Building a new cap

[Grand@ndy]

Hey everybody. I’m looking for a little bit of wisdom on building a new cap for my boat from scratch. It’s a 1970 flatback this is a 3 part hull. I picked the boat up cheap.Floor stringers and transom rebuilt. No cap.Needs body work and paint/gel coat. I was thinking about using Coosa or expanded PVC sheets. I would like to be able to screw hardware into the coring. I’m leaning towards expanded pvc sheets. Due to easy availability and pricing. Coosa is Extremely expensive. I’m trying to steer away from wood. If anyone has words or pictures of how they built there’s that would be great.

[Duffy1470]

There is an example on this site of someone doing that and the process was backwards, starting with the combing (never actually written this word so may be wrong) first. If memory serves they used a strip of pvc board. Search this site I think you will find what you're looking for.

[Grand@ndy]

Thanks for the response. I’d like to introduce myself. I am a certified marine technician. I work on Mercury, Yamahas and Suzukis Outboards. Been doing it for close to 15 years. I have an extreme amount of boating experience, not including The time that I’ve spent fishing off of boats not just working on them. Came across this boat because someone wanted to get rid of it and honestly, I’m gonna put an engine that comes right out of my garage on it and go fishing. Just looking for some helpful advice when I comes to backyard fiberglass work.

[Duffy1470]

Good luck with your endeavors. This site has some good folks and lots of info.

[dbiscayne]

Not sure if resin will stick very well to expanded pvc boards unless I'm thinking of something else? Might be better of with something like divinycell, cheaper than coosa but probably more than the pvc. Won't hold a screw like coosa though without extra backing.

[Duffy1470]

Yes, dbiscayne is right about the pvc. Perhaps it was divinycell

[Grand@ndy]

Thanks for all the Replies. There seems to be a lot of opinions when it comes to sell your PVC board. Originally, I didn’t think it was a bad idea to use it just for the coaming boards and top. Ideally, I plan on putting rod holders. Cleats. And a bow mounted trolling motor. Which I will most likely support from the bottom with a backing plate. I am also considering using honeycomb and just backing up all the through Bolts with scrap coring from work. Now, if I did use the honeycomb, I would most likely lower the height of the original cap to hide behind the rub rail and make it flush with the hull and glass it in. This would hide the open honeycombs on the outside of the board. Then for the combing board use something thin. glass both sides and Use it to cover the other expose side of the honeycomb.

[RickK]

I used the honeycomb board (plascore) for flooring and coring for lids (tank and storage) and also to core the bottom of the front portion of the gunwale/bow where cleats would go. Anywhere that had to support something I used Coosa and glassed that into the coring. I then drilled through that and ran the fasteners through that. Even did this where hinges were mounted.


For cleat and nav light


Popup cleat - the terminals behind the cleat are for connection to the trolling motor


Some coring for the trolling motor mount RTA-17

[Grand@ndy]

Thanks for sharing your pictures. Those are extremely helpful. This is probably the direction I’m going to go. The honeycomb seems to be a light and strong coring once you laminated it on both sides. The last thing I want to do is put a whole bunch of weight high and on both sides of the boat. Not to mention pretty affordable these days. Resin and biaxle is not hard for me to get through work but coring Material I have to outsource.