Lightweight Ducting

[skippydiesel]

I need thin walled, heat resistant, light weight, flexible,  about 30 mm (1.5") ID, ducting

 

I have wire reinforced SCAT tubing. The wire is in the way of what I want to do.

 

I have removed the wire but it leaves the "fabric" damaged - it does the job "at a pinch".

 

Would much prefer something similar to SCAT, without the wire.

 

Anyone know of such a product and where I can get it from????

 

All constructive suggestions welcome.😈

[T510]

I used this to replace the demister ducting on one of my classic cars.

 

https://www.amazon.com.au/Heater-Ducting-Connecting-Telescopic-Parking/dp/B0DFN8KQHL?th=1

 

[skippydiesel]

Thanks T510.

 

Unfortunatly my application has almost continual small (occasionally larger movement) .

 

I would be concerned that the aluminium would fatigue quite quickly.

 

Thanks again😈

[onetrack]

Skippy, the company in the link below has a very wide range of ducting for a substantial range of purposes. Scroll down the page, and you'll find all the available products, and their specifications and intended uses.

 

Flexible Ducting Australia | Industrial Ducting Hose Suppliers

WWW.PLASCORP.COM.AU

---

As the go-to suppliers of industrial ducting in Australia, Plascorp produces flexible duct hosing made from quality materials & provides the best results.

 

[skippydiesel]

Thanks Onetrack,

 

A quick brows would suggest that the ducting is either wire reinforced (too stiff) , to large an ID or has insufficient heat range for safety. 

 

Thanks for trying

😈

[skippydiesel]

If such exists- SCAT, without the wire would be perfect. 

 

Something along the style of lightweight lay flat hose. 😈

Edited Wednesday at 09:30 AM by skippydiesel

[onetrack]

Skippy - What level of "heat resistance" are you actually seeking? (precise temperature range). I fail to understand how you think you can acquire "thin, flexible, heat-resistant" ducting, without it having some kind of internal support.

 

You either have thin ducting supported internally by wire or PVC ribbing, or you have thicker wall, unsupported ducting. A thin wall is not going to support itself, that's why layflat hose lays flat.

[skippydiesel]

11 hours ago, onetrack said:

Skippy - What level of "heat resistance" are you actually seeking? (precise temperature range). I fail to understand how you think you can acquire "thin, flexible, heat-resistant" ducting, without it having some kind of internal support.

 

You either have thin ducting supported internally by wire or PVC ribbing, or you have thicker wall, unsupported ducting. A thin wall is not going to support itself, that's why layflat hose lays flat.

Ha ha!

 

The hose/duct need not be self "supported" because the gap between the carby  & airbox is only about 10mm.

Due to the short distance, the wire ribbing of the SCAT gets in the way & restricts some of the relative movement that needs to happen.

 

Temperature Range - From ambient Australian east coast winter, say a rare 0C,  to summer, under cowl , post engine shut down 80C. In operation the undercowl temperature is a consistent +10C above ambient. The duct will be supplying outside air, from the air box to the carby(s), so there is the potential for -C (?) temperatures at altitude.😈

[facthunter]

I don't think ANYTHING will do the Job you are asking. Moving in all directions and only 10 MM gap. Can't be reliably accomplished.  Nev

[BrendAn]

11 hours ago, skippydiesel said:

Ha ha!

 

The hose/duct need not be self "supported" because the gap between the carby  & airbox is only about 10mm.

Due to the short distance, the wire ribbing of the SCAT gets in the way & restricts some of the relative movement that needs to happen.

 

Temperature Range - From ambient Australian east coast winter, say a rare 0C,  to summer, under cowl , post engine shut down 80C. In operation the undercowl temperature is a consistent +10C above ambient. The duct will be supplying outside air, from the air box to the carby(s), so there is the potential for -C (?) temperatures at altitude.😈

silicone radiator hose?

Edited 21 hours ago by BrendAn

[sfGnome]

Silicone hump hose might help. The intent of the hump in the middle is to allow movement between the two ends. I don’t know whether the right size for your application exists, but it’s worth a google. 

[skippydiesel]

13 hours ago, BrendAn said:

silicone radiator hose?

Possible.

 

All the silicon hose, I have seen, is pretty thick walled/heavy stuff - I doubt a 10-15mm gap would allow much movement.😈

[BurnieM]

I am confused why this ducting is required.

 

I would have thought you already have ducting from the outside air to the airbox and airbox to carb. What are you hoping to achieve. Can this be achieved by modifying the existing ducting ?

 

[facthunter]

All tok tok. No Fix fix. Some clown mucking around with the airbox made the school gazelle use 23 L/hr instead of the usual 16, and guess who found out the Hard way.. Nev

[skippydiesel]

1 hour ago, BurnieM said:

I am confused why this ducting is required.

 

I would have thought you already have ducting from the outside air to the airbox and airbox to carb. What are you hoping to achieve. Can this be achieved by modifying the existing ducting ?

 

Hi BurnieM,

 

I apologise if I didnt not articulate my need in a more comprehensive manner. 

 

My airbox is a home made unit. It features a forward facing "horn" to the front R cowl inlet (fresh, cool, possibly pressurised air)

My Rotax 912ULS is installed in a Sonex using an Aerovee/Rotax adapter - makes for very tight engine to firewall space (Sonex have recently come up with a Rotax style "ring mount".)

The duct that I am discussing is between airbox & carburettors.

The space between carby inlet & airbox outlet, is about 10-15mm (not counting the mounting flanges ).

Previous ducting was a thick walled "rubber" hose.

I had a problem with the carby's ejecting fuel, from the float bowl, through the bowl breather.

After much trial, error & debate (mainly on Rotax Owners Forum) the fuel problem narrowed to the carby vibration/movement isolators being impeded by the connection to the airbox.

The solutions; # Take all airbox weight off carby(s) # Fit a more flexible duct between airbox/carby, has worked. 

The more flexible duct, I am currently using is the aforementioned, modified (wire removed) SCAT .

The wire removal damages the fabric. Great care is need to avoid punctures (wastage). After wire removal the surface looks a bit tatty & may have been weakened.

 

My only reason for raising this topic is in the hope that someone can recomend a SCAT like ducting, that would deliver a better more durable finished product.😈

 

This is a build stage photo (now has Hobbs 200hrs) shows test fit of airbox & inlet "horn" Note: how close air box flange to carby flange.

 

 

Edited 5 hours ago by skippydiesel

[facthunter]

I can only ask where did you get THAT design from? Nev

[onetrack]

Agree. I'd start by redesigning that mongrel-looking airbox. 

[skippydiesel]

24 minutes ago, onetrack said:

Agree. I'd start by redesigning that mongrel-looking airbox. 

It actually works very well - Appearances, lack of convention, whatever is spurring you to make negative commentary, is jumping to a conclusion that you have no practical basis for.

Quote

 

 

[onetrack]

Skippy, the practical basis I'm basing my opinion on, is that you have an airbox that doesn't have a satisfactory connection arrangement to the carburettors.

 

Extending the airbox past the carburettors at a very close clearance dimension, has resulted in an inadequate amount of room to install a length of pipe that would allow the insertion of a longer piece of silicone hump hose, that would accommodate movement, far better than the arrangement you currently have.

 

Don't take my opinion as negative putdown, I'm trying to supply constructive criticism.

[Thruster88]

Is the airbox mounted to the engine or the airframe? Given the way your engine is mounted, it obviously moves a fair bit at times. Is there a risk your airbox could pull a carb out of its socket?

 

Alot of rotax installations just have a pod filter on each carb, simple, light weight and it must work.

[skippydiesel]

Onetrack,

 

"......airbox that doesn't have a satisfactory connection arrangement to the carburettors."

 

Satisfactory??  depends on what you mean. The solution I have works, it's just not as elegant as I would like. 

 

As a whole the engine installation, is what it is - it actually works very well - not perfect but then what is?

 

The not insurmountable problem (carby to air box ducting) is "chicken feed" in the scheme of homebuilt problems that can arise. I have a working fix that has served successfully or about 100 hrs now. I did replace it at the 200 hrs service , as I don't know how durable it may be over time. Certainly I would like a better fix -  a durable hose/duct similar to SCAT but without the reinforcing wire. I don't like modifying the SCAT - I am concerned by the potential for damaging the fabric and the much lesser esthetic result (looks unprofessional)

 

As mentioned earlier, Sonex have recently come up with a Rotax 912 adaptable "ring mount" engine , which would likly result in a far better/more space in the engine bay - way to late for my build which has now been flying for 200 Hobbs hours.😈

[facthunter]

That lay-out is a crock. It will never be any good. You ask for advice then vilify those who try to give you advice.. Nev

[skippydiesel]

2 minutes ago, Thruster88 said:

Is the airbox mounted to the engine or the airframe? Given the way your engine is mounted, it obviously moves a fair bit at times. Is there a risk your airbox could pull a carb out of its socket?

 

Alot of rotax installations just have a pod filter on each carb, simple, light weight and it must work.

Originally the airbox was mounted/supported on engine & both carbys - far too rigid.

 

As you may know the carbys have a "rubber" inlet manifold section, specifically to minimise the effects of engine vibration & movement on the carbys. The above arrangement was effectively negating this system.

 

The airbox now has two supports on engine  itself - one a vibration isolator, the other a saddle - the idea being the airbox weight is no longer on the carbys but still moves with the engine.

 

Not sure but think the Rotax OM airbox & ring gear are attached. The airbox is far enough back from the carbys to have a longer /more flexible connecting duct/hose.

 

To minimise the potential for restricting the inlet manifold rubber flexing a very flexible duct/hose between carby and airbox needed to be found.

 

SCAT, with wire in place, was tried however the small gap (10-15mm) between airbox & carby meant that the wire effectively removed the ability of the two fixtures to move independently. Removing the wire solved that problem.

 

I do not believe there is a risk of the existing modified SCAT comming adrift - I have had one significant engine start/movement event - duct stayed in place.

 

My last aircraft ATEC Zephyr, used the two conical  Rotax filters - worked well. (Maxed out at about 125 Kt - Normal /Eco Cruise 100-110 Kt Indicated)

 

The Sonex is a significant step up in performance - outside/cool air supply to the engine, is part of this. (Max Cruise 152 Kt True - Normal/Eco Cruise 130 Kt True)😈

[facthunter]

You're going around and around in circles and still no closer to fixing your Problem. After all this. are you  NOW saying there's NO problem? Nev

[Blueadventures]

1 hour ago, facthunter said:

That lay-out is a crock. It will never be any good. You ask for advice then vilify those who try to give you advice.. Nev

Agree, Sonex need to checkout how the Vixxen is setup.