LB26

Power Boats only. Please include the boat type in your question.
les2021
Active Poster
Active Poster
Posts: 229
Joined: Fri Mar 05, 2021 8:21 am
Location: Crete, Greece

Re: LB26

Post by les2021 »

Morning Pee Wee, Fuzz, OrangeQuest.

It's good feeling to get it in place, I can now breath again :lol:

The engine is the Nanni T4 205 200hp, the shaft, shaft strut and prop arrive this week so will be able to do the final adjustments.

Hopefully I will have the electric drawing and spec arrive this week as well so I can order the materials to start running cables etc so expect questions :D

And it's time to get back to fairing and more fairing.....

Day off today ( so Nicki has told me ) :?

Cheers Guys
DA33C77D-A7E5-4D58-919C-280997DBF7C5.jpeg
075078CB-32F6-49D9-A1DE-D332C4C70687.jpeg
7DC101E9-B9F8-46E2-8EDC-7EB9055C04C6.jpeg

fallguy1000
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 10198
Joined: Tue Jan 12, 2010 12:25 am

Re: LB26

Post by fallguy1000 »

One thing I wondered about while considering the LB for a build...I wondered if the engine weight should be offset aft by marine foam. Now, I realize the boat is made with foam, but I think the boat if holed or a thru hull or seacocl failed might sink to engine weight.

Watertights are very difficult to fab with the sole, by the way.

Consider it friendly conversation. Each cubic foot of marine foam 2# offers you about 60 pounds of extra flotation. So I would at least entertain the idea to offset the engine mass.

Curious what designer would say.

As a foam boat builder, I am debating closing a wet bilge I made with marine foam..
My boat build is here -------->

viewtopic.php?f=12&t=62495

jacquesmm
Site Admin
Site Admin
Posts: 28215
Joined: Wed Aug 14, 2002 1:00 am
Location: Florida USA
Contact:

Re: LB26

Post by jacquesmm »

It is difficult if not impossible to provide positive buoyancy in a boat that size but we can get very close or even do it because this is a light foam sandwich hull.
Keep in mind that the tanks, even full, provide buoyancy. Water tight compartments are good as long as they don't impede access for maintenance.
Filling all little corners and gluing foam panels under the decks are good too.
Jacques Mertens - Designer
http://boatbuildercentral.com

fallguy1000
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 10198
Joined: Tue Jan 12, 2010 12:25 am

Re: LB26

Post by fallguy1000 »

Other ways for Les to make the boat less likely to suffer a sinking event would include making floodboxes around any raw water intake.

I did a calculation using hand layup of 1708 on each side of 4# foam.

Each yard of hull/sole/etc with this layup weighs 8.5#. Add say 1.5# for the tabbing and each yard contributes about 50 pounds of buoyancy. So, offsetting the engine weigh in watertights or foam filled areas and I'm pretty sure she is technically unsinkable.

Protecting the engine is my main thought. If you are pos buoyant, but not enough aft, then the engine might be under water before the rest of the boat contributes enough.

These are my wanderings on this boat. Of course, staying upright with foam is the real goal, so foaming in useless higher spaces just a bit above engine bottom or middle vertically would also be good.
My boat build is here -------->

viewtopic.php?f=12&t=62495

les2021
Active Poster
Active Poster
Posts: 229
Joined: Fri Mar 05, 2021 8:21 am
Location: Crete, Greece

Re: LB26

Post by les2021 »

Morning All

Dan / Jacques

Thank you for the posts..... Please forgive me if my reply sounds slightly concerned !!!

When I bought the plans and decided to spend one hell a lot of money on building the LB26 I thought I would be building a boat that was designed with a certain amount of safety built in. Reading Dan's posts It seems that if the boat is holed then it will sink like a brick....

If extra floatation is required should that not be part of the build ???

I have read both posts a number of times, If I need to add extra flotation / air tight lockers can I please have details drawn up. The main reason being if I have to have air tight lockers etc this will have an input in where I run pipes / cables / exhausts etc.

If this sounds a little grumpy sorry.

Les

fallguy1000
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 10198
Joined: Tue Jan 12, 2010 12:25 am

Re: LB26

Post by fallguy1000 »

The plans never said the boat was pos buoyant Les, unless I have forgotten.

The LB26 is a very safe boat.

Risks to vessels depend on vessel type. All boats have risks and risk assessment must always be considered by the captain.

For my Skoota, we have 11 watertight boxes, specified by the designer. The boat is an outboard. Now, Richard did not tell me, the primary risk to your vessel is X because he did not require the engine choice, nor did he specify where I operate the boat. Risk assessment is mine to do as captain.

The primary risk to my vessel, I decided, is fire. Mostly because gasoline boat. For this reason, I plan to build a small dinghy in case I am fishing 45 miles offshore. I also added egress or escape hatches to all sleeping areas. I recommend you do this as well. Epoxy/foam despite lower fire risk in a diesel is still very dangerous if fire occurs. And an escape hatch forward cuddy is nice for a breeze.

The secondary risk to my vessel, I decided, is drowning the outboards. For this issue, I went up to long legs and my engines are up higher than normal, but I don't care. Hopefully they will function well.

For a designer to make a claim a boat is unsinkable is really not done.

If you want to make sure the boat is pos buoyant; that is done here by all Mertens builders based on their own loading decisions.

So, tone down the grumpy and realize you are the captain, responsible for decisions around your vessel.

I, for example, do not even know the weight of that lovely engine. Nor do I, or Mertens, for that matter, know what you intend to load in the boat.

A refrigerator, two 40 pound anchors? Foam core or granite top for the galley?

And remember, if I have a tone, I am looking out for you as a fellow builder and trying to help you make good decisions that may be considered optional.

Buoyancy calculations are pretty difficult. But not too horrible for you and where you are in the build.

Basically, take each section of the boat and load the hull components, core, glass, resin.

Then add in offsetting weights. Engine. Fuel tanks, fuel is actually lighter than water, so I typically just leave it out of the calc, batteries, solar panels (see how this is hard for the designer as variable increase?).

I did it all on a massive spreadsheet. Hull and pos buoyants on one column and all sinking stuff in another column. It isn't too bad.

And when done, as Captain, you will know the safe loading maximums for the vessel.

ps-all my buoyancy calcs on the Skoota are estimated, when you estimate glass weights; you can easily guess resins with fillets at 110% of glass used
Last edited by fallguy1000 on Mon Sep 12, 2022 9:58 am, edited 2 times in total.
My boat build is here -------->

viewtopic.php?f=12&t=62495

fallguy1000
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 10198
Joined: Tue Jan 12, 2010 12:25 am

Re: LB26

Post by fallguy1000 »

All my comments aside, it would be good to hear from Jacques on the subject.

I do not trust below the sole watertights! The sole is never bonded well enough to comprehensively seal, so below the sole must be foamed in, imo.

There are only so many options for placing foam below the sole of the LB26. Foaming on the sides and aft sections will also make the boat quieter underway.

How much foam I cannot advise unless you calculate, but you have excellent opportunity now.
My boat build is here -------->

viewtopic.php?f=12&t=62495

fallguy1000
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 10198
Joined: Tue Jan 12, 2010 12:25 am

Re: LB26

Post by fallguy1000 »

I would like to add one or two more things. All to help you Les!

Foaming in is supposed to keep the hull upright, so technically, what I said about only foaming in low, is incorrect.

Technically, for example, foam would be added to the sides above dwl, in order to keep the boat from rolling over if she took on water.

For the LB26, I don't recall if the mechanicals have a seacock or raw water intake, but if you add this to wash the boat down with seawater or to add a watermaker, adding a floodbox is another way to minimize any problems with a seacock failure. This is another sort of optional way to build and something I did on the Skoota. Something to consider now versus later...
My boat build is here -------->

viewtopic.php?f=12&t=62495

joe2700
Very Active Poster
Very Active Poster
Posts: 629
Joined: Fri Nov 25, 2016 3:16 pm
Location: Massachusetts

Re: LB26

Post by joe2700 »

In the US, outboard monohulls under 20' in length with more than 2hp need level floatation, meaning they float upright when swamped. This is a requirement of builders, so not saying it applies to home builds, just providing context compared to commercially built boats.

https://www.law.cornell.edu/cfr/text/33 ... /subpart-G

Inboard powered boats under 20' have some other floatation requirments:

https://www.law.cornell.edu/cfr/text/33 ... /subpart-F

I don't believe there is a floatation requirement for boats over 20 feet.

Some larger boats will have this as well, but once you get to a certain size I'm pretty certain most boats are not built in a way that they will float if swamped. That's why you see videos of fishing boats sinking offshore. There are still measures you can take such as watertight bulkheads so for example a seacock breaking can't flood the whole boat, just one compartment. That said larger boats if they get a significant enough hole will sink. On larger boats far offshore we bring damage control equipment, and liferafts.

I don't know a ton about the LB26 but I suspect at that size there is a mix. A 26' whaler probably floats(all their boats are foam right?) but I bet most boats that look like an LB26 don't. Just my guess. I'd think about how far offshore you plan to use the boat and then decide how far you want to go to defend against different risks, and I'm sure the designer would be willing to help with that.

fallguy1000
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 10198
Joined: Tue Jan 12, 2010 12:25 am

Re: LB26

Post by fallguy1000 »

joe2700 wrote: Mon Sep 12, 2022 10:21 am In the US, outboard monohulls under 20' in length with more than 2hp need level floatation, meaning they float upright when swamped. This is a requirement of builders, so not saying it applies to home builds, just providing context compared to commercially built boats.

https://www.law.cornell.edu/cfr/text/33 ... /subpart-G

Inboard powered boats under 20' have some other floatation requirments:

https://www.law.cornell.edu/cfr/text/33 ... /subpart-F

I don't believe there is a floatation requirement for boats over 20 feet.

Some larger boats will have this as well, but once you get to a certain size I'm pretty certain most boats are not built in a way that they will float if swamped. That's why you see videos of fishing boats sinking offshore. There are still measures you can take such as watertight bulkheads so for example a seacock breaking can't flood the whole boat, just one compartment. That said larger boats if they get a significant enough hole will sink. On larger boats far offshore we bring damage control equipment, and liferafts.

I don't know a ton about the LB26 but I suspect at that size there is a mix. A 26' whaler probably floats(all their boats are foam right?) but I bet most boats that look like an LB26 don't. Just my guess. I'd think about how far offshore you plan to use the boat and then decide how far you want to go to defend against different risks, and I'm sure the designer would be willing to help with that.
The LB26 is very easy to make pos buoyant and safer than her commercial counterparts and why I mentioned to Les.
My boat build is here -------->

viewtopic.php?f=12&t=62495

Post Reply

Who is online

Users browsing this forum: No registered users and 9 guests