Question about screws

[eamarquardt]

The very best and safest material for holding the keel onto the boat is silicon bronze or monel. Stainless Steel is never used as keel bolts here in Oz by any yachties that I know. Silicon bronze is expensive but you can trust it with your life as a bolt for attaching the keel.
I have seen SS bolts completely wasted away from corrosion (3/8" dia down to 1/8" dia.) but the hexagonal head and nut still looked perfect. It's bad news stuff if your hoping to use it for protection against corrosion in a wet area and especially in timber that is often underwater.

Kody

The corroded area of the SS keel bolt nut I posted a pic of was on the underside against a washer and the hull. From the top it looked fine.

Cheers,

Gus

[Irmo Atomics]

On the campers that I've torn down and restored, wood rot was the cause of failure, not the fastener. I use deck screws on the parts that get covered.

[sleepy]

I believe there is an awful lot of overthinking. People have been making trailers, and teardroptrailers too, out of all sorts of screws and nails and glue for a long time. They all do very well. It is just not important what you use. The great number of the fasteners spreads out the stresses. The overall geometry of the pieces and mutual support they give each other gives great strength. Galvanized nails are very good too. I have built seven boats in my lifetime. I worked in a naval shipyard as a machinist for 30 years. I have seen how all sorts of metals corrode and rust. Hot dipped galvanized screws and hot dipped galvanized nails are my favorite. There is nothing wrong with any of the other screws either. Your teardrop will not be submerged in water, and certainly not seawater. I really don't think you can use the "wrong" fasteners. They are all fine.

[angib]

Ditto on the overthinking - similarly folk talk about which grade of bolt they need to bolt the body to the frame, as though it matters. The plywood floor isn't as strong as a Grade 0 bolt so higher grades don;t make a stronger joint.

[eamarquardt]

Ditto on the overthinking - similarly folk talk about which grade of bolt they need to bolt the body to the frame, as though it matters. The plywood floor isn't as strong as a Grade 0 bolt so higher grades don;t make a stronger joint.

Yes but the grade 5 and grade 8 nuts and bolts have those cool little marks on em and those little marks add considerable cool factor to any build.

Cheers,

Gus

[_Ryan_]

Wow, ask and you shall receive! Lots of great info but overkill when dealing with teardrop construction I think, unless you are planning an amphibious trailer.

How about screw length? Three times the length of the board seems to be the rule. Would this work in the case of sidewall attachment if you are planning to use glue in the joint as well?

And as far as sealing screws what works best? Silicone or poly sealer in the screw hole?

[angib]

the grade 5 and grade 8 nuts and bolts have those cool little marks on em and those little marks add considerable cool factor to any build.

And other men will gather round and admire how manly all those little marks are, signalling you out as an alpha male?

[webbaldo]

I used decking screws (dakronized?) for side walls and spars (As well as glue obviously) and starting to use stainless for the alu trim outside. They are soft like

[aggie79]

Ditto on the overthinking - similarly folk talk about which grade of bolt they need to bolt the body to the frame, as though it matters. The plywood floor isn't as strong as a Grade 0 bolt so higher grades don;t make a stronger joint.

And with only a single 1/2" or 5/8" pin securing your teardrop to your tow vehicle (pin that holds the draw bar in the receiver of your trailer hitch), why use 8 or 10 bolts of the same diameter to fasten your teardrop to the frame?

[Thawley]

Ditto on the overthinking - similarly folk talk about which grade of bolt they need to bolt the body to the frame, as though it matters. The plywood floor isn't as strong as a Grade 0 bolt so higher grades don;t make a stronger joint.

Plastic is harder than water, too. But that doesn't mean it's good enough for every swimming pool...

[KCStudly]

I just read a "paper" recently that gave a rule of thumb for traditional lag screws stating that a thread engagement of 7 times shank diameter (for harder woods) and 10 - 12 times (for softer woods) would generally result in a pull out strength equal to the fastener strength, so I guess that correlates well with a #10 at 1-1/2 inches. Just be sure to add for the thickness of the clamped piece.

The Wood Handbook Chapter 7

The rest of the book can be accessed from here

[Bogo]

Here is a picture of a SS nut that was on my boat. This is what happens to SS when oxygen is excluded:



It, in that state, wasn't entirely effective at holding the 3.5 tons of lead keel tight against the hull.

Ever hook that boat up to an AC line while in the water, say a battery charger? How about using the keel as a ground for a radio? Actually having the mast attached to the keel may provide enough alternating current from atmospheric charge buildup and discharge. Something else other than lack of oxygen was the issue. Lack of oxygen shouldn't have done anything to the SS except make it last longer. You need some salt, water, oxygen plus a bit of alternating current to corrode SS. You end up with crevice corrosion. Any scratch, or small gap can get the corrosion process started with a little kick from the alternating current. Salty or dirty bilge water and a bit of stray leakage current will do what you see there. BTW, Colorado river dam water is salty enough for crevice corrosion to take place. It will just go at a much slower rate than if exposed to ocean salt water or Great Salt Lake water. BTW: Never use SS for anything through the hull on a saltwater boat. A moderate case of crevice corrosion can eat away a SS through hull fitting in weeks, a bad case, just days.