Wee Rob - Bulkhead Hatches

[Songololo]

The Wee Rob build is coming along slowly. One of the things that needs deciding on fairly soon, is what type of hatch design to use.

Options seem to include:

• Plywood hatch
  
  • turnbuckle secured
  • bungie secured
  • bayonet locking
• Plastic screw or bayonet hatch (as seen below)

How good are the plywood hatches at creating a watertight compartment for flotation and/or dry storage?

I like the idea of a bayonet-locking-type plywood hatch cover as there are no turnbuckles or bungie cords required. Has anyone had any experience with using or making such a cover?

[Bill Perkins]

My old ME (whitewater canoe ) has a Perception saddle with a screw in access port of solid black plastic .This looks better to my eye than the clear piece you show of about the same size .There's no real need for a see thru hatch and it just looks more plastic to me ;more visually distracting from the rest of the boat . I think wear will only make the clear plastic look worse . The solid black,though battered like the rest of my boat ,still looks decent .

I would look at the white water canoe catalogs . Perception may still have parts , or someone else may make something similar . You'll also find bow and stern airbags for canoes and kayaks that are light and could be contained by a bulkhead and hatch that wouldn't have to be absolutely watertight in a capsize but would still protect lunch and gear during normal operation .

If rain and spray proof was all that was required the hatch could be a generously sized and attractivly shaped panel with a straight top edge to mount a piano hinge .This can be set to show only the pin. Any simple latch system would work .If you don't need the storage (use a dry bag) the flotation could be secured with a wooden lattice bulkhead ,which could look sharp .

[Ed Armstrong]

Hi Lance,

I just got my Wee Rob plans last week, and in studying the plans, figured I'd probably go with the plywood hatch with backing rubber grommet and turn-buttons, which seemed like it would be pretty water-tight. I used turn-buttons to hold down the floors in my Acorn dinghy, and they were pretty easy to make and work well.

A bayonet mount would certainly eliminate the turn-buttons, but it seems like it would take some more advanced woodworking skills.

I personally don't think a plastic or clear hatch would look good with the traditional design of the Wee Rob.

Cheers,

Ed

[bob easton]

I just launched a Fiddlehead canoe designed by Harry Bryan. Harry included drawings for interesting oval hatches, and I built them as designed. They are screw tightened, using a tightening bar on the inside and a foam gasket on the outside. They are likely more complex to make than some will like, but they are very watertight.





A few more details at: http://www.bob-easton.com/blog/?p=596

[Scot L T]

Interesting. Is there a reason that the inner part of the hatch isn't more form fitting to the hole?

[wtarzia]

Stainless steel or epoxy or polysulfide may not be appropriate to traditional wooden boats either, but many of us use them ;-) I ask myself what is important: looks, other people's opinions, or watertight safety. A good watertight and quick-acting wooden hatch must be a fine thing, but I like the utility and dependability of plastic screw-in hatches, and I never looked back. Clear covers are good to keep an eye on potential leaks. I also used these ports on waterproof gear boxes.

Here is an idea: make a wooden cover for the plastic cover. Fashion the wooden cover to cover the plastic flange too; clever people will pay attention to the required clearances. Don't forget to install finger-holes on the wooden cover. Then screw the wooden cover to the plastic cover, and squirt some 3M5200 on too (after scratching up the plastic), and tally ho! Everybody is happy. If you market this great idea I want my 15% cut. --Wade

[Dennis Rioux]

I did something similar to what Bob has done on my Penobscot 14 and MacGregor canoe. I used some foam on a recessed sill -- when the handle is tightened down (rubber washer seals the bolt hole through the hatch cover) the exterior surface of the hatch is flush with the bulkhead. Haven't had any problems with water getting inside on either one so far.





Dennis

[bob easton]

Interesting. Is there a reason that the inner part of the hatch isn't more form fitting to the hole?

Yes there is a reason. The assembly is rotated into place, sort of like a 1/4 turn latch. The hatch is inserted about 1/3 of a turn off of evel and then rotated until the innermost clamping bar lands on those two little blocks. The, the handle is turned to pull the clamping bar and compress the felt seal against the outside of the bulkhead.

The round piece and the stops provide accurate positioning.

A later post by Dennis Rioux shows a similar clamping mechanism, but positioning is more positively keyed by the squared shape, something we don't have with the oval.

[Scot L T]

Thanks Bob. I see how that works. I didn't realize it was all glued into one piece. Makes sense...I hate it when it all makes sense!

You guys are sure going to/do have some pretty boats there.

[ByronB]

This is what I did on "Spartina". Seems to keep the water out after a capsize. The water pressure on the hatch tends to help seal it.

Used a 5mm round automotive rubber seal fitted into a groove around inside of cover.

This shows the backing piece attached to the bulkhead to provide a lip for the cover to seal against.

[Songololo]

Progress ...

I eventually decided to go with a hatch design that uses a bayonet mount, similar to what one sees in lens mounts on many SLR cameras.

Here is the bulkhead seen from the cockpit side of the bulkhead:




Seen from (which will eventually be) the inside:



The hatch cover seen from the outside:



Seen from the inside:



A pic showing some detail of the the 4 plywood layers:

[Songololo]

How it all fits together:




Some details:

• 4mm plywood
• Cut out using a simple circle jig and a Bosch palm router with a 2mm bit.

• The hatch cover consists of 4 layers:
  
  • 1x Outer cover OD 220mm
  • 2x Spacer discs OD 190mm
  • 1x Lock disc OD1 210mm, OD2 190mm
  
  
• The hole also consists of 4 layers:
  
  • 1x Bulkhead hole ID 220mm
  • 2x Spacer rings ID 220mm, OD 250mm
  • 1x Lock ring ID1 190mm, ID2 210mm, OD 250mm
  
  
• Seal to be provided by 15mm wide 4mm thick adhesive neoprene seal (comes in a roll) attached to the underside of the cover.

[paladin]

Make them somewhat as above and use the compressible rubber seal designed for refrigerator doors. On my 27 footer I sed that system, and the deck hatches on the tri for stowage in the ama's and they were always dry.

[Typhoon]

I had a fibreglass naval launch once, it had simple fibreglass round covers like the plywood one shown above. They were tightened with a spanner and bolt, bolt screwing into a stainless steel bar that ran across the cut out horizontally and had simple gravity keepers (like an old barn door lock timber) to hold them in place.
Once they have water pressure behind them, they have increased sealing pressure on them, so they don't need much pressure to seal well initially.
So, I really like the simple plywood ones and on a small boat, you could just substitute a piece of aluminium bar or even some nice hardwood and a captive nut to secure the hatches. They could even be cut out of clear acrylic too.

Regards, Andrew.

[skuthorp]

Been sailing a Macgreggor for nearly 10 years now and it was built with ply and bungee hatches as plan. Found them not satisfactory as I seem to get quite a lot of water aboard sailing on rough days. I lengthened the cockpit about 14" aft to more easily accomodate two and fitted plastic screw hatches then. Not as attractive as wood but far more efficient.

[Canoez]

Progress ...

I eventually decided to go with a hatch design that uses a bayonet mount, similar to what one sees in lens mounts on many SLR cameras.

Here is the bulkhead seen from the cockpit side of the bulkhead:



Seen from (which will eventually be) the inside:



The hatch cover seen from the outside:



Seen from the inside:



A pic showing some detail of the the 4 plywood layers:

Songololo, is there any "ramp" on the tabs for the actual bulkhead cover in the bottom photo to compress the foam as it truns or are you simply pushing the cover in to compress the foam and then turning?

[James McMullen]

Those are good looking hatches! I look forward to hearing whether they work satisfactorily in practice. I've used plastic, round, pre-made hatches on my last dozen boats, for the utility and since they actually are watertight, but I've never been wholly satisfied with the appearance. Did you make your new hatches of a size where you could easily substitute in a Bomar plastic hatch in case they turn out not to seal well enough for safety?

I've thought about making wooden covers that were glued over the top of the plastic hatches, but in the end I just couldn't justify adding the weight or spending the time to make 'em.

[donald branscom]

I just installed an 8" Bomar plastic hatch in the rear compartment of my Typhoon. It's the one with the locking latch and it seems very tight and secure. Not the prettiest thing on a wooden boat, but quick and easy installation, low price, easily replaced, etc. I believe James McMullan has the same hatch on the fwd deck of Rowan, so you might ask him for a review.

Paint it brown to match your wood and then take a dry paint brush with much darker paint, almost black,some orange too. and put some streaks over the top. It will look just like wood.

[Songololo]

Canoez - nope, no ramps! I decided to keep the engineering simple and rely on compression to provide the seal. The neoprene seal is the same thickness as the ply i.e. 4mm. On the prototype, compressing the neoprene seal by more than about 1mm resulted in the cover being very difficult to turn. I plan on the 2 coats of epoxy and a few coats of paint to provide the thickness for compression.

James - agreed, the plywood looks better than the 'plastic' options; also provides a flush surface with no protruberances. Plan B is an 8'' Beckson deck plate, which requires a cut hole of 216mm diameter. The bulkhead hole is currently 220mm and so should theoretically be easy to install if plan A doesn't work out

The access hole (i.e. taking the locking tabs into account) has a diameter of 190mm, which is larger than that stipulated on the plans. The larger size will allow a small dry bag to pass through without snagging.

[Songololo]

Bulkheads with hatches now in place. Here is the fore bulkhead seen from the bow end. A large fillet was used on this side while one half the size was used inside the cockpit area.



Bulkhead held in place by notched tabs (to allow space for filleting) fixed with hot melt glue. Straight sturdy piece of timer clamped across bulkhead to keep it flat. Aft bulkhead:

[Geary]

Dennis, I like your hatches.

How did you make those wooden knobs? More specifically, how is the machine screw installed in it? (Is there a bung that I don't see on the top of the knob? Or is it just glued in from the bottom?)

Also, how is the latch arm attached. Is there a tee-nut in it?

When you rotate the knob, the arm is simultaneously rotated into position and tightened down, right? So I'm assuming that the latch arm (or maybe the knob) has female threads.

[Dennis Rioux]

Geary,

Yes, the machine screw is just epoxied into the knob. I scored the heck out of the hex head in the hopes of giving the epoxy better purchase. They haven't failed yet, but I do mean to re-engineer them as you suggest by drilling out the knob and feeding the bolt through from the other side and finishing off with a bung. That's got to be more secure.

Similarly, the latch arm just has a nut embedded in epoxy in a hole drilled with a Forstner bit. On one of the boats I got this "backward" so that the nut is on the same side of the arm as the knob which lends itself to getting pulled out -- go ahead, ask me how I know. A t-nut on the correct side of the arm would work, too.

The arm and knob will spin together as you point out, friction being what it is. So behind the sills I glue a block that prevents the arm from spinning so the hatch cover can be drawn in tightly.

Overall, it's a bit fiddly because you can't see what is going on and you have to do it by touch and visualization in your mind's eye which can be entertaining. Coupled with the fact that the gasket material is a bit tacky so I can't simply loosen the arm and wiggle the hatch cover, I sometimes have to spin the arm completely off the knob and let it fall inside the compartment because I can't (or don't have the patience to) get the arm oriented in the correct position to simply pull it out against the back of the hatch cover. (I made the arms specific lengths based on the asymmetric hatch shapes so that they go in/out only in one orientation with a modest amount of positional slop allowed.) Lots of words to describe simple problems, but I hope you get the idea.

I looked for some better documentary photos but I seem not to have any others. If you want, I can take some and send them to you -- just send me a private message.

Dennis

[Geary]

Thanks Dennis. I understand the setup now ... no need for more photos. Why don't you glue a block on the back of the hatch for the "open position" of the arm? Then after a little unscrewing, the arm will hit this block and be in the correct position to open the hatch.