MPX Testing and Development------Problems and Solutions
MPX Testing and Development------Problems and Solutions
Here are the problems encountered in the last test sail-part of which is shown in the video
1) Dynamic Pitch-up's: there were two dynamic pitch ups where the bow jumped up during a turn. Both those and the almost pitchpole were caused by abrupt rudder movement. In the one captured on the screen shot below, the hard rudder movement threw the boat completely clear of the water except for elements of three foils. Amazing power to do that on a 21lb scale boat. Solution is probably to enable dual rate and or exponential on the transmitter, though with practice a smooth turn could probably be learned.
--
2) Vang and downhaul--the gooseneck slides on a vertical rod. I tied the downhaul to the gooseneck so as the vang was tightened the gooseneck tightened the downhaul. Unfortunately, the power of the vang stretched/loosened the line dissipating the vang power-so when it was tightened to de-twist the sail it may have done that for 10 minutes but then nothing. Solution: decouple the downhaul from the gooseneck and fix the gooseneck so that it can't move down(or up for that matter). Maybe add a cunningham grommet if there is not room around the gooseneck for the downhaul to work. Increase the purchase of the downhaul to 8/1.
--
3) Peak Halyard and GCD-Gaff Control Device is the thing sticking up above the gaff to which the peak halyard is attached-line stretched. Solution: convert to spectra and /or increase purchase. I may change the position of the bowsie in order to make it easier to adjust when the Wing Tip is in place.
--
4) Sheeting system-line from the jib side of the drum jumped off because, under a lot of load, the sheet induces slack at the drum. This actually makes me happy-I was afraid I might have stripped the $380 winch! Solution: add a block with a spring to that side of the drum so slack never happens. Note to self: never subject the winch to loads outside its design range-reef, switch rigs or don't sail!
--
5) Rig slack. This happened because I didn't tighten the shrouds enough for those conditions which allowed the rig to go fore and aft a lot which allowed the top of the main to have undue influence on the pitch stability of the boat as well as screwing up the set of the jib. Will discuss the matter with the crew to see to it that the shrouds are always tightened.
--
6) Being overpowered:
a. I dodged a bullet this time by not ruining the sail winch-it is NOT set up for the load found with a 9-11mph breeze+boat speed+ waves. Will go with the SA limits I know and use the windmeter to make sure I've got it right.
b. Will design and build a new #2 rig instead of reefing the original main*. The reefing system I used on previous boats won't work with the rotating wing mast.
I was mighty impressed with the way the boat handled the fact that it was overpowered and sailing in big waves(for the model) so I want a rig that will hopefully allow sailing in almost any condition. Removing the jib in those conditions wouldn't help-too much wind for the main only.
* This will be expensive and take some time. In the meantime I have an old rig for a much smaller boat that I may use. Will at least have entertainment value when the mast snaps like a twig......
====================
Next test sail will be in wind between 5 and 7 mph*. The designer(that would be me) says the foils should work in those conditions and the boat crew(that would also be me) has been warned to not repeat the joyriding in unscripted conditions!
*I tend to use mph and not knots because the wind pressure table I have is in mph and the foil lift formula uses mph(ft/per second). If you want knots divide mph by 1.15.
Stay Tuned........