Went today to St. Johns river near a commercial airboat rides camp. It really doesn’t matter where I launch, they are everywhere. And, o boy, they are flying fast. Especially loaded with tourist, they want to scare them. I went myself couple of times and I WAS scared. And they make pretty decent waves. I mean decent for my 10’ rotomolded SOT. But that is not a problem, I usually manage to turn my bow toward them (good thing they are very loud), the problem is they don’t see me in the labyrinth of passages between small islands and tall reeds, I am too low. Today I had a close call, only good captain reaction saved me :))) I was told I need an orange flag so it will be visible over the reeds. I can make a flag (and I am going to!) but I cannot think of a way to attach it to kayak. The pole must be at least 6’ tall. I thought I can attach it to the back of my seat but in that case it will be pushing my head forward. No other place. Any ideas?
Post pictures of your kayak.
Flare gun fored at center of mass.
I would rig a tripod of skinny fiberglass (or carbon fiber) poles, and clip each foot of it to the bungie attachment points on your rear deck. Instead of a flag, I would think about a concept like a lampshade that is painted orange, so it can be seen from all around. A relatively narrow lampshade, not a big one from a floor lamp, that would look very silly …
Another approach would be to use the shallow round shape in the back that’s designed to hold a 5-gallon bucket. I would put a hole through the bucket lid for the flagpole, and put something in the bottom to keep the pole centered (an inch of quickcrete?). The bungie cords will help keep the bucket from tipping over. Then you could build it with a fiberglass pole, a wooden pole, or even pvc pipe. Ooh, you could use PVC pipe with a sleeve joint so you can pull it apart into sections to fit in your car.
My first idea would be be very simple and compact and light, and it would involve a permanent mounting bracket which takes up virtually ZERO space and would weigh less than two ounces, minus the flag pole, but it’s probably too complicated for someone without tools and tinkering experience. My second idea is simple enough for almost anyone, and is a modification of the idea presented earlier by RiverWay.
So I’ll just skip any discussion of the first idea, even though it’s the method I would use if you asked me to build the thing.
The second idea is to make a mounting base for the flag pole using that 5-gallon bucket described by RiverWay, but I would cut that bucket down to a height of about 6". Then, cut a circle of plywood to fit flush within the bottom of the bucket, and another circle of plywood that is slightly larger to fit flush within the “new top” of the bucket (3/8th-inch plywood would be more than thick enough since you might as well save both weight and money on this part). Cut a small round hole in the center of each round piece of plywood to match the outside diameter of a PVC pipe, with that pipe being roughly two inches in outside diameter and only about 6 inches long (or whatever is the full height of your shortened bucket). Glue both pieces of plywood into their respective positions within the bucket, and glue the section of PVC pipe within the center holes of both plywood pieces. The result is a permanently closed bucket, 6" high and with one end of that section of PVC pipe being at the center of the top cover. If you don’t have a saber saw / jig saw, you can cut these curved shapes with a keyhole saw (a hand tool which you can buy for just a few bucks), or maybe you have a friend who already has an appropriate saw).
Edit:
As usual, as time goes by, I modify my plans. It may be difficult to glue that upper piece of plywood into the top of the bucket, and it’s possible that typical glue will not adhere well to that type of plastic anyway (for the top piece AND the bottom one). So, here’s an alternate method. Cut the upper circle of plywood about one inch bigger than the outside diameter of the cut-off top of the bucket. Install four small bolts around the perimeter of that piece, just inside the edge by enough distance that when the bolts protrude through below, they are located just inside the wall of the bucket (more bolts makes this even better). This way, when that piece of plywood sits on top of the bucket, it can’t slip off in any direction. Then, use three or four short bolts to fasten the lower piece of plywood to the bottom of the bucket, and three or four much longer bolts going through the full thickness of the cut-off bucket to hold down the upper piece of plywood. A tight wrapping of string around the PVC pipe, further anchored with several wraps of electrical tape, “just” below the bottom of the upper piece of plywood will anchor that pipe section in place without the use of glue. If you want to be a little fancier, install a joint coupling on the pipe at that same location, so the top edbe of that coupling is immediately below the under surface of the top piece of plywood. This results in the same base structure as described above, but with no reliance on glue (which as noted here, might not adhere to the plastic of the bucket).
You could skip adding that section of PVC pipe to the base assembly, but the mounting of the flag pole will be less fussy to accomplish if that pipe section is included.
Now, get a cheap, stiff fishing pole about seven feet long. You don’t need good quality so it shouldn’t be hard to find one that costs less than $20, and virtually all cheap fishing rods have a ferrule joint so they can be broken down to half their length when not in use (one possible difficulty is that cheap fishing rods tend to be sold as a package deal that includes the fishing reel, and you don’t need the reel, but even then, this won’t cost a lot if you stick to “bottom-of-the-line” stuff). A cheap fishing rod will weigh far less than any other “pole-like object” that you can buy elsewhere and it will present less wind resistance too. Look for a fishing rod that does NOT have an offset section where the fishing reel would be mounted (rods with offset handles are becoming more rare than in the past, but they still exist). Instead, get one that is completely straight through the entire handle section. Get one that is designed for casting lures having a weight range of 1/2 to 1 ounce if you can, though rods that are a little less stiff than that will still work. Avoid “ultra-light” rods designed for casting very lightweight lures, as they will probably be too “bendy” in the wind when your flag is attached at the top (however, even a fishing rod that’s too flexy can be stiffened enormously by securely taping a thin (about 1/4" diameter) wooden dowel flush against the upper (weaker) portion of the rod. I know this because I salvaged a six-foot section of a broken fishing rod and made it into a high-rise mount for a battery-powered light to make a boat more visible at night, and that light weighs nearly a pound, and I stiffened the fishing rod by that method). Cut off all the line guides and add a wrapping of electrical tape around the handle until the handle thickness is “almost” as great as the inside diameter of the short section of PVC pipe within that “base bucket” described above (have this step in mind when choosing your section of PVC pipe, because you might be able to pick a pipe size with less than the 2-inch outside diameter that was recommended above). Attach one loop or even a few loops of parachute cord or heavy-duty string to the fishing rod with a wrapping of tape, positioned at a height of about two feet or more above the handle section. You will then provide a few lines radiating out in a few directions from from the one or more anchor loops down to the stretched bungie cords to keep whole assembly securely held down. Attach your flag at the tip of the rod and you are done.
And by the way, a simple flag will be fine. Small flags are normally quite easy to see even when blown by the wind so the alignment is not favorable for being seen (are you old enough to remember those bike flags that were popular in the 70s?). You could add some sort of a lightweight cross mast at the top and attach a couple of small flags to improve visibility if you wish, but too much extra weight and wind resistance are things you are likely to regret at some point, so keep that in mind.
Edit #2:
You can eliminate the need for the section of PVC pipe by raising the bottom piece of plywood off the floor of the bucket with wood blocks. In that case, that bottom wood section could just be a cross consisting of two boards of such length that the center of the cross is at the center of the bucket. Drill a hole thought the center of the cross. This would be a good method for anchoring the bottom of your pole using the full-size bucket as suggested by RiverWay, for a much lighter alternative than using concrete.
Recumbent cyclists use poles with flag for visibility. Check bicycle sites.
It might be worth looking around for kayak fishing rod holders. You might find one that fits, or is easy enough to attach that can be used to hold either a safety flag or fishing rod.
I mounted one of these on a recreational kayak. You could then use a 1/2" PVC pipe with a screw joint to screw into the pipe flange. You would need expansion bolts to attach the pipe flange and perhaps something like silicon chalking or polybutylene door/window seal around each bolt hole to keep any water from getting into the hull.
Put a round plate inside with matching holes to distribute the load. Lexan or gasket material, inner tube or rubber plumbing seats to seal.
That’s a good idea too.
Using the most heavy-duty style of drywall anchors would be a good way to attach a fishing-rod holder. They make those anchors for more than just drywall, and as such, they are available for clamping items to materials of various thicknesses, including stuff as thin as the hull of a plastic kayak.
Many fishing-rod holders will detach from their mounting base, so there’s not much attached to the boat when the flag is not needed.
I like EarlyBird’s suggestion for the bike flag. Just bend the bottom part of the mounting bracket 90° to horizontal. Attach to rear deck using #12 or larger stainless sheet metal screws. Anchors not needed. The polyethylene deck will hold the screws well enough and will likely be waterproof.
Very light, portable, and minimal wind resistance. There are probably many other bike flags available online. Some may work better.
I saw this flag for kayaks in a store this afternoon.
Looking at the photo of their SOT kayak It doesn’t look like there is any way to access the inside to put in a backing plate. Otherwise, I would have suggested that or oversized washers. If indeed there is then that is also what I would do.
Thank you, everyone! Need time to think 
I don’t like the idea of putting something like backet behind me because that is where my cooler usually stands so I can reach water anytime. Also I want small flag and thin pole because of wind. Yesterday it was 25 mph and there were times when I was holding paddle horizontally and I felt how wind was pushing it like a sail. That was pretty cool (not the way back though).
No, I cannot reach inside and put any plate there. When I bought this kayak I absolutely didn’t think about flags (and a lot of other things!).
Like the idea of fishing-rod holder. So here is a stupid question: can I drill a hole and put screws through the back of the seat? Will it harm the integrity of the kayak? Can put some washers under them. I am afraid that would not be very secure and wind can wreck the whole thing. There are 2 screws that were left when I removed the seat it came with. What if I put some wire through the back of the seat from new screws to these old screws?
Overlooked that it was a SOT.
A friend of mine made a go pro mount with a long pole (pvc pipe) with a male threaded fitting ( which is basically what you did). He had a female fitting similar to your plate but used rubber gasket material under the plate glued on with rubber cement ( the red can dap weldwood) and then used blind rivets through the small screw holes in the mounting plate to secure it tightly and water tight.
I expanded on the bucket idea which first presented by another poster because it would eliminate the need for screws/bolts, and I came up with the idea of shortening the bucket to minimize how much it robs space from that storage well. As it seemed from those earlier pictures, I thought cutting the bucket down to 6" high would put the top of the bucket pretty close to being flush with the bottom of the rest of the storage well, thus not decreasing the usefulness of that area, but I see from the new photos that the bucket would need to be shortened even more than I thought.
My educated guess is that those two screws behind where the seat goes are not suitable for a securing a bracket holding a flag, unless that bracket were custom fitted to fit the horizontal and vertical portions of the hull there, including the curves. Even then it would not be ideal in terms of the stress those two screws might experience. And, I’m afraid I could not understand your question about incorporating wire, but putting wire through those existing screw holes (if that’s what you were getting at) would create a situation that would be very difficult to permanently seal against leaks. Besides, as you already pointed out in an earlier post, mounting your flagpole at that location would put it so close behind you that surely it would be in your way.
Yes, you can use screws, or tiny bolts associated with some kind of blind anchor device, but you might as well start out with simple sheet-metal screws as another poster has recommended, and then only if they fail someday would you need to take the next step of drilling a slightly larger hole and installing bolts with blind anchors. Chances are, the screws would never fail, however. I’m leery of pop-rivets as fasteners because their holding power is poor in comparison with almost any other method, especially when anchored in soft materials like plastic, but lots of people like them because they are fast and easy to install, especially in situations with one-side access like this (“fast and easy” is actually the only reason pop-rivets were invented in the first place and it’s why they are popular in mass-manufacturing situations).
I’d be inclined to mount a fishing-rod holder or one of the other bracket bases described in this discussion on some area of flat decking, probably behind that storage well. Or, you could mount the bracket for that bicycle flag on a nearly-vertical surface such as the back wall of the rear storage well. I’d recommend against putting a 90-degree bend in that particular bike-flag bracket to allow mounting it on a horizontal surface because it already lacks reinforcing in the weak direction and after bending it that far it may become weaker, but mostly because there would be so few screw locations available for use, all extremely closer together (putting high stress on the plastic at each screw location). Left unbent, that bracket would be suitable for mounting on a near-vertical surface. There is reinforcing “in the weak orientation” immediately above where the existing screw holes are, and I would add a couple more screw holes alongside the upper part of the bracket where the reinforcing is (thus making actual use of that reinforcing and taking the stress off the non-reinforced portion below), and thus also increase the hull area that the bracket attaches to (the greater the spread between screw locations, the less stress will be applied to any of the screws, and the same principle applies to using more screws). (Lots of rambling on that topic and maybe the reasoning is not all clear but I tried to keep it short)
Most fishing-rod holders incorporate a “through” design, where the butt of the handle of the fishing rod sticks out the bottom end of the holder and the rod portion sticks out the upper end. That style of rod holder would be difficult to adapt to holding a flagpole, though it might be doable. Also, such rod holders will not tilt up to a fully vertical position when mounted on a horizontal surface. Other fishing-rod holders are nothing but a tube with a closed end at the bottom and an open end at the top, and when set to a vertical position (which can be done regardless of mounting location), this would work nicely, after you “expanded” the base of your flagpole to fit inside the tube “almost snugly” (as I described in my first post above for adapting a fishing rod as a flagpole).
You might want to peruse the pages of YakAttack. They have a lot of potential solutions. for example, don’t want to drill? How about a storage container with rod holders attached:
YakAttack® BlackPak Pro Kayak Fishing Crate 13" x 13" Orange - Kayak Fishing Gear
Need a flag that fits in a fishing rod holder? Here you go:
YakAttack® VISIFlag™, GearTrac™ Ready - Kayak Fishing Essentials
Want to do a little drilling and get a rod holder that can move around as you need? Maybe this base and holder:
YakAttack® MightyMount II with Fullback™ - Kayak Fishing Essentials
YakAttack® Omega™ Rod Holder with Track Mounted LockNLoad™ Mounting System
Lots of options out there. But as you say, you need to think about your objectives and how important each one is for you.
I remember long ago on a guided kayak tour in Maine. The leader carried a flag for visibility, and had waterman compliment him on how much easier it was to see him with the flag. His solution? He simply slipped a bicycle trailer safety flag in between his body and his PFD. Apparently it worked well for him.
I still can’t understand how power boaters can’t see a kayak of any color. People drive crowded streets and mostly miss pedestrians, dogs, wild animals, potholes and everything else. There is NO excuse. They’re ego-centric, revealing a defect in character.
A universal sign for danger is the black penant.
Combined with the orange hand implement, it provides an unmistakable symbol of your resolve.
A three pack of the other items would last at least a full season for you. Ignite, and if they dont see it, throw it into the boat as it passes. They’ll remember the penant.
It’s what I would do.