Hidden airbags to keep a yacht afloat in case of an emergency, like in the VDS example case

This thread is a split off of the thread: "Life Tender" as an alternative to life raft

( side note: there was a thread title change + moderator note in post #47 )

Below the split off posts #17 & 18

So I was surprised to see this feature on the Stadtship 70.

Van De Stadt Design ---> History

‘‘ In 2008 the STADTSHIP 70 was created. This high performance cruising yacht with 1 ½ t removable water ballast, offers an excellent sailing performance while being a comfortable and safe passage maker. A remarkable feature of this yacht is the extensive pneumatic system for operating bow thruster, windlass, bowsprit, transom door and water pressure system. The yacht also has hidden airbags which can be used to keep this large yacht afloat in case of emergency. ’’

VDS: Stadtship 70​

Length over all 21.00 m
Length waterline 18.60 m
Beam 5.10 m
Draft 2.90 m
Displacement 29.0 t
Ballast 9.0 t
Sail area 230 m²​

KM Yachtbuilders ---> Stadtship 70 ---> PDF Specs (drawings on page 8 + 9 + 11)

Length over all: 21.00 m / 68.90'
Length waterline: 18.60 m / 61.02'
Beam: 5.10 m / 16.73'
Displacement: 29 ton
Water ballast: 2 × 1500 L - (so 3 m³ ~ 3 tons there)
Draught: 2.90 m / 9.51'
Sail Area: 230 m²​

Now I'm wondering about these things...

- 1. - What areas are to be filled with the airbags ?
- 2. - How many m³ is to be inflated ?
- 3. - What will the new waterline be ?
- 4. - Is the airbag system set off automatically or by manual input ?
- 5. - Which spaces are planned to be used by the survivors ?
- 6. - Are those safe zone areas still dry or pumped out or drained after the airbags have inflated ?
- 7. - Are they able to reach freshwater and food supplies plus dry warm clothes ?
- 8. - What working communication options do they have there ?
- 9. - Will the boat still be a bit sail able ? (maybe with a jury rig if the mast also has broken off in the emergency)
10. - Will there even be some form of auxiliary propulsion available ?
11. - What will the stability range of the partly flooded / partly air bagged / partly safe zoned boat be ?
12. - Will the boat right herself after air bagging if she also has capsized in the unfortunate emergency ?
13. - Is the system ever tested, and to what extent, or is this based on theory only ?

Alas I'm not in the market for this boat, so rather than bothering the designer and builder with my curiosity I like to bring the topic up for discussion here . .

 

This firm or similar had a system in Aus such as that... FloatPac supplies FloatPac Solar, FishPac, Flexitank & RainPac worldwide https://floatpac.com/ pretty sure they had an embarrassing demo where the deck popped off an Etchells or Soling- all the same still did what claimed some drawback is that inflation can trap passengers if not clear and from memory there was a case where a valise liferaft inflated within a cabin. Maybe communicate with them for some background .

Regards from Jeff

 

IMHO, Airbags make more sense on the outside, above the COG, maybe something like in a RIB.

PC

 

Thanks Portacruise,

In post #1 I've linked the info that I know of, and it mentions the airbags but doesn't say where they are, so it could as well be they are to be deployed on the outside.

My initial thought for the inside came from the originating discussion on the previous thread, and it kept me wondering if VDS meant it as such, but indeed there's plenty of volume available on the outside, no one gets trapped, and a huge initial stability is guaranteed as long as airbags on both sides are sufficient and equally filled.

Maybe when deployed it's kinda similar to the Woods Duo 10' Sail Row Dinghy

On the linked page Richard gives many info plus pictures and drawings and videos, and also offers the download of free study plans.

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I have a 93 Laser that i bought not to long ago and i have one port hole installed (not factory) right next to the mainsheet block. I happen to open up the porthole and i noticed i have 2 very large cube air bags in the bow (each side)and it looks like one under where you would sit. Is this something the factory has in all boats or is it something a previous owner put in. A bunch of guys liked how mine had it and were wondering if their boats came with them or where you could buy them.

 

Airbags are an idea I have been mulling over as well. Outside has its benefits, but they would only be good for keeping the boat on the surface. Airbags on the inside may aid in pump-out, if the boat fills with water. Trapped crew is a serious consideration, but there may be locker locations or deck/hull seam locations that allow for survivable living/escape space of crew below decks.

I think, while the hull is compromised, there may be more immediate concerns than food supplies. I certainly would not rely solely upon the airbags as a life raft/survival system. The weaknesses should be known and accommodated before the voyage. Keep your ditchbag handy.

-Will

 

I'm all for it. Seems scary that your typical keel boat is going straight to the bottom, and fast, if the hull ever gets even a moderate sized hole, or even a small hole and boat is unattended. Talked to a guy who spent night on his buddies just completed yacht and about 3am notice the floor has about 6" of standing water. Fortunately they were still in the marina. Guy had turned a petcock the wrong way or something.

I'm a big fan of trying to use transferable side-to-side water ballast. I've got an idea of modding a MacGregor type boat with bladders in the water ballast holds. Bladders could hold fresh water, fuel or air.
IIRC tourist helicopters around SF Bay have inflatable emergency floats on their skids.
I think anything would be better than the boat going straight to the bottom, except of course being trapped inside it while it does that.
I think even a bunch of plastic garbage bags full of air and secured with rubber bands would do the trick, if you got time to wrangle them. Maybe pre-sealed bags with a device inside that can be activated by breaking something, similar to Glow Sticks. Have these units in interior and on exterior and be able to mass activate by yanking cords which would be accessible in cockpit, bow, rudder and top of mast, and keel under a door.

The idea of Daily Dingy doubling as life raft has merit, but these days with those emergency satellite beacons and helicopter search and rescue being able to travel after an emergency isn't as important, but surviving rough seas for 48hrs might be required.
Cruise ships use huge Life Boats to ferry passengers on routine shore excursions.

 

I wrote earlier about my niece in the middle of the Atlantic. They lost the rudder. I am not a sailor, sailing technology surprises me sometimes...

 

Seriously, I think maybe because all these boats are mostly in marinas, there are so few dead ones.

 

Sadler made unsinkable sailboats. They were 34 feet long. The hull has a liner and the void is foam filled. Obviously the interior volume is reduced, but the safety factor is much higher.

 

Tthey taught me not to use foam. PET bottles pumped up with soda instead . Foam is stuck, moisture comes. PET bottles can be thrown away, dried , switch.

 

IIRC Laser's originally came with foam blocks to make them unsinkable. Just to time and leaks, the foam would get heavier. So I know people who prior to 1984 were removing the foam and replacing it with other buoyancy methods (sealed poly quart milk jugs). The present ILCA handbook requires a Nominal weight (with fittings) of 58 kg and Positive flotation of 158.7 kg....so as long as you hit those two marks.... Additionally, the latest class rules I could find (21 Aug 2023) state in Part 3, Item 26.5

So maybe it is no longer the wild west it once was.

https://ilcasailing.org/laserinternational/wp-content/uploads/2025/02/HANDBOOK-2025.pdf

 

Have a look at this...

 

Firstly, a bottle full of soda will provide no positive buoyancy. Sencondly, closed cell foam will fill all the void if properly installed. Also, there will be no moisture if the void is properly sealed. Thirdly, a bunch of bottles will float away in case of a holed hull and provide no positive buoyancy.

 

Forgive me my weak english I mean CO2 made of baking soda and lemon juice.Buoyancy bottles closed in buoyancy chamber.