Actual Draft vs. Designed Draft?

[u079721]

I have a 1989 E-38 (which I guess is the 38-200 model) in shoal draft. The specs list the draft for this version as being 4' 10". But when we load the boat for a month of cruising for the two of us the actual draft of the boat is closer to 5' 4".

Now I will be the first to admit that we don't exactly travel light - but we don't carry scuba gear, or four anchors, or have the extra bow water tank, or have a dinghy on davits, or anything else that might add that significantly to the displacement. So I am quite surprised at the 6" difference between actual and designed draft. Then again, my neighbors tell me the actual draft of their Tartan 40 is 4" greater than spec, so I'm not alone.

What's your experience? Anyone else measure their actual draft and find it to be that much greater than the spec? (Or do I just need to lose weight?)

 

[Loren Beach]

Draft dodging??

Our boat has a "brochure draft" of 6 feet. I know that the transducer is *about* a foot below the dwl, and sure enough, when it reads about 5 feet, we run agound. Well, duh!
But this is kind of a loose standard to apply...
When the boat was last hauled, it seemed to be just about as stated, when I stood beside it and compared the distance from the ground to the waterline stripe. Interestingly, I know of at least 3 different brands of boat at our moorage who all have had their waterline stripe moved up and repainted in the last 3 years. They all needed to move the bottom-painted area up to reflect the reality of where the hull floated. I have moved the designated line for the top of the bottom paint upwards almost 2 inches on our Olson. I can only figure that: 1) Most production boats weigh more than the design specs, and sink a bit lower into the water, or 2) The factory waterline stripe represents an empty and very light unloaded state, such as when the boat would be entered in bouy races, where all the living/cooking/extra supplies detrius is off the boat. When I successfully raced our prior boat one season, I unloaded about 200+ pounds of "stuff" off of my 4000# sloop... and it *did* make a difference. (No pots and dishes, no canned food, no spare anchor and chain, all the extra hardware for use "someday", etc, etc)
So, it may be that the stated draft is accurate, measured from the bottom of your keel to the dwl where the original bottom paint ended...
But that's not where the boat normally floats!
Just my .02.
Loren
1988 Olson 34 Far Side, RCYC, Portland, OR

 

[Bob Ells]

I agree with Loren. I spoke with the owner of an Ericson 38 last spring. He was in the process of having his water line raised to reflect actual conditions. To add further credience to the matter I personally noted that there was evidence that the water line on an 38 that I was "looking" at had been sitting about 3" below the water surface at the bow and about 1.5 inches at the stern. Bob Ells

 

[Duncan]

going deeper

I too have a submerged waterline stripe. I put it down to overloading. Then I remembered talking to a maker of fibreglass boats and him telling me that a 19 foot runabout, if left in the water for two years, would take in about two hundred pounds of water. A friend with a family fibreglass business who built boats when other product lines were slow, confirmed that fibreglass took in water. The outside of the hull was saturated and it became drier as you came to the inside of the hull. In other words, water is continually migrating through and evaporating on the inside. In the late seventies his brother, who made fibreglass shower stalls, found that he could add 70% calcium carbonate to his resine mix and the stall worked perfectly. A similar mix might just produce some BIG blisters in a hull. Anyway, perhaps we are looking at significant water retention in the hull.

 

[Duncan]

hull water retention

My E34 is on the hard getting the blisters peeled and I have spent the last month watching the water run out of the fibreglass. After the gelcoat was peeled the hull just dripped -- day after day! My blisters were under the gelcoat and in the tight roving just below the gelcoat but not into the loose matt. He said that once it gets into the matt you are in trouble because the water travels laterally very easily and will spread throughout the hull. My blisters were localized and easily removed. He thinks that it takes about five years before the water saturates the gelcoat and starts penetrating the roving. A moisture meter will show you if your hull is saturated. He is replacing the peeled roving using vinylester resin. What all this means in terms of hull weight/displacement I don't know, but if you add water/weight you must go lower!

 

[Cary Diehl]

Why you draw 4 inches more...

Your location is Michigan... so you sail in fresh water. Fresh water isn't as dense as salt water... so you will float deeper. My J/24 had 2 scum lines on it this spring.... One from being in the water up here, and one from being in tampa bay during the winter. The one from tampa bay was about 1 1/2 inches below the other one.