Curved foredeck or completely flat?

19/11/2012 12:45:26
Chris.
This is geeky…but…

Can anyone tell me what the current thinking is regarding how much foredeck curvature is desirable? I ask because I have purchased a boat that does not have any deck surface or supporting structure and I need to now make these in carbon foam sandwich.

Looking at recent boats I noticed that the current designs seem to have little (or no) crowning of the deck whereas older boats (50s, 60, 70s, 80s etc) seemed to have a lot. Making a flat deck would be easier (I think) as it would allow me to make the deck on a flat surface.

Alternatively, if curvature is desirable, I could laminate one side and then install the deck (laminated side down) and then laminate the top surface. I just wanted to know if there was any clear preference, advantage, disadvantages re more or less curvature.

Many thanks,

Chris

19/11/2012 12:55:54
Andy Hay - Business as Usual
Deck curvature is pretty much an aesthetic decision. Our woodie has a bit of curvature, JT's Shabazzle / Dark Star has a flat deck. The Winder boats have some curvature too. So it depends upon what "look" you are trying to achieve.

The important factor here is the measurement point of the lower mast band which is measured to the sheerline. Therefore the deck camber is effectively included in the mast length. If you remove this during redecking, for example, you might have to lengthen the mast to get the lower mast band in the right place.

Other points to consider:

A flat deck requires more structure to give it an equivalent stiffness - the curvature adds considerably to the panel stiffness.
Do you need a deck at all? Build a carbon space frame and put a sailcloth cover over as the "desk" as per the Chipstow boats (3551, 3529, etc.)
Flat deck easier to build as it would not require a former to generate the shape in the first place. Just laminate a flat panel and cut to shape.

Sems strange that your boat has no deck / supporting structure at all.

19/11/2012 17:35:04
Mags
Curved in wood = beautiful.

But then, I own a 1980s MR...

19/11/2012 19:22:22
k.m.
I had assumed the curvature was to lift the gate height for hog stepped masts, providing a little more lateral stability by supporting the mast 150mm or more higher than the flat (nearer sheerline)point.  I had also thought for deck stepped masts it was beneficial to have the pivot point of the mast at the same level as the point the shrouds hit the side deck. I may have imagined both of these factoids, but it made sense to me.

20/11/2012 09:25:21
Terry 3591
With a fabric foredeck, how does the crew slide to the stem to get the spinny sheet out from under the boat?

20/11/2012 11:12:57
Chris.
KM: "I had also thought for deck stepped masts it was beneficial to have the pivot point of the mast at the same level as the point the shrouds hit the side deck."

Can you confirm why? Is it to maintain prebend as you rake?

Cheers, Chris.

20/11/2012 11:58:05
Andy Hay - Business as Usual
Terry - carefully.

20/11/2012 12:43:32
Andrew M
I had wondered about the geometry of this around the shroud base being at the same height as the shroud.  Having now drawn it out, if you look at the triangle which has the mast and the shroud as the 2 long sides, viewing beam on, dropping the shroud/raising the mast foot will mean the angle increases as you rake (= less bend) raising the shroud/lowering the foot means the angle decreases (more bend) both at same height will minimise the change in relative angle of shroud & mast, with a slight decrease on max rake, which is what we want.

Re foredecks, at least with a space frame if the canvas cover supports your weight it is all a good deal less slippery than either varnished wood or gel coat!

20/11/2012 14:37:30
Terry 3591
My wife (crew) has got pretty nifty sliding on her tum up the gel coat to the front of the boat to retrieve the spinny sheet (imagine penguin on ice). Fabric just wouldn't be the same.

20/11/2012 16:37:15
Andy Hay - Business as Usual
Of course, the smart alec answer is to not drop your sheets around the bow, unless of course there are other reasons for having your crew adopting that position on the foredeck ....

20/11/2012 16:53:44
Andrew M
It's always the guy that goes under the bow, our routine for the drop has the helm grab the guy as the pole comes off and pull in an armful.  Won't add a comment to Andy's post for fear of the moderator!!!!

20/11/2012 19:08:14
Dave Lee
Maybe to adjust the tension on the jib tack - what else could Andy be suggesting?!!!

21/11/2012 10:18:33
Ben 3634
If you haven't had sex on a Merlin foredeck, you haven't lived...

21/11/2012 11:05:31
David Child
So I guess how you do "it" depends on a preference for round or flat?

21/11/2012 11:54:55
Jez3719
It also depends on whether you are sailing at the time or in the dinghy park as you would be approaching from a different angle.

21/11/2012 12:15:45
Mags
Perhaps we need padded foredecks for extra comfort then.

21/11/2012 14:19:16
Tony P 3240
Perhaps we should also consider bringing back the Grab Handles as per the early boats (in very expensive Carbon Fibre now of course).

21/11/2012 14:45:00
Dog
In that case I would suggest a dimpled foredeck with 2 large dimples......

21/11/2012 17:49:54
Chris.
Thank you everyone. I have learned a lot.

21/11/2012 18:36:12
Jof
Sail cloth foredecks don't look as good as wood, but they do make it easy to access all the bits hidden away below them. As for accessing the bow to recover the spinnaker sheets, on my boat 3529 "Pass the Parrot" it is held on by velcro, so is it easily undone so that the crew can slid along the top of the bow tank without worrying about sliding overboard! A big bonus when contending with waves like those at the nationals at Lyme Regis this year. The attached links shows a couple of pictures, including the space frame.

http://www.flickr.com/photos/[email protected]/

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