Thread: New Boat Project?

Done some research and things are looking pretty good. Will go for HDPE and have found a local supplier and pricing. The stuff has about 20% increased impact resistance over aluminium and nearly 1/3rd the weight.

I'm not sure what shape or type of boat to build so I think a scale model or two will be in order and on that score I've found the perfect source of material for the models too. Just happens to be exactly 1/10th the thickness I want to use and a 1/10th scale model will be a good size for fat fingers to work with.

Living & Co Chopping Mat Flexible 2 Piece Assorted Colours | The Warehouse

I suppose other things to think about would be transom height, dead rise, ...

Since I want a handy little boat I'll go for a high sided pontoon dinghy. Will maximize internal space with taller and narrower than usual pontoons, and fill them with polystyrene. Pretty much got the design sorted and should come out with a 4.1m x 1.9m hull tipping the scales at around 130kg. Got my eye on a 30HP 2-smoke with a 20" leg. Will be on the water with a trailer for about $5k.

Has this been done before GM? All the plastic welding I have seen before hasn't lent itself to me having a great deal of confidence being pushed along the water at any rate of knots...

Originally Posted by Ryan_Songhurst

Has this been done before GM? All the plastic welding I have seen before hasn't lent itself to me having a great deal of confidence being pushed along the water at any rate of knots...

Yes it has. I've done some plastic welding before and the stuff was very well glued. Like good arc welding the parent material next to the weld was the weakest. I'm planning on my usual over-engineered approach, just the way I do things.

http://www.nzhuntingandshooting.co.n...59/#post542465

Picked up a sample of the plastic to cut up and stick back together. Also had a looksie at a motor to put on the back.

Are you building some frameing into this or is it just hull and side sheets glued together with the transom holding shape?

Originally Posted by veitnamcam

Are you building some frameing into this or is it just hull and side sheets glued together with the transom holding shape?

Going for some framing under the floor and pontoons for the sides, with voids filled with polystyrene or EVA foam.

This plastic is seriously strong. Testing with aluminium of the same thickness I can easily fold and dent the ali by hand but not the plastic. I'll chop it up and have a go at welding it together. If it doesn't weld that well I'll then try the standard PE which has more give, greater impact strength, cheaper and easier to weld.

Originally Posted by gadgetman

Going for some framing under the floor and pontoons for the sides, with voids filled with polystyrene or EVA foam.

This plastic is seriously strong. Testing with aluminium of the same thickness I can easily fold and dent the ali by hand but not the plastic. I'll chop it up and have a go at welding it together. If it doesn't weld that well I'll then try the standard PE which has more give, greater impact strength, cheaper and easier to weld.

How will you do your frameing? Can you buy extrusions or somehow heat and fold to make an angle? lots of welding otherwise.

Originally Posted by veitnamcam

How will you do your frameing? Can you buy extrusions or somehow heat and fold to make an angle? lots of welding otherwise.

I'll make the pontoons, then weld the frames to the pontoons, then stitch the hull skin on. Yes, can heat and bend.

Was that weight including the motor? I'm looking for a light weight boat around 4m that I can lift over fences and carry to launch with 2-3 people so this has got me thinking. An inflatable would be perfect but spearguns are a risk. I'll watch this build with interest

Originally Posted by distant stalker

Was that weight including the motor? I'm looking for a light weight boat around 4m that I can lift over fences and carry to launch with 2-3 people so this has got me thinking. An inflatable would be perfect but spearguns are a risk. I'll watch this build with interest

A 3000x1500x6 sheet weighs about 24kg this will use about 5 sheets for a 4.1 pontoon. There will be a fair few offcuts.

Originally Posted by gadgetman

I'll make the pontoons, then weld the frames to the pontoons, then stitch the hull skin on. Yes, can heat and bend.

Ah that looks nothing like the one in the first video!

Still half tempted to go bigger but want small. Bit scary thinking that the motor and tank will be about 80kg and the hull only about 120kg. Not sure 30 geegees will be required but the next step down in power is the same weight, and the next one down would be a but anemic.

Originally Posted by gadgetman

Still half tempted to go bigger but want small. Bit scary thinking that the motor and tank will be about 80kg and the hull only about 120kg. Not sure 30 geegees will be required but the next step down in power is the same weight, and the next one down would be a but anemic.

The answer is always more power.

Hull design and loading have a lot to do with power requirements, deeper V vs flatish bottom makes a big difference to both ride/stability/and power as the lift is vectored threw the hull angle and the wetted area is increased as angle is increased.

You will probably triple that hull weight fitted out and ready to go, My wee boat is around 780kilo all up ready to go with all gear aboard tho the 4mm hull and ply floor adds a bit of weight over "normal" for its size.

40hp is definitely min powered for that weight in my hull.

looking forward to seeing this