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HelicopterSynergy R/CSynergy N7 › Synergy Turbine Fuel tank opinions
03-14-2015 03:27 PM  3 years agoPost 1
Jim Cimino

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NE Pennsylvania

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Following in Dan's (dyecocker1) footprints, I have also started a turbine conversion on an N7. The few things that I am doing different which will add some weight is that we are making new frames to install a larger tank. I have been working with Michal Marcan to make these frames and we are trying to decide which tank set up will look the best and give the best service and flight times. Currently looking at two tanks that have been used in the Trex conversion and they normally mount them sideways. The round tank holds 1000CC's and the rectangular tank holds 1200. The helicopter is going to be a little nose heavy with the engine facing forward, so fuel in the back will only help. Currently we are leaning toward using the rectangular tank and mounting in lengthwise. This will stick out both sides a little so it requires us to square off the back straight down from the tail boom. The landing gear would be lowered 1/2" which will allow for clearance on the front landing gear support. If we use the round tank and mount it sideways, the landing gear will be lowered 1.25". The rectangular tank has a shelf in the front which would be on one side of the helicopter if I mount it sideways. I am just looking for your opinion on which way to go. The pictures are of a trex with the tank sideways and the drawing show the two tank installations that we are considering.

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03-14-2015 04:06 PM  3 years agoPost 2
Jerry K

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Houston Area

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A square tank will always give more volume for a given space, so your first drawing looks to be the best. You really want ALL the fuel on the CG. I know that you have to make consessions when dealing with this issue. Another item try to minimize the amount of tanks in series, If you have 3 tanks make the first 2 feed into the 3rd along with some type of trap. Fuel feed resistance is the down fall of most fuel systems.I would try to mount an air trap above the engine and push some of the electronics up. If you are ever going to fly inverted I think it is a necessity

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03-14-2015 04:22 PM  3 years agoPost 3
Jim Cimino

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NE Pennsylvania

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Thanks for the reply, but I am familiar with turbines. I really just want opinions on the mounting options.

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03-15-2015 05:10 PM  3 years agoPost 4
Josh Kussman

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Superior, NE

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Don't know any thing about tanks and how much fuel need to fly a turbine. But just wondering if u could run a oversized battery and place in rear behind the elevator servo for CG?

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03-15-2015 06:51 PM  3 years agoPost 5
Jim Cimino

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NE Pennsylvania

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Turbines eat a lot of fuel. That rectangular tank is about 40 oz. and should give 8-9 minutes of flight time, maybe a little more. The stock synergy tank gives Dan about 4 minutes doing 3D. The advantage to the larger tank will be the CG, you can fill it with as much as you like. I will also add a hopper tank and the battery to the back. The Whiplash I am building will have two, 25 oz. tanks mounted on the side, and should yield 10 minutes of flight time. I still think the power to weight ratio will allow this to fly great.

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03-15-2015 11:05 PM  3 years agoPost 6
Dan Minick

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Columbus, WI

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Actually I run a 24oz tank to get 4 min. Stock tank did not allow close to this. And my CG is actually perfect with a half tank of fuel and the 2700 FADEC battery on the rear

The CG is not as far off as you might think with the forward facing engine. One concern with such a large tank mounted so low in the frames is this will dramatically shift the CG downward away from the disk. Your flips and rolls could suffer depending what you are looking for

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03-16-2015 06:02 PM  3 years agoPost 7
Jim Cimino

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NE Pennsylvania

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Dan, what do you think about a sideways mount like the picture of the TRex?

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03-16-2015 11:42 PM  3 years agoPost 8
Dan Minick

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Columbus, WI

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That seems like a good enough design, I am sure there have been many of them sold. That tank must only be around 4-5 inches wide. I like that its not sticking much past the turbine outlets if any

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03-17-2015 10:32 PM  3 years agoPost 9
Chris Bergen

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cassopolis, MI USA

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4 min doesn't seem a lot from 24 oz.... What turbine rpm are you spinning? What rotor head speed?

Chris D. Bergen

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03-18-2015 01:15 PM  3 years agoPost 10
Dan Minick

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Columbus, WI

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My throttle is set to 82% I am guessing that is somewhere around 145,000 as I am not aware that you can check max rpm from a flight in the data terminal. And approx 1900 hs. I have had no one around to confirm with my tach as of the 4 flights this spring.

I need to get more kero and get some solid hs numbers.

Working on installing a magnet sensor so I can use vbar gov on the turbine with V-Control radio

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03-23-2015 06:40 PM  3 years agoPost 11
Jim Cimino

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NE Pennsylvania

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This is the latest frame drawings that I have. Using this design will allow for landing gear support and we will not need to widen the frames.

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03-24-2015 09:32 PM  3 years agoPost 12
Chris Bergen

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cassopolis, MI USA

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I should rephrase, what MAX RPM setting do you have in the ECU?

For instance, I run my Max setting at 185,000 in the winter, with a 1900-2100 HS. With 2 ea 20oz tanks I get appx 12 minutes of flight time.

During the summer months I run 195,000 RPM, same HS, and still get 10 minutes of flight time.

My G/R is 6.43 to 1, BTW... so in Idle 2 at 2100 HS, the gearbox output RPM is 13500. The gearbox ratio is 4.3 so the input is 58,000.

Its difficult to correlate the Turbine RPM to the input RPM, but I have typically surmised it to be appx double, when there is minimal load on the rotor system (ie in a hover). Doing a full power climbout will obviously require more power (RPM) to maintain the rotor RPM, so it varies and is regulated by the MAX setting that you input.

Chris B

Chris D. Bergen

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03-24-2015 09:36 PM  3 years agoPost 13
Dan Minick

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Columbus, WI

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Stock setting, 175,000 max

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03-31-2015 03:49 AM  3 years agoPost 14
Jim Cimino

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NE Pennsylvania

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I did the first trial fit of the new frames today, cut from G10 for now. We only cut one side to see how everything went together. Everything fit really nice, but there are a couple small changes that we are going to make before we cut the final version.

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05-23-2015 01:35 AM  3 years agoPost 15
Jim Cimino

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NE Pennsylvania

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Finally getting a little time to work on the turbine project, it has been a while since I accomplished anything. The frames are all cut and now I am trial fitting everything to decide on the best locations. I was held up for a while waiting for a couple parts and now I am waiting on a fuel shut off valve to finish the fuel system. I am putting the electronics in the front. I modified the front frames to allow for a better canopy fit and then added a doubler to the front for the landing gear. I also used a little thicker carbon fiber for the frames because of the added weight of the turbine. We lowered the bottom of the helicopter a little over 1/2" to clear the front landing gear support and allow for the larger fuel tank. Everything seems to be going together well and the only spacers I needed were from the engine mounts to the helicopter floor plate.

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HelicopterSynergy R/CSynergy N7 › Synergy Turbine Fuel tank opinions
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