Structure in stitch and glue build

Interesting find. Definitely will consider using this

 

Article about sealed floatation chambers of a stich and glue boat bulging at altitude. Altitude change and air buoyancy tanks | Port Townsend Watercraft BLOG http://ptwatercraft.com/blog/altitude-change-and-air-buoyancy-tanks/

 

Commercially built boats, plan and kit sellers have legal constraints regarding sealed flotation tanks.
The home builder in most countries does not have to have the boat inspected. The EU has changed their regulations since I last looked. ¿Maybe they backed off from inspections, but you have to keep the boat for a certain number of years?

 

I would not use a stick on vent because I do not trust a PSA for long term exposure to water and UV. There is a screw in version that I would expect to be more durable.

The Gore vents, address the pressure differential problem, but I didn't use them because I am concerned with condensation and the possibility that it would be difficult to dry the chamber once it got wet. Moisture in the air is a gas and will pass through a hydrophobic fiber filter easily. This is a major advantage of Gore-tex for rain wear where it helps keep you dry by blocking liquid water while venting water vapor out. It will work both ways in these vents as well, so an enclosure can both dry out and retain water depending on the temperature differentials and humidity cycles it is exposed to. If you try the Gore vent and find water collecting in the chamber later on, you can always install a hatch. If the problem never comes up, the vents are working for you.

The membrane vents are made by Gore and Donaldson, among others. This is a random example (minimum effort link) from Amazon which also serves as a collection of keywords for a search: Dusproof Waterproof IP 68 Breather Screw Air Vent Pressure Reduce Valve M12x1.5 Venting Screw Breather Plug. IP68 is an IEC ingress protection standard for electronic enclosures. 6 = dust proof, 8 = waterproof.

I have some concern about the hatch idea as well, since it may need to be left partially open at times. I felt that the ability to inspect and clean the chamber outweighed the convenience of a much smaller, possibly less expensive water proof vent. The best solution might be to combine an inspection hatch with a vent.

 

I don't see any reason to get too deeply into the topic of ventilating buoyancy tanks.It isn't hard to simply put a screw in bung at the lowest point of the tank and to leave it out whn the boat is in storage or on a trailer.An access hatch isn't a bad idea but some people are anxious about their integrity,I'd put them in as well as a bung. R2066 - Screw Bung & Socket & Seal (Pk Size: 2) - RWO Marine https://rwo-marine.com/store/deck-hardware/drain-bungs/r2066-screw-bung-socket-seal-pk-size-2-2/

 

I have 11 buoyancy tanks in my boat. A couple of them have a bulkhead and I used submersible vents with pvc housings. They were set with black mamba fhg. I also have 4 with 4” deck plates. One of them flooded in a locker mishap, but it was vacuumed out. I expect the vented ones are damp, but will dry out in Texas.

 

That's right, the EU's and UK's Recreational Craft regulations exempt self-built boats, as long as you don't sell it in the EU or UK within 5 years of launching.
In the UK we have a Boat Safety Scheme inspection that's required for registration on most of the inland waterways, but it doesn't cover anything like hull design or flotation. It's mainly concerned with things like fuel and electrical safety, fire extinguishers, and carbon monoxide alarms.

 

Off topic, so I'll be fairly brief. A forum search found roughly one person on the whole forum who ever mentions Black Mamba fhg. It isn't cheap and not a big box store item. If you can hang a sink under a counter with no mechanical fastening, it has to stand up pretty well to water and moisture cycling. It sounds a lot like a quick cure version of 3M or Sika PU adhesive with similar strength and flexibility. In one thread, you chose 5200 over mamba, which says you know both and have some familiarity with the characteristics. In a nutshell, what do you think of the stuff?

 

It has held up well. I use it for bonding pvc to anything. 5200 is so slow to set and a little soupy for finish exterior bonds. I have a 3” pvc conduit under the bdeck that enters both hulls. Because the boat is demountable (a decision I regret, but it is complicated), the pvc uses a rubber sleeve to cover the seams between the bdeck and each hull and the entire thing was bonded in place and then cut..

Anywhere I bonded pvc with epoxy failed even trying making the surface rough with a wire wheel.

 

Update on interior. I finally flipped her over and am kitting it out. Seats are glued in. I have decided against creating watertight cavities and filling with foam. I will glue in a canted motor well to add freeboard inside the transom cutout. Stringers are not bending tight to bottom. Might have to cut into sections.

 

Stringers are not bending tight to bottom?

care to expound?

stringers are not supposed to be tight to bottom; some gap is needed to prevent hardpoints

 

I wasn't aware of this. So would I use spacers and fill with peanut butter? Or actually fill with some other softer material? And this is the case even in stitch and glue construction?

 

I suspect you are describing a situation where the specified stringer size results in a piece that is too stiff to conform to the panels.the very nature of stitch and glue requires panels that can be bent to the finished shape of the hull and as such,they may lack the rigidity to retain a fair shape while the stringers are pulled into place.If the plans indicate that stringers are needed,rip them into thinner strips and keep adding the thinner strips until the specified dimension is reached.what you are likely to notice is that the first strip will need to be thin and if left to bond in place,subsequent strips needn't be as thin.If you laminate in one session they do have to be similar.I can't see too many places where you are likely to need stringers and if they are reinforcing for the bottom panel,do the plans indicate tapering the ends to reduce the hard point effect?

 

Yes that's exactly the problem I'm describing. I'm not going off of plans here so just doing my best to add strength to bottom panels. I'm considering now just putting in plywood stringers to get the twist I need and adding anothe couple bulkheads. I might have been going overkill with 1" fir anyway for a boat this size. Will find a use for it somewhere for detail I'm sure.

 

All types of boat construction, save perhaps welded aluminum, but I am not an ally expert, so not fully sure.

All types of boats need to minimize hardpoints, even a metal boat looks bad oil canning, but for s&g, the stringers do not touch, but are p/b bonded or bonded onto foam pads and then tabbed with glass to the hull. Pressing them or fitting them tight by scribing is an error. You should be able to template or set them in the hull full length and take a carpenter pencil and mark contact points with the carpenter and remove the unwanted material with a jigsaw.

You can hold the stringer in place with blocks hotglued or taped to the hull and temp spot bond with pb, or for one day service, make a top jig to support them and lift them off the hull a bit and pb bond/tab them in same day if you are really good at it.

You don’t want to laminate on the horizon. But you can laminate vertical sections, but that’s more than one day of work..