Did not expect it, but at 4:30am the wind kicked up considerably and for about a half an hour turbine output went up to between 3kw and 6kw. By the time I woke up and heard the wind and managed to throw the contactor switch it was too late, and it appears that the stator had been developing a short.

The graphs showing watts/amps output and turbine rpm confirmed it as shown below:

Output was peaking out at at around 100amps, 6000 watts, while at below 200 rpm!

The graphs also tell me that the furling still is not working properly, in spite of lightening the tail vane by 20lbs, so I will be finally adding about 2-1/2" more offset from the yaw bearing.

Initially I was hoping that it was the plug/receptacle, but upon further inspection it appears to be the stator. Using some binoculars I do not see any tell-tale discoloration of the stator, the turbine still rotates in a stiff wind but it does so very slowly.

So it looks like a stator replacement is due. The last stator I used 14 gauge wire, two-in-hand, with 59 turns per coil.

I am not sure but I will see if I can fit coils wound with 15 gauge, three-in-hand, if so will be shooting for about 52 turns per coil. Worst case is that I use same coil configuration as last time. This time, no matter which direction I go with the coils, I will be excessively insulating the coils and phase wires from each other to (hopefully) prevent this from happening again.

I know that others in the past have said that the wires in the stator vibrate (causing humming) and I have to wonder that if adjacent coils are actually touching if the vibration could cause a short to develop?

This whole situation is compounded by the fact that the day after I got the 17'er flying again I broke my calcaneous (heel bone) into 3 pieces, and am in a cast for at least 8 weeks...

But during the interim I am accumulating the wire and parts needed to fabricate the stator.

So unless there is something wrong with the cable (using 24" long kellum grip at top) the only thing left is the stator.

Got stitches out today, they put in a lot more hardware than I originally thought, a total of 6 screws! 3 length wise and 3 width wise, they put me into an air-cast and gave me permission to drive so I'm a little bit closer to a 'normal' life.

The cast is removable and they want me to daily do simple range movements to get some flexibility back, but still will have the cast for 8 more weeks. It is amazing how quickly you loose muscle mass, my calf looked like a wet noodle after 4 weeks of being in the splint.

Maybe next year after I can confirm that the furling finally works properly will I make another stator using #15, three in hand. One of the reasons to wait is that right now I use a .6ohm 6kw power resistor to help overcome stall, and I believe that the total stator resistance will be lowered slightly when winding with three in hand, so I think that it may just compound the stalling issue.

I have already ordered up some large bottles of cyanoacrylate (super glue), glue activator and some more phosphur bronze 3/8" bolts/hardware, and two 800' spools of #14 magnet wire (I already have three 800' spools of #15). I may wind up a coil using #15, three-in-hand, around 50 turns to see what the final size will be. Worst case is that I may make up two stators, one with current configuration (#14, two-in-hand, 59 turns) as well as the #15.

In either/both cases I plan on using lots of shrink-wrap and tape to insulate the inter-coil connections that get accumulated around the inside center of the stator. Also, so that the coils do not physically touch I will be putting a thin insulating spacer between them before I pot them in the fiberglass resin.

The plan is to build up strength and flexibility with my foot, and next month (Nov) climb tower and bring down turbine. Build new stator, add additional offset for yaw bearing, and in in Dec bring it back up and put into service - well at least that's the plan...

Previously I modified my coil winder to use a 15rpm electric motor. In playing with it I decided that I would rather turn the winder by hand as it is easier to track how the wire is stacking as well as keeping count of the number of turns, so I put the hand crank back on it.

I put some electrical tape along the outer edge of the coil forms so that there would be no possibility of nicking the insulation from the wire as the coils were being wound.

I also made up a nice little rack to hold up to 3 spools of wire, this sits on the floor while the coil winder is positioned directly above it and clamped onto the table. Both the coil winder and the rack use strips of teflon that I got from slicing up an old cutting board. These help to guide the wire without marring it, and keep some tension on the wires. Three in hand winding is doable but you have to have a reasonable setup to help you. As previously done, every other layer of wire I used super-glue to hold the windings together so that they do not 'spring' when removed from the winder. This setup worked out quite well and here is a picture of it:

Today I would all of my new coils for the stator, I am using #15 wire - 3 in hand, and using 50 turns per coil, 12 coils. After winding a couple of them I placed them over a template and decided that they should just barely fit into the space, so wound the remaining ones.

I have some 1/8" masonite that I cut into 3/4" wide strips, these will be inserted between the coils so that none of them touch. When I solder up all three phases I will be heavily insulating the wire runs as well. I suspect that one of these two issues are the reason that the previous stator developed a short.

I dug out the stator mold and started to remove any residual resin from the last casting, as well as giving it a good sanding to get it as smooth as possible, and put on a coating of mold release wax.

Previously I had found some small copper crimp connectors that made it easy to crimp each set of #15 wires (6 total) and soldered them together. They made it a much easier job than not using them! I applied flux onto the bared ends of the wires as well as the crimp connector.

Here is a picture of the newest stator, like I said the coils just fit!

I used shrink wrap on all connections, but where you solder the wires you have to cover it with electrical tape. I also taped up the bottom of the coils so that the phase connecting wires should not have any chance to short out on them.

Finally between each of the coil is a short length of 1/8" thick masonite to insulate between each of the coils. This time I am not planning on bringing out the center star connection, I did not end up using it on the previous stator so not doing it this time. It will lessen any chance on creating a short this way as well.

I have yet to solder the output wires from each phase to a phosphor bronze bolts.

I decided to perform some work and climbed the tower two more times today. I got the stub extension lowered so that the turbine is down to the top of the tower, and roped off the blades so that they could not turn. Once roped off I removed the wires connected to the stator.

Everything takes 2x longer when working on the tower, and after about 4 hours the tail, blades and generator were finally lowered to ground level. Good thing too as it was just starting to get dark by the time that I finally got everything buttoned up and brought into the garage!

Below are a couple of pictures of the burnt stator, looks to have gotten fairly hot as bubbles of 'gunk' coming from beneath the glass cloth appears to be melted zip ties and vinyl tape...

I got the tubing 'notched' to put the turbine at about 5 degree upwards angle to help blade clearance and notched the part that goes on the yaw bearing side as well. After a bit of grinding to get it as good as possible I MIG welded the pieces together and threw on some paint.

Here are a couple of 'before' and 'after' pictures for comparison:

Previously the turbine had very little forward offset with the back rotor only about an inch or so from the front of the yaw bearing outside diameter.

I moved the tubing as far back on the turbine as possible to give me about an additional 1" of forward offset. The other thing that I did was to put a forward angle on the 4 x 6 tubing of about 8 degrees, this made the turbine about 3/4" more forward relative to the yaw bearing.

In the mean time there has been some discussions of these larger machines on the FieldLines.com discussion board. Dave B who lives in PA has a similar machine and he recently left the following comment:

"Just to chime in here about my 16' machine and the changes I've made also. The 2 most important changes I've made and that corrected my late reacting furling is I lessened the furling hinge post angle by a few degrees (it does not have to climb as steep against gravity now) and the biggest change is the blade rotation with regards to the offset side of the hub mount.

My blades now turn counter clockwise when looking at the blades from upwind and the hub offset is to the right. A bit of un-advertised research will show that the Dan's have changed this relationship and Hugh has actually posted that he is now building this relationship into his new machines also. (note: this can be reversed as clockwise rotation and offset to the left but the relationship is the same.)

I have my own theory why to do this but the main thing is that for me and apparently now other's as well it assists the furling and helps to keep the blades out of the tower in radical yawing and high speed blade rpm as well. Take a look at Bergy, their offset vs. rotation direction uses this relationship as well and I have to admit I figured there just might be something to this. I call it precession other's may just call it blade seeking force when it works against and not with the furling action. For me, problem solved. Just some thoughts from many hours of changes and improvements.

No guarantees that the direction of rotation as it relates to the offset side will make a difference in the furling response but for me it was night and day. I have put this link up many times, make of it what you will but it sure explains to me why it fixed my problem
here is the link"

This phenomenon is called "Gyroscopic precession", and what happens is that a spinning gyroscope (aka wind turbine) has a rotational torque that makes it rotate about it's axis in a predetermined direction. This rotational direction is dependant upon the direction that the turbine rotates. Ideally this precession can be used to help a wind turbine *stay* in furling, or potentially if there is not enough offset (side/forwards) then it may help to pull the wind turbine *out* of furling. This sounds very similar to my situation where the turbine does furl, but at about 36mph it appears to be *unfurl* itself - thus generating huge amounts of power, and ultimately causing the internal short circuit.

Others also responded to the above suggestion giving it more weight, so I am doing my own research, and if I do decide to change the mounting point from the left of the yaw bearing to the right side - it will also require that I redo the mounting point on the tail itself, and switch the 'bumper' to the opposite side on the tail as well.

This epoxy has a maximum service temperature of 275°C (527°F), and while pricy at about $253 for a .8 gallon quantity from Allied Electronics. I also ordered up a 12 oz quantity as I need pretty close to a full gallon, and the .8 gallon may have left me a little short.

So as long as I am spending top dollar for a high temperature epoxy I'll go all the way and make sure that I have enough to complete the job! As you can tell I am taking this stator very seriously and taking as much precaution to make sure that it lasts a long time!!!