Refurbishing and improving Centerboard

[Wommasehn]

Mucklas Centerboard pivot - or rather the bushing in the trunks wall - has an issue: it leaked until I fixed it last summer from inside the cabin/the bilge. Since then it seems watertight but I fear, there might still be water ingressing into the plywood from inside the trunk. To take care of that, I had to take out the CB which is a nasty job. Only getting it back in is worse.

 

Now that the board is out anyway, I want to take the opportunity and put a little more lead in it. You might call the thing "swing keel" anyway if you like. 

It is made of 4 layers of 12 mm plywood , with the lower parts of the two middle layers being replaced by lead-plates. So the ballast is in the lower third/forth and in between two plywood parts (yes, meanwhile I know that solid wood would be stronger but this is how the designer specified it and it has held up for about 25 years now. Can't be totally wrong).

A few years ago, I sawed out  a chunk in the middle, made a mould from it and cast it in lead. Now, I decided to take out pieces of the outer plywood layers close to the lower end and cast them in lead too to create two more leaden pieces low down. They will weigh something like 4 kgs each. This will give a total of around 65-70 kgs of lead in the CB/swing keel.

 

 

 

The hole on the lower side of the picture is the pivot-hole.

 

 

 

This is the starboard side with the piece of ply already taken out.

 

Of course, I will glass the whole thing over which should add a good deal of strength  -but then again, I am not quite shure if this is enough. The critical region is where the CB exits the CB-trunk. There is the fulcrum which takes the load and there is the transition from the rectangular part inside the trunk to the NACA-profile. 

The board fits snugly into the trunk so there is hardly any room to make it thicker and hence stronger.

 

Now, finally here's my question: should I rely on the fibreglass for reinforcement (I could take off some of the wood to get in another layer of glass) or should I rather rely on metal ? 

 

For the latter, I have an idea: I might router a groove of maybe 20 cm lenghthwise on both sides through this loaded zone around the CB-slot and epoxy in  a threaded rod. This might give a lot of additional strengh.

What do you think??

[Wommasehn]

Meanwhile, I have bedded the outcuts in plaster , cast moulds from them and cast lead into the moulds.

Purchasing the lead was a bit funny: I called a scrap yard if they had lead. The guy on the phone said, I might come the next day. I went there and found nobody, no bell to ring, no open door, no office. While I looked around, someone opened a window in the next house and asked, what I wanted. It was the owners daughter who told me to come back later. Later I came back, the window opened again and a voice said that someone would come. Out she came and told me that her father was already gone. She showed me some kind of trash bin with scrap lead and said that I might take what I liked. I asked for a scales but ther were none.

"So how can I know what to pay?" - "just take what you want and give 10 Euros for the tip-box". And that I did. I gave her 10,- and took some weights, some pieces of old pipe and some folded sheet-lead until I estimated, I had 10 kgs.

I could have taken a lot more, including a crucifixus - but it felt too awkward thinking of melting down Jesus......

 

 

Here, is the dry fit of one of my leaden slabs. The casting did'nt go exeptonally well - but sufficient for my needs.

 

As for the reinforcing of the upper part of the CB, I decided to follow my gut feeling and go with the threaded rod. Here it is on one side , already epoxied in.

 

 

[Frank Hagan]

It's in amazing shape for being in the centerboard trunk for 25 years.

 

I haven't sourced lead in about 20 years, and have no idea how I would find it now. It used to be that tire shops would give you their used lead weights from tires they replace, but I'm not sure they still do that.

[Chick Ludwig]

10 hours ago, Frank Hagan said:

I haven't sourced lead in about 20 years, and have no idea how I would find it now. It used to be that tire shops would give you their used lead weights from tires they replace, but I'm not sure they still do that.

I needed some lead a few years ago. I was able to get some from a tire shop. They normally saved it to sell to a company that re-uses the lead. but they agreed to sell it to me for the same price they got from that company.

[Frank Hagan]

3 hours ago, Chick Ludwig said:

I needed some lead a few years ago. I was able to get some from a tire shop. They normally saved it to sell to a company that re-uses the lead. but they agreed to sell it to me for the same price they got from that company.

 

I live in CA and there's a lot we can't buy any more. I see that Amazon still sells lead sheet to us, so it must not be on the naughty list. Not that I am building anything that needs it right now. Now that I'm retired I might take on another building project.

 

Wommasehn - do you have a picture of the boat this centerboard is from? My Google search for a "Mucklas Centerboard" boat was unsuccessful.

 

[Wommasehn]

Hi Frank, 

 

the CB has been  maintained, repaired and altered for a few times. It did'nt spend all those years inside the trunk. 

,

This is me, doing some repair whithout taking it out.....

 

 

As for leaden wheel weights, they are hereabouts nowadays mostly made of zinc or steel and I found it easyer to ask at the scrap yard then go through all the garages in town.

 

"Muckla" is a "Diabolo", a 20 ft plywood sloop. Back in Jan. 2019, I posted a more detailed portrait of her in this forum incding some pictures. So if anyone wants more information.....

Mucklas btw are weird, small beings, some of them resembling various animals,  that appear in the childrens books-series "Petterson and Findus"

[Frank Hagan]

I looked back at your posts and found the pics! And thanks for the source of the name "Muckla" - the books have been translated to English here  in the US under the names "Festus and Mercury" (no reason given for the name change; in the UK they have the original names).

[Wommasehn]

It's been a long time now....

Of course, the CB is ready, the boat long time in the water and almost everything is ok. 

But I feel, I should complete my report.

I spent a lot of time and epoxy on profiling. Fearing that it won't make a noticable difference, I wanted a reasonably good NACA profile anyway. A template helped a lot.

 

Then, I glassed it over with biaxial and did the rope-trick.

 

To move it, I attached a tackle to the workshops ceiling and a loop through the second sheeve of the fiddle block. I hoisted it for clearence over the workbench and then I could flip it over. Understanable??

Then of course the painting with primer and antifouling. As I wondered whether epoxy primer or underwater primer was better, I used both.

 

Then, I moved on to restore the CB-trunk. Was worried whether the board would still fit in. It turned out that the trunk was wide enough - but not straght. So I tried to sand away the high spots from below. Then again the glassing and painting. 

I found out, that

sanding overhead in a dark and narrow space, lying on the ground  - or

applying goo and glasscloth overhead in a dark and narrow space, lying on the ground - or

painting overhead in a dark and narrow space, lying on the ground

is equally enjoyable......

 

 

Meanwhile, I reinforced the cabin-side of the trunk since the additional CB-weight must lead to additional loads. I put in bigger and newly taped fillets in some places.

Then came the biggest challenge: putting the thing back in. Just about the only task around Muckla which I can't manage single handedly.  I asked a friend who (besides a PHD in law) has a cupboard full of trophies for weight lifting. 

And I  fitted a caster-board with long nuts in each corner , reinforced the corners with additional hardwood blocks and drove 16 mm threaded rod through each corner (picture maybe later) . So I can wheel the thing around and lift it up by turning these rods (by hand and by cordless drill). 

Together we carried the CB from the car to the boat. The stern was lifted upwards . CB was clamped on its castered board (trailing edge upwards) wobbeled in position, then slowly lifted,  then I attached uphaul and downhaul, then we  shoved the CB forward. Then started a longish process  to line up the bushings of the trunk sides and the board itself. Then inserting the pivot bolt with gaskets washers and nut.

BTW: for gascets , I found some kind of paste, used by plumbers. You form a bit of it into a saussage which is put as a ring round the bolt. When the bolt is tightened, it is pressed flat and seals up the joint. It stays flexible and watertight. Works great. 

Everything seemed ready. Well, it was not quite ready: The rope-trick-rope was too thick, I had to plane away a part of it and the whole thing has way too much friction when totally hauled up. 

 

When everything else was ready, I towed her to her summertime berth to a small lake named Goldkanal (the gold channel) and launched her. When I have the CB up, it doesnt go down in spite of its increased weight , but I have to heavily pull on the downhaul to get it down properly. So I simply don't pull it totally up. Now there's already a job for the coming winter. The friction of the not-quite-fitting spots will abrade away the paint and show me where to take away more material. I hope, I can do that whithout taking out the whole CB again!

But otherwise the thing works very well: i can really feel the increased righting moment.

Two weeks ago, there was our annual club race. Fairly strong wind this time. I was glad that I could "hire" someone from "the other boating club" to join me as a crew. Allthough his main job was "living ballast", he too enjoyed the racing. And we even won in our class.