Drilling the Hull, Gunnel replacement

On a Royalex boat (20 years old), what is the opinion on gunnel replacement when it comes to the installation ? Should you use the old holes in the Royalex or redrill the new screw placement’s mid-way between the old holes in the hull ? I believe the old MRC gunnel replacement ‘instuction’s’ call for drilling new holes spaced inbetween the old. Would it make a big difference to use the old one’s or is it better to go with new ? In a discussion with someone he felt the drilling of new holes would further lessen the strenth of a older hull along the gunnel line. I think it wouldn’t make a difference in overall strenth or weakening. If anything it would be harder to try and line up the old holes to the new ones you’re drilling in the ash.

What’s the advise for this repair ? Could you, or should you, use the older, original drilled holes ?

New rails

– Last Updated: Feb-05-08 10:53 AM EST –

I agree with Eric and Mike - you couldn't hit all those holes dead center if your life depended. And no one else could either.

Mad River clamped the rails on the hull and started marking mounting screw placement with a compass.

We do it a little differently. We cut the rail to length, mark center, and then, on a drill press, countersink holes on centers in both directions. The countersinks are at 90 degrees and rail installation more straightforward.

If memory serves, always questionable with me, MRC used 7" center, so use another spacing.

Be sure to drop the center thwart in place when installing rails to improve the rails arc fitting the hull shape. [Or decrease the rails tendency to straighten hull sides, then put the screws in tension when thwarts are installed.]

A rule of thumb, don't shoot thwart or seat holes within an inch of rail mounting screws. Moving the thwarts and seats +/- an inch isn't a big deal. Another thought; replace the 1/4 Inch seat mount carriage bolts with 10-24 machine screws: smaller holes in rail, less weight, plenty of strength. Fastenal has 6" flathead machine screws, ~ $3.00 ea.

McMaster-Carr Supply
also has 10-24 x 6" flat-head Phillips screws, about $13.00 for a package of 10. For those of us who like to maintain a stock of spares.


I just dropped $75 on 6" carriage bolts.