Weekender/Picnic Vessel, Power and/or Sailing Catamaran

[brian eiland]

I may have to bring this subject back to life. I'm getting re interested in this shallow draft weekender cat idea again

 

[rberrey]

If you have not looked at the Spirited designs , I think they would be good concepts to build off of . Reduced hp , less draft , and shorter build time in the 8m range would be a good goal,s .

 

[brian eiland]

Or for something a little more modern...

It is geared a little toward fishing, but who doesn't like fishing?
Weekender/Picnic PowerCat https://www.boatdesign.net/threads/weekender-picnic-powercat.33751/#post-471223

Just looking back thru this subject thread. There is somethings to like here,..

 

[brian eiland]

....

All designs are a compromise and with this boat the decision was made to do away with 'sideboards' so that the only access to the fore deck area is via the electric actuated front 'door'. This allows for a much roomier feel to the cabin and lower levels and also gives better standing headroom in the hull areas. .

Interesting idea. If I recall properly the cat from Thailand also had a central exit/entrance at the front of the deckhouse.

Ah yes, here it is,..

 

[brian eiland]

I doubt jacking plates would be beneficial, you would lose prop disc area raising the props, reduce thrust and gain very little from a lessening of appendage drag, even assuming the props don't let go. The boat is too slow to get any value from it.

I got involved with a little racing of powercraft a number of years ago,...more specifically Zodiacs. It was year when Zodiac came out with their tunnel hull designs, and the factory thought it would be a good PR scheme. My partner and I had long been acquainted with Zodiac since their prime factory import facility was in Annapolis MD, and we had purchased the local retail outlet, Outfitters of Annapolis. So we got involved with the racing program.

During one such race up in Maine I believe it was, there was an old powerboat guy who opened our young eyes to the benefits of getting as much of that drive leg out of the water as possible. It made a BIG difference in our top speed.

There was a time a bit later when I experimented with adjusting the running height immersion of 9.9HP Yamaha outboard on the transom of the 37' Louisiane catamaran. It also made a difference in our speed. Just think of how much drag you create by simply placing one hand overboard when you are moving along.

 

[brian eiland]

That Thai cat has rather squarish/boxy lines compared to some more modern designs,...but think of how easy that is to build with flat pre-fab composite panels or lt-weight wood construction,...think economy of construction.

 

[brian eiland]

Matanzas 29 Powercat

Here is another article that spurred my new interest in this subject of a weekender/picnic boat. It appeared in this latest issue of ProBoat (#184, Apr/May 2020). I found this issue posted on line here,..
The Efficiency of a Foiling Powercat - Professional BoatBuilder Magazine https://www.proboat.com/2020/03/foiling-powercat/

Turns out that prototype boat is being built right here in St Augustine FL, where I am presently living. I do want to pay this gentleman a visit as soon as practical, taking into considerations this present virus situation we have in FL at the moment.

I see he is very interested in the same sort of vessel subject we are going to discuss here, but I do have a number of concerns with his chosen design. I'll make a list soon. Others are welcome to list theres?

Lets see if it allows me to make a link to one of the images in that article? ....yes it worked!!

PS:
Concerns about this Matanzas design:
1) too much emphasis on trailerability makes the beam just too narrow to be a true weekender, and likely what have in mind will need to be at least in the 35 foot long range.

2) he quotes 3-4 people for a daysail use, and 2 (a couple) for cruising. I would agree to both of these requirements as a bare minimum.

3) those 'peaked decks' up front,...bad idea, makes them unusable for any type of navigation by a human.

4) no side decks, nor other transit route around/thru the cabin to the front areas.

5) those outward facing foils look particularly venerable to damage. Why wouldn't one employ the Hysucat type foil between the 2 hulls,...less venerable, ….cheaper to construct, …..proven performance,....could be optional/removable

6) not a good fishing/fishing chair arrangement around that engine installation

7) too much wasted space with that engine installation arrangement

8) no real saloon/cabin/food prep area

9) not much of a berth, nor mini stateroom arrangement

Looks like I'm not the only one to find fault with this design,...I just found this subject thread, Professional BoatBuilder article: Foiling Outboard-Powered Catamaran https://www.boatdesign.net/threads/professional-boatbuilder-article-foiling-outboard-powered-catamaran.63617/

 

[brian eiland]

Just happened across this posting by Redreuben,...
Multihull Structure Thoughts

It's an old Kelsall design that sort of reminds me of the Stiletto 30 design,..

I have these pics variously labelled as 25 or 27 on my hard drive, I think they are all the 27, some ply some glass foam regrettably I don't think the ply plans are available any more and even if they were Kelsall's prices are astronomical.
Enjoy,

That central 'nacelle' mounted single engine and even the single rudder merits some considerations with respect to simplicity and cost to build.

If I recall properly Peter Wormwood also did a nice central saloon 35' design that had a centrally mounted outboard for power. And of course the Stiletto 30 had a centrally mounted single outboard.

 

[brian eiland]

Polycore Picnic / Weekender Cat


What would you think of building such a picnic/weekender cat out of the polycore material? ....(a polypropylene honeycomb/epoxy) as utilized on this 12M Solitary Island catamaran.

http://www.australiancompositepanels.com.au/index.htm

...:idea: In fact we might be able to turn one of these sailing designs into a power cat design something like the picnic cat I posted. I'm already talking with these fellows about a 'aftmast version' of one of their cats for an American client.

I see where this link I provided a few years ago has gone bad,... so I will post a PDF that describes some of the flat panel, polycore construction methods used with this kit boat

 

[brian eiland]

Construction Possibilities

In case anyone missed it that Solitary Island cat kit had a pretty neat construction idea. The 'hull shoes' were supplied ready molded,..

The main backbone of the kit are the two factory made hull ‘shoes’ on which the rest of the boat is built upon ‘the right way up’ (Remember all those nerve wracking photos of catamarans being suspended with two cranes while being turned over?). Not only is the most difficult part taken care of, but these hulls act like a strong back, another thing you don’t have to build. Just sit them in the supplied CNC cut MDF frames and start adding the bulkheads, bridgedeck etc.

So the shape of the hull bottoms of this weekender could be quite unique, and yet still manageable to the home builder who would not have to draft and build these 'shoe' portions of the hulls.

So it might even allow one to have a 'Tennant' type hull shape as I mentioned here for a larger powercat,..
Tennant Hull V ChainDrive http://www.runningtideyachts.com/dynarig/Tennant_Hull_V_ChainDrive.php

 

[Niclas Vestman]

Since my last post in the other thread, I did ponder much of the same questions as you have. And I do agree with points 3 to 9. Especially cabin space. And comparing a similar sized Skoota 28 with ample cabin space, despite having very similar performance specs. Skoota 28 claiming a projected mid 20isch knots om twin 60hp.
That also raises the marketability question. The foils and carbon parts seem to bring little to no efficiency benefit, despite what surely has to be a sizeable added cost and complexity.

 

[brian eiland]

More on Construction,...a suggestion I had make about constructing a Pilgrim 40 type trawler
Trawler Forum - View Single Post - Redesigning the Pilgrim 40 Trawler / Canal Boat https://www.trawlerforum.com/forums/showpost.php?p=175507&postcount=109
Combine these flat panel methods promoted by Kelsall with the 'shoe' of the Solitary cat I mentioned above.
**************************************

Booklet Explaining KSS Boat Building Method - Kelsall Catamarans
I've picked out some high-lights to excerpt from that 'booklet'

KSS stands for Kelsall Swiftsure Sandwich.

KSS is to forget all we know about traditional boat building. This is the hard part. The blinkers of what we know are very powerful. KSS takes the requirements of the final craft, the properties of the materials involved, the structure and what is efficient in the boat shop, and combines them into a common sense handling process.

A full size, flat mould table, usually of melamine covered chipboard, is the basis of the technique. Butt strap joins underneath, join the table surface sheets and trestles to support the table top. The first table was make in 1973. All structural parts start on the table, which allows ease of laminating and provides a smooth finish for one side. Vacuum Resin infusion has been adopted and refined to suit the table, as the standard laminating technique.

The Materials – PVC Foam, polyester or vinylester E-glass skins for the whole structure.
The basis – starting by making flat panels on a full size, simple, flat table.

The major time savings come from
* Working on a table, with a relatively small portion of the done on the boat.
* Picking up the finish from the table, for one side of all parts, plus edge treatment at the same time.
*Resin infusion which produces the full panel in one shot.

KSS has been applied to every size from 8ft to 100ft.

Resin infusion became a KSS standard 8 years ago. It is the “magic” which changes the nature of the whole process of boat building. The boat shop can be clean and smell free for most of the time.

For more than twenty years, we used vacuum bagging techniques, to make foam sandwich panels on the KSS table. The only incentive to change was the improvements resin infusion offered. A high quality panel in the least time, made neatly and cleanly, and with reliability. A panel, of any size, can be made by one person. This is not sales talk. We do it at every workshop. The last workshop group made three 32ft. panels, in four days of hands on instruction to people who had not done it before, with the first day spent in other preparation work.

While working with liquid resins, does it make more sense to work on boat shapes or to do 95% of the work on a flat table, from which a smooth finish to one side is free, letting vacuum pressure do the hard work, to achieve the best standards? Everything in KSS follows from there.

You might also go to his website and look under some of the specific headings. Here are two I might recommend:
Catamarans - Kelsall Catamarans - Boat Designs
Catamarans - Kelsall Catamarans - KSS Materials
Catamarans - Kelsall Catamarans - Boat Designs

….and another reference
http://www.stm-boats.com/articles/L8...sion_Story.pdf

PS:
If you look thru some of that KSS information and links I just posted, it's hard not to see that this is the ideal manner in which to build the relatively big flat panels of our decks, our cabin sides, and our cabin roof for the new Pilgrim design.

And these 'pieces' can all be built on a big flat horizontal table that produces parts with a 'finished side' to them, and the glass lay-up can be varied from part to part (main deck different than cabin side, different from cabin roof).

Set up properly this would all go much faster than traditional hand lay-up, with fewer people, be a much cleaner operation, and produce a superior resin injected piece.

Derek has worked with PVC foams like this for years, and much prefers them for this process. That said, there are no set rules that the Pilgrim redesign could not utilize the same foam-cored panels for its superstructure. BUT, I also think that the newer resin-injected-ready polypropylene cores could also be utilized in place of his beloved foam.
If you look thru some of that KSS information and links I just posted, it's hard not to see that this is the ideal manner in which to build the relatively big flat panels of our decks, our cabin sides, and our cabin roof for the new Pilgrim design.

And these 'pieces' can all be built on a big flat horizontal table that produces parts with a 'finished side' to them, and the glass lay-up can be varied from part to part (main deck different than cabin side, different from cabin roof).

Set up properly this would all go much faster than traditional hand lay-up, with fewer people, be a much cleaner operation, and produce a superior resin injected piece.

Derek has worked with PVC foams like this for years, and much prefers them for this process. That said, there are no set rules that the Pilgrim redesign could not utilize the same foam-cored panels for its superstructure. BUT, I also think that the newer resin-injected-ready polypropylene cores could also be utilized in place of his beloved foam.

 

[brian eiland]

Power & Sail Versions

I would hope that the primary platform that results in this design exercise would be adaptable for both power and/or sail versions. In other words the owner might be primarily a sailor, so he would want a version with a sailing rig, and a small aux power source. Then there may be that owner that wants more power (and perhaps no sails) for faster transits.

Thus it would be preferable that the 'base boat' does not have to be significantly altered to add either of these options. So
1) the fast power version might need foils that could be added or deleted.
2) larger engine or possible twins
3) the sail version might need a 'stand along rig concept' that would not require significant support from the hull structure,..
a) this type rig just might offer that feature, ...VPLP two-element wing sail
https://www.boatdesign.net/threads/multihull-structure-thoughts.62361/page-60#post-871921

b) or a small version of the new reefable wing sail developed by Randy Smyth on his small trimaran Sizzor
Hybrid wing sail-used by Randy Smyth to win Everglades Challenge https://www.boatdesign.net/threads/hybrid-wing-sail-used-by-randy-smyth-to-win-everglades-challenge.59514/


The sail options offer a potential longer range, and the ultimate 'get home capability' if engine failure or fuel problems occur.

 

[brian eiland]

Foil Assisted Version

I spent a considerable amount of time yesterday reading thru this subject thread,..
Foil Assisted Multihull Design
Foil assisted multihull design https://www.boatdesign.net/threads/foil-assisted-multihull-design.48462/

The gentleman, Groper, was building a relatively conservative weight 35' catamaran, and hoping to employ foils of some sort to help with efficiency and speed. It appears that the 'art' of adding foils to a vessel is more complicated 'art' than it first appears. And note worthy is that it does not appear that foils are that effective at speeds below 20 knots.

I'm not convinced that our weekender/picnic vessel needs to exceed 20 knots. When you think about it that is pretty fast for a relatively small leisure cruising vessel. If someone has to go faster then perhaps they need to consider a different craft,....with bigger and likely multiple engines. So for the moment I am going to put this option way down on the list of desirability.
( I wonder what the speed figures are for that twin engined sailing/fishing vessel that Jimmy Buffett had built??)

I will say that I was initially very encouraged by the relatively small single foil application I read about in this issue of ProBoat,..
Professional BoatBuilder - 160 - Apr-May 2016 https://pbbackissues.advanced-pub.com/?issueID=160&pageID=42

 

[fallguy]

The best picnic fastest build would be a modified Skoota 24.

of course, I am bias about the Skootas as I am building the 32 demountable in foam