How to Attach the Skeg?

Designs for inboard or outboard power

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Onplane
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How to Attach the Skeg?

Post by Onplane » Mon Oct 04, 2010 5:43 am

I'm getting to the point where the skeg will need to be fastened to the hull on my malahini. The skeg attaches in the center of the boat hull, which has a gradual "V" shape, but the bottom of the skeg will be flat when cut.

So how do you attach the Skeg? Do you 1) Flatten the hull "V" shape, by sanding the hull to a flat (and thereby probably going through the fiberglass and epoxy), or do you 2) Try to accomplish a "V" shape on the bottom of the skeg? Seems to me option 1 is easier to get an acceptable result, but I'm leary sanding through the glass work I just did... Any thoughts?

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billy c
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Re: How to Attach the Skeg?

Post by billy c » Mon Oct 04, 2010 6:13 am

either flatten a spot and feather in a patch or build up a flat pad of epoxy/glass
(insert Witty phrase here)
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ttownshaw
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Re: How to Attach the Skeg?

Post by ttownshaw » Mon Oct 04, 2010 7:30 am

I put down masking tape marking the beginning and end of the skeg location and sanded a flat spot with my belt sander.
Bill

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vupilot
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Re: How to Attach the Skeg?

Post by vupilot » Mon Oct 04, 2010 8:04 am

Not sure if the Malahini has more V than my Zip but I didnt do anything but put bed of plenty of thickened epoxy and set the skeg in place. Filleted all around with the excess thickened epoxy the squeezed out.

Dont forget to place the trailing edge of the skeg the specified distance forward of the transom edge. I think its 18" forward. I missed the fine print and mine is only 12" forward but I still dont get any cavitation.

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Onplane
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Re: How to Attach the Skeg?

Post by Onplane » Mon Oct 04, 2010 8:12 am

Thanks for the heads up...

I'm not there just yet, still need to cut it out, but the malahini's skeg is pretty decent size... I'm thinking about going the ttown way, and sand flat. I guess worst case, I sand through too much fiberglass, in which case I can either patch, or just coat with epoxy.

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Iggy
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Re: How to Attach the Skeg?

Post by Iggy » Mon Oct 04, 2010 8:23 am

Charles.. the only spot where I would have liked to sand a bit more 'flat' was up near frame 4. Frame 3 to transom is already pretty flat.. and my screws & filled epoxy kept everthing nice in true.

I had a small bit of tilt near the front end.. its pretty minor.. but if I had to do it again I would have flattened out the plywood a bit more. The skeg is pretty flexible in the front.. and while my bolts where pretty much vertical, after tightening it can tilt ever so much if there is some angle on the bottom.
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Jerry Lindamood
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Re: How to Attach the Skeg?

Post by Jerry Lindamood » Mon Oct 04, 2010 1:20 pm

I'm going with Chris on this one. I could be mistaken, but I believe that the Building with Plywood book says to build a bed of Epoxy for the skeg to sit on and then fasten.

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ttownshaw
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Re: How to Attach the Skeg?

Post by ttownshaw » Mon Oct 04, 2010 1:36 pm

Yep, I wasn't thorough in my explaination. Yes, after sanding a slight flat area, I bed it in thickened epoxy, attached with screws, very small fillets around it, filled the screw holes, prep'd, primed, and painted.
Bill

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vupilot
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Re: How to Attach the Skeg?

Post by vupilot » Mon Oct 04, 2010 2:15 pm

By the way, I did not think fasteners were necessary and did not use any.

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Iggy
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Re: How to Attach the Skeg?

Post by Iggy » Mon Oct 04, 2010 2:32 pm

I used Bronze fasteners because I know that the skeg will eventually hit something pretty hard.. and I know my boat will have enough mass to really put a lot of strain on the skeg.

I have no doubt epoxy alone would hold it on.. however I found the fasteners made it a lot easier to mount the skeg.

I pre-drilled the holes in the skeg using a drill press.. then I used that as a template to mark the holes on my keel/plywood.. then used a level drill to ensure my pilot holes where plumb.

Building up the edge of the keel to be able to sand it flat for the skeg is a novel idea.

Tom Drake
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Re: How to Attach the Skeg?

Post by Tom Drake » Mon Oct 04, 2010 3:47 pm

I elected not to sand a flat spot and disturb the glassed and sanded bottom. I set the blade on my table saw at a slight angle with depth 1/2 of the skeg's thickness. By cutting from each edge, a slight V was cut into the nesting surface of the skeg. I mean very slight. I then set it in thickened epoxy and drew down with bronze screws. As the epoxy oozed out along the length, I wiped off leaving a small fillet. Just another thought to consider.
Tom

Jerry Lindamood
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Re: How to Attach the Skeg?

Post by Jerry Lindamood » Mon Oct 04, 2010 5:42 pm

I don't know what horse power that you are going to use, but the book said, best I can remember, for higher horse power to shorten the skeg. The end of my skeg is four feet from the transom edge. After about three hours in the water, I'm satisfied with how it turns and handles with little cavitation and 115 hp. (my two cents)

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Bruce T.
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Re: How to Attach the Skeg?

Post by Bruce T. » Tue Oct 05, 2010 5:27 am

I installed my skeg with 3M 5200 caulk and used large diameter bolts into metal threaded inserts. The first time I had the boat out for a high speed run with tight turns I ripped the skeg off the bottom of the boat. I didn't hit anything. The force of turning was simply too much for it.

I have no idea how a skeg would stay on with only epoxy. There is a lot of lateral force on it when turning. I replaced the skeg and bolted it through the keel. It has been fine over the past 3 years. My boat is an 18' inboard with a 170 hp.

Of course, having only built one boat I'm not really an expert.

Bruce.
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Onplane
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Re: How to Attach the Skeg?

Post by Onplane » Tue Oct 05, 2010 5:30 am

Jerry,

No motor yet, so I'm not sure about how many ponies I'll be hanging on the back.
I am interested in how you did your skeg though... do you have any pics? I was just planning on building it to the dimensions on the plan... I guess on yours you just shortened the back portion, seeing as how you were 4ft. from the transom?

Tom,

I had thought about doing something like that as well... Only issues for me is that the malahini hull "V" shape gets gradually more pronounced as it moves from the transom to the bow, and unlike the Zip, I believe the Malahini's skeg is much longer... I may still try to cut a "V" just not completely sure yet...

All,

I believe the Malahini plans call out for installing 3" bronze screws through the Skeg into the Keel when permanently attaching. I will be using the screws too as I don't want any mishaps with ripping it off...

Oyster
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Re: How to Attach the Skeg?

Post by Oyster » Tue Oct 05, 2010 5:33 am

i have never had a skeg or runner type piece of wood along the keel area come off by itself on runabouts using wood screws such as the silicone bronze with a flex bedding compound much less epoxy. I counterbore and run the fasteners in and cover with fill.
On sailboat skegs i also laminate strips and throughbolt into counterbored holes into the inner keel and with the shallow draft hulls that rest and travel on trailers and sit on sandbars have also never had any issues.

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