Pocket ship tabarncle

I have cracked my tabarnacle at the topside edge where it contacts the the forward edge of the cabin. I have tightened my shrouds and the crack expands shouldn't this work the other way????? Am I tightening to much??? When I realese the tention on the jib halyard the crack is just a hairline when I pull the halyard so the bottom of the mast is it's right place (3/4 inch) away from the face of the rear tabernacle wall the crack spreads to a bit more than a 16 nth of an inch.  Any suggestions or repair advice would be appreciated.


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RE: Pocket ship tabarncle

   Sorry to hear about the crack. I assume it happened during sailing? Is the tabernacle just pulling away from the bulkhead? It's hard to say what a possible fix would be without seeing exactly where the issue is. Can you post a picture?  I would think if it just pulled away, you could glue it back. Did you put the two bolts in to hold it to the bulkhead as well as epoxying it? 

Thanks

Ron 

 

 

RE: Pocket ship tabarncle

It is a crack going port to starboard right across the top of the joint of the tabarnacle to the cabin, the tabarnacle is held with bolts and glue. I have re-glued. My question really should be how do I know I have the right tension on my shrouds. The shrouds being tight should pull the crack shut. therefore when I tighten on the jib halyard it should close, i doesn't the crack opens wider (I have reglued but have yet to put wieght on it). I believe that my shrouds are so tight that when I pull them the shrouds, themselves cantilever the tabarnacle. The tabarnacle should not hold a load at all. The shrouds and the jib halyard should hold all the wieght. The bottom of the mast should be floating away from the back of the tabarnacle. Mine does, it should only be able to crack if the shrouds are loose and the top of the mast has pressure applied and it pivots and cracks,but as I apply more pressure the crack opens deffying what I am writting.   Therefore now that it is fixed I'm wondering if anyone has a way of knowing excatly how to tell if your shrouds are tightened properly? Not to tight not to loose.

 

RE: Pocket ship tabarncle

I did a search on Pocketship.net on "shrouds" and it came back with a lot of information. One common theme was that they need to be tight. 

From reading the blogs they talked about the shrouds supporting both mast from going port to starboard, but also aft to bow. 

Not sure if you are using a turnbuckle or the spectra lines? But if tightening is causing the crack to open, you may be tightening too much? 

Is the crack actually the decking pulling away from the bulkhead? If so, you may want to apply some fiberglass tape on that seam. 

My experience is limited and I am still building mine. You might want to post on Pocketship.net. You may get more responses there as well as reaching out to John Harris to get his opinion. 

Thanks 

Ron 

 

RE: Pocket ship tabarncle

   

If I’m reading your post correctkly, it’s not the tabernacle that is broken, but the glued joint between the tabernacle and bulkhead 2. Since your problem gets worse when you tighten the jib halyard, I think your shrouds may not be tight enough. Why? Because when you tighten the jib halyard, you are pulling the top of the mast towards the bow, which will pull the tabernacle top towards the bow. The shrouds are aft of the tabernacle and counteract that force.

During a very windy day, I had the cleat holding the cabin roof and bulkhead 2 crack away from the plywood because of this pressure (in my case, the pressure on the tabernacle caused a slight deformation of the bulkhead 2 plywood, which caused that glue joint to fail). Thankfully there was no risk of mast failure since I had extensively fiberglassed that joint. The solution was to tighten the shrouds so that the mast/tabernacle can’t move foreward appreciably. A difference between my boat and yours is that I didn’t glue the tabernacle to the bulkhead. It’s remarkable to see a physical space open up between the plywood and the tabernacle back as force is applied by the jib halyard. I backed up the plywood with a doubler in the cabin to add more support, though John Harris has said on the Pocketship.net forum that a doubler isn’t necessary.

Long story short: tighten the shrouds. They should absolutely be tight enough to pull the mast sideways (if not counterbalanced by the other shroud). I pulled one side tight, then pulled the other until the mast was centered again.

RE: Pocket ship tabarncle

I have since spoken to John Harris. It's not the shrouds being to loose. In fact if anything I may have them a little tighter than I should. When I built the boat I built it with the R2K in mind and John suggested a larger sail. His is the only other boat with the larger sail, his also has a crack. I have my shrouds so tight there is no way the bottom of my mast could come in contact with the 3/4 inch spacer no matter how hard I pull on them. I think I need to reinforce my tabarnacle A doubler would do nothing as the crack is at the joint only, the bolts are still holding as is the big fill-its along the side.    Thank you all for the thoughts on this subject. I have spread the crack as far open as it will go, wet it with epoxy then filled it with epoxy silica mix. I'm going to sail and reef sooner than usual for a while and see what happens. Thanks again i'll keep you posted soon. 

 

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