Modifying a Karl Stambaugh design- when to hire a naval architect?

[northcoastollie]

Hi all,

I am in the "dreaming" stages of building my perfect adventure pocket cruiser, and the closest design to my dream that I've found is Karl Stambaugh's Meadow Bird 16 for it's apparent balance of beauty, seaworthyness, and small enough to easily trailer but just big enough to spend a few nights in.

However, I'd like to make a few changes to it to fit my personal preferences, and am not sure how crucial having professional help will be. Any strong opinions or advice on the following changes?

1. Integrating oarlocks: I would like an alternative method of propulsion for those windless days, and prefer a "human-powered" option, especially if I'd like to use this for something like the Everglades challenge someday. My guess is that with careful planning, I could just fix these to a bulkhead/ frame just like a chain plate an be okay, but I'm not familiar with how important accurate placement relative to the boat's center of mass, rowing seat position, etc. is.

2. Ability to fly a spinnaker: I love a good asymmetrical kite to help me surf on a great run. I acknowledge I'll never be able to get speedy, beautiful, and seaworthy all in one boat, but this feels like it may be doable with either beefing up the shrouds and moving them a bit aft, or maybe the addition of a backstay (though that may yield trouble with the long boom and/or ease of setup/ teardown).

3. Switching from plywood bulkheads/ stations to a steam bent white oak frame: This is the biggest one I'm sure. The primary reasons I desire this change is (1) May be able to increase storage space/ open up the cabin & deck plan a bit and (2) I just love steam bending and think it's such a cool method of construction All that said, I'd still love to strip plank over that, so I welcome opinions on combining steam bent frames with strip plank construction.

Thank you!

~Oliver

 

[Tops]

Have you tried to get in touch with the designer directly?
Boat Plans and Yacht Designs -- Chesapeake Marine Design https://cmdboats.com/contact

 

[northcoastollie]

Hi @Tops - I sent him an email a few months ago and never heard back. I'm not sure if he's still active, but that was my first thought!

 

[Tops]

I would try a phone call during business hours next, and consider purchasing the study plan if you haven't.
I bought a set of plans from a different designer earlier this year and he has been good about answering questions.

 

[northcoastollie]

@Tops thanks, I'll try that! I've bought the study plans and full plans, so hopefully a phone call will do the trick.

 

[gonzo]

Bulkheads are usually a structural member. They act in compression and tension, which a steam bent frame won't be able to do. You may be able to compensate with a thicker hull or other modifications. I am not familiar with the design though.

 

[TANSL]

They act in compression and tension, which a steam bent frame won't be able to do.

I can't understand why they "won't be able to". Any explanation or you are just joking?

 

[Rumars]

Hi all,

1. Integrating oarlocks:

2. Ability to fly a spinnaker:

3. Switching from plywood bulkheads/ stations to a steam bent white oak frame:

1. The boat has a cabin and high cockpit coamings, ergonomics will dictate where you can put the oarloacks. Actually fitting them is easy, you glue a block of wood to the underside of the hull/deck joint to spread the load into the skin.

2. Lengthen the bowsprit and install running backstays.

3. You can but it's going to be a pain. The boat is a strip plaked and glassed inside out job, it doesn't need a lot of intermediate small frames to keep the planking together. What you do is exchange the existing number of tall and thin frames for lower and thicker ones maintaining the same stiffness. You also need to fit separate floors to tie everything together. So far so good, here comes the pain. Steamed white oak doesn't play that well with epoxy, and you shouldn't rivet the frames to the double glassed skin. The best option is to laminate the frames with integral floors, that will give you the look you're after without the problems.
If you really really want to build with steamed frames what you need to do is the following: increase the planking thickness so you can fit plugs over the rivet/screw heads in the planking, install the frames and floors, then glass only the outside. A weight study should be done to determine how much this is going to eat into the design max. displacement. Not difficult to do if you have the plans and a rough ideea of scantlings.

 

[fallguy]

Plank on frame(pof) and epoxy glassed skins are really not a good pair. As Rumars has suggested, the plank thickness is thicker to support mechanical fastenings in pof. What is worse is the white oak frames might make the boat less than fair with a thin epoxy skin. Honestly, the idea is being driven more by your desire than good sense. At first, I was not going to respond, but perhaps this is what the designer did if you emailed him such a question. He may have considered you a pita. The marriage of the two ideas is just not great.

If you like steam bending; perhaps you can incorporate it in some other facets of the build that don’t compromise the hull. Say like a table or rudder components or under bowsprit, etc. Or even as some faux framing in areas where the framing might be visible. As faux framing; you could keep it rather thin and add it after the hulls were complete so as to not deform. I decided to post to offer this last notion, not really to disagree with Rumars, but inspired by the realization of how ridiculously difficult it would be for a net negative in weight. Most designers incorporate the bulkheads into necessary elements like the aft cabin wall, for example, and so changing to a steamed frame is of no value there, or further aft, a part of cockpit seating, etc.

Good luck.

 

[northcoastollie]

Thanks @fallguy and @Rumars, these are both very helpful suggestions!

I actually did catch Karl on the phone yesterday, and he was extremely helpful as well.

I'm definitely convinced to avoid steam bent frames (definitely don't want a pita job, just trying to learn a bit as a first-time boat builder), but I will definitely incorporate steam bent objects throughout the cabin/cockpit.

Two more questions from a novice as I continue hashing out the plans:

1. Oarlocks: does anyone have good resources about where to place the Oarlocks relative to seating for rowing? My primary experience is sailing, not rowing, but I'd like an alternate means of human powered propulsion when the wind isn't there.

2. Flying a spinnaker: The running backstays are a great idea- do you think I can simply "move" the shrouds back to avoid adding rigging complexity, or would I need both running backstays and shrouds on the side?

 

[Rumars]

1. Because of the design you will have to actually sit in the boat and try it out. An alternative option would be a yuloh, that's simpler to implement and if you learn to use it correctly just as effective.

2. Moving the shrouds back would involve angled spreaders. Running backstays are just a matter of getting used to operate them, a little bit of bungee cord will keep them contained. If you don't use the spi for short tacking it's going to be fine, you only set one whe raising the spinnaker.

 

[gonzo]

Are you rowing facing forward or backwards, and standing or sitting?

 

[Tops]

I saw this older website with a Pearson Ariel set up with whitewater-style oarlocks just outside the coaming.
Author was trying to accomplish sit facing backward and stand facing forward rowing.
Oars broke down into 2 or 3 pieces each for stowing.
A Pearson Ariel Page http://www.solopublications.com/sailario.htm

I like the yuloh idea but have never tried it.
Yuloh Plans https://sailingauklet.com/2015/03/26/yuloh-plans/

 

[Paul Scott]

1. Because of the design you will have to actually sit in the boat and try it out. An alternative option would be a yuloh, that's simpler to implement and if you learn to use it correctly just as effective.

2. Moving the shrouds back would involve angled spreaders. Running backstays are just a matter of getting used to operate them, a little bit of bungee cord will keep them contained. If you don't use the spi for short tacking it's going to be fine, you only set one whe raising the spinnaker.

As someone who has swept spreaders and running backs, I’d vote against either:

swept back spreaders mean your main will be plastered all over them unless you’re going upwind.

running backs are nice and secure once you’re not tacking or gybing, but especially during gybing they will, from time to time, clear your sinuses, and you’ll find yourself avoiding gybes for fear of losing the rig, which can get weird as far as what course you wind up sailing, or you just take down the main and sail under jib alone.

If you’re going with a gaff (or Gunter rig (either Gunter)), like the nifty lines drawing sail-plan above, I’d argue going freestanding which could use a short mast (which would limit the aero and center of gravity downsides of a thick unstayed mast) with a nice streamlined bendy gaff spar or upper mast (Gunter) for leach release/control. You could also go nuts and incorporate a freestanding rotating wing mast, since she is a small boat, and you might be able to use Delrin or Teflon for partner and collar.

My 2 cents.

 

[CDBarry]

Hi @Tops - I sent him an email a few months ago and never heard back. I'm not sure if he's still active, but that was my first thought!

I had lunch with Karl a few months ago, so he is probably still active.

Try an email again, sometimes these things get lost in the shuffle.