Commander Compression Post Discussions

[Tony G]

Thanks, captains!

I just wanted to see if it was more complex than I thought. Sure enough looks like what I found to be the typical 'outta sight' factory glass job on 113-get the fabric wet and stick in the general vicinity. I'd really hate to lose something and have to go fishing with a bare hand near there! I used to think cardboard cuts were bad until I got a good resin and fabric cut. (I just winced remembering.)

I was thinking about what design would still give the strength needed and let water pass underneath. I have the feeling I'm allready over-engineering this piece but it needs to be strong. Maybe something 'T' shaped that would allow water to pass on both sides, support the post over the upright body of the 'T' and be glassed to the hull on the top, flat portion of the 'T'. Or maybe just a block with a groove gouged in the bottom surface...

Sailor Jerry, is that a twist of duplex cable coming out of your post?

[Commander 147]

I thought the same thing when I first saw it. But believe it or not this is what it says on the cable (see picture below) which BTW has been removed. I plan to do away with the compression post and go to a strongback design which I will undoubtably over engineer like I do everything else.

[Tony G]

Now I'm really curious... Why are you considering switching to a strongback? I suppose a strongback and accompanying bulkhead (if you're adding one) would make it easier to close off the 'head' compartment. That does seem to be a issue from time to time and depending upon who's on board. And honestly, at first I thought a compression post looked 'in the way' because I got so used to having an open passage throught the main bulkhead. But given the open plan of the Commander it started to make sense to me as far as hand hold going forward in the cabin. It sure does uncomplicate things when it comes to mast support. I guess ultimately this decision boils down to how you sail and use your boat.

It's funny. I'm thinking about taking out the strongback in favor of adding a compression post and you are thinking the inverse. Crazy world we live in.

Seriously though, I'm interested in why or how you have come to your decision.

[Commander 147]

"One man's trash is another man's treasure".

I guess the single biggest reason could be summed up in a single word which is family. Which is also the biggest reason I chose the commander to be my next boat. My wife sails with me most of the time when I sail. And a private head for her is very high on her list of necessary requirements.

Also I have two grown daughters. One of the main reasons for the commander was the large cockpit which allows me to take my oldest daughter and her husband and our two grandsons sailing with my wife and myself. And when you have that many folks on board you need a private head area even more.

There are however many other reasons for my choice and here are a few.

1.) I really dislike the post in the middle of the access to the v-birth. A lot.

2.) While per your post it may offer a handhold the edge of the doorway can do the same while allowing me to carry things into and out of the v-birth area much more easily.

3.) The partial bulkheads in the commander seriously limit what one can do for built in storage. A bulkhead that goes all the way to the deck will allow me much better options for the sink and stove and storage of galley items.

4.) We cruise a couple of times a year for a week at a time and we have another couple we sail with. The new bulkhead and curtain for a door will allow a little more privacy for us and our friends to get ready for bed and dressed in the morning.

5.) My previous boat had a strongback and it functioned flawlessly. I really liked that setup and I have no doubt I can engineer somthing for this boat that will do the same.

In the end I guess it boils down to personal preference. There really is no "right" way just a matter of choice.

[John]

Today is the day I drill the area beneath the mast step.. We shall see what I have to contend with. My plan is to measure the thickness of the roof along side the hatch with a large C-clamp and mark a 3/8th's drill to about 1/4" less that I measure. No junk or mess, no problem.

Valhalla has a track across the cabin for a 2 curtains that is installed at the bunk ends. My wife and daughter have been happy with that arrangement for a long time. Of course, It does help to have the curtains installed.

[John]

My rough measurement of the roof thickness on either side of the forward hatch of Valhalla comes to a smidgen less than 5/8" thickness. Does this sound right? I plan to drill a holes on either side of the step about 5/16" deep.

This is rough and gotten by measuring the height of the clamp screw of a c-clamp clamped on the roof and then measuring the clamp opening after removing the clamp and resetting the clamp screw to the measured height.

[Rico]

John,
I see you are addressing the issues you posted a few posts above...

You'll be happy when you are done...

Your measurements should be in the neighborhood... But the thickness can vary in different areas so you might see something different at the mast base area.
In any case - don't be shy. You already have a failure there... So removing the glass in that area will likely be necessary. just tear into it! Then reconstruct that area to the correct dimensions.

When drilling through a cored area; you'll feel the drill work its way through the top layer of glass and then it will go through the soft balsa like butter. The next hard surface will be the lower layer of glass.so it is easy to know where you are... But as I mentioned, I think that the area beneath your step has already failed, so you'll need to reconstruct. Don't bother reconstructing the core. The area beneath the mast step is small, and a solid base will work best under compression...

Just some thoughts - Good luck!

PS. Pls take a bunch of pictures as the work progresses!

[Commander 147]

John

As Rico has said the thickness can vary in the area of the mast step. What you have is 3/8" thick end grain balsa with glass on both sides. The bottom layer is usually very thin say 1/16" and the top varies a lot as I am learning. I just recored the area under the mast step as part of a project I will post in my gallery after I finish a bit more and can photograph it. But the top layer of glass under my mast was over 1/8" thick. It took me 7 layers of 1708 biax to fill the core area and another 5 layers to bring it up to the surrounding deck area. While I was at it I recored the area where the hinges for the forward hatch bolt through the deck. Here is a photo of the recored area.

[John]

So I lifted the mast step and drilled 3 holes in the deck area underneath the step. There appears to be a void after I go through the deck skin and then I pull up gritty wood fiber. So my assumption is that I have water incursion in this area and rotten balsa core. As soon as I tap outside the step area the deck sounds solid instead of the dull thump I get where I drilled.

So the area seems to be restricted. Will thinned resin or Git Rot work well. One of the fellows I have breakfast with used Git Rot on his Ensign and it has remained solid.

John

[Rico]

I believe Git rot is plain resin (either vinyl or Poly - do not recall...) with lots of solvents to thin so that the mixture better penetrates rotted material. As I mention above - it is simple & easier to just clean out all the balsa & make this small area a nice solid pad. This will give you the best material for the compressive stress.

[Commander 147]

Directly under the mast is a pretty critical area. You really want a sound foundation for the mast. And recoring that area is not a difficult task. If I was in the position you are in and not in the total refit position like I am this is what I would do.

Your mast step is probably 8" diameter, so draw a circle around the step so you know where the outside diameter of the step is and another 5" diameter circle in the center of the place where it sits. cut the top skin out in the area of the 5" circle. This will give you free access to the rotten balsa. The rot may extend beyond the 5" area but you should be able to fix that as long as it does not go too far. Then dig out the rotten balsa. Sand of any bumps from the top of the bottom deck skin but don't sand anymore than you have to in order to make it reasonably smooth.

Now if you had to dig out rotten balsa between the top and bottom skins of the deck around the perimeter of the 5" diameter cutout you need to fill that area with thickened epoxy. I would use some microfibers to give the epoxy more strength and cabosil (also called fumed silica or aerosol) to thicken it to a peanut butter consistancy. Then with a putty knife force this mixture in around the perimeter of your 5" cutout to fill the void between the skins of the deck. Let this set up before going to the next step.

The next step is to grind a bevel around the 5" diameter cutout. You want to grind the deck to about a 1/16" thickness next to the cutout and make a smooth bevel up to the point where the 8" diameter mast step is.

Now you are ready to start putting things back together. The first step is to cut 5" diameter circles of biax (I use 1708 biaxal cloth) to fill the area where the balsa used to be. If you use 1708 biax it will take approx 7 circles to fill this area to the same level that the balsa used to fill it. Next you need to cut circles that are progressively larger to bond back to the top skin of the deck. You need to make one circle 8" diameter, another one 7" diameter another one 6" diameter and depending on how thick your deck's top skin was possibly another one 5" diameter. These circles will bond to the beveled area of the top deck and tie it all back together. As you epoxy these larger circles in you want to put the LARGEST ONE down first which will give you a continuous bond of the entire beveled area and the recored area below it and follow with the next largest and so on.

When all this prep work is done you are ready to mix a small batch of epoxy and start putting things together. First wet out the area of your repair with straight epoxy and then start putting the 6" diameter circles in one by one and wetting them out as you go. If you run out of epoxy just mix another batch and keep going. When all of the 5" diameter pieces are in place and totally wet out put the larger circles down in the order mentioned above and wet them out completely.

After your repair is fully cured you will have a few high spots that will need to be ground down flush and some low spots that will need filling to make the area fair. So do the grinding and then mix up some more thickened epoxy with cabosil to a peanut butter consistancy and fill the low spots. You may need to do the filling operation more than once (after sanding the filler smooth) to get all of the low areas. When all of that has cured you will have a solid mast step you will never need to worry about again.

While this is how I would fix the problem your milage may vary
Sail on ~~~_/)~~~_/)~~~

[John]

Thank you everyone. Now as I take a deep breath, it looks like I have 3 choices:

1. Sell the boat (any takers??? HI)
2. Open up the deck underneath the mast step and pour in filled epoxy and put mat on top and cover with mast step.
3. As above but fill the void using built up modern coring and filled epoxy.

The consensus seems to be that a solid area underneath the mast step is best. I am busy this weekend so by Monday, I think I will open up the deck in about a 5 in. circle. I will have to cut back my mast light and antenna lines as well. The open area will give me a good idea of what I am dealing with.

More to follow, I'm sure

What do I do to raise the ceiling in the cabin? Or should I just leave it as is ?

[Commander 147]

What do I do to raise the ceiling in the cabin? Or should I just leave it as is ?

John the ceiling in the cabin should remain as is because you are not removing the fiberglass on the bottom of the deck only the top layer.

I apologize if I lost you on my explaination of the process. I often assume the reader knows more about the materials I'm talking about than is often the case. Sorry about that. Let me try and show you some pictures of what I'm suggesting as a possible course of action.

This is a picture of a couple of the areas on my deck where I am reinforcing for hardware and doing the same basic process as I suggested in my prior post.

The one on the right is similar to what I had suggested you do under the mast. As you can see the bottom skin of the deck is still intact (except where some holes had been drilled previously) and the balsa core is removed from the center and the bevel and been ground into the top skin surrounding the hole in the center.

This picture shows what 1708 biaxial cloth looks like.
as you can see it is heavy fiberglass cloth that is 8 oz mat stitched to 17 oz woven fabric. This is what I use to cut the circles out of to build up a solid glass and resin core in the center and what I laminate to the top of the deck as a new skin. By making the deck under the mast solid glass and epoxy you drastically improve the compression strength of that area.

Hope that helps, and while this may look like a large a scarry project (I remember when these kinds of things were scarry to me) it really is not bad if you take your time and fully understand what you are doing before you cut.

[John]

Jerry,

My concern is the incursion of the top of the compression post into the ceiling. I don't see any problem now, but if I leave things as they are, then it is an issue if I need to move the compression post at some later date.

[Commander 147]

Can you show a picture of what is going on?