#70 - an amateur kit build

[simeoniii]

Sorry if I made the CB build appear overly complicated but you can put an awful lot of time into it if you are not careful.

I happen to have time on my hands at this stage and just kept fiddling at it.
My board ended up being 1.45 inches thick, from bushing flange to bushing flange. I'll probably make my trunk around 1.75 - 1.875 inches wide.

I made SCAMP #1's centerboard after the trunk was built and it ended up being too tight a fit in the trunk so it binds occasionally

Next weekend I'm going to drop the board and rework it so it's skinnier.
We might even install a mylar gasket to the slot if we are ambitious.

I'm not looking forward to all that extra work but it's worth making things right. Fortunately, when you are working with wood, epoxy and fiberglass, many errors can be corrected!

Live and learn!

Simeon

[chrisobee]

The epoxy impregnated glass will stick to the sanded epoxied surfaces. Just glass the surfaces of the blades if the glass won't lay smoothly wrapping the edges.

[Bcbimmer]

Good morning,

Some Centerboard progress and associated questions.

[Bcbimmer]

More centerboard

[Bcbimmer]

Final photos and questions,

QUESTIONS - I have rounded all the edges other than those on the top flat surface. Is there any reason those could not also be rounded to ease the fiberglass around the edge.

Simeons previous photos show a groove on the top edge of the board to allow clearance for the uphaul line. When I look at the diagrams it appears that this line is always going upwards at an angle to the top (when the centerboard is down). Is there enough slack in the cord or clearance on either side of the centerboard that this cord could get caught on the sides of the board?

Probably a stupid question that comes from never having sailed, but all the diagrams and photos show the up-haul line mysteriously coming out of the centerboard. There is a hole in the precut foil for the up-haul but it goes side to side and if you loop the rope through it and tie it off it looks like the ropes on the sides of the hole would bind with the sides of the centerboard trunk. Is the hole for a pin of some sort and was I supposed to make a slot running into that hole to take a loop of rope?

Finally about the centerboard pivot pin. I had assumed it was bolted through side to side but looking at the plans it appears that it is simply held in place by epoxying the head of the bolt to a cap of wood and screwing that to the centerboard doubler with silicone sealant (I assume so that it can be removed if needed). Is that correct? The manual shows a solid shaft with no threads. Do you just let the centerboard pivot on the threads of a regular SS bolt or buy a longer bolt and cut the threads off the end which would mean buying a larger diameter bolt as the shaft is narrower than the threads?

Thanks,

Dan

[simeoniii]

Dan,

Great job on the centerboard. Your method/technique looks great.
How many pounds of lead did you end up with?

Rounding that top edge would be fine to aid the fiberglass cloth wrapping.
It is also good to seal the wood with epoxy like you did before gluing the two halves together.

Josh and I made a discovery last week comparing my new foil cut board and his board I built for SCAMP#1 out of cedar laminations routed down with 18-19# of lead. That cedar board (the wood) is a lot lighter than the plywood used in the kit foil board giving it more buoyancy for equal displacement. That means that these kit boards should need less lead to achieve a good positive drop. I remember now that for Dan Phy's board (SCAMP #6), he only used 15-16# and was happy.

I'm prototyping the board I just built and have only 10# of lead. In salt water without any trunk friction, it will drop to about 15-20 degrees shy of vertical and I am going to rely on a downhaul to snug it all the way down.
I posted a photo of it earlier floating in the water at our marina dock.

That gets me to the groove at the top of my board that you referred to. It is to provide potentially needed space for my downhaul line at the front of the trunk when the board is in the up position. The uphaul line doesn't need one and seems to be fine staying always above the board. It doesn't tend to get caught/jam between the board and the trunk sides.

On SCAMP#1 we ended up using for the centerboard haul line a nicely handed 5/16" braided line instead of the 1/4" referred to in the plans. The pre-drilled hole in the board is ?" in diameter. I just measured mine and it's 1/2" but I may have drilled it out. You need to drill in at an angle a hole (5/16"?) for the cord which gets knotted off inside. Ramp the wood into the hole to avoid chafe. See page 72 of the v1.3 Build Manual & Sheet-8, Detail Centerboard Control. In retrospect, it may be better to make that hole 3/4" to better accomodate the knot.

For the CB pivot pin, I used a 1/2x -1/2 316ss Hex Cap Screw Bolt. That way you end up cutting the threaded portion off the end and chamfering the pin end. Not mentioned in the plans or build manual, we also used a small "O" ring on the pivot bolt between the ply pad the head is cemented to and the outboard bushing on the trunk. I posted earlier on my sourcing http://smallcraftadvisor.com/message-bo ... ?f=3&t=304

Hope this helps.

Simeon

[Bcbimmer]

Simeon,

Great help as always. I have 18 lbs of lead in my centerboard. Amazing I could read the manual multiple times and still miss the part on page 72 about drilling the hole for the line. Your description and pictures put it all into context. The hole in the premade foil is 5/16 and I think I will make it 1/2 to 3/4 inch as well to hold the knot.
The centerboard pin also clear now. I had used your previous posting with the photos of the pin but in the one showing the marked bushings there appear to be threads at the end of the bolt. I assume the marked areas on the bushings are cut off and the bolt then shortened as needed. I have ordered bushings from Aircraft Spruce. They have an outlet in Canada so no brokers fee. Used them before when built my rowing shell and had great service.
I had read all the posts prior to getting the kit and manual. Lots of comments and pictures in there that are very helpful. Now when I go back to those comments or get replies such as this, I print out those pictures and explanations and attach them to the back of the pages of my printed manual opposite the section under question.

Thanks again,

Dan

[simeoniii]

Dan, thanks for the nice feedback

Yes, the marked bushings in the photo indicate roughly where they were to be trimmed after the board was made. As you noted, the 4-1/2" bolt's theaded end had not yet been trimmed. For other folks who haven't yet bought bushings/bolts, the bolt doesn't have to be exactly 1/2". Just so the bushing/bolt and holes are all sized accordingly and somewhat close to 1/2"

Normally I like to over-drill the holes and fill with thickened epoxy, then drill to size.
I haven't done that for the pivot since the positioning is critical and I didn't want to take time with a jig or something to ensure my second hole was centered properly. With a glued in bronze bushing I don't think there is any danger of water getting in the end grain of the hole

Good idea on your expansion of the manual idea.

Simeon

[JohnT]

There I was, up to my knees in saw dust and shavings... One of the challenges in building a Scamp is that the plans are metric and the kit is cut to the plans. There are a few complications. Most of the natural wood pieces in Scamp are specified as 20mm x 30mm, and this is the size of the notches cut into the kit bulkheads. Unfortunately, 20mm converts to 25/32" and this is 1/32" more than the US standard "1" board which is actually 3/4" thick. I can't imagine that 1/32" matters structually, but it is nice if the various stringers actually fit the notches in the bulkheads. A solution is to buy "five quarter" boards and use a thickness planer to bring them down to 20 mm. In the process, you will generate a lot of shavings (two wheelbarrow loads in my case).

For Scamp 95, I've built the centerboard and rudder, pre-coated and glassed where needed, and machined the necessary stringers and clamps. I'll assmble the building jig and start dry fitting this weekend.

[julie]

Most of the natural wood pieces in Scamp are specified as 20mm x 30mm, and this is the size of the notches cut into the kit bulkheads. Unfortunately, 20mm converts to 25/32" and this is 1/32" more than the US standard "1" board which is actually 3/4" thick. I can't imagine that 1/32" matters structually, but it is nice if the various stringers actually fit the notches in the bulkheads. A solution is to buy "five quarter" boards and use a thickness planer to bring them down to 20 mm. In the process, you will generate a lot of shavings (two wheelbarrow loads in my case).

That is an impressive amount of shavings!

Out of curiosity, have you tried the method in the manual for cleat stock (same dimension as the stringers) on page 14?

Rip Cleat Stock. Use yellow cedar or similar clear wood. Suggested dimension would be 11/16"x7/8"

Hint: Dimensional 2x8(1-1/2" x 7-1/4") can be ripped with a table saw into 7 even pieces of 7/8", each to be cut again to give 11/16" thickness.

I'm sure it won't be as snug and perfect as a fit as your 20mm stringers, but it seems like it could be faster (although a thickness planer sounds infinitely more fun!).