Foam Core Princess

[Scott Dunsworth]

Brent I have seen so many lumpy looking finishes on factory boats I look at on ebay, that I am going to blow an 8x10 picture up of some of the worst ones and hang them in the shop. That way when I think I cant take fairing any longer all I have to do is look at the pictures and be motivated to continue on.

Keep up the good work.

Scott

[Oyster]

Great job Brent, If you get bored with not being able to work on boats, come down to a warmer area and help us and get some fishing done at the same time. Check in sometime.

[bruegf]

Looked at the website above, and happened to notice that they also sell teak. I have a bunch of burmese teak that I bought over 20 years ago, but never used that I'd like to get out of my basement shop. I have 250+ rough sawn boards that in range in size from 1x2x36 to 1x2x60 up to 2x2x48 to 2x4x55 inches. Most are 1x2, 2x2 and 2x3. Its rough sawn as opposed to planed and jointed like theirs is, but would also be a lot cheaper if anyone is interested. I'm located near South Bend, IN. PM me if you have any interest.

Fred

[Brent]

Here is the centerboard trunk coming together.

 

The trunk is built from high density foam up front around the hinge pin, with lighter density foam aft.  The pieces are cut to rough shape and laid out on the laminating table.  

 

 

The trunk is shown after vacuum bagging one layer of 1708 on the outside, and two layers on the interior.  There is peel ply and bleeder cloth on top of the lamination that is about to come off.  Once the peel ply and bleeder are removed there is a smooth hard surface waiting underneath.

 

  There is clean up of the edges and trimming prior to fitting to the hull that will wait till later, but here is the roughed in centerboard laying in the trunk.  The trunk is longer than I am tall, reminding me again this is a big boat.

[Howard]

Brent:

I agree. Once you see many of these parts to scale...including the CB...it IS a BIG boat!

The CB design is one of about 3 places where I have concerns. What concerns me is how much board (about 5 feet) extends out of the trunk and how little remains up in it (about 8 inches). Assuming the slot in the bottom of the CB trunk is the pivot point, that results in a leverage ratio of almost 8:1. My understanding is the pivot pin transfers that leverage force to the CB trunk sides and the doublers, etc, such that it is not that great, but from a side profile, it looks scary.

The second aspect of the CB is the lift mechanism, which uses a 4:1 purchase through blocks to lift the CB. That too looks scary and like a tremendous amount of strain, and might be hanging in the air, but in the water, the board becomes buoyant and has to be weighted to sink. In the water, there is very little strain on it and on Tony's P22, raising the stick took almost no effort. Long term, it would probably be wise to remember this when fitting the boat to a trailer, and try to devise a way to support the tip of the board to take the strain of road bumps off the lifting tackle.

Keep the pictures coming!

[Howard]

Brent: Had an additional question on the 26 CB plans that you may have already worked out. Width of board is drawn as 1.75 inches, plus the width of any cloth.......king plank width drawn for the trunk is 2 inches, leaving 1/4" play to work with. Plans say to leave 3/16" clearance or board will bind......no more or board will rattle. Question is the 3/16" inch allowance on each side, or combined total? My guess is each side, but if that is the case, then there needs to be at least 3/8" differential, meaning the board needs to be thinner or king plank wider. Since board is already thin (NACA 0010), my guess is the plank needs to be wider.

On the first post, forgot to ask about the actual slot entry itself. To Brent or anyone else with experience in these things, how much strain is there on the CB slot edge where the board and slot interface when the board is down? The actual fulcrum point of the long lever that is the CB? If the side of the board rests on this edge when under strain, it would seem to generate a lot of crush stress on the edge, which is edge grain plywood, with a layer of glass and behind that, a gap of thickened epoxy where the plywood bottom and CB trunk meet. Glass cloth seems to have a lot of strength in tension and compression, along the long axis, but not sure of it's crush strength. Or it could be the pivot pit is where all the strain is and the side of the board has very little side strain on it at the slot?

With 3 or 4 layers of biaxial glass tape on both sides of the CB trunk inside the boat, and all the doublers, etc, there is some serious strain coming from somewhere, just not sure where it's being transfered to or how.

[Scott Dunsworth]

Howard for my Belhaven, I mounted a 5 or 6 inch roller on the trailer to carry the board while trailering, to take the strain off the mechanics of the board. You just have to remember to raise the board fully to launch. I also only used half of the designed weight in the board tip and it was all I wanted to raise the board on the 4 to 1. If there is room I would do 6 to 1.

I wouldn't worry to much about the other stress's I'm sure Graham has worked through them.

 

Scott

[Howard]

Scott:

I would think the amount of lead weight needed to sink the board would depend on lumber used. The lumber I have for this is SYP, which is stacked in my basement, drying out. SYP is pretty dense, and would need less weight than something like SPF, western red cedar or cypress. I can weigh the finished board and calculate the volume and how much lead will be needed to sink it, but not the geometry and volume of the corresponding board tip and where to make that cut. That's going to take a designer! (Note: Design already specifies 50# of lead and where to make the cut but doesn't say what wood was used to base that on. SYP or douglas fir might only need half that amount).

A secondary question comes to mind and that is the need to design in a "weakest link". In the event of a hard grounding, I'd certainly want the board to snap before the CB trunk was damaged in any way. It could be that a lighter, less dense and less durable wood is the right way to go. Whatever the case, when I start making boards, I plan on making two of them so I'll have a ready spare. Best time to make the spare would seem to be when you are into it and have all the stuff ready vs. some time down the road and in some far off land with no tools or place to work. With a high aspect ratio board like that operating in close proximity to the bottom, it seems likely that loosing a board is not a matter of "if" but "when". Goes with the territory.

As the CB trunk widens to account for the wider board, it might be possible to fit in the third set of blocks to get that 6:1 purchase. Something else I've considered is to install a small, self tailing sheet winch in the cockpit to act as my cleat for the CB pendant. That is another option for additional purchase, but all of this is starting to sound like a lot of strain in the system, not to mention additional cost and complexity. Sounds like just the right amount of lead will be important to the long term success and enjoyment of this contraption.

[Scott Dunsworth]

No way I personally would go to the trouble of making spare boards. Too much work! The chances of getting swept away sideways and break a board is not that great. More than likely if you did and the board did take a hold to the bottom, she would just heel over. I rarely ever navigated and used my board as a depth sounder often, with no damage other than rubbing the tip down.

 

My nickels worth

[Brent]

Howard,

 

I have grounded the centerboard on my Coresound 20 uncountable times...In the shallows of Chesapeake bay the board is frequently scaring crabs or tickling oysters. No issues what so ever with strength of the trunk or board or the trunk to hull joint.  

 

The Princess is a little bigger, and considerably heavier boat.  Looks like I will have at least 10 inches of board buried in the trunk, and 56 inches maximum dragging under the boat.  Finished out the centerboard will be just shy of two inches thick, including a couple layers of 1708.  This board and trunk are plenty strong.  Perhaps the drawings don't do it justice, I had to see this with my eyes to really appreciate the beefy here.

 

i do plan to lay polypropylene rope along the leading edge,which I have found this very effective for taking abuse.  I also second Scott's suggestion of placing a roller under the CB.  Relying solely on the CB pennant is asking for a failure while trailering, especially with a weighted CB.  

 

A quick lever calculation assuming 50 lbs of lead in the CB with a center of mass 48 inches below the pin, levered against 6 inches on the other side of the pin suggest the pull on the CB pennant will be 400 lbs.  Either the 4:1 pulley system needs to be upgraded to 8:1 or less lead goes into the CB tip.  Haven't decided which yet, will probably do both. 

[Brent]

Howard, I am going for total clearance between board and trunk of 3/16". Not 3/16 plus 3/16.

[Howard]

Thanks Brent. 3/16th's combined sounds like a pretty close tolerance.

I've never worked with 1708 cloth, or even 1208. What is the thickness of a single layer of the 1708? I'd think the inside of the trunk pieces (my plywood version) should get at least a single layer......or two if it's the 1208.

Did you start out with a shaped wooden board of 1.75 inches as shown on the plan or something thinner that grew to the finished thickness with layers of glass?

Your board does not sound like a "weakest link"!!!

[Howard]

I checked with Graham and it is 3/16's total..........maybe less if there is good alignment and it is working smooth..

 

Had another thought on the lifting tackle ratio. The 50#'s of lead weight is needed to overcome bouancy to sink the board, but the weight will also have to overcome any resistance/friction from the lines running through the lifting tackle. As designed, that is 4 blocks, not to mention the two at the other end of the CB trunk to get the pendant to the cockpit. More blocks/purchase than 4:1 may create too much resistance  through the lifting tackle to still sink. On the other hand, while remaining pretty bouyant for most of the trip, the last few inches to rise up out of the water to a fully retracted position inside the trunk is going to create some strain. If 4:1 is not enough to overcome that it may be time to consider something else like that cockpit winch. Will cross that bridge when we get there. More on this another time.

 

Had a chance over the holidays to scale out the Princess 26 rudder. Here is a photo with my Spindrift rudder included for scale:

 

 

In many ways, the Princess 26 does remind me of a scaled up Spindrift. Really scaled up!

 

BTW, a big pile of plywood has been ordered and should be shipping this week. Will start laying out the bulkheads and scarphing side panels in the coming weeks. Once I do I will start a different thread as it will be the stock, plywood version.

[Brent]

Time for an update.

 

The cabin bulkheads went in as soon as the snow melted.  The interior hull sides are mostly glassed now, making the hull very stiff. 

 

I used battens to draw the lines for the cabin sides. 

 

 

Then laid out the cabin sides on a lamination foam panel

 

Then installed onto the boat.  There is some trimming to do to get the final shape, but her profile is coming together.

 

Then it was layout the side deck panels for lamination

 

They are vacuum bagging now

[Brent]

 

Here is a quick update.  

 

The boat was rolled to right side up in July.  Since then the interior glassing has been completed.  The centerboard trunk, head bulkheads, and seat framing are all now in place.  The head was moved to port to provide a large versatile open space on starboard.  There will be no bench in the saloon on starboard, only open sole.  The folding chair shown there in the picture will be part of the boat furnishings, stowed in its own special place and deployed when comfortable seating is needed. 

 

The cockpit seats are in and the lockers built.  The cockpit seats are angled, with the inboard edge 2" higher than the outboard side.   Port side has a propane locker and a large locker.  Starboard has a very large single locker.    Still deciding details for the aft end of the cockpit area just ahead of the transom.  Motor will be mounted on the starboard transom.

[Howard]

Brent:

 

Have been wondering what you have been up to with this. Now we know (a lot).

 

Looks like good progress is being made. Keep the updates coming!

[Miyot]

The boat looks good, but I like the little folding chair.  I bet many thoughts and ideas are made there.

[Brent]

The big goal for this summer was to get the boat far enough along that the cabin could be sealed up for the winter, allowing interior work to proceed even in the cold weather.  Getting there...

 

All the major components in the cabin are in place.  Anything left to go in there will easily fit through the hatch.  

 

Here the cabin roof foam is laid out for glue up and glassed on what will be the interior side

 

The laminated foam is epoxied in place after careful dry fitting.The foam bends with a little coaxing.  Care is required to bend slowly and gently to keep all fair and avoid cracking any panel.Note the proposed layout of the companionway to be cut later.  

 

The exterior of the foam is then glassed. The foam panels with glass on both sides are incredibly strong.  No additional support beams are required to support the coach roof. The forward section still has the peel ply covering in place giving a slightly different color in the picture.  The peel ply results in a very nice epoxy surface requiring minimal fairing . Dirt from feet crossing the bridge deck was easily removed with a rinse and a little sanding.  

 

Now the overall profile of the boat is coming out.  The cabin height is carefully tuned to the cockpit seat height providing just enough clearance to see over the cabin from the helm, while giving maximum head room below decks.  The string run between the temporarily placed tabernacles shows the lay of the masts when in the folded position.  

 

All the exterior glass work is complete except for some details in the cockpit and the tabernacles.  Fairing of the deck and house is underway.  I may get a coat of primer on before deep winter arrives.

[Brent]

Got the paint on.  That is Interlux Perfection in Platimum color.  

 

 

 

Shes got 6' plus head room and weighs somewhere around 2200 lbs.  The double layers of 17-08 on the outside with a single layer on the inside over foam core is very strong.  The composite tabernacles came out incredibly strong.  The keel is hollow, and gives a home for the bilge pump.  Pouring the lead keel went well with some help from a good friend.

 

 

 

 

The plan for the outboard on starboard is evident.  Immediately forward of the motor is a fuel tank well with a partial cover to provide a deck over the fuel tank while still being well vented  The deck drains through a scupper in the fuel tank well.  On port opposite the fuel tank well is a large lazarette.   I will need to build shelving in the seat lockers to prevent loosing stuff in the depths of the locker abyss.  Port side seat locker is divided with a large general storage locker forward and what may become the propane locker in a smaller volume aft.  

 

Currently I am contemplating the motor throttle set up, considering using a remote throttle either on the seat locker side panel or on the mast tabernacle.  I am planning on a 9.9 HP twin cylinder high thrust motor with power tilt.  

[Oyster]

I was just wondering how you were doing this past weekend. Its great to see that you are getting closer to completing your project. Hope all is well with the family.