Striking the waterline

[Splinterfinger]

Any suggestions out there for determining the appropriate placement of the waterline when the hull is still upside down? I've access to a laser level that works O.K. When it is almost dark out but how do you find the correct height? By guess and by golly I can do but I'm hoping that someone out there has a genius solution. Thanks, Steve BJ 28 hull #11

[jkeenan]

Splinter,

the dimensions for the DWL are not in the plans. For my BJ271 I was given "guidance" from another builder. I will find out very soon how close my boat is to his. I assume every boat will be a little differant. If you would like my dimensions from my boat I can measure for you.

Cheers

Jim

[Tom Lathrop]

The design location of the waterline in all Bluejackets is intended to coincide with the level of the pilothouse sole.  In all but the BJ28, this means that the waterline is approximately 9" above the outside of the hull bottom on centerline, not including any keel  The plans show this as the pilothouse sole being 8" above the inside of the hull bottom centerline.  This assumes a plywood and filet thickness of approximately 1".  It also assumes that the hull is trimmed to be level on both hull bottom (centerline) and pilothouse sole.

 

Actual waterline will be very dependent on how heavy the boat is built and loaded.  If you build it lightly per the plans with reasonable fore and aft location of added weights, the above estimate should be accurate enough. 

 

The above numbers for draft should be increased by 2" for the BJ28.  This is primarily because of the 2 degrees greater deadrise of the BJ28 hull which naturally results in a deeper hull in the water. 

 

I advise making the actual bottom paint waterline at least 1 1/2" to 2" higher for a couple reasons.  First is that it should be well above the at rest water level to avoid too much dirtying of the topsides paint due to wave action at a dock.  Second is that I do not see any negative aesthetic issue to having it higher.  In fact, I prefer to see the bottom paint well above the actual water level.

 

Perhaps some builders of launched Bluejackets will chime in of their actual experiences with waterlines measurements. 

 

If the painted waterline is not actually parallel to the water level, I prefer that the bow be the higher end and might bias the line to insure this.  If your boat sits a bit lower than the design intends, you are probably in the majority as most boats of any design tend to turn out this way.  If not at the first launch, then afterwards as people begin adding stuff and more stuff.  OK, I'm ranting a bit but it takes constant awareness of the overloading syndrome that infects most boat owners in order to maintain best performance.