Justaquickone
Member
- 346
- 72
Rudder bearing area would be no core just solid laminate .
All things Class40
- Thread starter furler49
- Start date
For those following the project: The last 10 days have been about installing bulkheads and stringers. Our process was to deconstruct our male mold a section at a time, vacuuming interior lamination and installing at least some of the reinforcements in that section before moving to the next. Among other things, this protected the hull from flex.
Bulkheads, transverses and stringers were vacuumed with minimal lamination before installation to achieve a compact structure...
...then typically glued in place using braces, and then each vacuumed in place with fillets and more glass plies.
We installed some of the bulkheads in an oversized form, and will trim to size as we fit the deck, ballast tanks, and other big features. The idea here is ‘margin of error’ – my favorite self-build principle! Better a piece is too big and trimmed than too small and fudged with a lot of putty. It helps ensure we fit everything as precisely as possible for strong joins and lamination welds. Also, some of the bulkheads have complex pieces, such as the mast bulkhead into which we're building diagonal composite compression beams (as opposed to a standard compression pole in the center of the cabin). By making a bit of trimming part of the installation phase, we figured that these pieces could be fit together as perfectly as possible.
Here you can see the transom into which molded rudder mechanism ‘slots’ have been installed, but which will be trimmed lower before cockpit installation.
(Alas, still tweaking the design of those rudder control/lift mechanisms… if anyone has advice...)
Thanks to all who have sent well-wishes.
Bulkheads, transverses and stringers were vacuumed with minimal lamination before installation to achieve a compact structure...
...then typically glued in place using braces, and then each vacuumed in place with fillets and more glass plies.
We installed some of the bulkheads in an oversized form, and will trim to size as we fit the deck, ballast tanks, and other big features. The idea here is ‘margin of error’ – my favorite self-build principle! Better a piece is too big and trimmed than too small and fudged with a lot of putty. It helps ensure we fit everything as precisely as possible for strong joins and lamination welds. Also, some of the bulkheads have complex pieces, such as the mast bulkhead into which we're building diagonal composite compression beams (as opposed to a standard compression pole in the center of the cabin). By making a bit of trimming part of the installation phase, we figured that these pieces could be fit together as perfectly as possible.
Here you can see the transom into which molded rudder mechanism ‘slots’ have been installed, but which will be trimmed lower before cockpit installation.
(Alas, still tweaking the design of those rudder control/lift mechanisms… if anyone has advice...)
Thanks to all who have sent well-wishes.
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- Thread starter
- #303
Watching your build come together has quite genuinely become my main reason for checking in..! Great to see it, keep up the good work!
bushsailor
Anarchist
bushsailor
Anarchist
Longbow looks like a very good system to me.
We have used a square post in the past to get better surface area for side loads but essentially the same principal as above.
Agree the project is very interesting.
We have used a square post in the past to get better surface area for side loads but essentially the same principal as above.
Agree the project is very interesting.
Thanks, bushsailor. I've studied photos of the OCD system but never had a chance to examine one in person. There seems to be a 'cinch' line at the bottom of the post that runs through gaskets (I think?) into the transom. Do you happen to know how these lines are rigged and controlled?
bushsailor
Anarchist
If I was doing it I would run it up on deck(or forward no leaks) to a cleat and set it up for roughly 4mm double braid (so it will break) and have a 2 or 4 to one system in there to tension it and also so it is a little bit stretchy to keep tension on the system.
All good ideas. 4mm double braid, yes. A couple times, over morning coffee, I've noodled on what the 'breakaway' strength of a cinch line should be by measuring it against, for example, max torque force on rudders, or max compression force of composite, etc. In the end, I've decided on a healthy dose of intuition!
For those following the project: The last two weeks have mostly been about 1) supply chain troubles, and 2) constructing the keel bulb. Typically, keels and bulbs are built toward the end of a project, but because we're waiting on some supplies, we attacked the bulb, which we'll fabricate in our own little DIY foundry.
Our bulb design is actually rather edgy (courtesy of designer Yves-Marie Tanton), notable for a 'flattened ellipse' shape and a 'beaver tail' which should produce a small bit of lift underwater. My first job was to generate accurate loftings, which we would then use to build a precise male mold... which we would then use to produce a concrete female mold in halves... which we will ultimately join... and into which we will pour molten lead with a small percentage of antimony for hardening. After hardening, we break the concrete mold, and presto.
Frames built from our loftings.
Sculptinging the top half of male mold.
Faired male mold, bottom half.
The 'beaver tail' of the bulb is finicky enough that it gets its own mold section.
An almost complete male mold for the bulb.
Into this box we pour structural foam around the male mold of the tail section, which will be fashioned out of epoxy.
And there's one female mold, ready to go.
Next step is to build the tub and related items (e.g., hoists) for melting and pouring the lead. We'll be recycling lead from the keel of a recently wrecked sailboat. We also thought about constructing a recyclable (i.e., re-usable) female mold for the bulb because we'd like to build future versions of the boat, but since we're just squeezing the bulb fabrication into a gap in our build timeline, we did it the simple way. As always, humility keeps the project moving.
And if our little team ever does build another boat, I'm going to be soooooo much wiser about supply chains... God help me.
Our bulb design is actually rather edgy (courtesy of designer Yves-Marie Tanton), notable for a 'flattened ellipse' shape and a 'beaver tail' which should produce a small bit of lift underwater. My first job was to generate accurate loftings, which we would then use to build a precise male mold... which we would then use to produce a concrete female mold in halves... which we will ultimately join... and into which we will pour molten lead with a small percentage of antimony for hardening. After hardening, we break the concrete mold, and presto.
Frames built from our loftings.
Sculptinging the top half of male mold.
Faired male mold, bottom half.
The 'beaver tail' of the bulb is finicky enough that it gets its own mold section.
An almost complete male mold for the bulb.
Into this box we pour structural foam around the male mold of the tail section, which will be fashioned out of epoxy.
And there's one female mold, ready to go.
Next step is to build the tub and related items (e.g., hoists) for melting and pouring the lead. We'll be recycling lead from the keel of a recently wrecked sailboat. We also thought about constructing a recyclable (i.e., re-usable) female mold for the bulb because we'd like to build future versions of the boat, but since we're just squeezing the bulb fabrication into a gap in our build timeline, we did it the simple way. As always, humility keeps the project moving.
And if our little team ever does build another boat, I'm going to be soooooo much wiser about supply chains... God help me.
Jethrow
Super Anarchist
I know you already know this, but make sure the concrete is well cured before you pour.
I used the concrete mold method once and thought the concrete was dry, but when I poured in the lead the moisture in the concrete boiled and the steam it produced put big pits in the lead and splattered lead all over the place as it escaped!
I used the concrete mold method once and thought the concrete was dry, but when I poured in the lead the moisture in the concrete boiled and the steam it produced put big pits in the lead and splattered lead all over the place as it escaped!
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Good point, Jethrow. This concern was discussed. After a decent cure time, our plan is then to 'pre-bake' the mold thoroughly -- heating it in advance and keeping it hot until such a time as the lead is poured. This involves making a sort of heat pit for the mold. Among other advantages, this technique does a lot to reduce/manage moisture in the mold. Lead builder Raoul has done dozens of bulbs this way without trouble. (My own experience is considerably less.) A well-heated mold also helps to prevent the lead from cooling too quickly, which is a good thing given the fairly large quantity of molten lead we'll be slinging around. Anyway, that's the approach...I know you already know this, but make sure the concrete is well cured before you pour.
I used the concrete mold method once and thought the concrete was dry, but when I poured in the lead the moisture in the concrete boiled and the steam it produced put big pits in the lead and splattered lead all over the place as it escaped!
RoseOfSangvinn
New member
- 27
- 2
Small update.
Since we’re still waiting on some supplies, we did our composite chainplates this week.
The chainplates are high strength Teflon tubes, wrapped-round with unidirectional E-glass strips which are laminated directly into the hull composite. The tensile strength of these plates is embarrassingly over-engineered, by many tens of thousands of kgs – just because it’s so easy to do for virtually no weight gain. (Each plate plus all its anchoring lamination adds around 1.25 kg total to the boat; so, much less than steel.) We will do composite chainplates for the shrouds, forestay, and the running backstays.
Our two shroud chainplates will straddle a ring bulkhead for general strength, so that portion of the bulkhead will be added later. We began by carefully grinding away a patch of interior lamination and foam, and then adding a couple more base layers of biaxial in this area. The lamination strips for the chainplates will insert into this reinforced pocket.
We hand-wetted and weighed the plies of unidirectional tape and epoxy, wrapped them around our shaped Teflon tube, and then inserted them into a slot cut into the chamfer of the hull, threading and then splaying them in the area prepared for them.
Then we vacuumed both the inside and outside to ensure good bonding and remove what turned out to be a very small amount of extra epoxy.
We will grind the lips of the tube a bit more to make them a perfect fit for soft shackles, trying to accommodate geometrically the exact angles the shrouds will take to the mast. In the end, we’ll cover the whole thing with thickened epoxy and fair it to make it pretty.
Since we’re still waiting on some supplies, we did our composite chainplates this week.
The chainplates are high strength Teflon tubes, wrapped-round with unidirectional E-glass strips which are laminated directly into the hull composite. The tensile strength of these plates is embarrassingly over-engineered, by many tens of thousands of kgs – just because it’s so easy to do for virtually no weight gain. (Each plate plus all its anchoring lamination adds around 1.25 kg total to the boat; so, much less than steel.) We will do composite chainplates for the shrouds, forestay, and the running backstays.
Our two shroud chainplates will straddle a ring bulkhead for general strength, so that portion of the bulkhead will be added later. We began by carefully grinding away a patch of interior lamination and foam, and then adding a couple more base layers of biaxial in this area. The lamination strips for the chainplates will insert into this reinforced pocket.
We hand-wetted and weighed the plies of unidirectional tape and epoxy, wrapped them around our shaped Teflon tube, and then inserted them into a slot cut into the chamfer of the hull, threading and then splaying them in the area prepared for them.
Then we vacuumed both the inside and outside to ensure good bonding and remove what turned out to be a very small amount of extra epoxy.
We will grind the lips of the tube a bit more to make them a perfect fit for soft shackles, trying to accommodate geometrically the exact angles the shrouds will take to the mast. In the end, we’ll cover the whole thing with thickened epoxy and fair it to make it pretty.
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