Flap Boards Build

Steve Sanford

Steve Sanford

Well-known member
Good morning, All~


I was just about to head out to the shop and put a topcoat of epoxy on a pair of flap boards - and glue up the last of 4 thatch rails. This pair is for yet another South Bay Duckboat for a friend on Great South Bay. I have had a couple of PMs recently about flap boards - so I thought I'd post my process.


If marine ply were easier to get hereabouts, it would be my first choice for flap boards. But, I typically use 1/2-inch AC fir plywood. I fill the voids on the C side with either Bondo or thickened epoxy (epoxy + fairing compound). For this set, I had some treated plywood on hand, so am using it (my first time).


After filling and sanding, I applied 4-ounce 'glass cloth to both sides. I did this to a 24" x 62" panel BEFORE I cut the flap boards to their final dimensions and shape. This photo shows the layers right after I ripped the boards on the table saw and then cut the angled ends on the radial arm saw. These boards will be 10 1/2 "tall". The ends were raked inward at about 15 degrees.


[CLICK images to enlarge]



View attachment sm 01 FB 01 4 oz cloth on half-inch AC.JPG



In the time-tested method, I use a can (spray can size here) to draw a radius on each corner - to protect the boards and the gunners and dogs....


View attachment sm 02 FB 02 Rounding corners.JPG



Corners are cut with a jig saw and then sanded - with orbital sander and sanding block. The outer face of each board is marked for two thatch rails, an upper and a lower.



View attachment sm 03 FB 03 B Rounded corners on boards.JPG



The thatch rails are ripped from 5/4 Philippine Mahogany. I made these a bit thicker (3/4") than my usual 5/8-inch because I want them to stiffen each flap board along its length. BEFORE I ripped each length, I rounded both upper edges with a router. I used the 3/8" round-over bit in my router table. I have also beveled each end and cut them to length.



View attachment sm 04 FB 03A Rounded edges on rails.JPG



I also ripped the spacers on the table saw. I typically make them 3/16" thick for Salt Hay (Spartina patens), but I made these 1/4" - to allow for a bit more grass where it counts most - near the gunner's face and hands. The inner spacers are 2" long; the ends are 2.5" and match the bevel on the rail ends.


I clamp the glued rails to the bench - much easier than without. I glue up just one rail at a time, allowing at least 2 hours for the Gorilla Glue to cure before un-clamping.



View attachment sm 05 FB 03 Clamping thatch rail spacers.JPG



I do not wear gloves unless I have to - but Gorilla Glue (and 3M 5200) is tough to get off my unprotected hands.



View attachment sm 06 FB 04A Gloves and Gorilla Glue.JPG



BTW: I always store my opened bottles upside down - to minimize air intrusion. I buy small sizes because I've thrown away too much unused polyurethane glue over the years.


View attachment sm 07 FB 08 Glue stored upside down.JPG


Off to the shop....


All the best,


SJS



 
Last edited:
Steve

Is the ply good and dry? Every sheet I've bought was wet and then warped during the drying process. It would be nice to have a supplier that stocked dry treated ply.

I am really glad you choose to photo-document your work. You may recall I mentioned building a hard dodger for my Broadbill. I'm trying to squeeze that project in before our season starts and have been looking at some of your old posts for ideas. I've gotten some good ideas and can better visualize an approach. Thanks.

Eric
 
Eric~


Yes, the treated ply was bone dry - stored inside at my local lumber yard..


Dave~


Although I've used tempered Masonite for tail inserts on decoys, I would not trust it on flapboards. It seems once moisture finds a way in, the game is over.


All the best,


SJS

 
After my wood boards rotted (they did not like sitting on the non-breathable aluminum deck), I replaced them with doubled up FRB. I scuffed up the smooth sides and epoxied two sheets together. I further upgraded from little 2" hinges to full length piano hinges spreading the load and adding stiffening. They have held up great. I will try to grab some pictures of the boards themselves. But they are in use with fast grass sheets in the first and down and ready for travel in the second.
Excuse the masked dude [ninja], I was some 3 or 4 months into chemo infusion and wicked temperature sensitive. Still got out ducking and ice fishing. Thanks Dave Morton, Dave Tripp and Wendell Avery!!!


View attachment RI hunt2.jpeg

Boards down:


View attachment RI2.jpg

Scott
 
Steve,
I'm going to attempt a similar job myself.
I'm making a flapper for my Estuary, as show in this picture below from David Clark. It would have been cheaper to buy one from Dave, since I bought a router table for the job, but I wanted to make my own.


View attachment 5.jpgmy question is why did you glass the board then cut it to size? Wood working and boat making are not my strong points. I'm trying to learn.
Thanks Steve and all.
 
Good morning, Mike~


I 'glassed the panel before cutting each board to size to make the job simpler. Glassing near the edges always requires special care - and usually extra scraping/grinding/sanding. It mostly just saves time because the sawn edges are nice and clean right off the bat.



As you will soon see, I do not 'glass the edges themselves. Instead, they get 2 soaking coats of resin when I top-coat each board. I rounded over the edges and then top-coated the outer sides (and so the edges) yesterday - and will top-coat the inner sides (and edges) later this morning. If I have any concerns about the integrity of the seal on the edges, I will add a third coat.


I 'glassed the boards - instead of just 2 coats of epoxy - mostly to provide a superior surface for the paint. I guess my thinking was similar to using MDO (Medium Density Overlay) - which I may use for future flap boards. MDO is made primarily for sign boards and has a smooth, paper-like phenolic skin that takes paint exceptionally well, and will never check like fir plywood can.


Hope this helps - and congratulations on your new router table!



SJS

 
Steve Sanford said:
Good morning, Mike~


I 'glassed the panel before cutting each board to size to make the job simpler. Glassing near the edges always requires special care - and usually extra scraping/grinding/sanding. It mostly just saves time because the sawn edges are nice and clean right off the bat.


Hope this helps - and congratulations on your new router table!



SJS
Click to expand...

Great advice, which I almost did not follow but thankfully I did.
I haven't used glass in 25 plus years. I gutted the interior of a 20' Sea Ray and put in a new floor and support, filling the void with A LOT of 2 part foam to deaden the sound of water on the hull and give the floor 100% support. I glasses the entire floor, then a few coats of resin with non skid compound.
So I'm an expert, lol, NOT! Just glassing both sides of the board was a big enough challenge. I forgot more than I remembered, but it came out well, thanks to Steve, and next step is cutting to size.
 
Mike~


I'm glad my thoughts were helpful.


My flap boards are now done and installed (one tiny detail remaining) - but I just need to find the time to take a few "completed" portraits and post an update.


Stay tuned.


SJS





 
Good morning, Mike et al~


Well, the South Bay Duckboat for which I built these Flap Boards is now back home on Great South Bay. And, I finally found a bit of time to post the last steps of the Flap Board build.


Once the spacers had been glued to the Thatch Rails, I rounded the ends - to avoid snags and chafe. A Stanley Surform and 80-grit sandpaper do most of the work. I finish sand with 120-grit.


View attachment sm FB 09 Shaped end.JPG



Next, they get sealed with a coat of Spar Varnish. I cannot locate my photo, but they next get a first coat of paint (Pettit 3303 - Dull Dead Grass) before they are screwed to the boards themselves.


View attachment sm FB 10 - Sealed with Spar Varnish.JPG



A topcoat of straight epoxy was rolled onto the boards - and the edges well-sealed. Despite my best precautions, they did not lie perfectly flat - but the 1/4-inch or so of lengthwise "cup" curled the right way - on the "in side" of each board. It is virtually invisible now that they have been installed.



View attachment sm FB 12 - Boards curing near stove - filled and marked beneath glass.jpg



The bottom edge of each base is beveled to match the angle of the decks. The top edge is left square so it will be parallel with the surface of Great South Bay.


View attachment sm FB 12A20 - Chock angle.JPG



Working the 2-inch Black Locust through the table saw blade is a fine time for "push sticks"....


View attachment sm FB 12B 21 - Table saw bevel.JPG



I never took a photo right after sawing. The "off-cut" piece is used as the backer board belowdecks. Because it is beveled at the complementary angle, the machine screw (10-24 flathead s/s) that passes through the hinge then base then backer board is fastened with a fender washer and lock nut that are square to the bottom of the backer. The base is bedded in 3M 5200.


The hinges are hot-dip galvanized with brass pins. I did not make these pins removable, but...one could drill the peen off one end of each pin to make them removable. The benefit is that the Flap Boards can be removed for highway transport or off-season storage to protect them and their thatch. This vessel will be garage-kept, though, so no need.



View attachment sm FB 13 - Chocks and hinges.JPG



The hinges are fastened to each Board with brass machine screws. They are ground off once tightened to minimize chafe. The Thatch Rails are screwed from the inside with s/s panhead screws (and the Rails are bedded in 3M 5200). Panheads are used for their low, flat profile - again to reduce chafe.


The neoprene bumpers - each screwed on with a 1/2-inch #10 s/s panhead - are located carefully so each rests against the coaming (when gunning) and the Hatch (when stored).



View attachment sm FB 13A 16 - Bumpers and flush nuts for hinges.JPG



Here's the full starboard Board down.



View attachment sm FB 13B 15A - Bumpers screwed to boards.JPG

Here's the bumper doing its job.


View attachment sm FB 13C - Bumpers in use.JPG



Continued in one more post....


SJS





































 
The home stretch....


I installed 3 of these bronze eye straps on the upper Thatch Rail of each Flap Board. They serve the 2 lengths of shock cord (bungees) that hold the Boards upright - either when trailering or when bouncing across the Bay.


View attachment sm FB 14 - Shock cord keeper.JPG



I use 3 so that one serves as a keeper when the cord is not in use.


View attachment sm SSB 28 - Flap board shock cords and keepers.JPG



Here they are in use - for trailering. Just the forward one would be used when crossing the Bay (if needed).


View attachment sm SSB 30 - Shock cord keepers up.JPG



Here are the flaps down...nice and tipped just slightly up above level.


View attachment sm FB 17 - Flaps down.JPG



Holding some decoys (Old Saybrook Wildfowlers) level - for when setting out or picking up the rig.


View attachment sm FB 22 - Flap boards down with decoys.JPG



Boards up - as for gunning.



View attachment sm FB 18 - Flaps up.JPG



All dressed up (with Salt Hay) and hard at work....(on another's vessel).



View attachment Weimann South Bay - all thatched up.jpg



All the best,


SJS







 
Very nice, Steve, has anyone considered adding cargo nets to the inside face to better retain decoys riding on them when down?
 
Steve

Looks like it came out fabulous as usual. All the little details add up, and your craftsmanship shines through. I'm going to use this post to guide me when I remake my flapper next summer.
I love the lines of the South Bay, especially the stern. It's a shame we cover up our boats with grass, maybe the ducks would like to admire our boats. 😄
I'm casually looking for a 2 man boat to add to my fleet to accommodate a buddy in small to medium waters. I'm leaning towards an all glass boat, since my wood skills stink, and rot scares me. I'll be seeking your advice on repairs and projects in the future. Your documentary skills are very helpful.
Thanks again
 
Good morning, Rick~


I have not seen that mod/feature - although decoys typically sit there for just a few minutes between the cockpit (loose or in bags) or other stool racks and the water.


Stock South Bays had narrower Flap Boards and they did not sit level when down. I did not take BEFORE photos of the originals. They were loose in the cockpit and had their mounting blocks/bases still attached to the hinges. They lay on the fairly steep deck angle so did not lend themselves to even momentarily decoy placement. Sea Level Flap Boards are an "exclusive offer" of Pencil Brook Boatworks (although I'm guessing other owners have hit upon the same idea over the decades).


All the best,


SJS



 
Good morning, Mike~


I'm glad this was helpful to you. And, feel free to fire any more questions my way.


All the best,


SJS

 
Steve,
Is the shooter is sitting on a stool or something when using the flapper boards? Seems like the grass would be a little tall to be laying down.

Zane
 
Good morning, Zane~


South Bay owners hunt them in different ways. This was set up so two gunners would sit up - so they could shoot athwartships. I believe they sit on cushions.


Flap Board heights and angles vary accordingly. Stock boats had narrower Boards (~ 5 inches) and lay almost flat when gunning - for a single gunner laying on his back (with a backrest) as in traditional LI grassboats.


All the best,


SJS

 
The South Bay is a interesting creature. Since I've found it impossible to hunt another hunter in the boat with me (I'm 6'3" 230lbs) I've either laid the boat up with the marsh to my right side and fired over the starboard transom corner or, rammed the boat up a drain and fired over the engine. I love the boat, it's never let me down other than sever pounding in a direct head on chop, but I try to avoid those.
 
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