Hatches for storage/buoyancy compartments?

[Aphers]

I'm just at the stage of fine tuning the fit of the aft seats of my Spindrift 11N.

I understand that the compartments under the seats are primarily there for buoyancy, but as a daily use tender they would also make excellent stowage spaces. I'm thinking of all those things that clutter up the bottom of a dinghy, like the grapnel and its rode, or the spare outboard fuel can. Etc etc.

I do like the idea of being able to lock the access hatch, just to deter the casual light fingered passers by from making off with low value items.

The smallest such hatch I have so far found is this design:

https://www.force4.co.uk/item/Force-4/Inspection-Hatch-with-Lock/11BQ

Which will*just* fit on the seat top of the Spindrift. But it's very tight. The design has a pretty wide flange on it, and the actual cut out is much smaller than it would appear. I would prefer a slightly smaller hatch, if I could find one.

 

Anyway the main question is- would this type of hatch compromise the buoyancy too much? I don't think it would have as positive a seal as the circular screw-in type. 

[Steve W]

I just put round hatches in all three of Suzy J's buoyancy tanks. Thieves  are pretty lazy and I'm not sure anyone is going to take a chance on looking in there on the hope they find something valuable. Also, the N series don't have a as much buoyancy as the regular ones and I'd hate to compromise it. I always put my keys and wallet and phone in the tank. I haven't capsized the 11N yet. Go figure.

[Joe Anderson]

Quote

 would this type of hatch compromise the buoyancy too much? 

I think you could get a variety of responses to that question.  The buoyancy is there to keep the boat afloat in emergency ideally providing enough freeboard that the boat could be bailed. Once you start putting access ports you are compromising the floatation. Some builders fill the floatation areas with foam so they can not be compromised. I think the USCG may require that floatation areas be foam filled on commercially built boats . It is tempting to use the area for storage, but the larger the hatch the more likely it will leak and using it for storage of commonly used items like an anchor increases the chance that the hatch may not be secured someday when it is really needed. I would consider a net bag or some way of adding a storage place for commonly used items. Just my 1/2 pence.

[Don Silsbe]

Aphers, now you’ve opened up a can of worms!  Opinions will range all over the place on this one.  The answers will be complicated by what’s available in GB.  But here’s my two cents worth.

 

My all time favorite is an Armstrong hatch.  It is smooth acting, and has a large O-ring on the back side for sealing.  All that is required for installation is to cut a hole.  The smallest they come in is 8”.  https://www.fisheriessupply.com/armstrong-nautical-round-watertight-compression-deck-plates
 

These screw-in plates are at the other end of the spectrum.  They are annoying to use on a regular basis.

https://www.fisheriessupply.com/tempress-white-screw-out-deck-plates
 

On my Two Paw 8, I did nothing in the stern.  But in the bow, I installed a sort of kayak-style hatch, adding a hinge along the lower edge.  These are a little complicated to make, but they are thrifty and effective.  They are made from scraps you probably have.  The only thing to purchase are fasteners and a bit of foam weatherstrip.  If you’re interested in knowing more about this, let me know.  I’ll get the applicable detail from some kayak plans I have.  The photo below shows the TP8.  If you zoom in, you can learn more.

[Aphers]

Thanks for those thoughts. I don't think I want to risk compromising the buoyancy, too much at stake.

Those Armstrong hatches look fantastic, but I don't think they're available over here.

 

For speed I think I will just install the hatches from my donor boat- it has three 4" ones on it. I presume it wouldn't be a big job to swap these out for larger ones at a later date?