Bunk board replacement with HDPE? Yea or nay?

[Jermy-Jinky]

So, I'm working on rehabbing a 16' 1990 Thundercraft bow rider that my wife bought me as a gift...that project is on another thread. What I found during my inspection of everything once it got home was that the trailer needs some TLC too (insert surprised face). There are supposed to be carpeted bunks that cover the wheel fenders (one is missing), and the main carpeted bunks need to be replaced as well as the guide rollers, some lights, winch strap (probably the winch too), etc... Long story short, we had just moved into our current farm house in February and the previous owner had left behind in the barn a huge sheet of 3/4" to 1" thick HDPE (I haven't taken exact measurements of everything yet, but it's big). If this HDPE is the size that I need to make these trailer repairs, would it be appropriate to use in place of lumber? Would I need to/should I carpet it?

 

[Scott Danforth]

nay.

no structural strength to hdpe

hdpe would make a good slick surface, however you need wood underneath to support your boat

they make hdpe or uhmw bunk slides that get nailed to the top of bunk boards to not use carpet

if your boat is light enough, you may be able to make a 4x10 out of the hdpe plate by bolting sections together and stand them on end. however the material will creep after a while in temperatures higher than 80

 

[Jermy-Jinky]

nay.

no structural strength to hdpe

hdpe would make a good slick surface, however you need wood underneath to support your boat

they make hdpe or uhmw bunk slides that get nailed to the top of bunk boards to not use carpet

if your boat is light enough, you may be able to make a 4x10 out of the hdpe plate by bolting sections together and stand them on end. however the material will creep after a while in temperatures higher than 80

Thanks, Scott! I did notice that even with it being about an inch thick, it still has a bit of flex to it. So if I use lumber for a base, I could top it with the HDPE instead of carpet?

 

[Scott Danforth]

So if I use lumber for a base, I could top it with the HDPE instead of carpet?

yes. just countersink the screws. make sure the screws are stainless

 

[Jermy-Jinky]

Awesomesauce. This boat is going to be a dream to load/unload. I'll be able to launch just by looking at it sternly, especially after I get the hull buffed out.

 

[89retta]

I installed some half inch on our bunks. Countersunk the stainless screws. So much easier launching or retrieving

 

[dingbat]

The problem with HDPE in this type of application is it's excessive thermal expansion of 0.00011" per inch, per degree F

0.00011 x 50°F temperature change x 96" long sheet = 0.53".......

Must allow for movement as the material expands and contracts with temperature by slotting the mounting holes. Need to machine slotted "pockets" to accommodate pan-head screws and fender washers.

In comparison, PVC has roughly 1/2 the expansion of HDPE.

 

[Jermy-Jinky]

The problem with HDPE in this type of application is it's excessive thermal expansion of 0.00011" per degree F

Must allow for movement as the material expands and contracts with temperature by slotting the mounting holes. Need to machine slotted "pockets" to accommodate pan-head screws and fender washers.

0.00011 x 50°F temperature change x 96" long sheet = 0.53".......

PVC has roughly 1/2 the expansion of HDPE.

So would you say a 1/2" slotted screw hole would be sufficient?

 

[dingbat]

So would you say a 1/2" slotted screw hole would be sufficient?

Depends on the temperature variability.

A 1/2" slotted hole would accommodate up to a 50 degree delta T