Strong back flatness?

[TKLUS]

I am building my strong back now and noticed that some of my sides have about 1/16 of a crown to them in the 8' span. is this OK? should I shim the top when I put it on or cut new sides? or can I live with it? I have not assembled anything yet.

I am using 3/4 particleboard with laminate on both sides (cabinet grade stuff) and I used the factory edge but it must not have been perfectly straight.

Thanks
Tim

[Patricks Dad]

I suggest you shim it (or sand/plane each span side) so that the top fits perfectly flat. Everything you do in the build will reference the strongback as the base. Take a little extra time now to get this part right and you won't have wonder if the strongback was the souce of every issue you may have later...

[TKLUS]

Thanks for the reply

That is what I thought. I plan to take one of my straight boards and use it as a guide to flaten them out with the circualr saw.

thanks
Tim

[pawistik]

Everything you do in the build will reference the strongback as the base.

Really? Don't you line up the stations in relation to each other, not the strongback? I didn't build a Bear Moutnain boat so can't say with certainty what the methods are, but I'm suprised that the reference points on the forms (centerline, waterline) aren't lined up relative to each other. I would expect that rigidity of the strongback would be far more important than the perfect flatness of the strongback.

Of course, if there is a problem that can be easily fixed, now seems like the time to do it.

Bryan

[Glen Smith]

It is comforting to have a perfectly flat strongback top surface for reference but the most important thing is to set up all of the forms in perfect alignment on all axis' as stated by Bryan.

[Denis]

I think the flattest truest levelest top on the strongback is quite important. Otherwise one would need three string lines to line up the centre line as usual and one on each side of the waterline to true them up. Otherwise would you not have a dip or a rise in the middle of the boat or a list? Being a little low or high is likely not cause for concern but as it isn't that difficult to true up the top why bother not to do it?

I just went through an exercise with a set of donated forms and noticed after I started the sheer lines where not correct ie not parallel to the table top, one was either high or the other was low. I chose to go with the plank i started with and with a level created a new sheer line which was now parallel to the strongback top which I had trued up and knew it was level.

my 3 cents worth ( used to be a nickels worth but our dollar has depreciated lol)

Denis

[Patricks Dad]

Bryan and Glen (as usual) are right. The waterlines must align. But the easiest way I know how to do that is to start with a flat/level strongback (and cut my forms precisely. I have also found myself at times (after the hull is stripped) trying to ensure that I have my sheerline marked streight befor I cut it. It's pretty much impossible to use those buried waterlines. I measure up from the strongback to double check my marks (and at the bow/stern it's difficult to look up under the hull to see the sheerline marks on the forms so there the strongback is the easiest reference to use).