Mizzen Mast Support

Hi Folks,

On our 1979 Whitby 42 we have a noticeable amount of deck compression under our mizzen mast. The mizzen is also raked aft appreciably compared to the main mast. Our boat does not have a stay between the mizzen and the main (triatic).

Some of the signs on our boat:

-- The deck aft of the mast step has sunk

-- The aft head door has been sanded / filed to close

-- The formica on the bulkhead in the head has a vertical crack

-- After removing the mizzen the head door now has 1/2 additional clearance at the top corner near the bulkhead

Now that we have the masts removed I am hoping we can address the compression issue by jacking up the floor under the bulkhead and adding a permanent support.

Anyone else added a support under the floor for the mizzen?

Scott

BTW - I have drilled some exploratory holes under the mizzen step and have only found dry hardwood core.

Oh, and I forgot to mention the base of my mizzen mast was not thru-bolted to the deck. The bolts in the base plate shown above were screwed into a fiberglass filler in the deck. I plan on fabricating a new support plate that is wider in both directions to allow thru-bolts to be used.

Read this article and you'll understand why.

www.landfallnavigation.com/harrowing.html

Scott

Hi,
Randy Robinson here. After a lot of research Diane Gorch and I just bought a 1979 Whitby Hull # 134 in Nov. 2009. We knew at that time we were 1 of 3 hull #’s that had lost their mizzen mast. In our case it was in a storm on Lake Huron. A triatic stay was added and no problems in the last 20 yrs. No compression issues.
Have you used a moister meter on the deck? You can pick one up on e-bay at half the price. I think it will be worth it to you.
Our boat is in Sarnia, Canada and we are in Michigan, USA. I will be going over to work on it this week and I will take pictures of what ours mizzen looks like and send them on. I hope it will be of help.
Good Luck……………rr

I happen to believe that the mizzen mast support needs to be beefed up. The internal lamination on the heads bulkhead, on TIH, has a bulge and the door frame shows signs of warping. In the case of TIH this is not an issue as the Mizzen has been removed. I don't believe that reinforcing needs to be a difficult project

First check the base to ensure that there is no compression of the core.

Then look at this solution I photographed during the rendezvous; (In case the photos don't show up here this is a link to my blog). Note that I left the photo of the owner in the shot so that he can be tracked down and questioned. If he objects and contacts me I will be happy to pixelate his face to protect his identity :-).

The Incredible Hull

Thanks for the responses so far and the pictures.

I checked out the pictures on TIH's website. It looks like a compression post was added under the cabin sole to the bottom of the bilge along with some reinforcements bolted to the bulkhead. I wonder what is under the compression post in the bottom of the bilge?

The bottom of my bilge looks like some smooth poured resin with a small sump towards the engine. I wasn't sure if this was a false floor or some sort of filler under it. Does anyone know?

If I can avoid laminating a new floor between the seacocks it would save me lots of time.

The aft bilge is pretty solid, at least on top. Not sure what they chucked in to fill it below the top few layers of fiberglass.






I whacked it a few times with a mallet with no result before I covered it with epoxy/sand mix. I would use as large a plate as possible to spread the load.

Gerry

theincrediblehull.blogspot.com/search/label/bilge

Thought I would give everyone an update and share some photos.

I cut a hole above the starboard cockpit drain seacock this week. It was a huge can of worms :-) This has been on my list of "todos" for a long time. I figured this way I will have better access to install a compression post and of course service the unreachable seacock. It was a messy job.

I found some more areas of concern that may be contributing to the sunken mast step.

-- The cabin sole around the hole was mostly delaminated due to rotten balsa

-- The bulk head under the mizzen is water logged in the bottom several inches (rotten)

I removed the bolts used to pin the aft bulkhead to the cabin sole molding and found wet wood. After drilling some more holes through the laminate it appears the wetness doesn't extend above about 4 inches. My next task is to cut away the laminate and see how rotten the wood has become.

Now I am thinking from the pictures that Gerry shared that I will be adding some additional vertical supports around the existing bulkhead. I am now wondering if the cabin sole is even compressing or if the bulkhead simply compressed from the rot.

Here are the links to the photos.

Picasa Album Whitby Mizzen Compression

Here is a pic of the new sole hatch for the starboard seacock access.

I don't know if this is any help to you. But here is the pictures I promised of our mizzen mast support. It sits on a 3/8 “ x 14 ½” x9” plate which is bolted on both sides of the 1 ½” thick wall for the head. In pic # 2 you can see the 3 thru bolts in the wooden trim. In pic #3 is the inside view of the head. Before I took this picture I didn’t know that there was a louse nut there. {not part of the plate}.

I guess I don't know how to post pictures.....I will keep trying......rr

pic #1

Sinbad

If you e-mail me the pics I will try and post them. Gerry.
whitby42 "at" gmail.com

Done: I think that pics need to be under 50KB(? open to correction) in order to post properly. Use a free program like IrfanView to re-size and edit your photos.

Your mast plate looks very similar to the one I ordered. Mine is 8.5 x 21 inches.

Ok, so I did surgery on the bulkhead to remove the rot. Found the source of the water too, it was dripping in from the two mizzen wire runs through the deck. Luckily it has been raining pretty hard lately which is helping me find all kids of leaks.

Rot, rot, rot.... I remember reading in one of the Pardey books that they kept their wooden boat bone dry down below by swabbing the decks with salt water. You think that works for "classic plastic" boats :-)

Here are some more pics of the progress:

I have my mizzen down right now replacing chain plates and am very interested in this large support plate for the mizzen. What material is it made out of? Where would you order something like this or would it be just as easy to make one out of aluminium or stainless plate?

Thanks,

On Sinbad the support plate is made of some type of hard plastic. Don't remember the exactly what it's called.Sorry........rr

Under my mizzen mast step was a 0.5'' aluminum plate no more than an inch or two wider/longer than the step. I am replacing this plate with an aluminum 6061 0.5'' thick plate that measures 8.5'' x 21''. It is way oversized to help spread the load of the mizzen and to allow thru-bolts to be used around the bulk head. The old plate was simple threaded into the plywood / fiberglass deck (scary).

I have a CAD drawing I used to send to a metal distributor who used a water jet machine to cut it out. I'll upload a picture and the CAD drawings as soon as I get back to my laptop.

Scott

Here is the new plate I had made at Greatwesternmetals.com

They are just up the road from me outside of Houston.