Composite Canoe Build

[charlie wilson]

Core Craft of Minnesota made a tri keeled chopper gun boat with Composite roll over rails.

Industry tooling guys sand out to 1500 grit before going to 3 M's three step Rub compound, buffing, machine glaze. That perfect mold surface translates into, hopefully, flawless hulls out of the mold.

The best laminated include three full fabric blankets and lots of partials to selectively reinforce where needed. Colden, Hemlock and Placid all have near thirty five pieces of fabric in their hulls. Swift hulls, with foam cores, have about 30.

 

[Beast388]

Doing a bit of infusion testing with layers of 5oz Kevlar, 5oz glass & 3mm Soric. The epoxy requires an oven cure and when completed is crazy durable.

IMG_2738-1 by bctc95, on Flickr

 

[Beast388]

My son and I finished wet sanding out to 800 grit and got one half buffed out today.

IMG_2765 by bctc95, on Flickr

IMG_2767 by bctc95, on Flickr

 

[Canotrouge]

That look really good!!

 

[Jim Dodd]

Nice !

Jim

 

[Muskrat]

Purdy

 

[Alan Gage]

That mold is really starting to look nice. Very anxious to watch this happen.

Alan

 

[Jim Dodd]

Obviously you have a great background for what you are building ! So here is two newbie questions.

Guessing Soric is the honey comb stuff, on the right side ?


Why aren't molds made of plastic, like a polyethylene. Something that epoxy, or vinyl ester wouldn't stick to ?

I know molds are meticulously waxed, and coated with release agent. It seems a lot easier to make the mold so it would release, instead of having to coat it.

Jim

 

[Beast388]

Obviously you have a great background for what you are building !

​Somewhat, yes. I actually manage the engineering department here. We did take on a large light RTM project 5 years ago that I was in charge of, which was very hands on...so I learned a great deal about fiberglass mold construction. The guys who produce the fiberglass products and maintain the tooling have mad skills...far beyond mine.

Guessing Soric is the honey comb stuff, on the right side ?

​Correct. Soric adds a great deal of stiffness to the laminate, but it is a bit heavier than other cores because it takes on some resin, or in this case, epoxy. By comparison, the Kevlar/glass 12" X 12" sample weighs 314g and the Kevlar/glass/Soric 12" X 12" sample weighs 432g.

Why aren't molds made of plastic, like a polyethylene. Something that epoxy, or vinyl ester wouldn't stick to?

​There are many of reasons. Fiberglass shops that make fiberglass parts can make fiberglass tooling fairly easily. The problem with polyethylene is the CETE (coefficient of thermal expansion). PE shrinks and grows drastically with temperature change. When we mold PE, we scale the tool up 2.5% to account for it. A part that was 100" long would need a mold that was 102.5" long. Another reason is that resin is exothermic as it cures. We see spikes of 180*F to 200*F in the curing process which is right around the temperature that PE starts to soften. I could write you a book on the voodoo magic required to form PE, but I would rather not bore you.

​Most olefin plastics (that nothing will stick to) won't polish up nearly as nice as a good FRP tool.

I know molds are meticulously waxed, and coated with release agent. It seems a lot easier to make the mold so it would release, instead of having to coat it.

​We don't use the wax/PVA method too much, although it is viable. This canoe mold will probably get sealed and coated with a semi-perm release.

 

[Jim Dodd]

Thanks ! The light is a little brighter at the end of the tunnel !

As a total amateur ! I played with some PVA, on a sample mold. I didn't like, that some came off with the part, and some stayed on the mold. It could have been something I was doing wrong !
Again, Thanks for your knowledge !

Jim

 

[Beast388]

As a total amateur ! I played with some PVA, on a sample mold. I didn't like, that some came off with the part, and some stayed on the mold. It could have been something I was doing wrong !

​Sounds pretty normal to me. Some shops don't do this, but we would buff out 6-8 coats of Partall paste wax and then spray PVA. Spraying PVA is an art...any puddles, runs, or flaws when it dries will show up in the gelcoat.

​When we would pull parts out of a mold, it was quite common to leave PVA on both surfaces. It is certainly not a permanent release. We certainly prefer semi-permanent releases.

 

[Sven]

Very interesting to see how a composite hull is made properly using a female mold.

 

[Beast388]

We got the other half buffed out today and then I started working on the foam profile for the infused gunwales. The heavily beveled profile will be easier to wrap in two layers of Kevlar, but will make attaching thwarts and the yoke more of a challenge. The more rectangular profile should work well for the attachments, but will more difficult to wrap. Thoughts?

IMG_2775 by bctc95, on Flickr

IMG_2776 by bctc95, on Flickr

​The mold is ready to seal and release. Getting close!

 

[Alan Gage]

Since you're into composites you could also build carbon over foam thwarts and yoke and glue/fiberglass them to the hull. Then the profile doesn't really matter. The seats could sit on cleats epoxied to the hull.

Another option is to figure out now where the thwarts and yoke will go and mill the foam gunwales to alter the profile in those areas for easier attachment.

20170102_003 by Alan, on Flickr

Alan

 

[Cruiser]

What Alan just posted is exactly what I have done on each of my builds, use a thinner gunnel and just widen it at the attachment points, of course I was using cherry and not composite, but it works well.

On my last build I decided to mount the thwarts and yoke from the top, instead of the more traditional bottom. This gives me a bit more room when sliding packs in and having the yoke mounted that way, puts the load on the building materials/gunnels, instead of the attachments. So far I haven't found any drawbacks to this.

For my next build, I am currently evaluating composite materials for use in the gunnel/thwart/yoke/seat areas with the goal of dropping some weight in that area. With a top mount for the yoke and thwarts, I am planning on eliminating the "bulge" I currently use and just angle the fastener to pass through the yoke/thwart and then through the gunnel (outside to inside). That's a little more difficult with the bottom mount, but with a top mounted thwart I think it may be easier.

Just a thought.


Brian

 

[Jim Dodd]

On my last build I decided to mount the thwarts and yoke from the top, instead of the more traditional bottom. This gives me a bit more room when sliding packs in and having the yoke mounted that way, puts the load on the building materials/gunnels, instead of the attachments. So far I haven't found any drawbacks to this.

For my next build, I am currently evaluating composite materials for use in the gunnel/thwart/yoke/seat areas with the goal of dropping some weight in that area. With a top mount for the yoke and thwarts, I am planning on eliminating the "bulge" I currently use and just angle the fastener to pass through the yoke/thwart and then through the gunnel (outside to inside). That's a little more difficult with the bottom mount, but with a top mounted thwart I think it may be easier.

I often slide my canoe on the gunnels, putting it on my truck rack. If the thwarts were on top. I'd be bumping them, and that could weaken them . I like everything flush or below the gunnels. Even walking portages, might be a problem, catching brush. I may be misreading your post ! A pic might clear it up for this rusty brain !

Neither would I depend on fasteners, to hold thwarts, to a composite gunnel. I'd glass them solid, with several layers of cloth.
Just my 2$ worth.

Looks good Beast ! I to am anxious to see how this is done !

.

Jim

 

[Cruiser]

Hi Jim,

Any excuse to load a pic, lol.

I load my canoes on the truck racks as well, you may have to change the process a little, but I don't really think that is a deal breaker ... at least I haven't found it much of a challenge yet.

It's not like these are 2x4s stuck on the top of the canoe, they are tapered and designed to flow into the gunnels ... so catching bushes on portages and the like really isn't an issue IMO.

This is my Freedom 17 build I completed last summer, you can see the mounting for the yoke and the thwart ... I wouldn't need the little mounting bulges if I just put the fasteners at an angle through the yoke (and thwarts) ... so visualize starting closer to the outside edge and going through the yoke top at an angle that goes through both the outer and inner gunnel.

I would make these slightly longer to accommodate starting the fastener further out.



Since I am currently doing this part of my planning process for my next boat, I am just sharing what I plan to do to accomplish that goal. My current wood working project is almost complete (dining room table), once that is done I will ordering in some material to run some weight and strength tests on a few gunnel material configurations. I have modeled Cherry (as the base), carbon/foam, carbon/cedar, carbon/carbon/foam, glass/cedar for weight, but I need some physical measurements for each to figure what is worth while and what is not.



Brian

 

[Jim Dodd]

Thanks Brian ! I remember now. That is a beautiful build !
Testing ! I'm guilty of just charging ahead, and have paid for it ! Mostly in excessive weight.

Stiffening a hull is a requirement of the gunnels. In my book ,as well as abrasion resistance. It will be interesting to see the winner your choices!

Jim

 

[Cruiser]

Back to your original point Beast, I like the heavier sculpted profile, it just seems like a better gunnel shape from getting water out of the boat and best use of material PoV.

If you are planning to epoxy them in, then there really isn't any issue as you will just be contouring foam, which the pics show you already do well. If you plan on a mechanical attachment, the top mount would be easy, bottom, as you state, not so much.

I am following this build and learning lots about the process, for my own interest and because the next build will likely be a hybrid cedar with composite gunnel/thwart/yoke/seat and as several people here are doing, using the cedar version as a composite blank.

One question I do have, most builders seem to use cloth to wrap the gunnels, instead of biaxial braid ... which would seem to be an easier solution and use the minimum amount of material (weight pov) .... am I missing something?


Brian

 

[wingnut]

Lighter boats seems to be everyones goal. I have been keeping it in mind on my current build as well thinking towards a better way next time. My 16 foot solo's hull glassed without any trim came in at 30 Lbs which was about where I wanted to be. I weighed the ash gunnels, molded but not trimmed and was surprised they weighed 9 lbs.