adding a sugar scoop to 46ft cross tri

[mpsm1957]

I have a 46ft cross tri built in 1975, I'm hauling out this month and was seriously thinking about adding a sugar scoop to the center hull. It is of a diagonal plank construction with epoxy and cloth on both sides. I was thinking of using high density foam wrapped in epoxy and cloth, but what I'm not sure of is how to attach this to the hull, and also is there a lot of stress at this point. If there is someone that can lead me in the right I would appreciate it greatly. thanks Peter Murray

[catmando2]

Hi mpsm1957, i've done a bit of this stuff before ou of Divinecell and Termanto foams in Australia. I'm sure you can get the 80 kg stuff in the states. I've usually just used 2 layers of 600gsm biax on a 20 mm core on cats around 50 foot. Make sure all exposed edges and areas that will get a knock have foam taken out and filled in with a high density filler with small bits of glass fiber.

Ataching to the hull.... if you put 200mm wide strip of packing tape onto your transom before you build you can then cove and glass with say a 600 gsm double bias direcly onto the hull. when insides off step is done it can then be cracked of the transom and glassed and faired on the outside with gravity on your side.

When finished you have a nice glass flange [where you had coved and glassed onto hull ] which can now be sanded ,and glue structure onto hull.

Glass outside joint with 600 gsm d/b.and fair it in.

I only ever use epoxy resins as the mechanicals are far superior [ in my opinion]

Hope this helps a bit, I may have an example of a step job I did on my last cat in my gallery, if not I'll get one on soon.
Dave

[mpsm1957]

Dave,
Thanks so much for the reply. I do have a couple of questions so I'm clear on what your saying.
us packing tape on transom so epoxy won't stick to it, correct?
when you shape the divinecell to the shape of the hull or what ever shape you want, what are you using to keep the shape (trade secrets)
after all the glassing is done to scoop, and now it's time to attach, you have the flange inside and a seam outside. how much of an overlap do you need to (glue?) the scoop on to the hull on the inside as well as the outside? I appreciate any advice you can give me
Thanks Again Peter

[catmando2]

Hi peter, I'd use timber in the vicinity of 3 X 2 spaced about 300mm/1ft apart. you will have to screw these to your hull and they need to be parallel with the waterline. Use chipboard screws with a coarse thread and long or short enough not to go through your inside skin.I put 1 about 1inch from transom and 1 about 500mm in. As you will have to fair and repaint, youll fill them back in anyway.Just be carefull as this is only meant to be strong enough to hold the foam, not you.

Overlap: depending on how much glass you have on the outside, you could feather it down over 200 mm and when step is offered back up , do a dry fit and check everything is where it should be and looks good to the eye. put a few pencil lines from step onto hull as a reference point, take off /grind/clean/glue,and let that cure.
By rights 3 inches onto the hull is all the overlap needs to be ,I go 4, so an 8 inch band of 600 gsm db and then a 5 inch band if you want to go belt and braces. let it start to kick and bog it. Of course then when you start to fair you can sand a bit of glass and as long as you don't hit the first layer everything is fine.

Have fun, hope this helps.
This how I've done a heap of this style of job and it works for me. But there is more than 1 way to skin a cat. this is the simplest i'd reckon.


Dave

[mpsm1957]

Thanks Dave, that helpes a lot, I'll let you know how she turns out.

Thanks Again Peter

[kach22i]

If you don't mind me asking; how does a sugar scoop transom work, what is it's function?

[catmando2]

I'm assuming it will end up being steps like pic. easy acsess to dinghy and more waterline length.

Waterline length is everything.Dave

[kach22i]

Originally Posted by catmando2

I'm assuming it will end up being steps like pic. easy acsess to dinghy and more waterline length.

Waterline length is everything.Dave

Longer tapered bodies flow thru fluids better than short blunt bodies, got it.

From a link Brian Eiland provided in another thread, some cool sugar scoops. I'm learning these boat terms, I thrust it's not too much of an annoyance.

http://www.yachtforums.com/forums/ge...l-power-3.html

[Tri guy]

If you are still looking for a sugar scoop transom on a Cross tri take a look at my website: www.thedawntreader.com Moxie is a Cross 46MkIIB modified with daggerboards and a "sugar scoop transom. It makes a great docking station and fishing platform.

http://thedawntreader.com/images/100_0492.JPG
http://thedawntreader.com/images/Pac...sing/pc021.jpg
http://thedawntreader.com/images/Soc.../IMGA0205a.JPG

The addition at the transom effectively gave us two more feet at the waterline and a much cleaner exit. In 23,000+ open ocean miles Moxie averages over 150 nm a day and on good days does over 200 nm. Our best day was 241nm.

Fair Winds and Following Seas,
-Dale
S/V Moxie
Ko Olina Marina, Oahu, Hi.