Weighing a fish, offbeat, physicists comment?

Thread starter #1
I've tried weighing my (somewhat waterlogged) Sunfish using a person at each end, standing on a scale. Too precarious and back-unfriendly for my taste, lifting and balancing the hull while squinting at the dials. I also don't always have a ready partner, when I want to weigh.

So necessity is a mother. The following idea was stimulated by harborfreight.com reducing their price for a 50 lb. fish scale to $2.99 (item # 03194-1BKA).

1) At EACH of bow and stern, hang the fish on TWO scales that are "end to end". That's FOUR scales altogether, total price $12. At each end, the two scales should read the same; in any case, total weight is the sum of all four readings.

2) The bow handle can hang on the cross piece of a sawhorse. The stern can hang on a timber (using a web sling) put over the top of two parallel sawhorses.

Physicists and others, feedback?

Just BTW based on carrying hulls over the sand way too often and FAR, I'm guessing there's more weight (by half?) at the stern (e.g. 150 lbs. would be 90 stern and 60 bow). Hmmm, maybe I'll get a third scale for the stern.

-Steve D.
The way I read, you will hang one scale from the hook of the second scale and then hang one end of the hull from the hook of the bottom scale. If so, no that will not work. To use multiple scales, each one will need to be hung from a support and each one will need to directly support the weight of the hull. Then add up the weights on each scale for your total hull weight.

Some where I ran across a way to weigh a boat on a trailer. It involved using a scale to weigh the tongue weight and then you shift the boat back on the trailer. You measure the distance you moved the hull and re-weigh the tongue weight. You can then calculate the total hull weight. Maybe someone here knows this trick and can tell you the math formula.
Steve D. Why go to all that trouble? Take your bathroom scale out to the boat, level and zero it and then roll the boat onto its side with the scale under it at the widest point. You can the balance the boat and read the scale pretty easy. You are looking for a hull weight around 130-135 lbs., 150 pounds is over in my book. If you are much over that, you need to get the water out. (Inspection ports and time) This may not be the most acurate method, but it definately gets you in the ball park. See tips and tricks on getting the water out and putting Inspsction ports in (or www.windline.net) How-To section.

Supercub may have the simplest way since a sunfish balances on the rail pretty well.

I have weighed various dinghies many times. You don't need a person to hold the boat on the scale at either end...you can just set the end down on the scale with the boat in the upside down position. In fact, you can just weigh the boat at either end with just one scale and add the weights, as long as the boat is supported so that it is in roughly the same position at both ends when the measurements are taken(ie: replace the scale with a 2x4 or 4x4 or some similar sized object so the boat is on the same lines). If you need clearance, you can support the boat on a 4x4 on the scale and then wiegh the 4X4 when you are done and subtract it out. I think the spring thing sounds a bit over complicated IMHO...although using a "fish" scale....nice :D .

Hope this helps.

Thread starter #5
Perhaps the multiple-scales thing was a bit Rube Goldberg-esque. I realize now that my memory from high-school physics (almost FORTY years ago) has SOME basis in fact: I think that scales in PARALLEL might have achieved what I was looking for.

Anyway, using the suggested much SIMPLER scheme of one scale at a time, with upside-down 'fish, I get 110 lbs. bow and 90 lbs. stern. Taking the average, that's only 100 lbs., so I guess I have a very light hull after all. KIDDING!

Actually of course, it's 200 lbs. Yikes!!! No wonder my back is so sore.

So unless the competition is organized into weight classes AND Brewster PAVES its beaches :) much drying will be needed. Thanks, I've read the FAQs, windline, etc. and do have an inspection port and a plan. I'll be adding another port for cross-ventilation, and a 24x7 60W. light bulb.

Please support my sunfish as she slims down for summer.

-Steve D.
Steve, where do you sail in Brewster? Is there open access there? When I am there I end up just sailing in cliff pond in nickerson. I saw the access by the fishing boats but I am looking for other locations.
I would like to add 2 cents; none of the drying guides mentioned airflow as an extra drying factor. I used several methods to dry my wet 'fish. The best involved black plastic and an air scoop made from large plastic jugs. I covered the hull in black plastic. I then positioned a wind scoop to help the prevailing breeze force air into the hull. My testing (bare hand) did not detect any appreciable airflow without the scoop either cool or hot. However, once the boat heated with the scoop in place, the air flow at my exit port was generous and warm. I once used a light bulb on another boat project and burned the gel coat!!!

I put the boat inside at night, and continued air movement with a small table fan. The exhuast air remained warm for several hours after I wheeled the boat into the garage. End result after five days of drying (in extremely humid conditions) each, I weighed the boats at 128 and 129. I have a digital bathroom scale. On smooth concrete, I stood the boats on their stern on the scale. A small block of 2x4 taped to the stern (extend a flat surface beyond the rudder gudgeon) made the job a little easier.
On ebay I happened across an old hanging scale used for weighing hay bales. It has a max of 300lbs so I bought it for about $15. I hung it from a beam in the garage and by running a mainsheet from the traveller, over the scale hook and then to the bow handle, the boat balances perfectly and is easily weighed! Check out the farms in your area and you may get lucky! It works so well we had a boat weighing party at our club one afternoon before racing. Some sailors were very unhappy to find out the true weight of their boats!

Good luck with the "diet". Just keep it away from carbs and it should be slimmed down in no time!

Thread starter #10
Sailing water access in Brewster, MA

> Paul Dierze asks:
> Steve, where do you sail in Brewster? Is there open access there? When I am there I end up just sailing in cliff pond in nickerson. I saw the access by the fishing boats but I am looking for other locations.


In addition to Cliff Pond in the state park, there's also the very large Long Pond, half in Brewster and half in Harwich. Brewster side has a beach where you can launch, but no place to park a trailer. Harwich side same deal, but with decent trailer capacity. This pond has a 2-mile fetch for (usually) great breeze.

There's a small (free ramp and plenty of trailer parking) pond called Upper Mill Pond which is the middle of a connected chain of three.

The Cape Cod Bay ocean access you cite must be Rock Harbor, actually in Orleans. I launch from there and sail down to Crosby Beach, one of several in East Brewster. Then I leave the boat above high-tide (chained to a buried cinder block) all summer. This needs some kind of dolly (30 feet to water's edge, mild slope), but also limits sailing to between two hours (MAX!!!) before and after high tide, due to the half-mile flats. Same holds for Rock Harbor.

Last November I pushed the season a bit, and a full-moon storm swept away both my hull and a neat dolly I built. :-(

You can also get a trailer fairly close to the ocean (30 yards?) at Linnell Landing (Brewster) and carry/dolly across the sand, but tide limitation applies there too.

Brewster ocean or pond (but not the above little mill pond shhhh!) parking requires a town sticker, buy it at town office on 6A. Harwich pond has a fee, pay at the booth. Before June 15, all above is free. Rock Harbor is free all summer, including some limited trailer parking. But Rock Harbor has a paved ramp with sourrounding rocks, so it kind of sucks for 'fish launching.

Go to http://www.town.brewster.ma.us/ and click through to Brewster Beach Info | Brewster Beach Map.

There are other secret locations but they'll kill me if I post here. Email me when you'll be down and I'll help or whatever.

-Steve D.
hey as for drying out your hull. when i had my old boat it weighed over 250 pounds no its not a typo. i put 2 inspection ports in (one before mast step and the other behind the cockpit). the best way i found to dry it out (even better than a light) is to take a hairdryer and put it on the low setting into one port. the air realy moves and gets allot of water out. then if you have one take a dehumidifier. then take a box top and a dryer hose and put them together. put the dryer hose in the other port. put the box top in front of dehumidifier and it realy sucks the water out. i took over 100 lb out this way
hope this helps you get your boat less waterlogged
Using the existing ports on my '68, I placed a box fan blowing into the forword port, felt a draft out the aft port. just let it run for week. I wish I could lose as much weight as my boat did!
I have made a 6 inch port last week and I decided to let it opened until over next winter (of course my boat will not sail!). How many pound will it lose? Winter here is very snowy and cold.

Recomend you add the second port now, get air moving thru the hull and start the drying process. A cheap fan (less than $10) from Wal-Mart, K-Mart or discount store will help a lot. Keep the hull (with the fan or heater blowing) above freezing and out of the weather during the winter and you should be happy in the spring. Mike Kilpatrick (http://mikekilpatrick.homestead.com/dollies.html), Yahoo Goups Sunfish_Sailor (http://groups.yahoo.com/group/sunfish_sailor/) (good article in the files section) and Wind Line Sails (http://www.windline.net/index.html) all have articles on drying out a SF. It will take time, but the forced air (warm dry air is best) will speed things up some.
MG 40,

Simply keep the water out, that's why many with older boats install inspection ports. Overtime, a SF will develope leaks, just from normal use. The mast tube, dagger board slot and on older boats with aluminum trim, along the edge under the trim. The most frequent (IMHO) is the bottom rear of the dagger board trunk when the dagger board gets slamed against it from hitting the bottom (you didn't pull it up fast enough) or an object in the water. Along the edges from hitting the dock, another boat and such. Hull fractures from improper trailering, hitting rocks and stuff when beaching, and dropping the SF are another source of leaks. Wind Line Sails (http://www.windline.net/index.html), Vanguard (http://www.teamvanguard.com/2005/base/index.asp) are just 2 sites that have how to's on these and other repairs. West Systems Epoxy (http://www.westsystem.com/) has a manual on using their products which is a general repair guide.
In addition to supercubs advice, you can also leave your inspection ports open when you are not sailing. My boat sits right side up on a seitech dolly with a deck cover on it and the ports open. It is bone dry in there. The dark cover probably helps heat up the air and having both front and back port open allows for maximum venting. If there ever was any water in there (in the foam where you can't see it) its gone now. Keep it open and dry and you won't have to worry about getting a fat fish.
Be careful where you weigh you fish. Gravity varies depending on where you weigh your boat. Those clever folk who run the America's Cup discovered that their boats weighed more when they moved them from Spain to Sweden.
I've got a simpler, far more handy way to weigh my old Sunfish: Using both hands, I pick up my boat by the lip around the cockpit. If it feels light, then I assume its still dry inside. If I pick it up (or try to pick it up) and think "Holy CRAP! This is HEAVY" then I know it's got water in it. Other than that, I don't worry about it.

(of course I have two ports in mine, so it's pretty easy to look inside..... and see if it's wet. Normally, it's dry. Curiously, the only time it's been wet inside was when my inspection port was leaking. Makes you wonder why the heck I put them there in the first place, doesn't it?)