Geoff_H

Why use steel? Heat conductivity of 45w/mK and weight of 7.6k kg/M3. When Aluminium 1/3 the weight and back the aluminium with 13mm Fiberfrax heat conductivity of 0.22w/mK and weight of 96kg/M3 so much lighter so much more (approx 250times) more heat insulation. A longer time before your plywood bulkhead starts to smolder and fill the cabin with smoke. It is also a driven system.

I suggest that you look at GA designs and copy one of them. That way you could fail to some nuance but overall you will probably get the best result. I would not copy a RAA nor an amateur built aircraft. Their designs have a high degree of problems. One of the things that worried me is the high proportions of plastic fuel lines that I have seen. I am designing and building a composite Cri Cri aerodynamic similar aircraft. I have found that it is extremely time consuming with very little previous designs to call upon, I have to research so much and end up making something similar that has been previously designed. It has worn me down and I am seriously looking at abandoning the prokect. I have had 40 years of designing and trouble shooting mechanical equipment, I also have a degree in mechanical engineering. To get it right on your own is possible but what if you get it wrong? What design review process do you use? How do you make sure that the reviewer is doing a good job. I worked for a company in Dallas that did nuclear design ( not me). They put the checker in a room, no telephones, no other personally allows in, max checking time without break was one hour. What I am trying to say is don't do your own thing, use the greater knowledge of the professional flying community, unless you have professional training, even then consult other very experienced people.

Aluminium and fiberfrax is far lighter and approximately same cost as Stainless. Aircraft Spruce sell it probably cheaper than stainless. A special high temperature glue is used. It will also be infinitely slower to heat whatever is behind the firewall

At the end of the day ( a strange statement lol,) a firewall is about limiting the temperature rise of the cockpit side of the firewall. An interesting one is for the CozyIV. It uses aluminium, light but conducts heat rather well, coupled with fiberfrax, a sheet of "stuff" that is a very good insulator of high temperature heat and is very light. I saw a demonstration of this stuff over 30 years ago, thin blanket of fiberfrax one side a hand the other an oxytorch! Impressive! But I was told that it's low temperature heat conduction characteristics are not so good.

I have never done an airflow through the engine but I think that the Reynolds number varies with fluid density, would these values and assumption be true for both sea level and 10,000ft? No idea just asking

After 40 years of designing constructing and commissioning I have learned that any errors in design and the working end product depends upon the accuracy of your assumptions. The best advice is to do your calcs three times. Once where you expect assumptions to be then do them twice with assumptions at their extremes. The results will be the worst possible outcomes. I was the lead engineer in the middle east in the early 90's. It was an American job and back in Dallas we had PhD people check all of our calculation in a multiday seminar. They were good calcs. Got the design running in Syria, it didn't work as expected. After a lengthy investigation we discovered that our assumptions were wrong! We did modify the plant and it eventually worked to spec. Ever since I question assumptions not the calcs (not as much anyway). Murphy was an optimist. My long held saying. Geoff

If I remember correctly you can use Reynolds number to calculate friction in pipes etc then use a circuit diagram for the airflow and solve it as if it were am electrical circuit.

Please take not that the cooling air will be blanketed from the wing flow. This technique is used in high performance gas turbines where a layer of air is run over the first row of blades to blanket them from hot combustion gas. Is

I was not very good at fluid mechanics, but one principle has stuck with me, the flow velocity of a fluid over a surface is zero at that surface. With respect the problem at putting a heat exchanger in the wing leading edge is the velocity at the leading edge will be zero hence: "Turbulent flow, due to the agitation factor, develops no insulating blanket and heat is transferred very rapidly. Turbulent flow occurs when the velocity in a given water channel is high. ... Laminar flow develops an insulating blanket around the channel wall and restricts heat transfer." Best regards Geoff

Would the talk about seat belts etc before take off and emergency outfield landing constitute passenger carrying? Can't think of anything else I did. Did my licence in 1980. Did a lot of FullSAR, SARTime and landing at international airports. Very different flying then.

All this passenger thing is a crock of...... It is somewhat intuitive, more important is cockpit management in case of emergency, I have used it once and should have on possibly my worst landing ever in front of a control tower. More important is landing without an ASI, I have had to do it twice. I was not prepared the first time on a relatively short runway, second time on a long runway. No GPS on first but GPS on second.

I did not get any passenger in my PPL when I did it in the early 80's. It came intuitively. I had a few times that I had to exercise it. I took a first ever flight passenger. I was worried what his reaction would be, worked out a way to get immediate clearance to land without him being worried by the request. He loved the flight, even the 60deg steep turn I did. I do however remember when learning outfield emergencies that it was an outfield landing, not a crash landing in my passenger brief. Maybe that constitutes passenger management.

In explosive atmospheres the explosive gas can and will travel up the wire into a safe area ( not so safe then). For safe installations there are sealing kits that use systems to stop the gas, only a few inches long but stop wire transfers.

Soldering can be done properly, but the joint has to be restrained, that's extra weight in the aircraft. It has to be done properly, a crimp tool takes almost all of the chance of error out. Space craft don't vibrate after the trip to orbit, long term fatigue cracks would not have time to occur, atmosphere almost certainly not corrosive.

I should point out that when comparing HV cable connection it was with respect to corrosion in the joint, not electrical conductivity. HV cables come with a steel cable for strength with conductors ( often anodised aluminium) wrapped around the outside. At these voltages electrons repel each other and crowd the outside skin. At these voltages you don't get electrocuted you get burner as the electrons run down the outside skin of the body. As another aside the aluminium conductors are often coloured to fit in with the surroundings, that makes them hard to see from the air as well. Makes low level flying really dangerous.

I definitely believe so. Same technology just very different sized crimp machines. The high voltage cable swayed came with petrol driven hydraulic pumps and piston driven swage dies. My crimper is mechanical advantage crimp that is getting harder to use as old age sets in 😒

A properly crimped joint is a galvanic bond and will only corrode around the edges. High voltage (330/500kv)I we are crimped, often near salt water, they are not known to collapse from corrosion of the joints.

A properly done crimp does.

Yesterday I had my latest encounter with soldered joints failing. A classic mini that had an upgrade to a solid state fuel pump, one we often see in aircraft. The short leads from the pump had an extension soldered to extend their length to a plug. Sitting near the rear suspension the pump even has its own vibration isolation mount. The joints (positive and negative) had heatshrink around them. Finally failed several years after installation. Unfortunately 200km from home. I am just glad it was not an aircraft. A motor mechanic soldered a new pump in, he did not realise what the failure really was. The owner and I have a date to replace the soldered joints with crimped ones. With a professional crimp tool!

Surely everyone knows that space aliens actually gave them antigravity stuff to build the pyramids. 😳

I think seals will be a problem. The surface velocity looks like it will be high, this will contribute to wear. Air cooling claim was suspicious, and we only saw the engine with apparently no load. However the concept fascinated me. I have an unusual curiosity, just ask the wife.😏

Not defending it but there is video at the end of the clip that shows something like this running. I don't think that the wear at the max speed would be acceptable. I just found it an interesting concept.

https://thekneeslider.com/omega-1-internal-combustion-engine-is-light-powerful-efficient-and-clean/ This engine is very interesting.

I did heaps of calculations on which is lighter an epoxy/ cloth design or aluminium. Strangely aluminium was the lightest, for a very unusual reason. The shear stress of aluminium is around 60%of the UTS. With any epoxy/cloth the maximum shear is the shear stress of the epoxy, after all that is in shear between the layers without cloth holding it together. When I designed the main spars they were heavier than aluminium by a significant amount, just to ensure that the spar would not fail in shear. A lighter spar could have been made using a carbon/Kevlar intertwined cloth. Still a little heavier than aluminium. The monocoque shell needed a foam core to get a good Euler's buckling force. Boeing don't use epoxy, a much high strength "glue". I am however a proponent of FRP.

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