Has anybody weighed their boat on bathroom scales? How would you do it? One under each hull and add them together?

Yep - the front two can go just forward of the front beam, and the back two go just forward of the rear beam. That'll keep your hulls off the ground. Easiest way, track it into position, lift the bows to pull the trax, and set it on the front scales. Then lift the stern, pull the chocks, and set it on the back scales. You might need some help with the math.

Rub it down, flip it and reverse it to take it off. If you have scales that can be zeroed and show one decimal place, they can be used to get an official weight. Most can show Kgs as well as pounds. 180kgs is the official weight for an F18 - check the rules for what can be included (compass, righting line) and what can't (wrench, sponge, empty beer cans). Weigh it dry and mast down to emulate weigh-in at a regional or NA Championship.

More accurate (but more difficult) is to use two scales. Balance the boat on two scales set on a hard surface. Mast down.

The scales' error is additive. If each scale's accuracy is +/- 1 lb, that means 4 scales = +/- 4 lbs; 2 scales = +/- 2 lbs. Just because the display reads to the 0.1 lb doesn't mean it's accurate to that amount. Calibrate the scales with a known weight that's close to the expected weight of the thing you're weighing. (For an F-18, 2 scales = 200 lbs each).

Load cells are still the best (most accurate) way to weigh boats.

thought he said "how to weigh it" ... not "how to make love to it"

Have you seen him sail?

Thanks folks. 2 scales was my goal as I'm just looking for a rough weight, nothing official. Don't want to go out and buy a bunch of scales just for one go.
Jdub, I'm not sure what to say to the "rub it" thing. Kinda makes me glad I didn't buy that boat from you after all.

Huh ??? Why so difficult with 2 or 4 scales?

Just place the cat on the trailer and lift one hull up somewhere in the middle. then you shift a box or something else with the weighting scale on it under the hull.
Do the same on the other side (on the same place of the other hull!

Add and done!

accuracy = 2 x scale accuracy + 2 x reading accuracy (only with analog scale)

That sounds nice and easy.I like it. Have you tried it that way?

Yes, I've done this numerous times.
Only problem with being single-handed, you have to shift the scale+box with your belly under the cat.

(for me, having no belly at all, only muscles, tht's difficult)

I've got plenty of belly, no problem. If you need some let me know.

This method is likely to produce errors. It is essentially a three point lift with one point on the scale. Then doing a mirror image on the other side.

Theoretically, it could work if everything is absolutely level and there are no torquing forces between the beams and hulls.

Fat chance of getting all those variables out.



Like Matt says, two scales will do it. All of the weight on one or the other scale at the same time. Calibrate beforehand with a known weight close to what you will be weighing.

Mast up is OK if there is no windage. Even then, if you read both scales at the same instant you will be fine.

If your trailer is symmetric and you place the scale under exactly the same point of the hulls, I don't see any inaccuracy.
Even if you miss some centimeters or having it not exactly balanced on the same level, the theoretical fault you make, is neglectable and falls problably within the inaccuracy of the scales

If you question the accuracy of a measurement, it's very easy to test this:
roll the trailer 1 meter further and start the measurement again starting with the last hull.

Check the difference with the first measurement. If it's too big, then I eat my shoe

I agree that it is about what your tolerances are.

If you are satisfied with + or - 5 pounds (10#), it is negligible.

More important is to calibrate your scale. Bathroom scales can be off by 10# at 200#. If you calibrate that same scale it can repeat within a pound or two.

if your scale can handle the total weight of the boat, "tare" (zero) the scale with the beach wheels on it, and then go roll your boat (balanced on the wheels) on the scale.

I wouldn't trust a bathroom scale at all. Have you ever seen a woman use one and believe it was correct or close?

This could work with two scales, but I want to see how you balance everything on one.

Also, you'd have to be damn precise about finding the balance point so you could let go of the boat long enough to read the scales (holding on to the boat to help balance it is going to throw off the measurement).

Yes. They always appear in line at regattas, refusing to be weighed in front of others...

Mike

The F18 scales are cart scales with four pads that give total weight and list the weight of each pad. I got my wife to stand on one pad while I stood on another telling her it was a combined weight and her not knowing the pads also listed separate weights.

I think use of a hanging scale or crane scale is best to find boat weight. But the weighing capacity must be higher so you can able to find the weight of Boat. I mostly use my truck scales to find boat weight.