Assuming two boats with exactly the same weight distribution and surface area, will a weightier welded boat ride noticeably lower in the water than a lighter riveted one? Seems like an obvious question, but what I really want to know is, would there be "much" of a difference...an inch or more...between the two?
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Do Welded Boats Ride Lower?
- Thread starter dsuden
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If a boat of the same dimensions weighs more it will displace more water. Since many welded boats are about twice as heavy as riveted boats they will sit twice as low, or have twice the draft.
When you are on plane the difference will be minimal and actually some heavy welded mudboats barely touch the water due to the smooth bottom and more surface area touching the water.
When you are at idle, or at anchor, the heavy boat will displace more water and sit lower.
I think that a cubic inch of water weighs .036 pounds. So find out the area of the boat actually in contact with the water. Say you have a 18 foot flat bottom 52 inches wide.... and of that length only 12 feet is in contact with the water. So 12 feet is 144 inches times 52 inches will equal 7488 square inches.
Lets say the welded boat weighs 1000 lbs. So divide 1000 by .036 pounds per cubic inch. You will have 27777.7 cubic inches of water displaced to support 1000 lbs.
Then divide 27777.7 cubic inches of water weight by 7488 and you have the answer: the boat will sit 3.7 inches in the water at rest.
If you had a riveted boat that weighed 475 lbs (Lowe 18 riveted) it will sit 1.76 inches.
Hence a riveted boat is usually far superior in draft at rest but up on plane has more drag and might be worse depending on how it is made and what you are comparing it to.
Now add 600 lbs of fat bodies to each and the differences in draft are reduced. The welded boat will sit 5.9 inches deep and the riveted boat will sit about 4 inches deep. So the percentage difference has closed from less than half to 2/3 as much as the welded boat.
Weight also effects acceleration and etc etc etc. Light is good... but so is strength which welded boats if done right have hands down.
When you are on plane the difference will be minimal and actually some heavy welded mudboats barely touch the water due to the smooth bottom and more surface area touching the water.
When you are at idle, or at anchor, the heavy boat will displace more water and sit lower.
I think that a cubic inch of water weighs .036 pounds. So find out the area of the boat actually in contact with the water. Say you have a 18 foot flat bottom 52 inches wide.... and of that length only 12 feet is in contact with the water. So 12 feet is 144 inches times 52 inches will equal 7488 square inches.
Lets say the welded boat weighs 1000 lbs. So divide 1000 by .036 pounds per cubic inch. You will have 27777.7 cubic inches of water displaced to support 1000 lbs.
Then divide 27777.7 cubic inches of water weight by 7488 and you have the answer: the boat will sit 3.7 inches in the water at rest.
If you had a riveted boat that weighed 475 lbs (Lowe 18 riveted) it will sit 1.76 inches.
Hence a riveted boat is usually far superior in draft at rest but up on plane has more drag and might be worse depending on how it is made and what you are comparing it to.
Now add 600 lbs of fat bodies to each and the differences in draft are reduced. The welded boat will sit 5.9 inches deep and the riveted boat will sit about 4 inches deep. So the percentage difference has closed from less than half to 2/3 as much as the welded boat.
Weight also effects acceleration and etc etc etc. Light is good... but so is strength which welded boats if done right have hands down.
krawler
Well-known member
The biggest difference that I noticed when switching from a riveted boat to a welded one was that the welded boat feels a lot more solid. When cruising through wind chop or wakes the riveted boat would flex and vibrate where as the welded would not.
It seems to me the biggest place where the weight would make a difference is if you get stuck. If you are going up some narrow channel that turns shallow and all of a sudden you are high and dry and stuck.... it is easier to move 500 lbs than 1000 lbs.
I was hunting gators with a guide who had a gatortrax 1754 with a mudbuddy motor. He was pretty fearful of getting stuck up some channels that I had no trouble going up with a light fiberglass skiff previously. His boat was superior but the weight of the rig meant if you got stuck it was a huge issue.
Of course welded boats are stronger and typically made of heavier gauage aluminum. In spite of this I think a riveted boat could be better in certain applications.
I was hunting gators with a guide who had a gatortrax 1754 with a mudbuddy motor. He was pretty fearful of getting stuck up some channels that I had no trouble going up with a light fiberglass skiff previously. His boat was superior but the weight of the rig meant if you got stuck it was a huge issue.
Of course welded boats are stronger and typically made of heavier gauage aluminum. In spite of this I think a riveted boat could be better in certain applications.
cva34
Well-known member
If your comparing rivited/welded ,same hull,same size,same thickness. and the only diff is welded or riveted there is not going to be much diff in weight (few pounds)...So draft will not change a measurable amount...Owned both and in the rough stuff I get in you can weld up a crack welded boat or tighten up a rivet or replace it now and then (thats a given) recently spent $748.00 on 9 hrs welding on my 20y old 1660 welded boat..So there not lifetime troublefree . There was not a wreck either just years of JB weld and epoxy in gouges /holes /cracks/electrolis where it sat on carpeted treated bunks..Removed all the patches with angle grinder /dremel tool/and lotsa bad words...then took to welder..I am almost finished ultra tuff inside duralux alu.duck boat paint outside..Motor hung console in ..wireing in progress...cva34
rickybobbybend
Well-known member
CVA 34 is correct about relative weight...there isn't That much difference...nothing significant and NOTHING like 2x. The difference difference in weight is in your wallet after making the purchase. And even that isn't much if you get the advantages you are looking for.
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