Originally Posted by
gunradd
For the gear I didn't go electric for the cost also this gear needs to rotate unless you remove all the scale parts from the gear and for me that's not an option.
On the fuel...
I think 2 180s is to much engine with to high of fuel burn. Have you thought about trying to sell them for smaller engines like twin 120s or the new 160s would be the ideal engine. The reason why is because you will need allot more fuel for twin 180s and that's allot more weight in front of the CG. When I was doing my CG with all 3 tanks I filled them up to see how much it changed and its drastic. Aircraft is super nose heavy with that front tank fuel. I would say full its at least 7 lbs all in front of the CG.
I flew mine full of fuel this way and it did rotate and fly but it flies much better now with the front tank smaller. So I don't want to say what you have wont work because it will work but I highly recommend getting smaller engines that burn less fuel and reducing the front tank.
Also I dont think their online manual is correct. I think they used smaller tanks on the build in the manual. The center tank in the kit is HUGE!
Gun,
The pilot animatronics and inlets look awesome, nice job man.
On the electric conversion it looks like they replace the air cylinders with a worm gear type of motor, I don't think you would lose the rotating function, I could be wrong though, I'll have to look at that in more detail. I'm still undecided and considering all options on the gear.
Regarding the fuel tanks and turbine. I'd like to say I simply went with more power and threw logic out of the window but I actually spent a lot of time trying to think it through and decide on something which made the most logical sense for me. Again, I could be wrong and have made horrible assumptions, I try and be a pragmatic as possible but when dealing with assumptions, it's difficult. Once I receive the model and components I'll be able to better test things and eliminate some of the assumptions and get to a final/final working design.
I'm certainly open to comments and ideas from you and the community, I'm the first to admit I get this stuff wrong all the time and have to rethink things as I go.
That said, let me share some of the points I tried to use as a basis for my decision, I'm putting this out there, and I'm soliciting for ideas and suggestions.
I won't cover the logic between single or twin turbines, that could be a whole other thread... I'll just cover why 180s in
my twin setup.
1 - I noticed that the position of a single vs a twin is different. The single mounting position appears to be closer, but still slightly aft, to the CG of the model. The twin mounting position appears to be more aft than the single, perhaps 3-6 inches. Again, my assumption here is "looks further aft", I can't measure this until I have the model. This could potentially have a CG effect and in turn make the model less nose heavy in a twin design.
2 - Twins require two pipes vs one. What is the weight penalty between two pipes vs one bifurcated pipe is probably marginal, maybe the weight of two bells vs one, who knows. Again, I'm using
probably, I'll have to weigh things to be sure. If there is a weight difference, it will be in the aft section of the plane, which may affect CG on a sliding scale.
3 - The conscious choice turbine manufacturers have made on recent turbines to standardize on a particular can design for multiple output turbines has to be considered. For example, if you take Jetcat's 90, 140 and 180 models, they are all based on a very similar can design. For sure the combustion chambers may be different, as I'm sure a number of internal components are, but the
weight, size and shape difference is marginal. The differences internally ultimately effect the output and thus the burn rate of these turbines, but I could do that too. I could cap the high end RPM range by 10 or 20 or 30K and reduce the output to a range which works for my setup, and thus the burn rate too.
What are the effects of doing this on the turbine long term, or running it at mid-range to mid-high vs at high range, I don't know. I need to test this to know for sure. What I do know is that I would rather own a 180 vs a 90 if there is going to be size and weight parity between the two models. Especially if I am going to invest in two turbines of the same size, future proofing your investment and applicability makes sense to be considered.
I don't think companies like Jetcat did this by accident, I think they know this and I think they believe the consumer will lean on the side of power and spend more of their $ on the high end turbine, plus you could debate that it's less complex or expensive to have 3 motors based on the same can design. That is debatable as I've seen concepts get really complicated for vendors when they try and standardize things. But that is a topic for an other thread too, and my personal option...
4 - Market value, I did not want to buy two turbines of the same size unless I had the potential to reuse them or sell them at some point in time, this is obviously taking into consideration the
biggest assumption of them all, one that everything goes well and I
still have two working turbines a year from now.
I certainly hope I do, but I wanted to buy two turbines which I knew there are several Jet models on the market as possible hosts for me to reuse and switch them around if needed. It sounds more fun that way. To add to that, if there are numerous models on the market in the 180 category, there
should be more potential buyers as well for a second hand turbine if I decide to sell one one day.
5 - Final point, if in a year from now the model has been flying great and I'm really comfortable with it and I foolishly decide to take all the RPM caps off, I'd love to see how it flies at full power. ggggrrrrrrrrrrrrr
Anyway, I hope this isn't too long of a response, I felt the topic is deserving of some supporting details and I hope it may help some other fellas out there which may be wondering what to do as well. Again, I'm putting this out there and I'm open to opinions and advice.
Thank you again.
sc