I'm not sure why there should be a need to use anything other than a good high flow heavy clunk that follows the fuel well, used in conjunction with a BVM UAT. This is the setup I have found gives the most consitant/reliable running in any install.

Rob.

Thanks John,

I thought the Keecat looked a little weak. It has a built up fuse. I do like the idea of the Falcon 120. I guess I can sell the Keecat or put an Electric motor in it!!!.

I do like a UAT in my models. I have had nothing but complete success with them on four turbine models so far.



Regards

Thanks John, where do you get the pleated paper filters? I have seen some in the auto acc stores but they are always enclosed in a plastic housing with a nipple on each end. Or do you have to take the enclosure apart, salvage the filter element & fit a pick up tube or is there a ready to use jobby made for line trimmers & chain saws? The tank is a Dubro unit so it will have to be small to fit through the hole.

The way I see it is I have 3 options:

1/ leave it the way it is (it works perfectly.)

2/ try to fit a paper clunk if possible.

3/ fit a small air trap (the model felt a little tail heavy on landing so a bit of weight up front may help anyway.

Thanks for all the opinions, guys. - John.

John, there was a thread a while back showing how to make paper filter clunks out of a cartridge type filter, as opposed to the type you're thinking of. It basically duplicates the filter clunk found in chain saws, so I'd go to a small engine repair shop first and take the tank along for sizing.

I would give SERIOUS consideration to an air trap though, regardless of clunk type. Very effective and cheap insurance for your multi-thousand dollar investment.

I have used felt clunks for years. Never had a problem

John

Try
http://www.rockauto.com/dbphp/prt,915,CG3388
For purchasing filters Fram CG3388

Also see
http://www.tecnopar.com/download/catalogo.pdf
For a list on page 13 of the various manufacturers equivalent parts

Very simple to make, you need to pull the rubber insert out and heat the end caps up so they can be removed. Ideally with a lathe make up a brass dome end and a brass washer fitted on a brass tube with cross drilled holes in it. Epoxy the ends on. I have made 12 or more now.

I have never used a UAT in any of my planes the pleated paper will draw fuel before it draws air and it will empty the tank to almost nothing. The weight of the UAT in small planes can affect performance and justify not having one. If you have a large plane with plenty of room fit one if it makes you fell happier.

Hope that helps

John

Listen to the gentleman from the south.

Felt clunks are good for smoke pump header tanks.

Out of many, many flights I've only ever had one UAT (that's less than 99.9%) ever give me a strange leak.

And yes, if you have a flame out and you get your jet back in one piece, kiss it when it gets back to you.

Even the lightest jet, well maybe not a foamie one with that 1/2N size turbine, will benefit from the UAT. Maybe in that foamie one, the only tank I'd run would be, just a UAT.

I'm just a poor little north american who needs to minimize his risk to have fun flying.

Raf

Unfortunately, a full UAT weighs in at almost 7 oz weight, nearly 1/2 lb which on a '44 sized aircraft is really excessive. Wish someone would make something similar with fittings for 3 mm fuel tubing, a normal sullivan type gas plug and about 2 fluid oz volume.

I have 200 or so flights on a JHH Sabre with a Green '44 using the Wren type felt clunk, without a flame out attributable to bubbles. I know Larry W has gone to using a lighter weight 'bubble trap' fashioned out of a little 4 fluid oz sullivan tank, but there still remains the undesirable added weight of about 4 oz or so.

I think I would maybe add a 2nd washer to the felt clunk, to compress the felt a little bit better, soak it in kero and shake it around a bit while pulling fuel through it to see if those tiny bubbles might not disappear. Make sure you have a large enough vent on the tank, perhaps 5/32nds brass, facing forwards to get a little ram air pressure. Works for me.

Cheers,

I suppose it's 'horses for courses' though I would not think a few extra ounces would make that much difference to wing loading/performance unless slow flying is important say because of runway restrictions. Having said that I have used a pleated paper clunk in my fuelling rig and it does seem to work well though the 'neck' of any airframe mounted fuel tank would severely restrict the choice of suitable comercial tanks.

Rob.

The pleated filter will fit through the opening of Dubro and Sullivan type tanks with just a very very tiny bit of grinding on the metal part.

Thanks very much John, could you post a picture of an assembled unit please?

My friend with the A4 made a tiny UAT using a pill bottle for his Twinjet foamy which uses a Lambert turbine. He made a UAT using the 2 oz Sullivan tank for his A4. I guess he won't be needing that now [&o] - John.

John

This is a few pictures that should help you. Let me know if you need more help. I used the thickest Araldite epoxy to avoid it wicking into the paper.

John

Thanks John, if a picture is worth a thousand words I make that about 3000, give or take a couple!. - John.

Just curious - Has anybody tried the "micropore paper clunk" available from Mick Reeves? If so, any comments?

Many Thanks,
=Adrian=

Thanks so much for the Pics, John. You use about a 1/8th inch inner tube, and Tygan to run to the bottle stopper? Looks about the same size as the Wren type felt clunk, and you certainly can't beat the price!

Here is a simpler way for a home made UAT or clunk.

Yes The brass tube I used was 1/8 inch and I connected to Tygon. I have used both Sullivan and Dubro tanks. I am able to make sure that the cluck will fit in the tank opening, but if the end caps are left on it is a tight squeeze.

John

UAT UAT UAT - make it fit. It's the standard. Why try to go against the grain on such a proven solution? Your investment is worth more than a cheap clunk.

Andy

UAT UAT UAT - make it fit. It's the standard. Why try to go against the grain on such a proven solution? Your investment is worth more than a cheap clunk. Btw, dreamworks sells them for around $35. Cheap insurance.

Andy

Here's more. You can actually make the entire assembly using JB Weld. The larger pleated paper filter will offer less resistance to fuel flow. >

( And yer better not call it a UAT if it's homemade and not from BVM, or BV's gonna sue yo butt. )

I followed John Wright's method after he published it in RCJI a couple of years ago, and it has been working beautifully in my F-104 with Wren Super Sport engine.
Harry.

Adrian,
I have used the pleated paper clunk sold by Mick Reeves for my JetCat P-80 and it is great.
It does not fit into a Dubro or Sullivan tank.
However I made a fuel tank from a 2500 ml bottle, laid on its side, on my test stand. The engine, at full power, drew pure fuel without bubbles until there was only 2- 3 mm depth of fuel in the tank. Using the felt clunk it started to draw bubbles at full power when the felt clunk was half exposed.

For my P-80 powered Rookie I used a fuel tank made from a 2 litre cider bottle and a Mick Reeves pleated paper clunk. No UAT, just straight from the tank to the pump. It has been perfect for over 100 flights. Not a single flame-out related to fuel feed (one due to faulty electrical connection).

On my Boomerang (Wren 54 with Dubro tank, felt pickup, plus BVM UAT) I did experience 2 or 3 unexplained flame-outs, by the way.

John,

Have you located a source for these filters in Sydney?.
I found one at the local mower shop. It was inside a transparent plastic case but I think I damaged it getting it out.

Let me know if you find any. It would be good in a small model if I can do away with the UAT.


The Bobcat arrived today. Looks good. I don't think the Keecat is suitable for turbine. It has a firewall at the rear and a built up Fuse. I might put an electric motor in it.


What size tank do you have in your Bobcat?

Regards

One thing I should add is that particularly when using a single tank, make sure the tank is tilted back slightly when at the flying attitude. This will make sure you pick up the last of the fuel on your last few circuits before landing.

John

To be honnest
i am using tilotson heavy fuelclunks for years.
and i have a square tank.
these should be according to you all a disaster waiting to happen.
a few of you maybe seen me fly at pampa,s this year.
on most flights i would come in with the main tank completely empty and the UAT half empty.
and yes i also have my tanks lifted by a few degrees in the front.
conclusion they all drain the tank empty.
and on those rare occasions where it will take some "foam"fuel the uat will save it..
i must add that i NEVER used tygon , but just a piece of Festo 6mm attached to the fueltank and clunck.
this way the fuel clucnk will ALWAYS stay in the back