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Original windsurfer type fin , replacement ,or box insert
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swchandler



Joined: 08 Nov 1993
Posts: 5888

PostPosted: Thu Dec 08, 2011 1:52 pm    Post subject: Reply with quote

U2U2U2,

If I were you, I would give Chuck a call for some ideas. I've found in the past that he usually has some old fins lying around that might be good candidates for your project. It would be quite easy to cut the base off an old polyester fin and skip the shaping and foiling steps. Still though, to get a viable base interface to your board, I still think that using a polyester/fiberglass panel is the way to go, because you'll get the best results laminating the fin to the base.

Another avenue that I didn't mention earlier is making a fin out of plywood. That's what we often did in the 60s. Of course, you need to do a series of laminations over the wood before attaching to a base of some kind. The laminations also help you fine tune the outline and edge foil. Needless to say, this type of fin would easily be subject to damage if you hit it on a rock.
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U2U2U2



Joined: 06 Jul 2001
Posts: 3079
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sat Dec 10, 2011 9:42 am    Post subject: Reply with quote

I have determined it best to replace the existing fin, and NOT install a box.

Thanks for the help and discussion.

Steve I have a fin coming, and will epoxy a base for fitment.

Not done this, do i just use some fiberglass & roving and epoxy together ?

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swchandler



Joined: 08 Nov 1993
Posts: 5888

PostPosted: Sat Dec 10, 2011 3:01 pm    Post subject: Reply with quote

The most important part of the process is the setup and fixturing of the components to ensure that everything is square and rock solid so that nothing changes as you work on it. To help in this, I would make the effort a multi-step process.

As a first step, I would rout out a slot in the base component where the fin will nest in. After everything is in alignment and held firm, then I would epoxy the fin in place, as this will join everything reasonably solid so that you can later work on it and not worry about components moving about. To give the epoxy some strength, I would cut up some fiberglass cloth to mix in. It's not necessary to do this, but it adds substance to attain a high degree of robustness.

The next step involves wetting the roving with epoxy and positioning it around the base of the fin. The roving will be the internal element facilitating a smooth transition overall between the base and the fin. I would recommend using a slower hardener to extend your working time. The next part of this step involves wetting the areas of the base and fin where you will be placing the fiberglass. I would use a number of layers of fiberglass, concentrating the smaller pieces at the interface of the base and fin. To get the best results in the lamination process, I would recommend using a professional grade squeegee. The idea is to create a uniform smooth radii around the fin leaving no voids. When glassing on a fin with these materials, you want to have a lead-in or ramp at both the leading and trialling parts of the fin. The lead-in on the leading edge of the fin will be stouter and a bit longer given the size of foil. The trailing edge ramp can be shorter and less stout to better coincide with the fin's thinner foil.

The third step would be the fill coat. To get the best results, I would use the normal hardener. Once the epoxy is fully hardened, you want to sand everything to blend in your work with the base and fin. I would work with increasing finer grades of sandpaper achieving a smooth slippery finish in the end.

If you elect to do it, the final step would be a finish coat over everything. In the past using polyester resin, one would use finishing resin to achieve a thin, even result. I'm not sure how to do this with epoxy. It just might be best to use a clear paint instead.

I would hope this information helps.
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pete1111



Joined: 16 Apr 2005
Posts: 138
Location: The Dude

PostPosted: Sat Dec 10, 2011 5:25 pm    Post subject: Reply with quote

Make a mold out of the fins old base, you can look that up on u-tube.
Drill some holes and stick some pins in the new fin and glass it in to the mold.
Good Luck
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U2U2U2



Joined: 06 Jul 2001
Posts: 3079
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sat Dec 10, 2011 6:13 pm    Post subject: Reply with quote

Steve , got it, the router bit makes a lot of sense.

Every thing is with my capability.

Thank YOU.

PK1111

don't have the fin to make a mold, but I can get pretty close by the measurements I do have.
Thanks

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http://www.k4fins.com/fins.html
http://4boards.co.uk/
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U2U2U2



Joined: 06 Jul 2001
Posts: 3079
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sun Dec 11, 2011 10:57 am    Post subject: Reply with quote

think I will do as much as I can , then this summer finish after I have the size of the base.
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http://4boards.co.uk/
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swchandler



Joined: 08 Nov 1993
Posts: 5888

PostPosted: Sun Dec 11, 2011 7:37 pm    Post subject: Reply with quote

U2U2U2,

Just curious, what brand, model and size of fin did you end up buying?
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U2U2U2



Joined: 06 Jul 2001
Posts: 3079
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sun Dec 11, 2011 11:06 pm    Post subject: Reply with quote

20.5 Angulo, used unknown model, right price
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mark



Joined: 10 Apr 2000
Posts: 112

PostPosted: Mon Dec 12, 2011 2:56 pm    Post subject: Reply with quote

For bonding the fin to the plate and also the plate to the board you may want to try the West system Six10 thickened epoxy adhesive (www.westsystem.com). The cartridge dispenser is very convenient and the viscosity is perfect for making a fillet at the base of the fin. It also will wet out glass cloth very easily so it can also be used for board repair.

Not to digress from the original topic but this is a product that can work well for a variety of repairs. My most recent use of the Six10 epoxy was to repair a troublesome leak between the edge of a bathtub and the lower row of tile. After cleaing out all of the mortar below the lower row of tiles and the tub I filled the space with Six10. Due to the 45 minute working time I was able to make a clean fillet using a plastic spreader with the proper radius on one corner. Taping off the tile and tub is essential becuase you don't want to try to clean up the overflow. After the epoxy hardened I taped off the fillet and sprayed it with white Krylon so I now have a leak free tub that will never need to be calked again.

The only downside is that it cost about $21 for a 190 mL tube. The tube seems to contain less material than a standard calking tube so it does not hurt to have an extra tube on hand in case you run out.
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U2U2U2



Joined: 06 Jul 2001
Posts: 3079
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sun Jan 22, 2012 11:30 am    Post subject: Reply with quote



started out as 2 fins, cut the least desirable one to make the base, used carbon to level things out , cleaned up the good fin

routed out a hole and this the result so far.

always a learning experience.

Will see how my calculations worked in July.

Steve , your suggestions were brilliant !!

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http://www.k4fins.com/fins.html
http://4boards.co.uk/
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