RCU Forums - View Single Post - Incompatibility with CAT air trap and Kingtech/Jetcat engines?
Old 01-24-2016, 08:05 AM
David Gladwin
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Join Date: Feb 2002
Location: CookhamBerkshire, UNITED KINGDOM
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Originally Posted by marc s View Post
Hi guys, thought I might chime in here as I make the CAT products - every one by hand, by myself using cnc machined parts from the UK and filters from one of the largest US filter companies!

The first I heard of the 'Kingtech' issue was via a customer of mine who indicated Barry may have had some clients with issues, I hasten to say I did not hear from Barry direct, which would have been nicer. Anyway I contacted and had an email conversation with Barry asking for the detail, replied to this feedback and then heard nothing back.

The CAT is a simple device using a pleated paper fuel filter as the pickup and filter, as said these are sourced from the USA and shipped to me direct, the cases are hand made by me on mandrels and are made of 8 layers of two different glass cloths using West resins, the end caps are black FR4 (G10 to the US guys), the barbs are machined to my own design here in the UK by an RC friend who has a large business machining parts for the oil industry, these brass barbs are now also chromed to make them more durable, the internal filter standoff is machined by the same company from high grade aluminium, these are bonded to the filters with Hysol following a process of keying and cleaning so NO debris is present when manufacture is completed.

Each CAT is pressure tested to a minimum of 30psi, which is what most of our modern day car tyre pressures are inflated to, so the case and bonding is strong, naturally jamming it into spaces is not ideal nor recommended as first you should be able to see the CAT to enable observation of fuel/air issues and second it could cause damage. I make the cases from glassfibre and epoxy and the ends from FR4 (epoxy/glass board) so that the materials being bonded are of the same family making the bond the strongest, bonding different materials for many adhesives can result is reduced bond strength.

Some 5 years ago Cranfield University here in the UK were working with NASA and Boeing on development of the X-48 and they contacted me to ask if they could test the CAT as they were looking for an air trap to use in the project, I shipped them 4 and following 6 months of testing they confirmed these were the best performing air traps they had tested, (I was not privy to the other brands tested) and the result was they were used with both Jetcat and AMT Titan turbines in the project and performed without issues. I would expect the testing followed some fairly well documented and tried processes.

I appreciate that this does not provide a guarantee, but it does prove the system and concept have been tested by authorities who have undergone lab and field testing to a very high level.

The filter in the CAT is designed to act as a filter, and I would expect it to do so, debris is going to get trapped in it on occasion and this would highlight potential issues with fuel, pre-filtering or something else. The filter size is very large when compared to many other UAT products and this provides a huge surface area for filtering but also allowing fuel to freely flow through it. All filters will gather debris, in sintered types the debris embeds itself in the honeycomb of the filter making observation difficult and not easy to detect until restrictions build up and something then results.

The CAT does have one issue, the O ring fixing system. It is one area that I am reviewing to improve, O rings are easy to replace however, available from me or Todd at Dreamworks and cheap as chips, even if they need replacing every 3 months its only going to cost you a few $ a year. If there is a problem with the extra $ then email me with your address and CAT size and I will send you some FOC

The CAT may not be the solution for everyone, the choice you have is much bigger now, I remember back to the days when the good old BVM air trap was being widely used and some loved it and others did not, many still use them and love them, many don't, there is no right way or wrong way but I know the CAT does what its designed to do, its been tested at the highest level and I know each one is made exactly the same way as every one before it, I do not outsource any assembly processes, apply the Hysol myself, tap each barb hole, layup each tube, cnc each mounting base myself and test and package each too.

Finally I have had no direct feedback or comment from Jetcat, in fact I would be surprised if there was, one top German kit manufacturer who sells a huge jet kit supplies a custom 450ml CAT to them to use as these jets are mainly powered by the P400 turbine. BF turbines also recently purchased 450ml CAT's for use with the B500 turbine following testing.

If anyone has a problem or a comment or a suggestion around making the CAT better please get in touch, I'm very happy to provide help, suggestions and learn from your experiences.

Safe flying.

Dont worry, marcs there absolutely nothing wrong, and everything right, with the CAT which is why so many of us, including myself, use them with complete success. It's the OPERATORS who are getting it wrong by improper and/or insufficient fuel filtration. Rather like those who blame Festo filter leaks, which are designed for gaseous vacuums, because they leak occasionally leak when improperly used under fuel pressure !!

Following fullsize practice I filter fuel multiple times BEFORE it gets into the aircraft so that its clinically clean and the final filters including the last chance filter present on some engines. should have, and don't have, anything to do.

Some advice:

Obtain fuel from a known, clean source, you'd be surprised how dirty some fuel is from GA airfields. Kerosene from UK hardware stores such as B +Q is incredibly clean.

When transferring fuel to your bowser use a MR Funnel filter.

If there is ANY trace of water or debris repeat until clean and without water. Mr Funnel may not remove all water at first pass.

Use a filter on the entry side of the bowser, field, pump, and another after the pump in the line transferring it to the model.

Use an onboard filter in the refuelling line feeding the UAT, CAT or other header tank,and on to the main tank.

Use a very fine filter on the inlet side of the pump. JetCat metal filters are perfect (but must be tested under pressure before installation)

Result, perfectly pure fuel to the tanks and on to the engine and in jet aviation, (fuel) cleanliness is next to godliness !

All of my jets are configured this way and the filters in my two BobCats, my high time models, have been installed for about 13 years and hundreds of flights without replacement.

Of course the guys who replaced the CAT with another brand after it became blocked with debris, had no problems, the CAT had precleaned the system for him !

Enjoy the CAT, ( a far from delicate device when installed and used properly !

(Lets not abuse it !)


PS for Fenderbean its INTAIRCO not Interairco, and that trap is also excellent.

Last edited by David Gladwin; 01-24-2016 at 08:46 AM.