Caravelle 16 pre build questions

[Iain]

Hi all

So I now have the plans in hand and will be starting the build when I get home end of Sept. As I have been reading through I have one or two questions that I hope someone can help with... first, I am using this build to learn for a bigger build next year. With that in mind I am wanting to use scarf joints instead of but joints, so I won't have the but joint to use for mounting my mid frame. The plans show the mid joints on two separate parts, but the notes say to remember that the mid frame must accommodate the centerboard case, to first install the frame without expoying it, then remove it after the hull has cured and cut it in the middle....now I am not sure if I should cut the mid frame as a single piece, or cut it in the two halfs (as in the plans) and join it before installing. If I have to join them, do I need to add the width of centerboard case? My last question may be pretty stupid, but I have never had any fear in the looking stupid department .... for the mast step, do I build a round footing into which the mast would slide in and out when setting up and taking down for storage? If so, any advice on best method to do this? Do I need to put in a pin to hold the mast in place and prevent rotation? I know you like aluminum masts, but I am going to make a birds mouth mast and boom as aluminum tubing of decent quality isn't particularly easy to get hold of where I live. Can I confirm that I can use the same dimensions of them in this case, I.e. 65mm tapering to 55mm mast, and 38mm boom (should I make the boom a solid spar?). Thank you all in advance for the help and look forward to starting and sharing the build as I go.

[jacquesmm]

.. first, I am using this build to learn for a bigger build next year. With that in mind I am wanting to use scarf joints instead of but joints, so I won't have the but joint to use for mounting my mid frame.

No scarfs please. I worked hard on locating the butt blocks just under the mid frame. In that boat, the butt blocks are reinforcements. If you use scarfs, you must add a butt block.
Scarfs are not better, not stronger and easy to to mess up.

The plans show the mid joints on two separate parts, but the notes say to remember that the mid frame must accommodate the centerboard case, to first install the frame without expoying it, then remove it after the hull has cured and cut it in the middle....now I am not sure if I should cut the mid frame as a single piece, or cut it in the two halfs (as in the plans) and join it before installing. If I have to join them, do I need to add the width of centerboard case? My last question may be pretty stupid, but I have never had any fear in the looking stupid department ....

You can't assemble the hull around a mid frame cut in half. Leave the mid frame in one piece, plank the hull around all the frames and asin most of my designs, remove the framing to glass the inside. Before you put the mid frame back, cut it in two etc.
Or if you prefer, use a temporary fram made from MDF but my method is simple and fast.

for the mast step, do I build a round footing into which the mast would slide in and out when setting up and taking down for storage? If so, any advice on best method to do this?

? Just epoxy glue the parts together or you may buy a mast with a mast step.

Do I need to put in a pin to hold the mast in place and prevent rotation?

The mast is held down by the standing rigging. Rotation is good for the sail shape, let it rotate but the standing rigging will keep it from rotating much.

I know you like aluminum masts, but I am going to make a birds mouth mast and boom as aluminum tubing of decent quality isn't particularly easy to get hold of where I live. Can I confirm that I can use the same dimensions of them in this case, I.e. 65mm tapering to 55mm mast, and 38mm boom (should I make the boom a solid spar?). Thank you all in advance for the help and look forward to starting and sharing the build as I go.

Make it 20% bigger. Al is stronger.

Don't over think the project. Build the hull first and things will become clear as you progress.

[Iain]

Thank you for the reply. I appreciate you taking the time. The one thing I would like to clarify is on the plans (page 1 of the large drawings....base of the mast) what looks to be a round sleeve on top of the mast step into which the mast would fit, but I have not come across any particulars on this. I get epoxy glueing the 2 10m ply boards for the mast step, but I am assuming that the mast does not just stand on top of this flat plank?

I do know that Al is stronger, but out here in the Philippines it is really not easy to get, so will have to go with the birds mouth method.

[ks8]

Oops. Sometimes posts are overlooked... I hope you are continuing in your build. I've been off the forum for awhile, but spotted this, so..

With the aluminum spar kit, there is a mast foot (shoe?) made of aluminum that gets screwed/bolted to the plywood mast step. The mainspar/mast then fits onto that. If you are building a bird's mouth, look into the methods used to ship and secure such a mast into place on the mast step. It is true that the standing rigging holds the mast down, but you should still have something that the base of the mast fits into or onto. My first sail in my CV16 stretched the standing rigging as the wind picked up.. really picked up! I'm glad the base of the mast was secure and not free to roam. By the time we were at dock again, there had been quite a bit of *shiver me timbers* with a few inches of play at the top of the mast. That's a lot of stretch for a relatively short length of steel rope. With new shrouds I *will* pre-stretch them somehow!

Over tightening the standing rigging to the extreme is no solution to keep the mast down as this would put additional strain on the hull, particularly the mainframe/chainplate holes, more so if you use cheap wood (if possible, don't use cheap wood). Reasonably tight standing rigging is easily done with the lashing method shown on the plans, but the steel rope shrouds may stretch first few times out. Even that can be corrected on the water, with the sails lowered, in a pinch, but do have some structure to secure the base of your mast laterally (front to back and side to side) and maybe something about an inch to inch and a half (3 to 4 cm) vertically so that it can't easily jump up and out off the step, and dream of freedom through the bottom of your hull.

I went extreme on mine, making my CV16 configuration something like a swiss army knife, with many swappable options, including my mast step area, with an optional tabernacle for the aluminum mast or a shorter box wood mast. So my gallery might not be the best for demonstrating the very simple and effective method shown on the plans. Explore some options for use with a birds mouth. I've seen some where an extra inch or so of plywood is added above the specified mast step thickness, with a round cutout in that additional buildup for the mast to slip neatly into, sometimes with a slight grove added for water drainage out of that mast foot *cupholder*. Lots of examples for traditional or plywood methods. There are plenty examples in the galleries here, but also in other forums and blogs all over the internet. Explore searching the Bateau galleries for mast step (which is what I prefer first),

Bateau gallery search for mast step

... and then use your favorite search engine where you will find many more like these that show various creative approaches elsewhere ....











Clearly, it is important to secure the mastfoot to prevent side to side shifting, and to have some sort of *vertical wall* structure in case loose shrouds invite the mast to defy gravity and jump up a little and out to chaoticaly dangerous freedom.

Let us know how you are doing in your build.

[Iain]

Hi there ks8....thank you very much for taking the time to reply. It was exactly what I needed. Unfortunately life got in the way of me starting the build and it has been pushed till December when next I am home. Will certainly post pics once I get it started.

[ks8]

Looking forward to it, when I'm back online here. I've been busy too, and sometimes that is very good.

I started around 2000, I think making templates and laminating the transom and midframe in the basement, and now have done lots of floating around and fishing in the boat since its launch, and still haven't finished painting the seats. Yes, schedules are sometimes ... hopeful suggestions. No, the seats will not be painted this year. Maybe next year? The primer is still holding up well.

[jacquesmm]

Besides what you see in the picture, you can build that mast step almost any way you want.
Get your mast first. If it is new, it will come with a mast step, metal casting.
That casting will be fastened to a block like the one in the pictures or as on the plans but flat, no need for any holes.

[ks8]

He's planning a birds mouth Jacques. Should look good on a CV16.

What rig are you going to fly from the mast? Area? How tall? You need to stay aware of a wood mast becoming too top heavy for the boat. The CV16 has plenty reserve stability, but keep aware of the weight of the total mast and the upper half of your birdsmouth, particularly if yours will be as tall as the specified aluminum. There are resources to help you engineer the final approximate weight of the mast and the final expected CG, compared to the specified aluminum spars. To simplify things, just calculate the final weight of the birdsmouth, and you can compare to the aluminum spars weight, since a tapered wood mast will be lighter on the upper half, in theory, except for perhaps the dimensional inserts as re-enforcments for mounting tangs and blocks, etc.

I weigh about 185 pounds and was near standing on the railcap for this picture, with only my arm inboard to hold the camera for the picture. Note the angle of the water in the bottle. Of course this was without the full aluminum rig, but it was with the lower part of my utility mast which is fairly heavy for its size. One of these days I'll take the same sort of picture with the full mast.

[Iain]

Thank you for the advise on the mast. I do not think the weight will play that big a part in the build. I have based my calculations off the following:

As per Jacques, a 20% increase in diameter, so using the calculator on http://www.duckworksmagazine.com/04/s/a ... irdsmouth/ I will have an octagonal build with staves of 30X15, giving me a mast diameter of around 76mm with am M value of 2.56. Using Douglas fir, and assuming a volumetric weight of 550kg/m3 the mast would be 6.89X0.03X0.015m per side, thus giving me 0.003kg/m3X8 sides. This works out to 1.71X8kg or 13.64kg. After rounding that I would imagine that I would loss around 10-12%, so around 1.5kg bringing me to just over 12kg. That would give me a top half weight of 6.2kg or so..... The DM2 mast is 0.776lb/ft or total weight of 8kg, so 4kg for the top half. If I were to taper the top half to 52mm I would loss around 1/3 of the diameter over the 3.5m, cutting the top weight by around 20%, giving me a weight of 5kg for the top half and around 11.2 over all. Of course there would be some additional inserts that would increase the weight slightly, but not by a huge amount I wouldn’t think. I think that should be OK right? If you have anything to add, of can see any flaws in my thinking and math (good chance of that ), please let me know. Thank you again

[ks8]

I am very glad to see you are working the numbers. I can't confirm them now, having just moved, with most of my books still packed away. Assuming that your construction produces a mast with the final weight(s) of your calculations, I am trying to put it into a way of looking at it in comparison to my rig.

The aluminum mast is, in theory, by your estimates, 8 kg, or 17.6 pounds. I would like to go out and weigh mine now, but that is not possible for a few weeks. At that time, perhaps I can weigh it with shrouds attached, masthead, etc. For now, I'll stay with the numbers in your post. 17.6 pounds. (I think it is more than that, but that is to the advantage of your final wood mast differences).

The wood mast, assuming it is not tapered, by your numbers is 12 kg, 26.4 pounds. If you did not save weight with proper tapering, in my imagination, that is like asking me to strap on 8.8 pounds to the center of my mast.

I built my cv16 like a tank. It is very overweight. I tried to keep most of that extra structure and weight close to or below the waterline, to keep the cg from drifting too high. I'm going to guesstimate that I still essentially raised the cg about 8 inches, 20 cm. I keep this in mind when breifing crew regarding their awareness of their position in relation to the centerline of the boat, as dynamic human ballast, and, it has convinced me that there is much wisdom in a mains'l that has several reefpoints. I'm not racing, or singlehanded voyaging across an ocean in a small open boat, but I do want to relax and enjoy relaxing, instead of enjoying non-stop adrenalin. The picture I posted in my previous post helped me much for the relaxing part, while doing my best to balance on the starboard rail, only holding my arm inboard to hold the camera and take the picture. btw, my heavy four-stroke engine is also on that starboard side, when that picture was taken.

That acceptable angle of heel is in calm water. Still a very good initial stability. I do not have a *stock* hull for comparing that heel angle. None the less, this image is confidence building. However, I stay aware that if this is not as good an angle as it may be on a stock hull, built to specifications, there is greater risk in conditions and seas that might push the hull's stability to its edge. In other words, my hull will find that edge of stability sooner than a stock built hull. Significantly sooner? I do not want to find out, but it would be nice if someone with a stock hull, next to shore, would get out of the boat, place 185 pounds on the rail, and take a picture of the heel angle. That said, I have never had a problem motoring or sailing, but my responses to conditions are very conservative, while still having plenty of what I consider to be edgy fun. How does all this translate? If I had an additional dead weight of 8.8 pounds secured to my mast, about 10 feet (3 meters) up from the mast step, That adds quite a bit to the situation, again, shifting that edge of stability. 4 kg (8.8 pounds) is a lot of weight up there. So I am hoping that your tapering efforts will be successful without too much weakening compared to an aluminum mast. And I also keep in mind that your rig may not be that much different from the performance sail rig option with its taller mast and larger area, regarding the moment arm or force of heeling toward the edge of stability in various winds.

Actually, at one point I was considering a birds mouth mast, and now I may get to see the results, with you doing all the work for me. Of course, you have the joy of completing and using it.

Please do post with the final mast weight, and the location of its cg. And the details of the hardware you will use. It would be wonderful for the community to see the results, and have another option with published test results.