Screws , Bungs , and Bondo

[Bill Perkins]

I was reading the chapter on bungs in the WB book on planking when I came across the recommendation to just use polyester putty like Bondo under paint . I’ve got allot of screws to cover on various removable strips and like the idea ; heck I’ve Got a partial can ! Has anyone done this ? I saw “Marine Bondo” in some catalogue , anyone know about that stuff?

The book also stated that the makers of the Beetlcat used plastic wood instead of bungs under their varnish work . I didn’t think this could be true of the old boats , and sure enough I got a look at an old one over Christmas and it was bunged . Are they really using plastic wood under varnish on new Beetles ?

[mariner2k]

I've heard of using bondo under the water line. Reasoning being, it doesn't swell like bungs and is supposedly easier to get out to check fastenings, is cheaper and easy to apply.
mariner

[imported_Conrad]

I know a bit about Bondo... First thing to be aware of is it comes in a lot of different "flavors" with varying resins and fillers. The cheapest is polyester with ground talc as a filler. Next up are polyesters using micro ballons and other specialty fillers. Then come the vinylester resins with all glass fillers. This last one is the "marine" grade.

I've used it to bung screws on a number of boats. It's very easy, fast, and holds up quite well, even with the cheapest grade of product. The main disadvantage you'll hear is that it's hard to pop out when you want to refasten. But in my experience the right tool is the key to success. I use a spade style wood bit with the tip ground down to just a nib, and they work great. An awl will easily clean the screw slots.

The paste hardeners come in different colors, for reasons that aren't important here. But you can tint them by inter-mixing so that when added to the filler you'll end up with a wood colored paste. The result doesn't look too bad under varnish, especially the amber colored traditional products!

A couple of points to be aware of. The filler may sand at a different rate than the wood, making it harder to achieve a perfectly flat surface. You can minimize this by using different brands and faster/slower cure rates. Also, it won't swell at the same rate as the wood, so if your boat experiences a lot of shrink/swell cycles there will be times when all is good, and times when you may see the puttied spots. I'd stick with the brands that use less talc when using it below the waterline, and save the cheap for hull sides, decks, etc.

Now stand clear, as the more traditional boaters will be complaining soon.... ;)

[Jack Heinlen]

I've used plain old auto bondo on screws that were set too shallow to bung. It works fine. I think for deeper set screws a bung is still preferable because if it's done right it makes things easier the next time the pieces have to come apart. The traditional way, and still the best I think, is to set them in shellac. This doesn't foul the screw slot, is tough enough and yet fairly easy to remove. Epoxied bungs are a nightmare for the next fellow down the road.

I can't believe new Beetle Cats have plastic wood in the place of bungs on their bright finished pieces. It wouldn't seem to make much sense, as I think it would be more work getting things fair than bunging, and would be really ugly to boot. But who knows. Bad idea, in anycase.

[carioca1232001]

Just finished replacing the first two planks on either side of the keel on my (1961) 32 ft powerboat.

We are talking here of some 500-600 screws that were covered using wooden bungs+epoxy-glue .

And had no trouble getting out those few screws that had missed their frames and consequently needed to be redone.

The polyester+talc putty used extensively on the hull during the face-lift-type overhaul done some 4-5 years ago, wasn´t effective at isolating the screws from the surrounding water. Wood was kind of shot around screw heads.

Have a feeling that the wooden bungs+epoxy-glue will do better in keeping water out of screw territory .

Any comments ?

[On Vacation]

I’ve got allot of screws to cover on various removable strips and like the idea ;

Not going to get into the bondo=polyester arguement with anyone here, but from reading this line, I take it that you are attempting to countesink your screws and fill the holes. Two things, countersunk screws do not come out that swell, unles oversized, with or without filler, after the wood has some age on it. Please reply with actual application. There are better items to use, flexible in nature and paintable, that can be used to fill that will come out better than a solid hard mass from countersunk holes.

[ 01-03-2004, 05:53 PM: Message edited by: Oyster ]

[Bill Perkins]

Thanks All for responding . Mike I'm using 3/4 in. Oak for a sacrificial strip along the keel , a pair of spray rails set along the chine , and some rub rails up near the sheer . The first two I expect to take a beating . I'll probably be the one who replaces them so easy out is a factor .

The topsides are of Occume ply planks ,and I may use an LPU topcoat on them . I've invested in a quart of Interlux Hatteras White and the flattening agent which I'm going to try on some scrap soon .Maybe I should recess the screws on the keel batten slightly and cover with putty? On the topsides though aren't my choices a hard filler or flathead screws set flush (Could look good)if I chose to use the LPU?

[ 01-03-2004, 08:31 PM: Message edited by: Bill Perkins ]

[On Vacation]

Several suggestions on the rub rails. If you are using any metal on the rails, just let the rubberized caulking bed the screws. A nice awl will remove any caulking from the slots in the screw heads. Did I mention to use flat head slotted screws on your rail pieces, even if you don't use a metal chaffing strip. Did I fail to mention a nice brass or stainless steel rubrail will almost eliminate the need to replace the wooden rub rail?

And if you choose to replace the wooden one, then if all else fails, you can chisel the rail, and then take the screws out with a set of good vise grips, on the shaft.

The keel strip, I would suggest that you drill the hole a size larger than the screw head. In removal of screws from holes that fit the head, it will almost always hang on the sides of the hole when attempting to unscrew, and almost always will spin free, if you are using wood screws for your job. Did I fail to mention to use wood screws for this job?

I hope you are using silicone bronze slotted head screws?

And last but not least, the new 5200 fast set, sikaflex 240 series and even the PL Door and window caulk works great, cheap, and paintable, but a little slower to dry, for just the job you are doing there. When it comes time to remove it, the rubber is flexible and removable with a flat head screwdriver or awl.

Keep in mind the type of caulking you will be bedding these pieces for removal with in the first place. By the way whats your poison for this application?

One more thing, add a little extra of these caulks over the heads, and let dry. Then grind flat so you will end up with a smoothe surface over the heads.

[ 01-03-2004, 08:59 PM: Message edited by: Oyster ]

[Bill Perkins]

I'll follow your suggestion and oversize the boreing on the keel batten .Should I do this on all the pieces ?What goes under the strips ?I could use bedding compound . I'd like to hear your opinion on screw size and spaceing .The keel batten is 2 3/4 in. wide . The spray rails taper from 2 1/2 to 1 in. I could use an adhesive caulk like 4200 ( I've bought it !) and space the screws further apart. Fewer holes in my boat and fewer screws to buy .Can I use the 4200 over the screws and paint with LPU? The keel batten gets bottom paint of course .

[On Vacation]

I have never painted over 4200, just because I have never uses it for this type of a job. The distance between the screws depends a lot on the actual thickness of the strips. When a strip is thicker, you can space the screws a little further apart, depending on the section of the bend you are working on. I get by with eight inches, most of the time. But if the strip is only 1/2" or so thick, you will need them to be closer than eight inches, more like six inches. With a width 2 2/4 wide, you will need to stagger like two rows of screws. How thick is the pieces?

If you use metal rail, you screw your wood screws at five and seven, starting at one inch from the end. The reason for this is stainless steel railing is six inch on center. Plan ahead. If you use brass rail, you will need to counterbore and predrill holse in the railing, as it comes without holes.

Lets talk about buying woodscrews. ;) Buy them by a hundred to the box. Many times you will strip heads, or need more than you think. Buy a hundred more than you plan to use. Yoou will use more than you think, When you have bedding on the parts, running out to get more, is a royal pain, because you will probably have bedding on you and your clothes by then, and will end up on your steering wheels or seat covers. tongue.gif

Tape the areas adjacent to your strips, and dry fit them before caulking. Do not cut too big of a hole in the tip, and make sure the bedding is warm . Check for the base of the caulking. MOst can be cleaned up with mineral spirits. Cut small rags, the size of a wash cloth, and have then readily avalaible along with a small garbage bag, to drop the tap in when done. This will keep it off the floor and out of your house and carpet.

[ 01-03-2004, 09:45 PM: Message edited by: Oyster ]