30' plywood sharpie

´Progress at last

Its been a long time when I made my last post...

In my project there is some progress, that ist docomented in a german forum. I finished my fourth spiral in the design process and decided that its time to build a Scale Model of my Coastal Sharpie. It will be equpped with radio control and will go sailing with it.

Planking with self made plywood has begun at New Year and the Hull is finished now and off the building frame, the first reincorcements for the Main Mast are in. Foredeck and Sidedecks will follow next week.

After that the RC will go in and then its time for the cabin and cockpit.

 

It looks like your scale model is around 1/10th.

I had real trouble getting weights for radio control right at anything under 1/5th, and even that wont give me proper sailing performance evaluation.

One win I have had recently, is getting an interested, enthusiastic qualified engineer to specify the scantlings. My project was going to be foam and fibreglass, but the weight penalties for plywood were acceptable, so I am planning to do a plywood prototype of my 28ft trailer sailer. It will basically be my 'scale model', where I can test sailing performance, motoring performance, gear setup etc.

Your design appears to be almost a 'Norwalk Island Sharpie', where they already have proven designs and building methods, so I am not sure what features you are incorporating in a whole new design to justify all the effort you have ahead of you.

 

See post #467

Cheers,
Angel

 

Hi Michel,

Congrats on your progress..!!

About the shallow keel that houses the centerboard... look at CMD's Sharpie 36... that one also has a shallow keel but in addition to that she has has twin rudders behind twin skegs so she will be able to sit upright unaided when dry out . . :idea: also an idea for your sharpie . . :?:

Chesapeake Marine Design Sharpie 36

Good Luck
Angel

 

A 40hp outboard motor ? did I read that correctly ? That must be a challenging motor well installation.

 

Yes, you read that well. But the complete read is ‘‘A single 40 hp outboard or a diesel sail drive’’ so I guess ‘out’ is an error an must be ‘in’.

Cheers,
Angel

PS - Sorry Michael, I didn't read well, I overlooked ‘‘or a’’

 

I looked one up, that one has a daggerboard instead of centerboard, but no info about the engine, the outfit of the boat makes me think inboard diesel there...

(I am open to better readers )

Cheers,
Angel

 

Ah yes, I remember it well. The differences between the two boats dont leap out at me straight away - please feel free to educate me if you think of it.

Thanks

Ray

 

In the Norwalk Island Sharpies range only the 43' has the kind of keel we're talking about, it's not on the smaller ones. Michel is designing a 26'

NIS 43

(twin rudders is an option on the NIS 43)

Cheers,
Angel

 

Thanks for that info. To my mind it appears you are losing one of the great advantages of a small boat - the ability to creep up in skinny water. For a 26 footer does it provide a performance advantage with all that drag ? I dont think it will be any more seaworthy.

 

I use the stub keel trick all the time on shoal draft designs. Though the NIS shown does appear to have a "slice 'o pie" style centerboard, which intrudes more, the stub keel can greatly clean up a yacht's interior. In many designs, you can lose the centerboard case under the sole completely. In a flat bottom boat, where bilge depth is at a premium, this is even more important. This keel stub can carry a substantial potion of the yachts's ballast, which is a good thing for it's stability curve and lastly, even though the appendage is low aspect, it is effective enough to offer leeward resistance, even with the board up. Of course you do lose some of the shoal nature of the hull form as RWatson mentions, but she appears to be fairly shoal still. My point is what is the difference between a hull that draws 10" without the stub keel and 20" with it. Calf high water or knee high water is about it and this isn't enough to get excited about, considering the advantage of housing the majority of the board, if not all of it, below the sole.

In terms of Angélique's design, I'd use more "appendage" housing then previously shown and also concentrate on getting the leading edge slope right. One of the most difficult things to live with on this style of hull, is the damn centerboard case and it's intrusion into the cabin spaces. One way around this is the stub keel, but another effective technique is to use a higher aspect board and use the forward end of the board, instead of the after end as done in a slice 'o pie style, to resist twisting. This means the forward end of the case needs additional support, compared to the slice 'o pie arrangement, but I've found it's much more effective at reducing it's internal foot print and you get a better plan form on the board itself too, for a free preformance boost, just for making the design change.

 

PAR, as always a very informative and valuable contribution

But . . .

Thanks, but it's Michel's....

Glad you're back on the forum and on this thread..!!

Cheers
Angel

PS

I guess you meant... ‘‘draws 10" without the stub keel and 20" with it’’ . . ? ?

 

Would it help to lower the drag of the stub keel if it was not flat on the underside but has a NACA shape all around..?? (except the topside of course which is against the bottom of the boat)

And would it still be able to provide some leeward resistance when the board is up..??



Picture is just an example of the form and is a plug of something completely different. For the stub keel form I meant it should be narrower and extended on the aft side till the hight and width are zero.

Cheers,
Angel

 

why not lee boards like the bolger As-29?

relatively unobtrusive inside and a flat bottom

 

AS29 is a centerboarder, aren't you confused with an other Bolger design or a modification..?


Bolger AS29

Cheers,
Angel

PS - just saw... it are twin swing-keels which are actually enclosed leeboards.