Extending a Lagoon 40

[Fore and Aft]

I have done a fair few transom and bow extensions on mono's and cats. Certainly none have cost $100,000. All have helped improve the boat to some degree. Sugar scoops and plumb bows modernise alot of older cats.
Spiv I would love to have seen you reverse those bows. A foot of rake would have looked awesome. You know Spiv to be right out there you could have plumbed one and raked the other!
Paul Howard I hope your transom extensions looked better than that aft cabin you put on your steely.
Cheers

[Franziska]

Hi, we are considering to do this on our boat.

Your result looks great Btw.

Ours is not a Lagoon, but it will definitely benefit from more buoyancy volume.
I am aware that the whole thing needs to be lighter than the added volume to make it worth while.

One question, did you fill the void volume with foam, shaped it and glassed over, or did you leave the void empty?

If foam, what kind of foam did you use?

Your how-to with pics would be awesome.
I am a trained boat builder, but it surely helps to see how others have done it.

Originally Posted by spiv

A lot of people don't know what they are talking about.
I read the first few replies and got fed up.

I've done it on my 380 bows, covid stopped me from extending the transoms, but I will do it soon.
Attachment 232830

Just with the bows extension, boat goes faster, points better and pitches less.
Attachment 232831

Didn't cut the boat, didn't get extra internal space, just buoyancy.

Doing the transoms will improve more than the bows, it's a known fact to those that understand hydrodynamics and cats.

Where are you?
I could give an excellent contact in Tunisia, he assisted me, but he alone could carry out the extensions now that he got the know-how.

I don't have time to help, but if you were to make me an offer that I cannot refuse, I could write down an "how-to" and give you lots of pics.

[Cadence]

Originally Posted by Uncle Bob

I think you are being overly generous with your praise.

I guess beauty is in the eye of the beholder. As long as they were happy with it but I wonder about resale value?

[Franziska]

Depending how well it's done, the price might even go up.
Especially if the midifications show up positive on a sea trial.
Beauty is in the eye of the beholder. I like the new looks better.
Not sure I would have extended the bows so far though.

Originally Posted by Cadence

I guess beauty is in the eye of the beholder. As long as they were happy with it but I wonder about resale value?

[spiv]

Fore and Aft, the pic I posted didn't show the forward rake, this does.

I did a combination of Divinicell full foam filling underwater and void filling above. All epoxy and 1200gsm DB cloth.

As far as resale value, I will probably die before I sell my boat. BTW, now she's only a two cabin cat, so only suitable to circumnavigations, not marinas or armchair sailors.

[Franziska]

Thanks, looks good. Will look better once transom is done too.

Divinycell below makes sense.

Few more questions, feel free to PM if you do not want to post it, even though posting would benefit all, so that would be nice.

What did you fill the void with?
How many layers biaxial did you use?
Any plywood or foam girders/bulkheads?
Or just solid foam and glass over it?

Originally Posted by spiv

Fore and Aft, the pic I posted didn't show the forward rake, this does.

I did a combination of Divinicell full foam filling underwater and void filling above. All epoxy and 1200gsm DB cloth.

As far as resale value, I will probably die before I sell my boat. BTW, now she's only a two cabin cat, so only suitable to circumnavigations, not marinas or armchair sailors. Attachment 232894

[Cadence]

Originally Posted by spiv

A lot of people don't know what they are talking about.
I read the first few replies and got fed up.

I've done it on my 380 bows, covid stopped me from extending the transoms, but I will do it soon.
Attachment 232830

Just with the bows extension, boat goes faster, points better and pitches less.
Attachment 232831

Didn't cut the boat, didn't get extra internal space, just buoyancy.

Doing the transoms will improve more than the bows, it's a known fact to those that understand hydrodynamics and cats.

Where are you?
I could give an excellent contact in Tunisia, he assisted me, but he alone could carry out the extensions now that he got the know-how.

I don't have time to help, but if you were to make me an offer that I cannot refuse, I could write down an "how-to" and give you lots of pics.

That is a very nice looking job.

[Sanddallor]

[QUOTE=Roddu;3345534]Anyone got any views on extending a Lagoon 40 by a few feet to improve seaway and performance? Both bow and stern, or one of these only?
We really don't need more interior space, but are looking for a bit better performance and better seaway. From experience (chartering) i get this if I go a few foot bigger, but that quickly adds +$100k to the bill, and space I really don't need. I understand that the boat will still be under-rigged with a too small main and jib....but I am wondering whether from a boat-building perspective just adding 2-3 foot to bows and stern might make sense?
Also, if anyone has a view on whether the stern extension is even feasible or makes sense (re location of saildrive and inclination of below-water line stern), please let me know as well!
Thanks![/QUOTE
I extended my St Francis 44 to 47 with a 2 HP net gain (installed a 3YM30 to replace a 3GM30(27hp)) , replaced our 2 blade fixed props with Autoprops noted the following:
Dual engine WOT speed is 10.3 kts
Single engine motoring speed increased by 1.2 kts. My wake did not sound like a “ waterfall “ when over 6 kts. I now have a smooth rooster tail starting at 7.5 and continues up to 13kts(fastest I’ve had the boat post boatyard). Additionally, it’s much easier to transfer from the dingy to the stern (our reason for extending ) our boat has “cutter bow” that had plenty of reserve buoyancy so I didn’t see the need to extend the bows. We are very pleased and now have a good looking as well as efficient boat. For all those armchair sailors and spreadsheet commandos, I derived by my numbers by using the boat and no science was harmed gathering the data above . The extension meets my needs, dingy access, good looks, and faster.

[FlyingScot]

At least two older Leopard 40s have had stern extensions since they tend to squat at the rear.
Bow extensions without moving the cross beam and forestay makes for an interesting look I can't get behind.
I'm considering ripping off the hard top bimini and making or having one made lighter with integrated solar panels, instead of having the heavy hard top and big solar frame.

[Jweyndling]

I have been looking at the same idea for my 41' catamaran. My thought is to just add about 2' to the sterns to increase waterline length and to help prevent the boat "Squatting" which seems to add a lot of drag. I got a ball park quote from a fibreglass contractor of about $10k per hull. It would not interfere with the saildrive or steering and it would not breech the existing hull. It would be bolted and glued to the existing stern structure and then glassed in to create smooth transition.

[Jon Hacking]

LOTS of cats do this. Most cats we know want to extend their transoms.

I don't think you want to extend the bows. Ours were very blunt, so we sharpened them up a bit, which extended them maybe 4"/10cm, but that's not going to affect performance. We did it for cleaner entry, less wake, & to provide a bit more crush-space up forward (that we hope we'll never need). Extending the bows much more will really mess up your forebeam, & therefore your headstay, & that opens a whole can of worms.

When the boat is initially built, they try to maximize internal space, which is fine. But this usually produces pretty stubby transoms. So extending the transoms to give yourself better swim platforms is very common. But you want it to look organic, like it was originally designed & built that way.

As an engineer, I wanted to design it & loft everything, but we were working on the beach in Phuket, Thailand, so that wasn't going to happen. In the end we did it mostly by eye, with a laser to make sure they were both the same where they came out of the water.

It was pretty basic. We ground the gelcoat off our sterns, slit some foam so it would bend, stuck it back on the back temporarily, used some string & sticks to pull it into the shape we wanted, then glassed it up. We wanted the curve of the hull (rocker) to continue up until the hulls just cleared the water (our sterns were very underwater as originally built). This extended us about 3'/1m, which was about what we wanted.

Added some internal strengthening members, figured out where the swim platform should be, built it up to that height, & glassed it up (everything done with foam, epoxy & biaxial glass). Then we tried (mostly successfully) to make the other side look the same. Ended up needing a bit of grinding & filling, but not much. The swim platform should be sloped so water drains off.

Our swim platforms are about 6"/15cm off the water, & this is really too low. At speed, we get a wake/wave building up at the sterns, so the swim platform is often covered. It would have been better to raise it another 4"/10cm. This would still have been easy to hoist ourselves out of the water & onto the deck without needing the ladder if we want, but would make it easier to get out of the dinghy (we're now stepping down a bit).

We left the inner walls as they were, but we wanted the outer wall to be higher & to extend to the end of our extensions, so that was built up & glassed. To get the curves how we wanted them, we used long wooden battens. Stuck them to the deck, then pulled them down to the ends of the transoms & pulled on them to get a pleasing line. Left them there while the foam was cut & stuck on.

Our original transom steps were almost vertical, so we designed nicer, large, curvy steps, since we had lots of extra room. Again, foam & biaxial, with a center support. Also needed to cut a hole, since our engine-room blower outlet comes out there.

One part I'm quite proud of: Our old swim ladders were teak & SS disaster areas, folded in half & lying on our aft-deck, always waiting to twist an unwary ankle. I had SS ladders made up with pivots at the very back of the transoms, so they could hang vertically (we actually cut vertical grooves for them). They pivot 270 degrees & fall into a ladder-shaped recess in each transom, so they're flush with the floor when stowed, & easy to rotate into the water when you want them. You need to do this when the floor is still foam, of course. The glassing gets a bit finicky, but biaxial is very flexible & conforms well.

We wanted a SS railing down the outside, so we needed to cut out the foam where it was going to come down & fill it with fiberglass, so the screws would have something to bite into. Then gave the dimensions to the SS worker for custom rails.

We've got a targa bar with lights in it, & they light the swim platforms fine, but you might want to think about lights, if you want to light the steps down. Also, some boats like to put a blue LED in the bottom of their transoms, to light up the water. It actually looks pretty cool, but we didn't want an extra hole in the bottom of Ocelot. Check out swimming-pool lights, they're cheap.

Finally, it seems that every RIB wants to run into our transoms, so we had custom SS edges built, to protect them, just along the inside edges & the very back.

Despite working on the beach, we're very happy with how it all came out. We've had one guy (who built his own racing cat, & knows cat design) ask us if we extended the transoms, but only one. He noticed because the mast now looks like it's a bit too far forward, but most won't see this. She feels fine on the water, sails well, & doesn't hobby-horse as much.

While we documented much of the work, we did LOTS of other work as well, & I haven't finalized pulling the transom extensions out & giving them their own page. However, I've pulled out LOTS of photos for the first half of the project. To see more, you'll have to go to the links at the top of the page & look at the raw work (chronologically, but mixed in with everything else we did).

Good luck!

[Ndavies]

We have a 2019 L40......Sails great. Not sure why you would ever consider this. Lagoon paid one of the best marine architects a lot of money to design this boat. But Bubba knows better???

[Amapola]

We don't have a Lagoon but the previous owner of our trawler extended the stern 4'. She has a large "back porch" that we love. In 2000, he paid over $50,000 to have this done.

[Roddu]

Great advice thanks!

[Roddu]

Thanks, appreciate the good advice!