Marty d's CH-701 build log

[skippydiesel]

On 21/12/2024 at 10:44 AM, Thruster88 said:

Calibration is done with a correction card, like a compass card. 1/4 =20litres etc.

Far easier to calibrate the gauge.

Choose your increments  eg 5L

Make a blank card in the shape of an arc, to suit the gauge - could go under glass or over

Add 5L mark position of pointer on gauge card 

Repeat until tank full.

You now have a calibrated gauge.

 

As other have noted DO NOT RELY ON THE GAUGE TO REMAIN ACCURATE - always cross check with dipstick or sight gauge.

[skippydiesel]

Hi Marty, 

 

I am a tad disturbed by photos of a fuel tank with what looks like short piece of fuel hose with some other (plastic?) hose pushed into it - is this your kit suppliers recommended practise.

 

Further hose concerns - in one or more photos, there were semi transparent hoses depicted - these are rarely suitable to be in contact with fuel.

[skippydiesel]

Hi Marty,

 

Propeller thoughts;

 

Before fitting your blades - weigh each in total (vertical if will balance on scale) and at each end by using a "bridge at the non scale end. You will need a good solid flat surface out of any drafts to do this.

Compare weights - If single bled heavy, adjust the heavy blade down.  If single blade light add weight. If blade root hollow, this is where weight can be added. subtracted

When adjusting pitch angles; If your blades are a friction/clamp fit ie can be rotated with loose clamp, try using a smear of Carnuba Wax on the root. This will allow you to apply some clamping pressure, while allowing smooth movement of the blade. This will reduce over/under adjusting movement and the tendency for the blade to change pitch as the hub is tightened.

Balancing of the engine carbrettors (static followed by dynamic) is a must but will not help an out of balance propeller.

Have your propeller dynamically balanced - you and your engine will be glad you have this done.😈

 

[Marty_d]

20 minutes ago, skippydiesel said:

Hi Marty, 

 

I am a tad disturbed by photos of a fuel tank with what looks like short piece of fuel hose with some other (plastic?) hose pushed into it - is this your kit suppliers recommended practise.

 

Further hose concerns - in one or more photos, there were semi transparent hoses depicted - these are rarely suitable to be in contact with fuel.

Hi Skippy,

 

Be not concerned - as I said, that was simply the breather barb which I haven't YET run a line back to the tank.  

For the purposes of the test I simply filled the header then put a crimp in that plastic hose with a clamp on it so I didn't get fuel pissing out of the breather barb.

On my to do list is to run 1/4" alloy fuel line, which I have some of, back up from the breather barb to the wing root, then thru to where the existing return line goes into the top of the starboard tank and put a T joint in there.

[Moneybox]

1 hour ago, facthunter said:

I'd be keeping an eye on all this stuff. Any "0" ring must not be able to slip out of it's groove. How long does that PLASTIC last?  Does it get brittle.?  Nev

 

The majority of our modern motor vehicles have their fuel tank manufactured from the same product. It has reasonably low melting point and flows well when liquified allowing it to be rotationally moulded creating a smooth inside surface. It's meant to be chemically resistant and has proven itself as fuel resistant for perhaps the last 30 years.

[facthunter]

No plastic Tank in a motor car resembles that type to my Knowledge. I've seen similar on some Motorcycles but they definitely have a limited life.  Nev

[onetrack]

The PLASTIC is called HDPE, High Density Polyethylene. It's a very durable polymer, UV resistant and fuel resistant. However, as with all PLASTICS, it doesn't last forever, and petroleum fuels contain many potent chemicals that are well-known as solvents.

These solvent-type components of petrol will eventually migrate into the HDPE and make it brittle and more prone to cracking and leaks. However, it would take at least around three decades or more for the effects to become visible, by which time one would expect to be starting to look at replacing the HDPE tank.

 

The article below is from 1996, when manufacturers were still tossing up the "pros and cons" of plastic fuel tanks. Since the early 2000's, the vast majority of cars produced have had plastic fuel tanks, and I can't recall too many downsides. At least internal corrosion is eliminated.

 

Steel VS Plastic for automotive fuel tanks - https://www.tms.org/pubs/journals/jom/9607/alvarado-9607.html#:~:text=High-density polyethylene (HDPE),has been on the increase.

 

 

Edited January 22 by onetrack
added informative link...

[Moneybox]

22 minutes ago, facthunter said:

No plastic Tank in a motor car resembles that type to my Knowledge. I've seen similar on some Motorcycles but they definitely have a limited life.  Nev

 

That tank only looks crude because somebody has formed a very basic mould without much consideration for athletics. The inside will be better looking than the outside. I had a pattern maker make our most complicated mould in wood then it was cast from aluminium. This particular mould was not for fuel but for all the air-conditioning ducts inside a dash. Same material and same process but a much more complicated design. The original mould was expensive but the end product was inexpensive and virtually indestructible and perfectly smooth on the inside. The outside finish will match the inside of the mould but in most cases its not important. 

[facthunter]

Look I've seem them on Motorcycles (off road)and a lot of Plastic stuff is going very brittle with age.. Often sunlight is part of it. I'd like to see what is often done to race car  tanks where they are pretty crash resistant.  Nev

[Aero28]

Hiya Marty,  Have you done a weight and balance yet?  If so could you share the weights, I would like to know if my RO 700 project is in the ballpark.

[Marty_d]

8 hours ago, Aero28 said:

Hiya Marty,  Have you done a weight and balance yet?  If so could you share the weights, I would like to know if my RO 700 project is in the ballpark.

Hi,

Nope - not as yet sorry!

The front wheel stays on the ground with the engine attached and doesn't when it's not, that's the extent of w&b to date...

[rgmwa]

1 hour ago, Marty_d said:

The front wheel stays on the ground with the engine attached and doesn't when it's not, that's the extent of w&b to date...

That’s the big test. The rest is just paperwork.

[facthunter]

I think the process has become a lot more complex. Did the plans suggest a CofG to expect? if so keep track of the Variations and apply them (Wt change x Distance) for balance and add or subtract for Basic wt . Nev

[facthunter]

Just weigh the nosewheel and you will get a pretty good idea. IF you also do the others you can get it real close ( for your own purposes)  Nev

[Marty_d]

First attempt at lock wiring today. 

The prop bolts are nice and accessible, not so much the ones at the top of the nose leg...

 

[IBob]

Very nice!

[Marty_d]

Question for the brains trust.

What type of tubing can be (or is generally) used for brake line - and where can I get it?

As per the photos my U/c is off a Sav. There's a threaded fitting which looks to hold a tube about 6mm od, around 5mm I'd.

Marking on the stub of tube I pulled off the cylinder says PA12 DIN 73378.

It appears to have a flange at the end but I'm not sure if manufactured that way or formed by the clamping action.

Been googling but no luck.  Any thoughts?

 

[Moneybox]

2 hours ago, Marty_d said:

Question for the brains trust.

What type of tubing can be (or is generally) used for brake line - and where can I get it?

As per the photos my U/c is off a Sav. There's a threaded fitting which looks to hold a tube about 6mm od, around 5mm I'd.

Marking on the stub of tube I pulled off the cylinder says PA12 DIN 73378.

It appears to have a flange at the end but I'm not sure if manufactured that way or formed by the clamping action.

Been googling but no luck.  Any thoughts?

 

 

Marty, I can't be sure but with this plastic hose it usually has a hollow ferrel up the inside to prevent it squeezing in and then an olive over the outside that compresses between the nut and the fitting it fastens to. Mine are tiny, 4mm OD tube so I bought original tube and fittings from Evektor in Europe just because I had other parts coming.

 

If I need anything tubular air and hydraulic I think Coupler's in Malaga, WA are as good as any place to get this sort of thing. I just went there with the brake fittings off Ripper, my 1980 grader. IT took them about two hours to replicate the flexible hoses that were imperial thread and they supplied all the tube and tube nuts at the same time. Pretty much blew the budget but I got exactly what I needed.

 

https://couplers.com.au/ 

 

[Thruster88]

6 hours ago, Marty_d said:

Question for the brains trust.

What type of tubing can be (or is generally) used for brake line - and where can I get it?

As per the photos my U/c is off a Sav. There's a threaded fitting which looks to hold a tube about 6mm od, around 5mm I'd.

Marking on the stub of tube I pulled off the cylinder says PA12 DIN 73378.

It appears to have a flange at the end but I'm not sure if manufactured that way or formed by the clamping action.

Been googling but no luck.  Any thoughts?

 

It is important to get the correct tube, the wall thickness has to be right for the connector to work. The nut squeezes the tube against the inner piece on the caliper or master cylinders. Look up the type of brake system you have, Matco, etc,  they should have the tube type listed in the parts.

 

Also important to use the correct fluid for your system. Most aircraft use red hydraulic oil or ATF. Some use automotive brake fluid. The seals are not compatible with the wrong fluid. 

[facthunter]

Good Motorcycle stuff would be best practice. IMO.  Nev

[IBob]

Marty, I believe it's exactly the same stuff that is commonly used for small industrial pneumatics.
The offcut I have is a snug 4mm ID and 6mm OD.
The way that fitting works is you push on the tube, then when you do up the nut, it squeezes the tube in such a way as to form the olive at the end.
You may want to practise and count your tightening turns: it is easy to apply too many turns and if you do it tries to pull the olive off the end of the tube. And there is nor real 'feel' to it: if it finally starts to feel tighter, you've probably gone too far.

[IBob]

PS as noted by Thruster88 you need to use the right oil.
My Sav manual states that it must be mineral based oil NOT synthetic.

[rgmwa]

There's a lot of very useful information in this document from Vans: 

Section 5 General Information - Van's Aircraft Total Performance RV Kit Planes

WWW.VANSAIRCRAFT.COM

 

 

[Moneybox]

On 22/03/2025 at 8:25 AM, Marty_d said:

Question for the brains trust.

What type of tubing can be (or is generally) used for brake line - and where can I get it?

As per the photos my U/c is off a Sav. There's a threaded fitting which looks to hold a tube about 6mm od, around 5mm I'd.

Marking on the stub of tube I pulled off the cylinder says PA12 DIN 73378.

It appears to have a flange at the end but I'm not sure if manufactured that way or formed by the clamping action.

Been googling but no luck.  Any thoughts?

 

 

Marty, Take a look at Page-33 in SP issue 111. HP Aviation hoses.