Reefie's LB26

[peter-curacao]

Those tile spacers/levelers are a great idea for this purpose

[reefie]

Is there any shear concerns with all those direction changes? I think you better check with JM to see if you need to modify the lamination schedule.

Thanks for your question Fallguy, but I have no concerns with the strip planking orientation. In the lamination schedule, it is not the core material that provides the full structural hull strength, but it is there to provide a cold molded hull form on which the glass laminations are laid. It is the glass laminations which contribute to the overall hull strength, and the glass lamination schedule for the LB26 is very robust. For example, the bottom plates have a combination of alternating weave (biaxial, double bias, and CSM) totalling 84oz (2700 GSM) externally, and 50 oz (1600GSM) internally (plus additional layers at the keel and chines).

Also, with the method I have chosen, I will be gluing in between the planks (the 3mm space) with 50:50 cabosil and q-cel mixture. This further increases the overall strength by essentially inserting epoxy "I" beams into the overall lamination.

However, and notwithstanding what I have said above, if JM determines that my strip plank orientation needs revision, I will modify the layout.

As a side note, I started off laying the planks longitudinally, but with the complex LB26 hull shape, I could not get the planks to lay this way without edge set and/or snapping the planks - hence the layout I have gone with.

[fallguy1000]

The intermediates are very wise for this hull. The other build I watched; the builder had to fair like crazy.

What wood is that?

[TomW1]

Remember Fallguy that in Jacques designs that the plywood is only the form of the boat. The fiberglass provides the strength.

Tom

[reefie]

Those tile spacers/levelers are a great idea for this purpose

Yeah Pete they work great at getting the planks laying fair.

What wood is that?

Kiln dried DAR 15mm X 42mm Kiri

[fallguy1000]

I will only add, since JM hasn't had the last word, that shear forces work when the boat is say coming down with all its weight off a wave and the front of the boat, for example, plunges into the next wave.

The shear forces can impact a boat, especially if the boat has an area of significant strength near an area of deficit. That would be stringers ending or bulkheads near a place with any potential deficit.

In a core boat, not all of the strength comes from the skins. So if you introduce a weakness to the core, say by making it thinner at the bow for an odd example, you would increase the potential for shear. In fact, in that example, shear forces would probably result in mechanical fatigue and failure.

As for edge set, I understand it. Sometimes using narrower boards addresses it. Sometimes not and you have to make a direction change. When you do a direction change; the longer the bond; the better, so for LB26; you might go a few frames up and stair step the curve, or put the join on a 45 instead of transverse. Note: I originally thought from one picture they were transverse, but now they look on 45s in another frame. Since reefie hasn't glued anything, better to make sure now!

It is the stuff of naval architects and engineers and not me. I have just never seen it done this way (again, I am referring to what appeared to be transverse, but are actually closer to 45s on another picture)

[reefie]

Hi Fallguy,

The point you are raising would be an issue in "traditional" boat building techniques where the strength of the hull is derived from the planks and their orientation to each other in the overall shape of the hull - coupled with the framing of course. However, we are not building the LB26 using the "traditional" method - we are using modern composite construction.

With composite construction, in raw terms it is the thickness of the core that provides the "stiffness" of the panel, and it is the glass laminations that provide the "strength". Notwithstanding that the internal framing (including their spacing) is also a critical factor.

Also, as you have noted, none of the plank directional changes are less than 45 degrees.

Similarly, do you see a concern with a panel that has been formed by joining multiple 8 foot sections together to form a longer panel? This technique would also introduce 90 degree transverse joints to the hull core ...as is the case with the panels for your hull - do you see a problem with this?. No... because this is a valid construction technique with modern composite construction. In fact, it is specifically listed in the construction book of the LB26 for the bottom plates to use full foam sheets (or plywood) for the aft flatter sections, and to butt join them together with glue (also creating transverse joints) and do the forward section of the bottom plate with foam (or plywood) strips also butt joined with glue to the rear panel (creating even more transverse joints).

Therefore, and with all due respect, I see no concern with what I have done... but if you do, you should also be concerned with your hull.

[Browndog]

Your doing great work. The planking is not an issue at all. I can’t wait to see what it looks like once you have glass on it and begin fairing. Mighty sexy is my guess. It will give us all something to dream about. Build on! Thank you for inspiring me. I still have in the back of my mind a CS 30 down the road.

[fallguy1000]

Mine was mainly a misinterpretation of the photos. One photo especially is something of an illusion. I called out my mistake in the prior post. And I said transverse; they are not.

Composite panel joins with plane changes or chines usually have extra reinforcement. It was hard to tell if you have plane changes in the same pic. And the joins must be stronger than the core as well. I don't know how DAR and the glue compare either. If you use a glue weaker than the core; it would be a problem, again especially near internal strength. This is ditto all composite or strip. I believe the best glue for you would be cab, ballooms, and flox, but I don't like the flox components roughness here. If you only use balloons; not sure that is right either as I don't know the numbers. It is very interesting leaving a 3mm gap. I had figured you'd need to edge glue as you go, which is damn slow. So, again very interested in the method.

And the reason I'm watching close is like the method you chose; not to criticize strip building. I think building in wood would be very enjoyable. More so with the open glue method.

How are you going to keep the glue from squeezing out? Perhaps I missed that, too.

If you weren't 6000? miles away, I'd be a grunt for you.

All the best. It is my favorite JM design.

[reefie]

Thanks everyone for your encouraging and motivational words... I really do appreciate it
I am very much enjoying this project and watching, as each plank is laid, the LB26 slowly reveal her beautiful hull shape.
I think the extra effort put into getting the panels laying fair and true at this point will pay dividends later when it comes time to bogging and fairing - which I am under no illusion will be a pretty big job for a boat this size.

How are you going to keep the glue from squeezing out?

Its a matter of adjusting the glue consistency. I will be using empty caulking tubes filled with the epoxy glue mix, and It helps to have an extra person on the other side of the panel to scrape off any excess that squeezes through and also fill in any gaps.