Plastic Boats

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Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2016 at 11:28am
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I think we can all agree that the macs would be better with a much thicker and stronger transom plate. Plastic is flexible and the flexing could fatigue the aluminum over time.
Then when it gives way the plastic can't take the strain by itself.
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Post Options Post Options   Likes (0) Likes(0)   Quote MikeAqua Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2016 at 12:00pm
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Originally posted by Kevin.S Kevin.S wrote:

I don't know of any NZ aly boat builders who glue hulls together though and it was a glued joint that failed on that boat.


Welded one side, glued the other.  Supposedly the only adhesive failure they have had.
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Originally posted by OneWayTraffic OneWayTraffic wrote:

I think we can all agree that the macs would be better with a much thicker and stronger transom plate. Plastic is flexible and the flexing could fatigue the aluminum over time.
Then when it gives way the plastic can't take the strain by itself.


Pouring reinforcing resin into transoms on old fibreglass boats seems to be a well-used technique. 

I wonder if something similar could be done with roto-moulded boats? 

The transom is two skins of plastic.  If you can fill the gap between them with something non compressible , then flexing won't occur.

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Post Options Post Options   Likes (0) Likes(0)   Quote lemmy Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2016 at 12:17pm
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Originally posted by MikeAqua MikeAqua wrote:

Originally posted by lemmy lemmy wrote:


As far as I was aware they still hav,ent invented a plastic that does,nt break down in sunlight


Mussel floats are made the same
way as mac boat, smart wave etc - rotomoulded polyethelene.

If you know your floats ... in the Marlborough Sounds you can still spot floats that were made in the 1980s and 1990s.

If you don't break them, they last 20 years in UV 365 days a year with zero maintenance.

Bolt an outboard on to a mussel float drive it for 5 years through choppy conditions and see how long it lasts.
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Originally posted by lemmy lemmy wrote:

 
Bolt an outboard on to a mussel float drive it for 5 years through choppy conditions and see how long it lasts.


If the float is in one piece (i.e. you haven't cut it in half) and the outboard is attached to the handle you would be surprised.  5 years boating is probably only 250 hours planing time for an average trailer boat.

I could just easily say drop a fibreglass boat onto a concrete wharf from 2m high and see how it does.  A mussel float will routinely survive that.

My point is, you can make something mechanically  tough that lasts and resists UV from roto-moulded polyethylene.  There is nothing inherently wrong with the material.
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Originally posted by MikeAqua MikeAqua wrote:

Anyone been in a 5.7M Macboat?
Yes been out in an older one when looking at buying a 420 to check out years ago - not that many around compared to 360 and 420 I think?
Good fishing trip nothing breaks, great trip catch fish.
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Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2016 at 1:10pm
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Originally posted by MikeAqua MikeAqua wrote:

Originally posted by OneWayTraffic OneWayTraffic wrote:

I think we can all agree that the macs would be better with a much thicker and stronger transom plate. Plastic is flexible and the flexing could fatigue the aluminum over time.
Then when it gives way the plastic can't take the strain by itself.


Pouring reinforcing resin into transoms on old fibreglass boats seems to be a well-used technique. 

I wonder if something similar could be done with roto-moulded boats? 

The transom is two skins of plastic.  If you can fill the gap between them with something non compressible , then flexing won't occur.


With old fibreglass boats rot setting into the wood is the problem. Best fixed by ripping out the whole transom and rebuilding it from scratch. 

I think plastic will still creep over time. I think the easiest solution is a sufficiently strong transom bracket, and the Mac420 bracket was known to be a bit thin. Galloway reinforced it for a reason in their newer models. 

What would be the cheapest way to reinforce it? Gussets?


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Gusset should work.  So would sandwiching it between two sheets of something rigid.
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Originally posted by OneWayTraffic OneWayTraffic wrote:

Originally posted by MikeAqua MikeAqua wrote:


Pouring reinforcing resin into transoms on old fibreglass boats seems to be a well-used technique. 

With old fibreglass boats rot setting into the wood is the problem. Best fixed by ripping out the whole transom and rebuilding it from scratch. 



If the fibreglass skins either side of the rotted wood are sound, you can remove the wood and fill the gap.  I haven't used this product but I've done similar repairs to a little fi-glass boat I bought with a soft transom.

Like this https://www.youtube.com/watch?v=cLF0V2Wfs3I
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Post Options Post Options   Likes (0) Likes(0)   Quote CanadianJohn Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2016 at 2:53pm
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i think the best way to distribute the torque on the mac transom is to secure the pod/battery box to the floor. it is only bolted to the plastic longitudinal ridges inside the box. i think for the age of some of these hulls the frequency of issues is pretty low. 
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There's a pretty good shot of the transom support on the SW4200 on this link. Was wondering how it compares to the Mac as I haven't examined that part of the 420 close up.

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Originally posted by OneWayTraffic OneWayTraffic wrote:

There's a pretty good shot of the transom support on the SW4200 on this link. Was wondering how it compares to the Mac as I haven't examined that part of the 420 close up.

Nice looking boat looks like transom support spreads load more than Mac one which is quite small - heres a picture of my Mac 420 after repairs if you look carefully you can see gussets added by top engine mount bolts, I then powder coated in black to match motor.
 
Good fishing trip nothing breaks, great trip catch fish.
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Post Options Post Options   Likes (0) Likes(0)   Quote MikeAqua Quote  Post ReplyReply Direct Link To This Post Posted: 10 Aug 2016 at 9:33am
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If only Smartwave would extend their gull-0wing hull design to the 4800. 

It's neat boat layout but wet as a shag.
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Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 10 Aug 2016 at 11:44am
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I'm guessing that will happen eventually. It costs a lot to change a mould, so plastic designs don't evolve as fast as aluminium ones can.


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