Home |
Search |
Today's Posts |
#1
posted to rec.boats.cruising,rec.boats.building
|
|||
|
|||
Flying Pig Repairs
I just posted this to the Morgan groups, addressing Charley Morgan,:
rbc/b has had some opinion on the subject points so I duplicate them he Hi, Charley, Repairs are coming along on Flying Pig, which appear to promise full restoration. We're already applying bottom paint, and are rounding third on the rudder rebuild. Meanwhile, one of the guys working with me in the rudder restoration suggests using a "ducktail" on the rudder to improve the autopilot stability (it hunts busily, now, and has since we have owned the boat). I'm assuming that if that were efficient, today's high-priced yachts would have them. To me it seems counterintuitive - even the lowest-slowest airplanes don't have such a configuration to the rudder or elevators, and anything which creates drag (as I assume a blunt end, particularly one increased in size from the exit, to perhaps the width of a foot into the chord from the aft, would do) isn't a good thing, either. Back to the repairs, despite the pounding and associated flexing suffered in our grounding, we have found that the bulkheads have largely remained in the exact same position, despite much delamination of the vertical tabbing (nearly all of the hull-side tabbing has not been disturbed) on the bulkheads from forward galley to aft head. I have two questions: Pete Brown (QC and service Manager(s) 1978-1984) has suggested using a thin wedge to expand the gap between bulkhead and tab slightly, flowing expoxy into the crack, removing the shims, then screwing copiously (maybe on a 4" grid) to both pull it in and make a mechanical as well as chemical bond. I'm thinking using boards to spread the load, and jacks, to compress, would be both as effective (mechanical aside), probably much faster, and would not leave a bunch of screw heads out which would have to be dealt with in some fashion later. Your thoughts? Second, and related: on our return to Salt Creek, with only either a staysail or a spinnaker, our two primary sails having been removed as damaged, in one of our staysail periods, we were swinging through a 40-45* arc with the large waves and following seas. Much creaking below the cockpit was noted. Going below, I discovered that even in the largest, most severe, hull-bulkhead delamination areas (in the ER), there was no movement, vibration or noise coming from those joints. Instead, I could feel movement (slight, of course) and vibration at the bulkhead-ceiling liner joint. Those were not tabbed, originally, but also didn't move (or, at least, didn't creak). How was that secured originally, and how would you suggest resecuring, presuming that no motion would be better both from a peace of mind (no noises) and security (less hull flexing) perspective? Related, the tabbing delamination, even in the worst case, doesn't extend beyond the area where it was being pounded. Thus, higher up on the hull, the tabbing is still attached to the bulkhead - and thus the bulkhead is in its original position there. From that I presume the hull/bulkhead shape configuration is likely pretty much the same as was before, with some potential for, particularly in light of the wood rot seen elsewhere in the boat as we've exposed stuff, some beating-up/ compression of the bulkhead in the impact areas (at the hull-bulkhead contact points), but only at that low point next to the hull. It's my presumption that with new expoxy and compression to secure the existing tabbing to the bulkhead, once cured, those bulkheads would be functionally as the original. Do you concur? Thanks for any wisdom - this is new territory for me... L8R Skip and Lydia Morgan 461 #2 Disaster link: http://ipphotos.com/FlyingPig.asp SV Flying Pig KI4MPC See our galleries at www.justpickone.org/skip/gallery ! Follow us at http://groups.google.com/group/flyingpiglog and/or http://groups.yahoo.com/group/TheFlyingPigLog There is no such thing as a problem without a gift for you in its hands. You seek problems because you need their gifts. |
#2
posted to rec.boats.cruising,rec.boats.building
|
|||
|
|||
Flying Pig Repairs
"Skip Gundlach" wrote:
snip Meanwhile, one of the guys working with me in the rudder restoration suggests using a "ducktail" on the rudder to improve the autopilot stability (it hunts busily, now, and has since we have owned the boat). I'm assuming that if that were efficient, today's high-priced yachts would have them. To me it seems counterintuitive - even the lowest-slowest airplanes don't have such a configuration to the rudder or elevators, and anything which creates drag (as I assume a blunt end, particularly one increased in size from the exit, to perhaps the width of a foot into the chord from the aft, would do) isn't a good thing, either. Focusing only on the autopilot issue presented, I would suggest that the hunting issue is not likely related to rudder shape. The autopilot is just a servocontrol loop, with PID configuration (Proportional, Integral, and Derivative). Feedback comes from the fluxgate compass or wind direction transducer. Your percieved hunting behavior is typical of servoloops adjusted with too little forward, or proportional gain. They cannot react fast enough to changing conditions, and are forever correcting for the situation of a few seconds ago. Under certain circumstances, a servoloop with too much forward gain can exhibit instability in a way that resembles hunting, even though the mechanism is different. Some servocontrollers also allow adjusment of the integral and derivative parameters. The integral feature (sometimes called "reset") improves the accuracy of response when conditions don't change much. This is often automatic and not adjustable. The derivative adjusment stabilizes the control loop, allowing more forward gain and hence quicker response by introducing the rate-of-change of the feedback The short version is; experiment with the adjustments available in the autopilot and on its control panel, and note whether increasing/decreasing each parameter improves the response of the system or not. If it makes things worse, go the other way. I know this is a little obtuse, but I hope it might lead you to another possible cure for your control problem. John Hart -- -------------------- http://NewsReader.Com/ -------------------- Usenet Newsgroup Service $9.95/Month 30GB |
#3
posted to rec.boats.cruising,rec.boats.building
|
|||
|
|||
Flying Pig Repairs
The ducktail will probably cure the hunting problem but it's a crude
treatment of the symptom rather than the cause. It's a terrible thing to do to a sailboat, you'll be dragging that thing 24 hours a day. Does it hunt under sail or just under power? See the other post for better solutions. -- Roger Long |
#4
posted to rec.boats.cruising,rec.boats.building
|
|||
|
|||
Flying Pig Repairs
Thanks for any wisdom - this is new territory for me...
L8R Skip and Lydia Morgan 461 #2 Disaster link:http://ipphotos.com/FlyingPig.asp SV Flying Pig KI4MPC See our galleries atwww.justpickone.org/skip/gallery! Follow us athttp://groups.google.com/group/flyingpiglogand/orhttp://groups.yahoo.com/group/TheFlyingPigLog There is no such thing as a problem without a gift for you in its hands. You seek problems because you need their gifts. Several things, the wedge and screw is a good idea but its going to make work later, a fillet and strip would work to provide a chem and phys bond. second if she is seaking really bad and you are in the yards have her tanks drained (yes everything drained) set her in the water and see how she sits. I'd be willing to bet she will not sit fair and you will need to adjust her perminant ballest. third, rudder size, shape, and how it's fit to the boat might also need some looking into. Ive built a couple big wood fishing boats that have cought a rock or two and had them come back for repair. most times it's not a big deal but i always check a boats set and check her rudder and fittings if she is off. most times ballest is a problem. 2MT |
#5
posted to rec.boats.cruising,rec.boats.building
|
|||
|
|||
Flying Pig Repairs
I doubt that the duck tail would help with the autopilot hunting and
it will make the boat slower. If the pilot is hydraulic I would check the pilot's rudder angle sensor to make sure it is operating correctly and is properly centered. Fiddling with the gain controls may help and the manual should have some set-up procedures to follow. A gyroscopic rate change sensor can be added to many autopilots these days. They can reduce autopilot induced oscillation and also help with radar targeting. -- Tom. |
#6
posted to rec.boats.cruising,rec.boats.building
|
|||
|
|||
Flying Pig Repairs
In article om,
"Skip Gundlach" wrote: Meanwhile, one of the guys working with me in the rudder restoration suggests using a "ducktail" on the rudder to improve the autopilot stability (it hunts busily, now, and has since we have owned the boat). Check how much play/flex is in the autopilot system. I found that a very small amount of play translated into a whole lot of wandering. After that, playing with the gain & damping settings was more consistent. -- Jere Lull Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD) Xan's NEW Pages: http://web.mac.com/jerelull/iWeb/Xan/ Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/ |
#7
posted to rec.boats.cruising,rec.boats.building
|
|||
|
|||
Flying Pig Repairs
wrote in news:20070314163424.069
: -------------------- http://NewsReader.Com/ -------------------- Usenet Newsgroup Service $9.95/Month 30GB John, for less than $4 more, on a 3-month payment at a time, you can download 24/7/365 with unlimited GB and 100 days retention at 99.9% completeness on www.usenetserver.com, which is FAR greater than any other news server I ever encountered.....works great! I download about 15GB/day...(c; Larry -- How much price inflation is caused by illegal aliens gobbling up goods and services, creating shortages for the natives? I heard 40%! |
#8
posted to rec.boats.cruising,rec.boats.building
|
|||
|
|||
Flying Pig Repairs
|
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Flying Pig Chronicles, Current Edition | Boat Building | |||
Flying Pig Chronicles, Current Edition | Cruising | |||
Flying Pig News, late edition... | Cruising | |||
NEWS FROM FLYING PIG... | Cruising | |||
Logo contest! | Cruising |