Pearson Hull Deflection

[ifmdalvey]

I have an 1987 Pearson 31 with a fin keel that draws about 6 foot.
I noticed last year and again this year when the boat was put on stands that the hull deflects upwards at the back of the keel, to me, it looks like it cannot support the weight of the boat without deforming the hull shape.
Has anyone else with a similar boat noticed this and if so, what is the solution, my temporary solution is to use 9 stands to support the boat.
Thank you

 

[RichH]

Common problem when IMPROPERLY blocking the keel on many Pearson models.

Especially the higher aspect keel models need to be blocked VERY carefully or the keel will seem to 'rotate' towards the aft of the boat. If improperly blocked the result is usually large 'hull deflections' aft of the keel ... and the defections will not be necessarily only along the centerline.

Here's how to properly block a Pearson with a fin keel:

1. Put one block under the keel near the forward/leading edge of the keel.
2. Visualize where the ***AFT of the keel meets the hull*** ... and imagine a straight line going straight down from this 'interface' of hull/keel.
3. The second block should be placed AT or IN FRONT OF THIS imaginary LINE.

4. NOTHING should be used to block under the keel aft of the 'imaginary line' ... to do so will cause a 'moment force' causing an apparent 'rotation of the keel' INTO the flat bilge section aft of the keel.

;-)

 

[RON20406]

Hull deflection when blocking a boat is common on all boats with light to medium displacement that have been improperly hauled and blocked. The deflection is usually a consequence of insufficient/incorrect blocking of the keel where the jackstands carry the main load and/or improper placement of the stands in unsupported areas of the hull. When blocking a boat properly, you should position your primary stands at areas where the bulkheads meet the hull. These are very secure and well supported points. Improper storage is more common in boatyards with inexperienced or uncaring employees. I once hauled my Pearson 34-2 in a yard in Miami that didn't know how to properly block a wing keel and scattered the jackstands by sight. When I returned from the office, I saw a minor deflection on starboard aft where a jackstand was placed in an unsupported area and a incorrectly blocked wing keel. After an hour of bickering and repositioning, the boat was properly blocked and secure and there was no deflection in the hull. If your boat is properly hauled/blocked, four stands for the hull and one for the bow is very sufficient for a 31 foot boat. There should be no hull deflection. Many owners don't know or don't care and the yards get away with sloppy work. Ask your yard to do the job properly and you'll be fine. You paid for it. Good luck, Ron

 

[ifmdalvey]

Pearson hull deflection

Thank you very much for the two helpful replies, i will check out my block positioning again.
Should i be considering installing a strengthening stringer in the bilge? or is this me being over cautious.

 

[RichH]

The addition of stringers on a P31 is probably unnecessary, in fact unless it is very carefully designed it may cause a 'hard spot' which will promote delamination. On other Pearson models you can add longitudinal stringers to help stiffen the oilcanning as is found on P30s, Flyers, and P26s ... rarely on a P31.

Even with the sometimes severe deflection cause by inappropriate blocking, at least until Pearson went out of business in the early 90s, there was never a report of delamination or fracture/breakage at the area aft of the keel .... dont know the history after that time.

BTW .... you should mark along the waterline the exact position of the bulkheads ... as this is the only place for a jackstand along the side. I prefer 6 stands on a floppy Pearson ... one v-poppit at the bow, one v-poppit at the stern between the prop and the rudder, and 2 on each side at bulkheads ... also leave the rigging at the same tension as for when you sail, dont 'relax' the rigging for winter storage.

 

[RON20406]

I would not suggest structurally reinforcing your "floppy?" Pearson since the Shaw design team knew more about boat design and construction than your average sailor would learn in a lifetime and built their hulls to a high standard for a production boat. My "floppy?" Pearson 34-2 is 20 years old and has never had a blister, delamination, ruptured bulkhead or any serious structural issues in 16,000 mostly offshore miles and sails like a bandit, for a cruiser/racer, in both light and heavy winds. Don't lose confidence in your boat when the yard is the problem and don't compare your vessel to some of the smaller, older Pearson models that were built to lighter designs primarily as daysailers. Good luck, Ron

 

[ifmdalvey]

Pearson hull deflection

Thanks everyone, i will sleep better tonight, i moved the aft keel block forward to the position suggested and also moved the stands to coincide with the bulkhead positions. It all looks a lot better under the hull now. Thanks

 

[higgs]

I set a lot of boats each year and we never allow any of them to show deflection at the pads. Proper support of the keel along with proper positioning and adjustment of pads WILL take care of deflection problems. the pads are not meant to support weight - it should be all on the keel . the pads just balance the boat. if they deflect the boat is improperly stored and could be damaged.