My Savannah S model rebuild Blog

[Kyle Communications]

I can now finally see the light at the end of the tunnel. This cowl has been the bain of my existance. Just a couple of small indents to fill and it can be prepared for painting.

Finally got my tig back today. Its been used by my mate for about 6 years...like pulling teeth 🙂

The cowl has been fitted so now I can get the headers for the engine to the muffler properly repositioned. Then its a matter of finish hooking up the radiator system. I need to finish the avionics to a point where I can start the engine at least.

 

There is a comparison pic between the 2 lower cowls. The genuine one is a plug I made 4 or so years ago so I have that one as a plug its way to heavy to be used on a aircraft. The top cowl has been extended by 25mm so it sits over the top of the skin on the dash front properly. 

 

 

[IBob]

Big job, Mark!
And I never did come up with anything to (easily) fill in all the little mat holes on my kit supplied f/glass bits: sourced various products, but every sand/spray iteration showed more holes. If only they'd used a gel coat....what have you used there?

[Kyle Communications]

I used this ultra fine filler. Its a auto one. Almost like a super smooth cream when mixed

Lovely to sand as well

 

 

[Paul davenport]

Blokes like you amaze me   I am in awe of your talents and wish I had just a small portion of them   Great job

[Kyle Communications]

My cowl is finally finished..just have to wet rub it when I am ready for paint.

The next big thing was to get the water plumbing done from the waterpump to the radiator and the return to the resovoir. Because the exhaust pipes are so close to the radiator hoses in the Sav its a real PIA. So the idea of metal pipes between over the hot areas is the go...Like the pipes Mike (Blueadventures) got for his Ninja. But we have come up with what we think is easier and cheaper. ICP have been supplying this corrogated SS pipe for fuel and oil but it seems awfully thin to me and I dont like it but locally you can get a much better albeit a bit thicker and slightly heavier much better corrogated SS pipe. So after mucking up some sizing I got the right size pipe which is their 20mm which has a OD of 26.7mm and the inner of the rubber/silicone pipe used is 25mm so its a nice tight fit. I used a thin film of lithium grease to lube the inside of the rubber and silicone pipe to allow getting the SS tube into it. The beauty of this tube is you can bend it to shapes or curves you need and it is just held onto the rubber/silicone with good hose clamps. The SS tube is super strong so you literally cant crush it and over several ridges it will creeate a great seal with no leaks. So will get that done this weekend and bribe Danny to come over and see if we can finalise the cutting and welding of the exhaust system in the 2 places I need a little more room.

 

I also have the same stuff but the diameter for the oil..so thinking of doing the same with the oil lines

 

A few pics attached to see what its like. The 20mm SS pipe is about $20.00 a meter

 

[IBob]

My S kit was dated Dec 2014, Mark, ICP supplied steel pipe for fuel, oil and coolant. And you're right, it makes for a wonderfully compact installation, as I recall I formed the big coolant pipes in place.

[Kyle Communications]

I thought that ICP only supplies fuel and oil pipe from what I had seen. I didnt realise that they did the water as well. As I said before I wasnt keen on how thin the pipes I saw were. I am much happier with this locally sourced stuff though. To the point where I think I may use it all the time...it is a little heavier of course but I feel more comfortable using it

 

[IBob]

Mark, my pipes were further secured against vibration after those pics were taken. I also made little aluminium heat shields where the rubber is close to the exhaust, spaced from the rubber but held in place by the hose clips, you can just see the LH edge of one here.
I've read a lot of critical opinion on the metal pipes, but much of it seems mainly to be resistance to something 'new'.
I figured if they were failing, we would have heard about it.........the proof of the pudding and all that.

[Marty_d]

16 hours ago, Kyle Communications said:

My cowl is finally finished..just have to wet rub it when I am ready for paint.

The next big thing was to get the water plumbing done from the waterpump to the radiator and the return to the resovoir. Because the exhaust pipes are so close to the radiator hoses in the Sav its a real PIA. So the idea of metal pipes between over the hot areas is the go...Like the pipes Mike (Blueadventures) got for his Ninja. But we have come up with what we think is easier and cheaper. ICP have been supplying this corrogated SS pipe for fuel and oil but it seems awfully thin to me and I dont like it but locally you can get a much better albeit a bit thicker and slightly heavier much better corrogated SS pipe. So after mucking up some sizing I got the right size pipe which is their 20mm which has a OD of 26.7mm and the inner of the rubber/silicone pipe used is 25mm so its a nice tight fit. I used a thin film of lithium grease to lube the inside of the rubber and silicone pipe to allow getting the SS tube into it. The beauty of this tube is you can bend it to shapes or curves you need and it is just held onto the rubber/silicone with good hose clamps. The SS tube is super strong so you literally cant crush it and over several ridges it will creeate a great seal with no leaks. So will get that done this weekend and bribe Danny to come over and see if we can finalise the cutting and welding of the exhaust system in the 2 places I need a little more room.

 

I also have the same stuff but the diameter for the oil..so thinking of doing the same with the oil lines

 

A few pics attached to see what its like. The 20mm SS pipe is about $20.00 a meter

 

Brilliant Mark.  Who's the supplier of the tube?

 

I have to pull my finger out and order a radiator so I can get my engine install completed too - I'd like to start the engine at least once before I die of old age!

 

Are you using some kind of standard mounting for the radiator or making one yourself?

 

[Kyle Communications]

Hi Marty

Pacific HoseFlex..... they are in the Gold Coast and Victoria and Perth..I believe they actually manufacture it. You want the annular hose and no outside sleeve

 

Download the chart and just be away the size is the ID. so the OD is much larger. The water pipe I used is the 20mm and the SS0-A. tube

 

 

https://hoseflex.com/product/metallic-hose-annular/

[Kyle Communications]

2 hours ago, Marty_d said:

 

Are you using some kind of standard mounting for the radiator or making one yourself?

 

I used the std Sav radiator bracket which is just 2 smallish bent brackets but because my radiator is more facing forward I have 2 straps coming back to the bottom noseleg plate to achor the bottom of the radiator...I will take a pic later

 

[Kyle Communications]

Another thing about the hose...I used the 25 to 40mm clamps to grip the rubber/silicone hose to the tube..but make sure you get the 12mm wide clamps not the 9mm wide clamps..and the SS tube doesnt crush at all the clamps tighten down nicely and will make a perfect solid seal

 

[Kyle Communications]

Still need to put a clamp on the radiator end...I am waiting for more of the 12mm wide clamps

 

 

 

[IBob]

With any pipe type/diameter there is a fluid velocity point where laminar flow becomes turbulent flow, and resultant flow actually deteriorates. Lots of irrigation 'specialists' have lost the plot on this over the years: it doesn't matter how big a pump you fit, you're not going to get any more fluid through it.
 

There are readily available online pipe flow calculators, including for this annular pipe (though I have no feel for how accurate they may be for the smaller IDs eg. 9 or 10mm as used for fuel).

As you would expect in what is a corrugated pipe, the laminar to turbulent cutoff is especially sharp.

[RFguy]

Bob, you beat me to it by a second...

 

help me understand here, you are using it for fluid, or encasing a hose ?

 

Mark, just watch out here because the Rotax flow rate is high! higher than you'd think, 65 litres per minute.

 

I thought rotax radiator was 25mm ID on the radiator and  combined flow pipes (17 on the branches) .

 

for 20mm ID pipe, 1m long, roughness 1mm , that will be 0.21 bar pressure drop. no bends. the bend probablty costs another 0.05 bar or something.

 

I think that is quite alot of pressure drop.  -  25mm smooth is 0.03 bar drop

 

run it up and check the flow rate you end up with. 

 

BTW- I have verified this calculated is good over a wide variety of scenarios

http://www.pressure-drop.com/Online-Calculator/

 

 

 

 

 

Edited August 19, 2022 by RFguy

[IBob]

Older 912 cylinder heads take a fitting to monitor head temperature. As of about 2013 the design was changed so the fitting now monitors coolant temp, not head temp.
Max head temp was 135'C.
Max coolant temp is 120'C.

See MPD 2017-001 at https://publicapps.caa.co.uk/docs/33/2017-001.pdf

 

FWIW my 912ULS with the annular pipes has coolant temp monitoring, which generally sits at 90-100'C and I've never seen it go over that.

[RFguy]

But Bob your ambient temp that close to the Antarctic  never goes over 10degC 🙂

Edited August 19, 2022 by RFguy

[IBob]

33 minutes ago, RFguy said:

But Bob your ambient temp that close to the Antarctic  never goes over 10degC 🙂

True enough: your ambient temps are obviously higher than ours.
And I understand Mark is tweaking his engine some, and has also remodelled the cowling.

So head/coolant temps will be something to keep an eye on throughout the test flights.

 

I have steam gauges marked up with red lines.
The Sav has monitoring on front LH and rear RH cylinders and the front has always run cooler, as you might expect.
For coolant temp you don't want to get to 120'C as this is boiling point.

[IBob]

PS: I should have said "The Sav has monitoring on front LH and rear RH cylinders and the front always appears to run cooler"

 

Working on industrial hot water systems, we found we needed to be careful positioning temperature probes in pipework etc: since part of the sensor is outside the pipe, it can conduct heat away from the sensing element inside the pipe, resulting in incorrect low temperature readings. This was especially the case with smaller pipes and shorter temperature probes, and we adopted the policy of mounting our probes into a 90deg bend in the pipework, allowing us to insert a longer probe along the pipework, rather than a shorter probe across it.

Since the coolant temp probes on the 912 are short, with no thermal insulation on the outside, it is quite possible that the front LH probe reads cooler due to the cold air playing on the external part of the probe.

[Kyle Communications]

Yes I am aware of the slight reduction of ID on the pipe. I have now though probably almost twice the cooling area of the radiator due to the new opening. Having a big bore kit fitted I am expecting more heat. The engine is the pre 2013 so the temp senders measure the head temps not the water temp. I am thinking about fitting some sort of water temperature sensor as well. The metal pipe will also help dissapate some heat as there is a lot of surface area of the pipe when you consider the corrogations on the pipe. Danny was over yesterday and we were talking about how we are going to mod the exhaust pipes. Hopefully next weekend I can get that done and if I get my backside into gear this week I will have the avionics ready to start the engine and have all the monitoring going. There isnt a huge length of the steel pipe on the pax side its only about 300 long and the pilot side is about 450 long. Now the radiator core is fully exposed and also the angle in the airstream is much flatter...it still is angled though so its a suck it and see thing I suppose. I am not expecting anything too dramatic

 

[RFguy]

For other's info :

20mm ID with 1mm roughness at 1m and 65 lpm  is same restriction as smooth pipe of 16mm ID.

 

I think the important issue (apart from having enough radiator performance ) is the flow rate- for 65 litres/minute, that's  *MAYBE* implying that it is important to keep the delta T across the heads low. .

 

IE if slower flow,  means higher delta T on the heads.  .. and low flow in the radiator  means higher delta T on the radiator.  (radiator appears to do more work) .

 

And for fast flow, delta T is low across the heads but also low on the radiator. For that flow rate for that size radiator and engine , I'd be mindful of meeting the flow requirement to minimize delta T on heads. 

 

Both will work, but depending on the flow in the heads, if the water gets a chance to get hot early (in the lower side inside the head housing) then it wont be able to remove the heat as effectively on the high side of the head. and you might get a hot spot....

 

If that makes sense, sort of made a mess trying to explain myself.

 

[IBob]

5 hours ago, Kyle Communications said:

............The engine is the pre 2013 so the temp senders measure the head temps not the water temp. I am thinking about fitting some sort of water temperature sensor as well.................

 

It's really the coolant temp coming off the head/s you want.
Rotax must have had good reasons to move to that, I guess it gives a clearer and/or steadier result.
I'm just not sure where you could readily insert a probe, and I do think it needs to be inserted: I have commissioned a fair few industrial hot water and refrigeration systems, at one stage we tried a probe that could be strapped or bonded to the outside of the pipework, but we found them at best not very accurate, and wildly inaccurate unless the probe and all the surrounding pipe was heavily lagged.

[facthunter]

There are instances where lack of coolant occurs so measuring the hottest part of the head might be safer. Nev

[Kyle Communications]

38 minutes ago, IBob said:

It's really the coolant temp coming off the head/s you want.
Rotax must have had good reasons to move to that, I guess it gives a clearer and/or steadier result.
I'm just not sure where you could readily insert a probe, and I do think it needs to be inserted: I have commissioned a fair few industrial hot water and refrigeration systems, at one stage we tried a probe that could be strapped or bonded to the outside of the pipework, but we found them at best not very accurate, and wildly inaccurate unless the probe and all the surrounding pipe was heavily lagged.

I was thinking of just adding a small piece of normal metal pipe inline on the return side and screwing in a LM135 or similar probe in there. I made the temp sensors in the girlfriend Just heated up the old resistor ones and pulled the guts out then wired up a LM135 and epoxied it in there..worked a treat for all my other sensors so that maybe a solution. I think I will monitor the rear one in the head as that is the hotest and the water in the pipe for the second one

 

[Blueadventures]

6 hours ago, Kyle Communications said:

Yes I am aware of the slight reduction of ID on the pipe. I have now though probably almost twice the cooling area of the radiator due to the new opening. Having a big bore kit fitted I am expecting more heat. The engine is the pre 2013 so the temp senders measure the head temps not the water temp. I am thinking about fitting some sort of water temperature sensor as well. The metal pipe will also help dissapate some heat as there is a lot of surface area of the pipe when you consider the corrogations on the pipe. Danny was over yesterday and we were talking about how we are going to mod the exhaust pipes. Hopefully next weekend I can get that done and if I get my backside into gear this week I will have the avionics ready to start the engine and have all the monitoring going. There isnt a huge length of the steel pipe on the pax side its only about 300 long and the pilot side is about 450 long. Now the radiator core is fully exposed and also the angle in the airstream is much flatter...it still is angled though so its a suck it and see thing I suppose. I am not expecting anything too dramatic

 

Mark You could make up a short alloy pipe to place in the 17mm hose on the top of engine for the coolant and weld a female piece to take a sensor and fit it into one of those pipe.  Not sure of flow direction so better in a hose leaving a head coolant outlet to radiator.  Let me now what you think.  Also such a fitting could be fitted to any Rotax 912 and then you could compare the temp with the coolant temp gauge in the test aircraft.  Also even the LPG alloy rod brazing method may work to place the female alloy piece into the 17mm o.d. pipe 'T' piece.  Hope this explanation is understandable.  Cheers.