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A couple of IOM yachts

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Eddie Lancaster17/02/2021 19:24:03
849 forum posts
644 photos

Hi.Tim, My first IOM build was a Boxkite, and I have had some good sailing with it, so now on to my second, another Graham Bantock boat, Nimbus 3.

The first hull I have planked with balsa and two layers of lightweight glass fibre on the outside and one inside the hull, that hull is now ready for a final coat of gloss paint, as soon as we have some warmer weather.img_1001.jpg

I have made a few changes to the design, but only cosmetic, the original deck is flat but I have given it a raised fordeck the same as Boxkite, I have also moved the rudder servo from the side of the finbox to closer to the rudder stock, again as in the Boxkite.

img_0982.jpg This is the laminated fin for the first hull, laminated from vertical pieces of 1/4" x 3/8" spruce, and I thought a hull would look good with a hull planked and varnished, so hull No. two is on its way.

It would be nice to see some pictures of your refurbishment of a Boxkite.

Regards.

Eddie.

Ray Wood 218/02/2021 08:19:51
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2505 forum posts
864 photos

Hi Eddie,

As suggested by Tim, could I borrow your Nimbus moulds on the board when we meet for barge racing in the summer ?? I have a keel of an IOM somewhere

Your spruce goose looks great . I may try Obeche.

Regards Ray

Eddie Lancaster18/02/2021 08:50:04
849 forum posts
644 photos

Hi. Ray, yes that will be fine, they are laser cut by Sarik, so are very accurate.

The drawings specify any of the hardwoods but not balsa. You will also need the drawings for the finbox and mast step as they are rather intricate, although I am hoping to use the drawings for Boxkite for my second build.

Regards.

Eddie.

Eddie Lancaster18/02/2021 13:20:55
849 forum posts
644 photos

Hi.Tim, That hull looks fine, but is it difficult to see on the water with that dark colour?

I sail with another club member who has an IOM and we sail a set course around the bouys in our lake, when I first sailed my Boxkite I couldn't even keep up with him, on our last sail day before this lockdown I was able to catch him, overtake him and stay in front, so I am quite happy with my first IOM build, and look forward to sailing Nimbus against him, We don't race as such but we do keep an eye on each other and comment on any mistakes either of us may make.

The hull of the Nimbus is difficult to hold to work on so I hope it will be just as slippery in the water.

Going back a few weeks this is the shadows set up ready for planking to begin, I used cling film to stop the glue from fixing the planks to them.

img_0976.jpg

The first six or so planks were the most difificult to fit as they had to twist 90deg. in the fisrt 3".

img_0977.jpg

img_0992.jpg

I had to make a jig,a piece of flat steel twisted 90deg. to clamp the planks to after boiling them in the kettle for a couple of minutes and allowed to dry before fitting hem.

img_1011.jpg

It had have a right hand twist and a left hand one.

Regards.

Eddie.

Eddie Lancaster19/02/2021 18:28:50
849 forum posts
644 photos

The hull has now been removed from the building board and shadows, I am quite pleased with it as there are just a few small lumps of adhesive to sand away.

img_1012.jpg

The fordeack panels have been formed to match the hull, with the same planking, they have had a layer of lightweight glassfibre and resin on the back to reinforce them while I cut the access holes.

img_1014.jpg

Regards.

Eddie.

Edited By Eddie Lancaster on 19/02/2021 18:31:04

Tim Rowe19/02/2021 19:40:34
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570 forum posts
577 photos

Nice work Eddie.

What thickness are the planks and what wood are you using? You may have told us but I have forgotten.

Following with interest.

Tim R

Eddie Lancaster19/02/2021 21:21:01
849 forum posts
644 photos

Hi.Tim,thanks, the wood is spruce 1/8” thick, it will make a heavy boat but that doesn’t matter for this build, as I am only doing it this way for the fun of the build, and it will share the rig with other hull.

I am having a problem with the fin at moment. it is too flexible, with a 2300 gram weight it flexes by over 3/4” I may try a 1/8” thick aluminium core planked with the spruce.

Regards.

Eddie.

Tim Rowe20/02/2021 10:00:26
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570 forum posts
577 photos

Hi Eddie

What glass reinforcement are you using on the keel?

Tim R

Eddie Lancaster20/02/2021 12:36:08
849 forum posts
644 photos

Hi Tim, it is one layer of 1oz. With two coats of epoxy resin, I do have 2.3oz /75gram, do you think a layer of that would help?

Eddie.

Tim Rowe20/02/2021 13:17:08
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570 forum posts
577 photos

Hi Eddie

The core of these keels only contributes a relatively small amount of stiffness. Moment of inertia and all that.

The stiffness comes from the skins that are furthest away from the neutral axis. Glass cloth generally has half the fibre content running the wrong way. To get stiffness on these high aspect ration fins you need the fibres to run along the span IE from top to bottom. You could stick with a spruce (cedar is good) core and then build up "tows" of carbon fibre arranged to get close to an aerofoil shape. I would finish off with a few zig-zags as tis will give some torsional stiffness. A small amount of filler will complete the profile followed by painting. That will make a stiff fin.

The strands of bundled carbon (tows) are easily available.

Tim R

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