Getting Opinions - Glue (and screws)?

[Bob Perkins]

Hi Everyone,

I'm just about finished longboarding and fairing my cold molded Biscayne 22 mahogany runabout.

(Slightly old pic, but you get the point) http://www.imagestation.com/picture/sraid122/pa3efeb0079228769fddb36c7464e2416/f8324b38.jpg

The instructions call for screws every 3 inches along the keel, chine, sheer and transom. Essentially everywhere the layers meet at a seam. The bottom is 1/2" thick and the sides are 3/8" thick.

Mark Bronkalla (see ->Mark's Riviera (http://www.bronkalla.com)) Did not use the nearly 700 screws to do this on his boat. He said he has put 300 hours of HARD use on it and not even a hint of a problem.

The designer said it's my boat do what you want, but recommmends screws of course.. Another builder did use screws.

The hull is rock solid and the planking has excellent contact to the internal structure. My gut says I don't need them, but maybe a couple of you pro's out there can give your opinion?

Finally, the topsides get a layer of 4oz epoxy and the bottom gets 6 oz.

Hope this makes sense..

Thanks,
Bob Perkins

My out of date site is at:
http://robert.perkins.home.comcast.net/

My Current project is at:
http://www.imagestation.com/album/?id=4291051329

[Bob Smalser]

The designer....recommmends screws of course... That's enuf for me. He did the engineering, I didn't.

He probably engineered it for the worst-case idiot...which I'm not...but no telling what will happen to the boat after my time, yet my name will still be on it.

[Ian McColgin]

The screws may slightly reduce the chance of a seam failure but more importantly should the glue fail the screws will limit the damage. Easily the difference between getting home while bailing or not getting home at all.

Screw it . . .

[RonW]

BUY A SCREWGUN.- and bite the bullet and finish the job. We all make changes to the boats we build, at least to some degree, and we all have preferences as to type of plywood, wood, glue and paint.But your question is a structure integrity question, leaving out some of the fasteners.
Mark built a nice looking boat, but he is also a part time hobby woodworker, Mr. Glen is a full time marine architect.I know who's opinion I would take. All architects, marine or building, slightly over engineer things. It is called a SAFETY FACTOR.

[Bob Perkins]

Thanks for the feedback..

I'm not worried about drilling and screwing - that's easy smile.gif The real pain is that if I countersink the screws and plug them (above the waterline, where they will be visible..) I'll have to make 1/8" thick little plugs/covers and try to get them to stick in place..

Remember, the topsides are only 3/8" thick in the first place.

But, based on a few different opinions pushed together.. I think I could do the following:

Everywhere the screws are under paint... I can just add them to the existing hull - which is pretty much everywhere except the sheerline. However - another builder added screws at the sheer under the Chrome rub rail after the decking was in place and covered all the screw heads with chrome.

So - I may be able to follow recommendations and not have hundreds of little dots all over the perimeter of the hull (which would not look good at all! And for the effort - looks matter ;) )

Thanks,
Bob

[htom]

Screws. Think of them as an anti-Murphy policy.

[Del Lansing]

Screw it! Imagine motoring along at around 18 knots, let's say that exerts_only_2 psi on the bottom, that's 288 lbs/ sq ft. of bottom area. Over 2 feet of length that is well over a ton of force. Now let's add a chop to the picture and a race to port in front of advancing squal. I can't imagine the forces exerted on the bottom. Colorful anecdote; just for giggles Dickie and I strapped my 18 hp outboard on his 10 foot plywood skiff; we went screaming around the harbor for only 10 minutes or so when fear won out and we noticed we were taking on water. After returning to the dock we figured out where the water was coming from, the straight line force of the water had ripped the two oak skegs off the bottom, they had been screwed every 10 inches and were just disappeared. This had been a calm day with no pounding or wave jumping.

[ 08-11-2004, 09:38 AM: Message edited by: Del Lansing ]