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Modifications to Avocet

Don Silsbe

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2 hours ago, Don Silsbe said:

Currently, there is no knee.  I have a choice of adding a 1/2” or 3/4” thick one.  One is shown on both Graham and Chief’s boats in those videos.  Also, there is even less room on a 17 for packing this all in.  So, my current plan is to go straight with the roller (like Graham did), put the cleat just to port of the tabernacle (like you did), through bolt the base plate, straddling the knee, and using T-nuts to attach the roller to the base plate.  Before I do, I want to make sure I can get those beefy T-nuts in stainless.  I would also appreciate hearing from others, before I glue in the knee.


Ok, that makes sense.  It does look better to have a straight bowsprit. 


Glad you answered because it sounds like I should also put a knee in place, which makes sense given the potential forces involved (and installing a knee is easy enough).  I think I'll just offset the knee a little bit if I need to in order to prevent interference with the through bolts.


I'll bet we're both overthinking this, but that is part of the fun!

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When I made the C-board case for Skeena, my giant worry was keeping it abrasion resistant and waterproof. The instructions were to lay glass on the interior. My concern here is how to do that in a situation where you are building in place. Are you just going to but join the two halves of the trunk together? 

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You are doing good work Don. Having done this mod to Carlita and observing the Chiefs mk3 trunk extension, I am enjoying following your turn.


Here is a pic of Carlita's trunk extension with the outboard trunk side installed and testing the centerboard fit . I chose this pic to help answer Steve's question about glassing inside the trunk extension and to show the downhaul that I added following Steve's catastrophic capsize.  


It is important to glass the inside of the trunk. It is easy to glass the inside of the trunk halves on the bench. After the board was removed following taking the picture I glassed the vertical seam inside the trunk and glassed the bottom of the trunk to the boats bottom. 


The inboard trunk half is more fiddly. To glass tape the inside butt joint I wet out a length 3" glass tape and compressed the glass between two flat surfaces and plastic release to make the glass as thin as possible and smooth as I did not have a lot of room. After cure I sanded the faying side for a good key and glued it to the trunk half butt edge with 1 1/2" left out for bonding to the old forward trunk joint. Before gluing in the final side I rigged up a backing board and wedges while I could still see inside. After reading this I cannot remember if I glued the tape to the original part of the trunk or the new part first. Remember a taped butt joint is stronger than the ply. If the tape is on one side only it is strong when loaded on one side and worthless when loaded on the other side.


It worked well and you will have to look hard to see that the modification was not original.


Was it all worth the effort? For me there is no question, I did the mod before my Delmarva circumnavigation and blessed it many times. Carlita is definitely more weatherly under a wider range of sail combinations.


The line in the picture that goes thru the lower cheek block is the standard uphaul and the line thru the upper block and going forward to the newly drilled termination hole is the downhaul. Does it work? I do not know because I have not come near to capsizing her let alone turtling. I have been working on a gold fish mast float. We intend to do a capsize test in the spring. 

Carlita trunk21l.jpg

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Thank you Graham!  We discussed this on the Sunday of the Messabout, you, Alan and me.  You said that you glassed the starboard side of the extension before installation.  It was laid on a flat surface to cure.  To ensure a flat mating surface to the existing surface, the glass “tail” was pressed against the flat surface with a releasable plate.  This part was installed the next morning, while the epoxy was still green.  Hard to describe.  But I’ll be doing it this way in a week or so, and will take photos.


 By the way, the photo you attached is priceless.  It told me to install the c/b before installing the starboard extension.  That is brilliant!  I’ve been having nightmares about fiddling the c/b into place after it was all glued together.

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9 hours ago, Don Silsbe said:

I’ve been having nightmares about fiddling the c/b into place after it was all glued together.

I haven’t had a nightmare… but I have thought about this task upon waking up… how the heck to position the board for the pivot pin.  I remember doing this on Norma T but I don’t recall the specific process I used, just that it took a while and I decided I didn’t have an interest in doing the process on a regular basis. The advantage of the CS15 pivot pin is that the centerboard “horn” protrudes through the top of the trunk… something to grab onto for manipulation.  I managed the task alone.   Avocet’s centerboard trunk is closed on top and manipulation is done from… what… underneath??  I assume a second person will be needed.  Aaaiiieee. 

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