HDPE bottom plate instead of FG / Anti-fouling paint?

Hi all!

I'm working on a boat design, and have some (many!) questions.

Background: I want to build a displacement power catamaran or trimaran of about 20 to 22 feet. It will be in the ocean and if I finally get a #$%$% mooring it will be moored.

While I love the idea of an HDPE boat, and find the videos of plastic welding fascinating, I know it is really heavy, and my attempt at welding with a small welder wasn't encouraging.

I'm interested in it's ability to shrug off abrasion and no need for anti fouling painting. I'm wondering if it would work well to put a 1/4" skin of HDPE on the bottom of a flat bottomed plywood boat. Is there any reason it wouldn't work? I'd like to minimized my use of fiberglass and make it easier to maintain. I figure if the bottom of the hull doesn't need anti-fouling then I can just scrape and paint the sides below the waterline as needed.

I know about the thermal expansion problem and think I can work around it. I'm wondering if having stationary water between the HDPE and ply would accelerate rot? I wouldn't think so?

Thanks!

-Jeff

 

How are you proposing to attach it ?

 

Great fantasy.
Let us know how it goes.
But if you want to avoid antifouling, why not plate the sides also.
What are you going to do to protect the plywood, if not glass epoxy?
You did say it will be moored in the ocean. Right?

 

I am in the middle of a HDPE 20' cat build. The hulls are ready, working on bridgedeck structure now. Dont be too discouraged, HDPE has its advantages. Even in my small HDPE cathedral hull I can run all over Hervey Bay on days where other boats cringe on getting on the plane. Cant wait to launch the big one.

 

What is your boat's make saqa, the cathedral hull I mean ?

 

Smartwave 3500

 

You have given it a good review, I will have a look.

 

Have a look on FB groups, Smartwave owners. I think its a wierd combinatio of why HDPE is so hated here that somehow come together to actually make it the ideal material for a lazy boater who works the boat hard. Yup 10+ marks as my review

 

I guess it is also a relatively quiet boat ? Plate alloy, moreso than pressed alloy, is like listening to marbles rolling around in a can, when drifting. I think a major demerit, and I wonder whether in shallow water, it doesn't spook some kinds of fish.

 

It is very quiet, and the wave smash is very dampened underway. Very comfy

 

Clever people those kiwis.

 

The Smartwave boats do look very neat - here is a review of three of them -

SMARTWAVE 3500 / 4200 / 4800 POLY BOAT REVIEW https://www.tradeaboat.co.nz/reviews/1408/smartwave-3500-4200-4800-poly-boat-review

Although if you click on the link to the manufacturers,
Web smartwaveboats.co.nz

it takes you here instead - where is no mention at all of Smartwave boats - maybe they are no longer in production?
Advantage Plastics https://www.advantageplastics.co.nz/

 

Smartwave and Mac Boats are the two brands from Advantage Plastics. Also apparantly Macca's playground equipment. Google Smartwave or Mac Boats. The new Mac 700 is a beast and very well suited for some of my comercial aspirations

 

Anyway, sorry for the thread hijack. I think its time anyone who wants to open their mouth to downtalk HDPE as a valid boat building material should take a pause and field study the production designs in existance or be thougth a fool downunder where thousands of these vessels are actually as a matter of hard real fact are running around happy

I would love to see these experts offer a 3.5m design in "regular boat building materials" that is MORE robust, cheaper and easier to maintain, more sea worthy, that I can beach up under power on pebble stone or rock, that doesnt need any paint or finish, that is repairable in a single pass, will not be affected by UV or chemicals, that will not break if dropped, where a tinkerer can keep drilling holes to fit things and keep changing mind and repairing the hole in a single pass and drilling another, get some air off wakes and waves and land without shock (my fav ) while being cheaper to buy or build and own over time then my Smartwave 3500........then open mouth and go for the rubbishing of HDPE

https://macboats.co.nz/

Home - SmartWave Boats https://www.smartwaveboats.co.nz/

 

Saqa, I don't think that anyone on here has criticised HDPE as a boat building material?

Thank for 're-doing' the link to Smart Wave - I don't know why my link went straight to Advantage Plastics.

Would you like to post some photos of the 20' cat that you are building, or maybe start a new thread about it?