to the CG and will not change flight during the race....

Scott
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< Message edited by scausey -- 10/19/2007 3:17 AM >

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RE: 2 Questions about Viper? - 10/19/2007 3:13 AM   
Fxrs_tim


 

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Status: offline 		I mounted a 4oz Tetra in the conventional (front) compartment. All you have to do is enlarge the hole in the 1st former to make it fit, then drill a couple of holes on the right side of the fuse for the lines to come out.

Tim

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RE: 2 Questions about Viper? - 10/19/2007 1:01 PM   
Jezmo



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Status: offline 		I did mine the same as Tim. It's working great so far.

I forgot to add that in addition to the site listed above they can also be purchased from Darrel Cady RC http://www.darrolcady.com/ . Dubb Jett also sells his own brand of bubbleless tanks at Jett Engineering http://www.jettengineering.com/ . I believe Central Hobbies carries Tetra as well.

< Message edited by Jezmo -- 10/19/2007 1:14 PM >

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RE: 2 Questions about Viper? - 10/19/2007 1:05 PM   
Ed Smith


 

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Status: offline 		The picture shows a typical tank position. The airplane is not a Viper but the fuselage is the same size. The tank is a Jett six ounce tank placed on the balance point.

Ed S

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RE: 2 Questions about Viper? - 10/19/2007 3:06 PM   
Jim Duda



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Status: offline 		I wanted to keep the tank as high as possible so I laid the Tetra on it's side and relieved the front former enough to allow a good fit. The wing pads are reinforced with 3/16 in. ply because I use 1/4-20 nylon wing bolts...they are plenty strong enough!

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RE: 2 Questions about Viper? - 10/19/2007 5:59 PM   
dwbebens


 

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Status: offline 		Jim;

It certainly is important to have the fuel line (and also the pressure line) make a "smooth bend" as you mentioned to prevent kinking. As an added bit of insurance, I slide a piece of a flexible drinking straw over the line in the area where it makes the sharpest bend.

Doug Bebensee

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RE: 2 Questions about Viper? - 10/19/2007 7:35 PM   
jaka


 

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This is how I mounted a 5oz Tettra tank in my Viper.
Bought the tank from Dave Shadel, Performance Specilaties, in Nevada

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< Message edited by jaka -- 10/19/2007 7:42 PM >

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RE: 2 Questions about Viper? - 10/20/2007 1:26 PM   
daven



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Status: online 		I did mine just like Jaka's, although I don't use 3 lines, just 2.

It kinda depends on how you like the plane to fly, I prefer a slightly tail heavy racer, and having the tank closer to the CG helps. If you put it way up in the nose, you will get a significant cg change during flight as you burn up to 5 oz of fuel.

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RE: 2 Questions about Viper? - 10/21/2007 6:14 AM   
SmokinJoe



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Status: offline 		The combat guys have been making their own bubbless tanks for a long time using baby bottle liners inside "normal" tanks. They work fine.

The third fuel line in the photos puzzle me. I couldn't see a non return valve in the fuel supply line. I am only used to two lines with these tanks, the pressure line from the muffler to put pressure between the tank shell and the bladder and the fuel pick up line inside the bladder.




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RE: 2 Questions about Viper? - 10/26/2007 5:52 PM   
jaka


 

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Status: online 		Hi!
The third line is for overflow (goes straight up inside the tank, tells when the tank is full).


< Message edited by jaka -- 10/26/2007 5:54 PM >

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RE: 2 Questions about Viper? - 10/26/2007 9:41 PM   
wkevinm


 

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I am curious about the bottle liners, what is the capacity, material and the durability of the liner. From what I have seen of the combat planes, quality, reliability or long life is not a high priority.

Kevin M

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RE: 2 Questions about Viper? - 10/26/2007 9:52 PM   
vicman



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Status: offline 		The baby bottle liner is an interesting concept to me also...do tell.

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RE: 2 Questions about Viper? - 10/27/2007 1:18 AM   
dwbebens


 

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Status: offline 		Vicman;

I've made a number of bladder tanks using baby-bottle liners. The liners come in a number of capacities (4-8oz) and seem to be made of polyethylene.

The best way I've learned was told to me by Wayne, the owner of Danniel's hobby shop here in Nashville. Also, I added some small refinements myself.

Select a somewhat rigid plastic (polyethylene) bottle from something like Old Spice aftershave that has a solid screw on lid with one hole in the end where the liquid spurts out. I'll use this example, but there are many other bottles used to contain shampoo, conditioner, etc on the store shelves. There is a surprising number of sizes and capacities available. You just have to look. Have your fuselage dimensions with you when you are "shopping" for a bottle. Of course, if you or someone else can actually "use" the product inside, then so much the better.

I used a 4 oz Old Spice aftershave bottle that was oval in shape and had a hard plastic screw-on lid. The lid end is the front end of the tank. The lid had a hinged snap lid which contained a plug for the hole. I removed the snap lid. The hole was carefully and SMOOTHLY enlarged to a diameter equal to the OD of the silicone fuel tubing that I would use to go to the engine. If your lid doesn't have a hole, then make one. Again, the hole edge should be smooth. A smooth but small chamfer on both sides of the hole is also a good idea. This chamfer should be burnished rather than cut. Prepare a piece of fuel tubing for the fuel feed line by "fish-mouthing" the end that goes inside the tank. The other end can be as long as you like. The next step is very important. Insert a 3/4" piece of antenna routing tubing inside the fuel tube at a position so it will be coincident with the hole in the lid when the fish-mouth is in the center of the tank. Use you ingenuity as to getting the plastic insert into the silicone tubing as the fit will "fatten-up" the fuel line. Now PULL the tubing through the hole in the lid until the plastic tube insert is lodged equally in the hole in the lid thus tightening and sealing the tubing in the lid. The "fish-mouth" end should now be at a distance half way down the tank when the lid is screwed fully onto the bottle. Test fit this assembly onto the bottle and then remove it.

The pressure inlet was made in the side of the bottle by carefully piercing the bottle with an ice pick. It is necessary to pierce the bottle without spitting it. The piercing angle is back and along side the bottle - - somewhat parallel to the side and slightly inward, pointing to the bottom end of the bottle. First use an ice pick and then enlarge the hole using an awl. It should not be necessary to heat the ice-pick if a polyethylene bottle is used. Again, make the hole size the same as the OD of the fuel tubing. Then prepare another silicone fuel tube for the pressure line in a similar manner as done for the fuel feed line. The trick with this one is to insert the tubing from the inside and PULL it outward through the "ice-pick" hole until the plastic insert is lodged there-in, again tightening and sealing the pressure line to the hole in the side of the tank.

You now have the two lines secured and sealed to the tank.

The next step is the easiest one of all. Buy a package of appropriately sized baby bottle liners. Make sure that the liner is at least 1" longer than the distance from the bottom of the bottle to the top of the lid. Fold the liner lengthwise in an accordion like manner, NOT around itself. Slide this into the bottle until it hits the bottom and then slide it a little more, maybe 3/8". Hold it in this position while you open up the liner at the neck end of the bottle and fold the protruding liner evenly back over the threads. Poke your little finger into the hole to open up the liner at the open end of the bottle. Now, insert the fish-mouth end of lid/tubing assembly into the bottle/liner assembly, making sure that your grip on the liner doesn't slip. Screw the lid firmly onto the threads trapping the liner between until the lid seats. Tighten the lid firmly. The combination of the male and female threads crushing the liner and the lid crushing the liner to the bottle neck will seal the tank air and fuel tight. The friction of this interference fit will keep the the lid from un-screwing.

Test the tank for leaks by first sucking out the air with a fueling syringe and then filling with fuel until resistance is felt. As with any bladder tank, avoid over-pressuring it when filling. The capacity of this bladder tank should be a little less than (maybe 1/3 oz less than) what the bottle label says.

It will be necessary to tape a pop-sicle stick to the tank to keep the lid from hitting the firewall to prevent the fuel feed line from kinking.

It only takes a few minutes to do this. If you mess one up, then throw the liner away and try again.

I've crashed planes with this type of tank a number of times with no tank failures.

I recently edited this post and modified references to heating the ice-pick. It is very tricky to get a nice clean round hole by melting.

Doug Bebensee





< Message edited by dwbebens -- 10/28/2007 11:20 AM >

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RE: 2 Questions about Viper? - 10/27/2007 2:44 PM   
StanDouglas


 

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Status: offline 		Really Big bladder tank
This is not a Viper tank, but some may find the techniques interesting. It's not in English, but one can follow the pictures.

About that third line: most of the pylon racers don't use it or even install it. When you complete;y evacuate the tank air by pulling back on the fueler plunger and then fill the tank, you can tell when the tank is full from the pressure. It's just another line to manage when fueling and needs to be plugged when the tank is full. The main thing is to get any air out of the tank prior to injecting the fuel.

Hope this works:
---------------------
@@@@@@ Tubing@/
@@@@ Fish Mouth@\
---------------------
(The @ signs are just filler to get the slashes to line up with the end of the tubing I made out of dashes)

The idea is to cut the tubing in a V so that it is less likely to suck on the bag as the tank empties.

< Message edited by StanDouglas -- 10/27/2007 3:00 PM >

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RE: 2 Questions about Viper? - 10/27/2007 2:47 PM   
John Raymond


 

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Status: offline 		I have a few questions about the above tank,

What is a "fishmouth" a clunk? or what?

I would suppose the above is the fuel tube to engine, but why does it only go halfway in the tank?

Can you post a few pics especially showing how to position the pressure tube?

Thanks for the very descriptive response

John



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RE: 2 Questions about Viper? - 10/27/2007 11:46 PM   
dwbebens


 

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Status: offline 		John;

I've taken a few photos of a tank mock-up. This particular tank itself is suitable, but the lid us not because it is a child-proof one which has two parts. It leaks. Use a bottle with a thick one-piece lid.

The "fish-mouth" is how the inside end of the fuel feed and pressure lines are cut. See photo. This prevents the liner from getting sucked against a flat-cut tubing end thus choking-off the fuel supply. No clunk is necessary. The position of the fish-mouth end in the tank is not critical. The air will be first be sucked-out with the syringe. Then the tank will be filled with fuel. The whole intent of a bubble-less tank is that there is no air in it. The short stub of fuel feed line inside the tank will feed a solid fuel stream, assuming that you've first removed ALL the air.

The position of the pressure inlet into the tank is also not critical. Put it in a corner facing rearward. The pressure line pressurizes the space BETWEEN the tank and the liner. You do NOT need a third line for a vent. Also, after the tank has been filled, you must clamp-off the fuel feed line somehow in order to keep air from getting in or fuel from draining out. Un-clamp the feed line just before starting the engine.

In the photos, take note that there is a short length of antenna tube already inside the fuel feed and pressure lines.

Doug Bebensee



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< Message edited by dwbebens -- 10/27/2007 11:50 PM >

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RE: 2 Questions about Viper? - 10/28/2007 1:40 AM   
John Raymond


 

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Status: offline 		OK I understand better now, thanks for the explanation.

Could I use like a Hayes tank, and modify it to use a bladder?, it already had a seperate pressure fitting?

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RE: 2 Questions about Viper? - 10/28/2007 11:29 AM   
dwbebens


 

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Status: offline 		John;

I suppose you could. The trick would be to get the liner to seal around the opening of the tank. I've tried to use the Sullivan type tank with the rubber plug in the end with mixed results. The beauty of using a bottle with a hard plastic screw-on lid is that you can tighten the lid so tightly that the baby-bottle liner gets crushed so that it will seal, in spite of the fact that of the folding and layering that occurs in the liner.

Doug Bebensee

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RE: 2 Questions about Viper? - 10/28/2007 3:10 PM   
StanDouglas


 

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Status: offline 		You can convert a standard tank to a bladder tank. I have successfully converted the 8 oz one that comes with the Raider Mark II. It is difficult to get a seal with the rubber stopper. The tanks with the caps are easier to seal.

The process is pretty simple and there are alternative systems that you can use. For instance, in the June 2007 issue of "Fly RC", there's an extensive article on "Optimize Your Fuel System for Best Engine Performance". You do get Fly RC don't you? You do read the How To stuff and not just look at the pretty pictures don't you? Of course you'll have to do some reading for comprehension as its 5 pages long.

Anyway back to bladder tanks. Since I have one that is working, writing up a process hasn't been at the top of my list. The largest size baby bottle inserts I could find where 8 oz. This is ok as we don't need more than 8 oz to race ten laps. There are 125 bladders in a box!
See image parts.jpg

I happened to have an old Tettra tank that was cracked from a crash and I robbed the pressure nipple from it for my project. Now don't get all excited; you don't need the special nipple. You can get a pressure fitting at your local hobby shop. They’re actually called a pass through for the firewall. Just remember that it needs to stay external to the baby bottle liner. Here's a shot of the nipples installed.
See image parts.jpg and with-tank-cap.jpg

Next you put the bottle liner inside the tank and inflate it by blowing on the tank neck. After that you get the black rubber plug into the tank. I sealed the whole mess with some silicone. And let it set over night. Note the fuel tubing over the feed line. You can't see it here, but the end is cut in a "V" shape. This so that as the bladder gets to the end of the fuel it won't seal off and stop the fuel flow. Note that the back plate for the stopper is not yet installed.
See image liner.jpg

Duane Gall, who actually builds stuff, told me he uses heat shrink tubing over the aluminum feed line and seals the bladder to just the feed line by turning the bladder inside out, and heat shrinking over the bladder material and wire wrapping over the heat shrink. Then installing the whole mess in the tank. This also eliminates the need for a nipple as you can just use a second line in the stopper for pressure.

All that having been written I like Doug's screw cap tanks better! It looks like its easier to get a seal and the price is right.

SD



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RE: 2 Questions about Viper? - 10/28/2007 5:28 PM   
John Raymond


 

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Status: offline 		Thanks all for some really great info, I'm sure many will use this info as I will John

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RE: 2 Questions about Viper? - 12/27/2007 2:06 PM   
mrmustang1976


 

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Status: offline 		i also been playing around building bubbless tanks. i haven't used them for long period of times yet tho. to help with the seal at neck i use elmers rubber cemet. i took some and painted the inside of a zip lock bag then filled with some fuel and it dont seem to efect this glue. as for the bags i use zip lock bags and cut them to size and reseal with the seal only setting on a food saver kitchen vacume sealer. for the opening at the top i take tinfoil fold it up to make it thicker to leave a hole in the sealed part just make it the size you want the hole and fold it over the part you don't want sealed then put it in the sealer.

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