Building an Aluminum BBIII - what modifications would you make circa 2017
- Thread starter Troy Brown
- Start date
Bill Clark
Well-known member
Alweld boats out of Lonsdale,Arkansas builds custom commercial jon type boats. Perhaps they could build something in the marsh series that would meet your requirements then you could deck it over in glass over wood for a custom gunning rig. Just a thought.
Yes there is a difference and its a major difference at that. USCG standards test to 2 stroke. ABYC standards test to 4 stroke. and what the boat will legally hold depends on more than just the first calculations being done. However for a custom build home made boat you will be fine. Hope this info helps.
Its all about floatation. If your building this from aluminum you will need even more floatation due to the material your using buoyancy factor to begin with. a wood boat would be much easier to meet ABYC standards than a Aluminum one because woods Buoyancy factor is Huge compared to a metal boat with a negative buoyancy factor.
here is the USCG weight tables for outboards.
http://newboatbuilders.com/pages/table4.html
and the ABYC tables. which will at some point become the new standard I am certain. Its just a matter of time.
Understanding the hull shape in relation to how you want the boat to perform should be a primary consideration before deciding on a design. You may want to do some thinking about what you want in the boat.
Additionally, I'd be sure to guarantee that commercial builder you are paying to build the boat will take care of the flotation considerations and USCG capacity plate for the boat. (Also it seems like you should make sure that it doesn't leak on delivery.)
Troy Brown
Member
Now I have to pick a motor. I've looked and Yahama, Honda, Tohatsu all have 30hp and 40hp (new) but no 35hp. The weight for a 40HP 4 stroke is 223lbs, 214lbs, and 209lbs respectively.
Any idea how much weight you'd save on a used 2 stroke?
Troy Brown
Member
Agree. I want the planing hull shape of the bbIII vs. the displacement hull on the bbII. i'm rarely in 'rough' water more than 1' in height, and I want to get from my house to 'my spot' fast - about 2 miles away.
what do i want in the boat? the following:
2 dozen duck decoys
4 goose decoys
my momarsh seat cushion
my gun
my duck 'go bag' (ammo, 911, hot hands, food, flashlight, range finder, calls, extra gloves, water, etc.)
my ghillie blanket (which I toss over everything)
gas can
battery
paddle
retrieval stick
anchor
wet weather coat
lifejacket
this was helpful. it made me realize that 'all shelves' would be a mistake. very little of this fits on shelves. I should do shelves up where i'll be hunting for all the little stuff.... but in the back, i think i'll do more like a 'bin' with either a 2" lip (with drain holes) to hold in e.g. the battery, or a 'half door' on a hinge (or a slider) to open up and expose the storage area.
also reminds me to ensure canvas is installed far enough forward and wide enough beyond cockpit combing to create 'dry' storage on the deck, under the canvas, for bulky items like coats.
#awesome great input!
By the time enough floatation is put in this boat for USCG standards (if you require it) there won't be much storage room left. Made from Aluminum that is. It will require about 6 cubic foot in the transom area. another 3-4 cubic foot along the sides and another 3 cubic foot in the bow to support level stability and that kind of HP. Our 14ft Predator sneak boat has roughly 13 cubic ft of floatation in it to rate for a 15hp 4 stroke outboard via ABYC standards and your doing a 40 and aluminum construction not composites. It will take some serious designing if you want to adhere to USCG standards with the build. If not then your fine as a home build boat. Or if you go to a commercial welder who will build it for you. However might be possible for a 1 off if you sign off as the builder yourself. Honestly I'd drop the HP to a 25hp thats going to be plenty of power for that craft. It will be a rocket ship with a 25hp. For example we could have rated the Predator for a 25hp 2 stroke no problem. But then it wouldn't have met ABYC standard and with everyone buying 4 strokes now that made no sense to take that risk.
Last edited:
Phil Nowack
Well-known member
Based on what BBIII's do with a 25 or 30 out of wood... it will be a stable, great boat.... but it will be anything but a rocketship.
IN aluminum it should be almost half the weight of wood. If we claim it weights 250lbs with a 25hp motor it should run between 30 and 40 mph. and thats cruising in that small boat. With a 40 it probablyu would only gain 8mph based on the calculaters we use for figuring boat speeds. is 8mph worth the extra 1500 plus for the motor and all the lost space for the extra foam?
Phil Nowack
Well-known member
It will not be half the weight using 3/16" .... Over 30.... show me.. Especially with the payload... sorry. not happening.
I have been in know people that weight nearly 100# less, and carry a fraction of that gear, and do not hit 30 mph with a 30hp...
I have been in know people that weight nearly 100# less, and carry a fraction of that gear, and do not hit 30 mph with a 30hp...
Last edited:
I would assume only the hull would be 3/16th the sides and deck would be 1/8th at most. and all stringers etc would be drilled to reduce weight where ever possible. After all if he is going to build this rig it should be done right. And if done right he should be able to hit the 250lb weight or close. We build the Predator in glass in this range and they are very similar boats in size. It would not be economical or wise to build the whole boat from 3/16 at 85lbs a sheet. the boat would weigh 500lbs and create even more problems for floatation requirements and foam placement not to mention HP. i couldn't imagine a 14ft boat that weighs 500lbs and has a 225lb motor hanging on the back with a 400lb payload inside with a side height of only 12 inches. If He is going aluminum he has to cut weight to be able to make up for the buoyancy in foam later.
Troy Brown
Member
So a 4 stroke Suzuki DF30A EFI Electric Tiller ATHL 30 HP weights: 163lbs.
The Evinrude Inline 2-Cylinder E-TEC D.I. 30HP weights: 150lbs, or with power trim, 183 lbs.
So 2 vs 4 and why?
Evinrude claims the following, but this has to be an over zealous marketing guy right?
AUTO-STORAGE
Extend your fishing/boating season. The engine fogs itself automatically in minutes, with no trip to the dealer. So easy, you can do it any time. In the North, you’ll be able to go fishing if you get a winter warm spell. And in warmer coastal regions, you have no worries about salt air and corrosion.
The Evinrude Inline 2-Cylinder E-TEC D.I. 30HP weights: 150lbs, or with power trim, 183 lbs.
So 2 vs 4 and why?
Evinrude claims the following, but this has to be an over zealous marketing guy right?
AUTO-STORAGE
Extend your fishing/boating season. The engine fogs itself automatically in minutes, with no trip to the dealer. So easy, you can do it any time. In the North, you’ll be able to go fishing if you get a winter warm spell. And in warmer coastal regions, you have no worries about salt air and corrosion.
Tom I disagree. By the time you seal the wood and coat it with fiberglass it will be very close If the aluminum is designed properly and especially when you take into consideration the absorption of the wood over time. A book worth reading that will answer alot of questions pertaining to all these concerns is Boat Building with Aluminum by Stephen Pollard. a great read and very very informative in regards to aluminum boat building.
And fiberglass using foam core can be pretty dang light now days as well. Technology isn't slowing down nor is the materials being used.
J.P. Ward
Member
On my BBIII I had a problem with the outboard hitting the inner corners of the sponsons. It occurred when the motor was turned full left or right and raised for shallow water. That was with an Evinrude 25HP 2 stroke. I suspect a larger engine would be more likely to contact the sponsons. If you don't have your motor to build to I would plan to bob the inner corners of the sponson to avoid the issue.
Cody Williams
Well-known member
Having built a BB3 I would personally do away with the motor well and move the motor back to the transom. That way you don't have to deal with the motor clipping the sponsons and you gain some planing surface at the rear of the hull, plus you will have more room for flotation since you have gained volume where the motor well was. That's the mod I made to my BB3, along with removing the rocker from the rear of the hull, and I was really happy with it.
I wonder if you could solve some HP vs. flotation problems by moving up to the Scaup 16? It's basically the same boat, just scaled up a bit.
I wonder if you could solve some HP vs. flotation problems by moving up to the Scaup 16? It's basically the same boat, just scaled up a bit.
Michael McCord
Active member
Why do you think you need 1/8" or 3/16" plate for your hull? Properly braced, .100" will do all you ask of it, and at a fraction of the price and weight of the other options. We have always run .100 boats in some very shallow rivers where hull strikes with logs, gravel bars, and rocks are common, with little damage to show for it.