Why are screws bunged on the bottom?

[sdowney717]

Why not just screw them in flush to the wood.
Does anyone really think water is kept away from the screw by using a bung over top of it? Most wooden boat bilges are wet and I believe the screw is wet as well. I am just talking about the bottom. It would be easier to rescrew with no bungs in the way.

[Elco's]

Think of it this way then....
with the bung cut off and sanded flush, the bottom is smoother and the flow of water past the screw has less interuption.

Water can migrate alongside screw threads.

[SC-Lion]

Remember that the bung is dipped in your favorite goop first (white or red lead, epoxy, 5200….). Copper and Bronze will corrode much faster when exposed to oxygen and water, stainless of course requires the oxygen to survive. Copper in particular does not like being exposed to oxygenated water. The surrounding wood is wet but the water is, for the most part, stagnant and will soon be deprived of oxygen through the oxidation of the fastener.

Seal your fasteners with a bung dipped in your favorite goop (much has been written here about what goop to use).

-Gary

[John E Hardiman]

The real question is could you even get the screw out if you didn't bung? Most likely the slot would be so buggered up after 15-20 years exposure to the environment and critters that it couldn't be used. Now I personaly wouldn't use epoxy (you have to wax all the screwheads without getting any on the planks first which is a painful job), but after sealing with a soft sealant, you can come back 20 years later, pop the bung, and the head "should" still be fresh which will allow for removal.

[Scott Rosen]

A properly fitted bung, i.e. snug, will keep water out of the screw hole and prevent it from wicking its way in through the fastener.

In other words, there are about a gazillion people who actually think bungs help keep water out. And they're right.

[Tom Robb]

Stupid question No. 17:
If dimples on a golf ball reduce drag, why not on the hull bottom?
Yes, they'd obviously be ugly, but golfers got used to it didn't they?
You could putty the screw hole but leave it dimpled below the surface of the plank.

(I admitted it was stupid, didn't I? :D )

[Frank E. Price]

The boat doesn't plane, the ball does.

Frank

[Pete Dorr]

Re: dimples

They experimented with dimples on windsurf boards a while back. I never sailed one so I can't comment on how they sail. I don't think they do it anymore.

I'd say it would only work with high speeds.

Pete

[ 07-31-2004, 06:38 PM: Message edited by: Pete Dorr ]

[Gary E]

Doncha think that if dimples would help, these fellows would have found out long ago?

http://www.dt.navy.mil/

[Tom Robb]

Would they tell us if they did? :cool:

[John E Hardiman]

For the dimples and drag see my posting in this thread (http://media5.hypernet.com/cgi-bin/UBB/ultimatebb.cgi?ubb=get_topic&f=2&t=003466&p=) from June.

[formerlyknownasprince]

Good to see a bit of Aussie innovation featured (the HSV2) on the navy technology website :D

[Ian McColgin]

Back to bungs - there are many traditional boats that use underwater seam compound (paintable) rather than bungs. It's supposed to be a tad more obvious even under a little bottom paint if changes in the wood during a winter hauled out have caused any problems. I found Goblin's bottom a mix of bungs and seam compound and never could determine which was really better.

Seam compound is faster and easier to apply, comes out of the hole easily enough, and clears out of a proper slotted screw in one fast pass.

Point is that whether compound or bung, the whole screw is better protected. There's always a bit of wear on the wood from a screw as the decades pass. Not enough to immediatly refasten but after about five years or so an un plugged screw will weep water through the plank and into the frams.