Series or parallel?
 

Hi

I am installing the fuel tanks in my F18F. All is left to do is install the turbine (first I have to buy it....)

Although I have special clunks, I found out they are to big to fit in, so I installed simple clunks. The line is to stiff to come up and down, but with the fuel inside will it softs and be able to move more freely?

Also regarding the fuel tanks I am planning to install the saddle tanks in paralle and the install these in series with the main tank and UAT.

I would prefer to install all in series but won't this affect the CG (roll side)?

Any comments welcomed

Nuno

RE: Series or parallel?
 

I would NOT trust the tubing to loosen up after the fuel is in the tank. Maybe you can wrap some solder around the end and make it heavier. I always like series for plumbing tanks.
V..

RE: Series or parallel?
 

I run my tanks in parallel but I have a friend that runs his tank in series; there have been several posts that have argued this point and I do not wish to add to them. I will try to lay out the facts as I know them and you will have to make your own choice. I use a parallel setup because I believe it is important to keep the airplane as balanced possible for best flight performance. Most guys that fly with them in series say they do not notice any difference in the airplane throughout their flight. I'm guessing that this would be dependent on were your tanks are located, I believe that as careful as we are to ensure that our planes are balances on the CG how can you say that having about three pounds on one side of the aircraft doesn't affect the handling in some way. You can make your choice. If the fuel tubing in your tank is to stiff now it will not get any better by soaking in fuel. Normally fuel tubing gets stiffer with age. Try a different brand of tubing BVM sells some good stuff. Give that a try.

PS: with a parallel setup it is important to keep everything symmetrical, fuel and vent line lengths, tubing diameters. Then test it for even feed and adjust line length if not even; more work but I think worth it in the end.

RE: Series or parallel?
 

Go with serial tanks, and change the tubing, it will not get any softer and you may get air in your system while performing inverted maneuvers.
Tor

RE: Series or parallel?
 

I changed the tubing that came with my FeiBao F-18 because it was not 'real' tygon. There were some complaints about leaks and air bubbles after some time. Suggest you do to.

Should be ok to do the twin saddles in parallel with the maintank in series.

RE: Series or parallel?
 

Thanks for the support guys...

Is there any link to that thread?

I have already changed the tubing for Dubro Tygon, but it stll feels stiff and when I invert the tanks the clunk does not come all the way down. Either I will add some weight or I guess that when I fill it with kero the tubing will soften a bit.

Edgar, have you already tried yours? What is your gear and set-up?

Regards

Nuno

RE: Series or parallel?
 

the tubing will NOT soften w/ kero...Vincent was trying to tell you that too but made a typo. I like his idea of wrapping solder around the clunk for more weight.

I used the Dubro heavy clunk and it works great. Small diameter, too.

RE: Series or parallel?
 

[link=http://www.miliamperios.com/foro/viewtopic.php?t=78926]Here[/link], but it's in Spanish;)

Not yet. Started assembling it now. Using Weatronic, Skymaster Struts/wheels, Tam cockpit. Hitec Servos. Came fully rigged with doors and cylinders.

RE: Series or parallel?
 

OK

Thanks Edgar. I already have real Tygon tubing (Dubro), but from my experience with this tubing in gas engines, when it is put in contact with gas it will soften a bit and allow a full up and down travel even with a relatively light clunk.

Since this is my first contact with kero, I realy do not know but I thought that might happen the same. I am talking about a new line.

If it does not softens a bit I really have to think about another solution for the saddle tanks because the line has about 3"" or 80mm of tubing and thus do not allow full up and down travel unless I put a ton in the clunk. Under my point of view this is realy important to avoid flame outs.

I could put a longer lenght of line in the saddle tanks but these have a lateral belly and the clunk could get stuck doing a manouver like a tonneau. On the other and I would like to avoid solder the clunk, because might be prone to come apart any time during flight unless it is silver solder.

Any imputs and links welcomed

Nuno

RE: Series or parallel?
 

Thanks highhorse i did make a typo. I like series because you get every drop of fuel out of each tank with no issues on tubing length etc.

V..

RE: Series or parallel?
 

I am planning on two parallel tanks feeding a hopper tank in a new jet. I planned to install a cross feed line between the two main tanks. Does any one see a problem with this idea?

RE: Series or parallel?
 

Hi

The cross line should work well to keep the tanks equal. Seems a good idea, but I just started the thread to ask for help:)

RE: Series or parallel?
 

As long as you fly straight. What about knife edge????????????????????

RE: Series or parallel?
 

Aerotrend makes fuel line that is more flexible than Tygon.

http://www.aerotrend.com/shop_subcat...9c7cd973c9eeaf

Marty

RE: Series or parallel?
 

Hi Marty

Any link for an European dealer?

Nuno

RE: Series or parallel?
 

Anybody....

The clunk I have in the 3 tanks weights 13gr. I am planning to make new ones at the lathe from brass. Soimething arround 20 to 25gr should work...

Regards

Nuno

RE: Series or parallel?
 

One important consideration when plumbing in series, is that the very first tank (next to the UAT) takes a lot of abuse. When the engine is running, it is under suction..generally not a bit deal as long as it is full of fluid, but it will start to empty at some point.....BUT, when you are fueling, there is so much resistance in the fuel lines (depending on line length, number of tanks etc,) that the tank is under pressure...enough pressure that it can crack thin wall fiberglass tanks. (don't ask..)

I don't see any value in a crossfeed line unless the jet is held straight and level at 1 G. A passive cross feed depends on gravity to equalize the fuel level in the two tanks. With the way most of us fly, the fuel is always sloshing around and there would be very little pressure differential between tanks to cause any net flow one way or the other. Besides that, once the first tank empties, you are sucking air anyways. .. needless complication, weight, and potential source for leaks in my books.....

RE: Series or parallel?
 

Not that I know of but Aerotrend does ship international.

Marty

RE: Series or parallel?
 

Thanks Marty

Pick the lathe and made 3 clunks with 28gr each from brass. Now the weight is more than enough to hang arround in every position.

This semms a little thing but is very important to keep the turbine running for the all flight in any flight attitude. I guess several flame-outs are due to incorrect fuel systems.

Now it sounds like a clunk, clunk clunk......

Have to take care with g force now or I can break the tank:D


Nuno

RE: Series or parallel?
 

There is a translucent fuel line BVM sells that is much softer than Tygon for inside fuel tanks. It also will stretch some once it is in fuel so cut it a 1/2" to 1" shorter.
You can find it located on BVM's website..if you go to JET ACCESSORIES then KEVLAR TANK ACCESSORIES you will find it $6 for 3 feet. This will allow your clunk to move more freely.
BC