Your reduced pilot weight (165+ 15 parachute) only reduces the fuselage load by 20 # below my LS-3a example, and that still leaves you something like 50# over the max allowable fuselage load. I’d nail down all these little problems before committing to the project..........you will find plenty of unforeseen issues that you haven’t even thought about.
I agree that a pylon motor mount is far superior to a FES, because there is no big CG issues to deal with. The FES nose motor weight must be counterbalanced with an aft battery which is located as far behind Your CG, as the nose motor is in front of the CG!
A big problem in selecting a ship to modify is the area you wish to install a pylon is the area where the wing controls are located on most ships.........ailerons, flaps and dive breaks......... need to come up with a plan on how to redesign the control linkage? BTW, installing a ballistic parachute shares this same problem........the chute and rocket need to go in the area where the wing controls are located.........?
I would think batteries located inside a wings D tube should be attached to the vertical shear web and strong enough to withstand a 5G load, none of which is taken by the wing skin? I’d place the batteries as far out in the wing as they will fit and you will need to design a way to get cooling air to all the battery cells. Make sure to properly repair any holes you cut in the D tube as that section takes some of the bending load and all of the twisting load seen by the wing!
What have I missed? Oh, how about a fire extinguisher......Inside the wing would be nice?
Have fun,
JJ




O
On Monday, February 8, 2021 at 10:20:20 AM UTC-8, David Scott wrote:
On Sunday, February 7, 2021 at 9:41:30 PM UTC-8, Nicholas Kennedy wrote:
David Scott
I don't know what your budget is.. But If you want to work on a electric glider a good choice might be to get a Antares.
From what I've read their very high performance, very nice to fly, but need ALOT of hands on work to keep them running.
Building something from scratch sounds very daunting to me.
JJ's post above is a eye opener.
Hanks posts are too. He's a full time professional in the Glider Biz, and look at the hurtles and challenges he had to overcome.
It seems to me you could easily spend a bunch of money, get in way over your head and end up with a very expensive, unflyable, unsafe, un airworthy, piece of junk.
Good Luck!
Nick
T
Nicholas, I am on the very low scale of budget now, which is why I am looking at the cheapest options, but expect the future will improve. To be clear, I will not cut up a good glider and not finish the project. Touching a glider would be the last part, after the power module is fully working and debugged on the bench. I fully understand it is not a small project. This really isn't a hard project there are many ways to accomplish it. I have embarked on bigger ones without knowing how to solve all of the problems involved, and failed at one. I have enough experience not to fail at a project like this.

John, this is something I have kept in mind. I am 165lbs dressed and can lose 10 with no problem, and should. I also think I could keep a power setup well under 100 lbs.

The FES distributor I found is indeed Blanik America.

Here is an interesting video showing the difference of a small prop vs a larger prop with gear reduction. Other than that the complete drive system is the same.
Small prop is 26kg of thrust @ 168 amps, large prop is 40kgs of thrust @ 138 amps. The video is https://www.youtube.com/watch?v=WgNMc35zqYo&t=154s.

Kenn, I PMed you about joining your Slack group, thank you. As for the drag of the pylon, yes, that is a big issue and one that going electric could really make a difference on. I think the unit that GP Gliders uses is the only one that tries to reduce the drag. The Grasshopper unit really fails in this regard, but wouldn't be hard to fix later on.

Thank you to J. and Kenn for the drag numbers, that is very informative. It looks like 110lbs of thrust would perhaps work pretty well. This is kind of the low end for electric paramotors and they don't operate on a streamlined pylon.

At the moment I am really liking the idea of a custom retractable pylon module and steal the rest from a paramotor to take advantage of their scale of economy and leverage what developments they make. This also means using a fixed 60" 2 blade propeller for improved efficiency. Or the closest I can get to match the motor used.

Hank, I already said I didn't think the FES system was viable for what I am looking for and fully understand why they would want nothing to do with it for the reasons you mention. As a machine shop I deal with it too. Thanks for the $$$$ info, looks like I was close but a little low.

Dan, seveal electric gliders store the batteries in the wings. I think the Antares does and know the GP Gliders do. I wonder how viable that would be for a retrofit? I also wonder how Antares and GP deal with thermal stability and fire control in the wings?