When to Use Bolts versus Screws

[chuckt]

My frames are bolted to stringers and the chine log bolted to the frames. If I am eopxying all my joints and meeting surfaces and doing a West system bottom. Are screws sufficient? Or should I reinstall the bolts? I assume in traditional construction the bolts are just giving extra strength at a place where there is going to be some movement and they will hold longer than screws?

[Peerie Maa]

You will need to tell us some more info. What size boat is this and what are the scantlings?
Bolts are better than screws as they have a very reliable mode of gripping the wood, and they are normally thicker, so that they bear against a greater area of the timber. Your question relates to the area of the faying surface fastened by the epoxy, and how this compares to the friction forces in the faying surface and the compression loads resisted by the diameter and length of the bolts.

[gibetheridge]

Any reason not to just use the bolts?

[chuckt]

I have replaced pretty much all the original frames. They are all about 3 inches wide and 1.5 inches thick (some are 2.25 in thick). My replacement material is Douglas fir. The stringers are about 2 by 6. The chine logs are roughly 2 by 2.

The boat is a 30' Chris Craft Cruiser (shown in my profile pic)

Bolts are just more expensive but its not a significant cost to me. I am really more asking to educate myself. Big silicon bronze screws are expensive too.

[paladin]

Use bolts anywhere there is possible pressure or someone getting hurt if a screw pulls out...I have seen idjits use screws to secure lifeline syanchion bases on an ocean going sailboat......

[chuckt]

Use the old bolts? I have read never to reuse really old screws but these bolts are pretty thick 3/8" and 1/2" and I doubt they were wet as the lowest ones were still a couple of inches above the lowest part of the bilge. This boat was always fresh water. But they are 60 years old.

[htom]

When to use bolts versus screws ... as often as possible. Especially if the joint is critical.

[Peerie Maa]

Use the old bolts? I have read never to reuse really old screws but these bolts are pretty thick 3/8" and 1/2" and I doubt they were wet as the lowest ones were still a couple of inches above the lowest part of the bilge. This boat was always fresh water. But they are 60 years old.

Age is not an issue. If they have not deteriorated re-use them.