Reverse chine and spray rails

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silentneko
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Reverse chine and spray rails

Post by silentneko » Fri Oct 27, 2017 9:12 am

I've seen some guys adding spray rails over the years and some using moulding to create a reverse chine. I'm thinking about adding small reverse chines to the FS17 bottom using some 1/2 round or other kind of stock. Question is, is it worth it? Did it make that big a difference on a boat that already has decent bow flair?


Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe.....FS17 coming soon!

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Capt UB
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Re: Reverse chine and spray rails

Post by Capt UB » Fri Oct 27, 2017 9:19 am

silentneko wrote:
Fri Oct 27, 2017 9:12 am
I've seen some guys adding spray rails over the years and some using moulding to create a reverse chine. I'm thinking about adding small reverse chines to the FS17 bottom using some 1/2 round or other kind of stock. Question is, is it worth it? Did it make that big a difference on a boat that already has decent bow flair?
I'm not sure if this will help you, but it does show how well they work on a FS14. Go almost to the end of the video to see the FS14 run.

https://www.youtube.com/watch?v=vrIypJEmG_E
FS14 (SandPiper) launched 10/20/2018

LM18 Starting build in November 2018

cape_fisherman
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Re: Reverse chine and spray rails

Post by cape_fisherman » Fri Oct 27, 2017 11:19 am

Bear in mind...bow flare isn't actually what keeps you dry. That's the job of the chines.

silentneko
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Re: Reverse chine and spray rails

Post by silentneko » Fri Oct 27, 2017 12:41 pm

Capt UB. Thanks, I've seen that clip before I believe. Problem is he is running in a very calm river, so I don't think the spray rails are doing anything there.

Cape, in my limited experience bow flare can make a huge difference in keeping you dry. I know it's not the primary function, but it definitely makes a difference in a chop to me. On a boat this small though I'm not sure if it's enough. I think I'd rather a small reverse chine then a full spray rail, less to get damaged and a little more aesthetically pleasing
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe.....FS17 coming soon!

cape_fisherman
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Re: Reverse chine and spray rails

Post by cape_fisherman » Fri Oct 27, 2017 2:31 pm

You can always add on an "exterior" chine like traditional Carolina sportfishers have. A build in reverse chine would be beneficial, but you can add one to the outer chine as well.

Those big, ugly spray rails are about as ugly as anything you can put on a boat.

I will agree that I also see spray being deflected by our flared bows...but it only deflects what gets past your chine. Stop it at the chine as much as you can.

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Re: Reverse chine and spray rails

Post by cape_fisherman » Fri Oct 27, 2017 2:46 pm

A perfectly working chine rail.




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silentneko
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Re: Reverse chine and spray rails

Post by silentneko » Fri Oct 27, 2017 3:35 pm

Think I'll start with reverse, and work from there if needed. Thanks.
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe.....FS17 coming soon!

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BarraMan
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Re: Reverse chine and spray rails

Post by BarraMan » Sat Oct 28, 2017 3:11 am

I really have no idea, but...................

If you look at my build thread you’ll see that I used 45mm cross-section stock split along the diagonal to create reverse chines and spray rails.

Do they work? As far as I am concerned they do!

I think the reverse chine has more to do with helping to lift the boat onto the plane and with handling. I think it gets onto the plane very well - at about 14 kts and it’s handling is superb.

The only other Mangusta hull that I know od doesn’t have reverse chines and spray rails like mine and was described by the builder as a “wet” boat, whereas mine is a very dry boat - spray rarely enters the cockpit area, even in the most rough and windy conditions I have experienced.

If I was building another boat would I do it again. Yes, but I would probably make the reverse chines a little wider.

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silentneko
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Re: Reverse chine and spray rails

Post by silentneko » Tue Jan 02, 2018 4:36 pm

Still thinking about this one. Not sure if it's worth all the hassle, but I might do it anyway. Just a very subtle reverse.
I'd love to hear from a FS17 builder on how their skiff runs a chop.
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe.....FS17 coming soon!

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Re: Reverse chine and spray rails

Post by jacquesmm » Tue Jan 02, 2018 5:16 pm

Step chines and strakes have several functions:
- deflect sprays
- increase lateral stability at planning speed, reduce or eliminate chine walk
- reduce drag by separating the water from the hull
- improve tracking

Except for sprays, all that matters little on moderate speed boats like the FS17.
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