Yup, they are polished from factory and should bling up real nice with some TLC.

Ya they need a little work but sure look nice with the Gemini Logo on them....

Three Guesses!!!!!! :)

https://cimg1.ibsrv.net/gimg/www.rcu...8f6f784ca4.jpg
https://cimg2.ibsrv.net/gimg/www.rcu...5c752dd678.jpg

I would guess that is a craptrap intended to go between the mufflers...

Barf trap? i.e. vent regurgitation tank.

I wonder about 3d printing one out of PLA since I believe PLA is gas resistant.

Sorry Guys... Forgot I had asked this question... :). Lonnie got it - Its the "Barf Trap" but it incorporates the adjustable bleed I need for the Air pump setup.. Thats what the "needle" is for.

Will have to draw it but I have the plumbing figured out to be pretty simple.... i'm going to try the uniflow setup as I think the tank might siphon still at full - no check valve though.. This little barf tank has a shallow funnel in the bottom so any fuel pushed back should drain back As soon as pressure returns - it will have an overboard dump (Needle outlet) in case it fills up. Doing this as a bit of an experiment - Easily changes back to normal operation if required.

:D :D :D :D Simply LOVE the nomenclature :D :D :D :D

Am I close in thinking it will be mounted vertical in the plane, pump line, needle and dump up and, connection to tank at the bottom? So any regurgitation would fill up the barftrap from the bottom, and any regurgitation gets pushed back eventually, regardless of that being because of fuel consumption or pump pressure?

You got it Bert…. Tank has three lines. Feed clunk, vent clunk and a top vent. Top vent is plugged except when filling. Feed clunk is right to carb. Vent clunk goes to the bottom of the BT but will loop outside the fuse for filling. ( through the vent clunk)

Dave, I have played with printing tanks (mostly control one for Glow fuel) and what I found is that most plastics do OK for general exposure but filling them with fuel brings different issues - The only consistent plastic for Gas seems to be PETG which is used for fuel tanks regularly (water bottles). Some PLA's did OK but others didn't in full Exposure. Glow fuel is tough and I ended up giving up on my printed tank attempt..

Recently had some very nice prints with a PETG - Should revisit the Crap Trap/Barf trap printing maybe.

a 3d printed barf bucket is what i was thinking. i would never try to print a fuel tank, although a tank with barf bucket in one would be a nice setup.

I have not the faintest clue about the resistency of printed plastics, but IF it works, integrating tanks and barftraps or craptraps opens up entire new dimensions when it comes to compact, clean and tidy set-ups

OH Man Dave... Great idea and it lit a candle... The combo of a tank/trap with baffling as Bert suggested is a very good idea... I am running a few tests with my "new" PETG (lexan) and things are looking very good.. Stay tuned. I had kinda given up on printed tanks as I was trying to make them withstand Control line glow (medium nitro 15-25%) and that was tough - Gas and Oil are much easier.

Be sure to share the fusion 360 files. I'm very curious.

A combo main tank/header tank would be neato Frito too.

Yup... indeed the "printed tank" thing opens up a world of possibilities but also cans of worms.

But way I see it, up until now, fuel tanks are simply plastic bottles "of the least inconvenient shape" which means they are always very sub-optimal when it comes to fitting an acceptable tank volume in the availlable space, and having to locate the ignition somewhere as well, sometimes things still get cramped.

Printed tanks first and foremost allow a tank to be shaped to the availlable space, AND to be shaped "around" the ignition box, and for especially the smaller planes, that could prove to be extremely helpful.
Just as an example: the plane I have here in indonesia, it has its nose crammed full with a 6 oz tank and an ignition box and the remaining space jammed full of rubber foam, and loced in place by a balsa beam across the fuselage directly behind the tank. Although there are no issues with it, servicing or maintenance is going to be a chore because that nose is cramped.
A printed tank design could have allowed for something that is way easier to disassemble and servicable.

So many options here if this is viable - I have a few test pieces on the printer tonite for trials.. Made a barf tank to better fit my layout.

Here is a very quick tank and baffled Crap trap. few issues with this drawing but you get the idea of what's possible.

https://cimg5.ibsrv.net/gimg/www.rcu...f5287684b3.png
https://cimg0.ibsrv.net/gimg/www.rcu...5b2baa80b9.png

Will any petg work or is there a specific flavor that you think is best? I couldn't find any good data on gasoline resistance of 3d printed material. Also how many perimeters and top and bottom layers are you using for best sealing the extrusions? Are you overextruding a bit on purpose perhaps for better sealing between extrusions? I'm just brainstorming because results vary widely with fusion deposition machining.

By the way, I've switched to klipper and modded my machine a bit because I like to tinker.

Aehm... although I think that the baffling is a good idea, none of my traps have it and I have zero pass-through. However, the craptrap as drawn, is strictly non-aerobatic... A prolonged inverted flight WILL dump the contents into the fuel tank. In order to have the best effect all around, the passage from trap to tank should end in the physical centre of the crap-volume.
Regurgitation from fuel tank to craptrap is, if anything, a nuisance (worst I have seen was about 10 ml of regurgitation per full flight on an F3A plane, with a practical crap-capacity of 30 ml) but crap passing the trap into the tank will end up being quite a bit more than a nuisance: Because of the effects being initially ambiguent and only increasing gradually, the crap issue will have anyone chasing his tail for quite a while at first. Better to prevent it at the root.

Bert, I am surprised you would see as much as 10ml of regurgitated fuel in the CT. A result of repeatedly reducing throttle during inverted flight, I suppose.

Have you ever accually tried to run your setup without a CT for long periods of time?

Arlyn (AA5BY) has over 300 flights on his gas conversions with no tuning issues using only a felt clunk. One of his conversions has over 200 flights with no fuel tank maintenance at all. He states having no issues with condensate in the fuel tank or fuel jug either, which honestly has me a bit puzzled.

I have no doubt that a CT is better than having no means whatsoever to stop carbon particles and condensate from entering the fuel system. The question is just a matter of necessity. I rarely get more than 100 flights on any given aircraft equipped with a gas engine before having to perform tank maintenance anyway e.g. change out the hardened tygon fuel lines.

It's an F3A (competition aerobatics) plane. I do not fly competition, but I do try to practice some of the manouvres (not very good at it). They call for sudden and switchlike throttle changes that always and as a matter of the nature of the thing coincide with changes in direction of G. A simple Hammerhead is full throttle in the upline (tank vent not immersed, full muffler pressure) for about 3~4 seconds, immediately followed by a vertical downline (Throttle at idle, minimal muffler pressure, tank vent immersed) for another 3 seconds. That gives a maximum reflux, and that kind of situation is occurring at least 10 to 15 times per flight.
This plane is the only one that does that specific type o flying, and also the only one that does it. My "free" flying style is much more relaxed, less harsh changes of G direction and way less harsh changes of throttle setting.
Yes... I started without a craptrap, and a quick glance in my logs shows that I I started gasoline conversions in a helicopter in May 2015, first fixed wing plane flew in summer of 2016 and the first time I make mention of a craptrap was in december 2017, so I am guessing that I started having unacceptable dirt issues a few months before that.
From memory, I remember the helicopter having had several issues with dirty clunks in the roughly 2,5 years up to that point, that I solved by washing or replacing. Then (from memory, all my planes that up til then flwe relatively without issues all started to show the same behaviour, and I concluded that the reason was that they all ran on the same fuel from the sam can, and that that can got polluted by defuelling after flight. This defuelling turned the fuel in the fieldcan black. In hindsight apparently the pollution level of the fieldcan became unacceptable.around that time given that all models started to act up in the same manner.

Since for me not defuelling was unacceptable, I had to do something that kept the fuel clean in the tanks of the models, and that solution was the craptrap.
Since then, my fuel has always remained clear and bright red (my oil is red, and gasoline in the Nethrelands is undyed) and I haven't had one single issue with a blocked clunk ever since.

I have NO explanation for why Arlyn has no issues. But you knpw, since I sell these kits (even if it is at total zero profit) for me it would be extremly bad service to anyone interested in gasoline conversions, to NOT advise the craptrap. That will lead to people running into trouble a few months or a year after the conversion, and resulting in reputation damage for gasoline conversions.

My three most flown engines, the FS 52, the Boxer and the FS 91 have (in that order) the equivalent of 420, 325 and 250 10 minute flights, give or take.

The FS52 and the FS91 were among the planes that had issues with dirt, the Boxer was set up from the beginning with a craptrap (all other planes got one too around that time), and never had an issue. None of the later planes ever had an issue either.

I cannot explain Arlyns experiences, I can only share my own data and experience and what I did to counter the issue.

One thing that must be mentioned: the solenoid, provided it is well set up and adjusted, seems to drastically reduce the "crap-load" on the trap. (OK, I know that was a bit of a bad word, but I thought it funny :D ).

Another thing that is conspicuous (to me) is that all planes that have flown without a craptrap, the material of the fuel tanks is "dirty" and has a grubby appearance, but the planes that have only been operated WITH a craptrap, the plastic the tank is made out of remains near "new" bright and clear.
I have never needed to do maintenance on any tank that I fitted out with the Stihl fuel bung:
https://www.modelbouwforum.nl/attach...2534-jpg.6851/

Which is Stihl part number 42293587702.
I have not done ANY tank maintenance since end of 2017 (installation of craptraps all around) and hundreds of flights since, Haven't even been taken out of the plane... I simply have never needed to...

i think with chris experimenting with the digitally controlled airpump, craptrap is probably the wrong description as there's no crap from the exhaust to get into the tank. this is simply a barf recycling sump and everything in the barf sump is intended to be returned to the tank.

Aw, dang... and here I was being so clever... :D

You're right... but if that's the case, better bring the pump connection to the physical centre, to avoid gas getting in the pressure line to the pump, because probably the fuel will mess up the pump...

I think the pump is always somewhat on so a simple loop in the tubing would be sufficient to protect it.

:D yeah, that is my "abundance of caution".... Dang, where did I hear that before?

Testing will prove if it is a problem or not...