Platinum Princess

[graill]

Havent posted anything in while due to my fathers passing a few months ago, kinda lost the drive to do anything but slowly getting that back. Will be handling his estate so posts will be off and on when i get time as i have to go to a couple other states, back and forth to handle business. Moved into his house in Tumwater last month.

Got a bit of the posting bug so here are a few pics of the parts so far. Duplex Stainless steel duct work was done by a local gunshop with laser welding through out, my designs. High temp ceramic liners and ducting made by me. The fully baffled fuel tanks are stainless but also low carbon alloy and are not as brittle as the exhaust ducts but they wont be taking 800 degree heat either.

Fittings are Beswick high flow quick disc made of stainless. Intakes are fully functional and will be used to assist in cooling the exhaust along with the main duct work (not shown) and for Turbine intake both sets flow a combined (4) 170 CFM/80.2LPS. More than enough for both turbines running at max rpm. Eventually i will be using a CF dual intake feed ductwork with a center K&N 200 CFM flat filter, that way i can get rid of the restrictive intake screens these jetcat turbines have. Mockups of a couple parts are in the photos for comparison, they got them pretty much exact. Keeping the Princess To scale with intakes and exhaust.
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[graill]

More.

The exit tube still needs to be trimmed below the ceramic liner, right now it is just sticking out a bit. need to final fit before trimming.

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[graill]

Another bunch.
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[graill]

Last bunch.
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[electric]

Nice job. Really a whole another facet of boating with those engines. I love the sound of them.

[ManuelW]

amazing job done on the welding, whats the weight of one fuel cell? Your exhaust system looks pretty amazing too.

At the gearbox cover, what is the 2nd 90° Festo connector beside the connector for the fuel line (lubrication) ? That 2nd connector does not exist on a "standard" turbine

regards,
Manuel

[graill]

amazing job done on the welding, whats the weight of one fuel cell? Your exhaust system looks pretty amazing too.

At the gearbox cover, what is the 2nd 90° Festo connector beside the connector for the fuel line (lubrication) ? That 2nd connector does not exist on a "standard" turbine

regards,
Manuel

You know why Manuel, Grin. The short version for anyone else is it is for extra fuel bleed off as the original cooling (lube) slots for the shaft are much larger now and i do not need excess fuel pushing out seals.

[graill]

Manuel, the fuel tanks weigh a hefty 2 and a quarter pounds each, they are crash rated to 100 mph (Guaranteed by the manufacturer not to rupture, no other tanks on the market can claim that). This boat will not see speeds over 75-85 range, there is no reason for that, plus it still exceeds scale speed by a large margin.

There is some rumbling in our state legislature (washington st.) regarding RC Models that use hydrocarbon fuel of any type and crashes, this has mainly to do with planes and helis crashing on property and catching things on fire because of ruptured fuel cells. Since i use JET-A i figured better safe than sorry. The fuel tanks are fully baffled too to help feed and prevent tank ruptures on impact, again this is simply a safety precaution. 3 extra pounds of extra stainless steel verse what it would have been wont hurt a thing.

[graill]

The exhaust ducts were sent to Dallas Tx to get a PYROSIC coating (see link) not even a pound of extra material but it will drop the exhaust temp by 200 degrees plus and then I can forgo the heavy ceramic insulators I had planned. The video link shows a ducted fan exhaust but the temps for bare Pyrosic are way to high for inside a closed boat without cooking it.

http://www.high-temperature-composites.com/video-aircraft-engine-heat-exhaust-duct.htm

Attached are pics of the inside cores for the new heat shields made with micro louvers. Shown with the stock heat shield. They will be part of a sandwich of high heat aluminized Kevlar. I will make a set of extenders for the transmission later.

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[ManuelW]

Definitely a lot of engineering necessary for the special exhaust types you want to use. Imho for that solution not an option but a must-have. From what I see it will come out pretty decent. My round exhaust cones will be shipped on Monday, hope I can present them here at the end of next week.

Not as spectacular as your parts, simply "adapters" from the square stock exhaust to a round exhaust with 85mm diameter.

regards,
Manuel

[graill]

We are both doing some neat stuff but I have no doubt about your end project result being a cut above mine Manuel. Ideas, that's what makes hobbies great.

[kingwrench]

Neet stuff

[ManuelW]

by the way when I was again looking through your thread, I wondered what surface area your exhausts have at the exit?

Reason I ask, my stock turbine has a rectangular surface with 81x55mm (equals 4455mm²). I've then chosen the diameter of my new exhaust pipes with round exit the way, that the surface area stays equal or gets bigger to avoid additional pressure and therefore temperature increase in the system. And my new ones will have an outer diameter of 85mm and inner diameter of 83mm giving a surface area of 5410mm².
Basically a diameter of 75mm would have done it but right at the point where it gets from rectangular to circular it would have decreased diameter.

Your exhausts look smaller in area, therefore I'd be interested to hear your approach to the system as I'm pretty sure the dimensions did not just come from nowhere

regards,
Manuel

[graill]

@Manuel

Indeed there was a lot of thought that went into the method and madness. Some history, I worked on turbines at all levels from depot to on site user for 22 years, including maintenance, troubleshooting and repair. The project. I contacted some folks at GD and went through a question and answer about the exhaust duct on our AGT 1500 and picked their brain about exhaust velocity verse pressure and heat, ultimately the simple solution...and it was very simple, is to keep the (exhaust pressure) positive under all ramp modes and ensure hg increased and did not stall or decrease as the turbine ramped up. That is from idle to max power. Plus there must be a positive pressure when the engine is stopped to prevent negative (exhaust pressure) which will let hot gasses heat soak or basically flow back against the cooler parts of the engine creating heat damage. You read about melted Festo fittings from time to time in helis or aircraft and this is the cause. Backdraft in a stopped turbine is very bad.

The original design did not include the "Hump" you see with the finished ducts they used to be a big rectangle 90x50 (4500) slightly up from the stock exhaust jetcat has which is 83x36 (2988) at the base exit point which was way more than enough considering the small exhaust pressures of these toy turbines so we lowered the cross section until velocity picked up and pressure went up past the 18hg mark ensuring enough flow. My friend then backed the cross section toward the exhaust outlet and created a high pressure area that did two things, first it provided a static low pressure area where air would not pass after the engine was shut down and the primary reason was to create a ramp to maintain velocity exiting at a near 90 degree angle, which it does not do now. The exhaust is a convergent type to the vertical exhaust point at which it expands to a lower pressure stack and exiting, a perfect situation, high pressure to low pressure. Finished current cross section is 90x35 (3150). With the velocity it is plenty. Probe temp is almost 600c at max power which is well under spec (750) provided by Jetcat.

The actual exhaust cross section is very tiny on the "ground" unit JetCats. The volume is almost 1/3 less than the total exhaust diameter cross section after figuring in the transmission bell that blocks a huge portion of the exhaust exit. So any figures over with a cross section over 2500 will be sufficient at all levels. The one thing needed for any Turbine exhaust is to ensure velocity increases under the entire operating range and hg does not stall when using an exhaust duct. We do not have the luxury of free flow exhaust or cooling air that aircraft do.

I am eager to see your exhaust and what you have done for a solution to prevent hot gasses from flowing back into the stopped engine, compressor stage, as from what I understand your exhaust system is full divergent.

[graill]

Couple shots of the finished Radio box with heat shield. The top frame is removable. Though nice looking I am going to remove half the screw studs as the maker went overboard with them.

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