Historical multihulls

I too have always admired Peter Spronks work,especially the glued lapstrake plywood construction I continue to be surprised that others designing multies in plywood have not picked up on this excellent method of building lightweight hulls. I wish someone would write a book on Spronks work. Its not easy to find info, even in the internet age.

Steve.

 

I think it is a good build method and had a long talk with Dick Newick about building one of his tris that way. He thought it fine.... Peter built them 2 ways, glued lap and glued lap with the lap on stringers.

 

I don't recall the exact details of his 'lapstrake plywood construction', but I imagine it is not as straight forward as this radius chine epoxy plywood construction of this Dudley Dix 55 cat
http://www.dixdesign.com/55cat.htm
...click on the 'build photos'

Certainly the radius chine method may not give quite te same bottom shape obtainable with the lapstrake method, but you can certainly make the radius chine vessel a longer lasting vessel with less effort

 

The glued lap covered with glass of the Spronks has held up well. It is lighter than the radius chine method by a large margin with no strength loss. The skill set isn't that hard to achieve with lapstrake on a multihull because of the gentle changes in shape. You can find this construction in power boats such as the Thompson where it was used for strength with light weight and durability. One of the construction benefits is a round hull shape is possible while using less epoxy than either strip planking or double diagonal to say nothing of foam/glass. There are other benefits as well.

 

Certainly the radius chine is another method, neither better or worse. Im not sure of how Spronk built his boats either, I just havnt seen any magazine or internet articles on his work, but I think a lot of folks perceive lapstrake as being a more difficult method, it really isn't and his b
oats sure were attractive.

Steve.

 

I can't imagine it is easy to glass over numerous lap joints.

How can it be that much lighter?

 

Now don't despair, a boatbuilder needs a good imagination! They can be cultivated.....Seriously it is easier using cloth like dynel or polypropylene, not hard at all then.

Lapstrake is lighter because it doesn't have the heavy glass layup on the inside and outside of the planking joints like radius chine. Less epoxy and glass = lighter weight.

Theoretical other advantages involve lining the planking with the water flow to aid lift and reduce skin friction by introducing air into the boundary layer surrounding the hull. The Navy is working on this one by adding bubble nozzles on hulls but lapstrake does it for you. There is also spray reduction that you don't get with radius chine which has bumps with no benefits.

 

Does anyone have any photos of trimaran called hired hand. I am curious as to what it looked like. I have a memory that it capsized I think in a brisbane to Gladstone race alone with a twiggy (sailmaker?) and another multihull. I think it had a reverse sheerline and alloy beams

 

Digging deep into memory bank - Hired Hand was a very mean and minimalist trimaran, 31 feet or so length, and painted green? I know there were a few articles in Modern Boating. I had ripouts but loaned the collection to a famous Auckland sailor ... and that was the last I saw of them. Yes, there was an accident and boat damaged or lost. I'll check through stuff I've got in the back shed. But there must be some Aussies who remember the boat.

 

Hired Hand was a Lex Nicol design I believe, he had a number of cool, lightweight foam sandwich racing tris around that time and then seemed to have dropped off the face of the earth.

Steve.

 

I agree that sheathing using dynel would not be difficult at all, if I were to use glass cloth I would pre glass the sheets before making up the planks and then tape the laps, a lot of dicking around but easy.
You seem to be more familiar with Spronks construction methods than i, do you know of any magazine articles on his work? There are a few designer/builders who are no longer with us who i wish someone would publish a book about, John Spencer from New Zealand is another.

Steve.

 

I've always liked the Spronks, most of the magazine stuff i saw was a picture here or there. We had one in the PNW for a while in the 80s rigged as a schooner but the winds weren't enough for the trade wind rig. Interior views could tell all. The most printed information I've found is in the 1976 Multihull Symposium book. It is a treasure trove transcript of all the top designers of the time an Spronk describes his build method. You can still find used copies from time to time. Good to buy with the Capsize Bugaboo from the same publisher about the same time. Paddy was among the hosts of that meet way back when.

 

Gary it would have been most likly the modern boating magazine I read about hired hand, There was an account of the capsizes of the race as well. I was counting on the Aussies for that one Catsketcher may know more.

 

Thanks Cav, ill see if I can find a copy. Im curious if he used glued lap construction or more traditional with ribs. I think you could reduce the plywood thickness a bit with glued lapstrake vs a sheet ply hull.

Steve.

 

I met Peter a few times, and have been on a number of Spronk cats, but not sailed one myself

However the ply planking overlaps mean that the area of ply used will be at least 10% more than a smooth hull (say 200mm wide strips with 20mm overlaps). And lapstrake/clinker hulls are noisy when sailing. Also it's harder to make a fair hull as every plank has to be fitted so it looks fair from every directions, so its more time consuming to build. On most boats you only have to worry about the gunwale fairness (underwater chines are less of a problem visually - unless you are hull flying - but obviously unfairnesses tend to slow the boat)

Not a multihull, but the National 12 dinghy started life as a clinker boat, but the rules changed to allow round bilge hulls, which proved quicker

Richard Woods of Woods Designs

www.sailingcatamarans.com