planning a 30'(ish) flat bottom landing craft

5086 Aluminum Plate. Alloy 5086 aluminum plates have even higher strength than 5052 or 5083 and its mechanical properties vary significantly with hardening and temperature. It is not strengthened by heat treatment; instead, it becomes stronger due to strain hardening or cold working of the material.

I just pulled this off the net
Almost all the aluminum smaller boat builder use 5086

 

No on the front jets. All you will do is stir up dirt.

I honestly think a hyd jack plate and jon or barge bottom is the way to go.

You just lower the plate or trim down if you get stuck. And when you build the beast, find some way to keep the buggies off the bow. Like park two way back side by side and one only in front. Seating on the sides of the front wheeler....tip down chairs maybe.

The ride won't be too easy, but you can always chalk it up to part of the experience as long as the captain can take it.

 

yeah fall guy, i figured jets would be a pipe dream, another thought as to the grounding issue... the parking scheme you mentioned was kinda what i had in mind, but a buddy of mine had an interesting idea he threw at me a while back so i guess now is a good time to share it, it may be similar to what your talking about, im not certain. he suggested a modified jack system up front. basically when underway they would be stored right on top, one on each front corner. they would hinge so you only had to swing them up and put the bottom plate on before it hit the ground. the bottom would hinge also so when the boat came free it could freely rock back. so you swing it out, jack it up and pop yourself off the sandbar. i havent really drawn it out or thought about it that much but its an interesting idea anyway.possibly even hydraulics to power it? i dunno, just spitballing.

as for the aluminum composition from what i read 5052 is capable of bending a bit more than other aluminum's. i guess i had best look into it a bit more before i make that call, i definitely want a good balance between damage absorption and raw strength.

the trim/stand off plate is going to be another issue altogether, it needs to be adaptable and yet strong enough to hold at minimum a pair of 90 hp to 150 hpmotors.

 

Outlaw Marine, Red Deer, Eaglecraft, Vancouver Island, Marathon Marine, Edmonton build landing craft, some with outboards.
Look at a PWC 3000 as gas powered winch to get you off bars, biggest feature, endlass rope, not limited by a drum

Re What Aluminum Alloy Should I Use to Build a Boat, and Why? https://info.naimormetalfabrication.com/blog/what-aluminum-alloy-should-i-use-to-build-a-boat-and-why
Just one of the numerous articles comparing 5052 to 5086, note higher strength. I believe the alloy that we used was 5086-H116, interior material 5052-H32
You can just look at again numerous aluminum boat building sites and many will quote their alloy. Or just type in best alloy for boat building, or compare properties of 5052 vs 5086
If you make the call to use 5052 you are flying against the wind of the thousands of 5086 boats in service, but it is your choice.

You will note the mention that 5086 is slightly harder to bend without cracking. This is true but our bottom die width was about 2 1/8 inches, which is quite narrow for bending 1/4 inch
90 degree bends, so we just did a couple of bends about 3/8 inches apart. This really only comes into play when bending stringers, the 1/4" - 90 degree issue.

If the major small boat, say up to 40 feet, use the 5086-H116, you may as well follow their experience. Eagle craft used to post a picture when one of the boats ran into an immovable object and the 5086 was almost inverted at the bow of the boat, with no leakage.

Make the hull flat bottom, lots of reinforcing, if running and encountering lots of rock impact or groundings, add UHMW, you will see this in some of the pictures, you may need some steering strakes on the flat bottom though with the outboard PROPS there is less chance of a victory roll, or slipping sideways through a turn. Also make it as wide as what you can tow in Alaska. Not sure of wide load regs. In some states and provinces you can buy a overwidth permit for a year for $100 and tow up to 10 feet without issue. If so, build wider than a standard 8 foot width for easier weight carrying capacity, ie less fuel comsumption

There should not be any issue getting off an on a boat when the use is for hunting and fishing, just put someone in waders. Obviously the quads can run in a foot of water, your boat will float. Alternatively, lots of deeper back eddies in the river bars to select.

Horsepower estimate guess. Probably twin 125 - 150 would do the trick.

 

you see barry i looked into a lot of this stuff very thoroughly myself, then i came here to ask ppl who know more than me, while what i found on alloys may be accurate, what your saying about the industry using a different alloy is done for a reason. ill check it out at some point myself, but if its basically industry standard i doubt i will be going against that grain.

i also agree with you that i dont think grounding will be a major issue, but you learn to anticipate problems in alaska and have a backup plan for them whenever possible. its the on;y reason i mentioned it. just another minor detail to sort out.

the overwidth permit is an interesting idea, ill need to look into that.