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Experimental Plug for a mini-Merlin

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With this quarantine going on, I’ve got a little experiment going on in the basement. I have just enough leftover 9 oz Kevlar to make a 15’4” solo canoe. I want something fast and light I can trip with, but also with a little rocker to play around in my local lake. Northwest Canoe’s Merlin plan seems to fit the bill. I shrunk the plans so it maintains proportional dimensions at the shortened length. Being the first time I’ve ever made forms or a strongback, there was a bit of a learning curve, especially trying to precisely measure the odd form spacings with shrunken plans. Huge thanks to all the people who have posted builds here to show how it’s done in detail. The I-joist strongback works like a charm!

I really just want to make a plug to build a composite canoe, and my woodworking skills are quite novice compared to the professionals I see building beautiful things here. The Moran method calls for a foam stripper with drywall mud, and many folks seem to build a cedar strip canoe then use it as a plug or mold. Both require a whole lot of work or mess, and sanding. Did I mention sanding? There is also Rizetta’s method of a sort of skin-on-frame plug, but the frame telemarks through the finished product. The newest method by Mp214parks goes straight to the divinicell foam which might be what I try if this whole thing flubs.

Anyway, here’s the experiment: See if I can clad the canoe forms using 3mm hardboard (Masonite). It already has a smooth finish, is hopefully sturdy enough for a plug, but bends enough to form. It’s really easy to cut different size strips with a saw and can be trimmed and cut with a utility knife.

I feel a bit like Wile E Coyote in this comedy of errors, except my equipment should be labeled Menards instead of ACME. After a few failed attempts of wrapping the whole sheet around it and then trying to strip it thick like a WC, it appears that I’ll have to strip the sides with 1” strips, but I can get away with much wider strips at the top. I have an electric trim nail gun that works pretty slick to bury the nail heads. I’m Gorilla taping the backs of the strips together since wood glue just soaks into the hardboard. From some tests, it looks like I can plane down the edges and fill in gaps with wood filler but we’ll see how it goes. Hope you get a good chuckle from the fail photos!
 

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Beep Beep !! I'm pretty slow these days ! I can't believe I missed this thread !

Yes, it looks like you are you are heading into Unknown Territory !

It's good to see !

Once you have the hull assembled, I have in the past used Heat shrink plastic. but beings the Merlin has Tumblehome, it is a challenge to get the plastic to hug the mold in that area !

I love how easy the plastic makes removing the hull from the mold, and I would advise using it just on the Football area, and over the bilge. for the rest, I'd wax, or use Partal.

Remember the mold is the inside of the canoe, and doesn't have to be as smooth as say a Female mold !

I hope you plan on using some S-glass, as you find it to be stiffer than the same amount of E-glass.

Sweets Composites can help with lay up questions !

Good Luck Mike

Jim
 
Thanks Jim! I hadn’t even thought about how the tumblehome would affect the shrink wrap, shoot. Maybe a strip or two of packaging tape in that area would work? Also, how have others handled laminating over tumblehome? I’ve seen Jim’s method of tilting the canoe and doing one side at a time. Hoping I can clamp a strip or something over peel ply to hold it down.

I’ve done S-glass for the football in the past, but never for the entire hull (1 layer E, football S). Does it make a big difference in stiffness?

thanks!
Mike
 
Tilting the strong back and doing one side at a time was the best for me. You only need to do that with the first layer. After that you can clamp something wrapped in plastic, if you feel it is needed.

Again waxing with Partal should hold the cloth tighter to the hull. My complaint about Partal, was cleaning it off my male mold ( and unvarnished stripper hull.)

I can't give you a measurement of how much you gain by using S-glass, and I know one's pocket book comes into play here. I will be using it, when I do another ultralight, or composite.

At my age I'm really leaning to Light weight !

Looking forward to seeing more, especially as the weather warms up !

Going for a short Paddle today, and Missing Midwest Mtn's Spring event and Auction, this year.

Jim
 
Also, how have others handled laminating over tumblehome?

I've never had a problem with fabric pulling away at the tumblehome without having to resort to anything special.

Alan
 
I used Partal when I built my carbon copy Kite, it released OK.
I did have a difficult time to get the carbon fiber to follow the crease, the subsequent layers of glass went on easy and conformed waaaaay better than the carbon did.

If I could get 2 layers of carbon fiber to mostly conform to the crease on the Kite, I would expect you'll have no trouble with glass on any amount of tumblehome.
Do you plan to leave the stems open until the hull is off your plug? Or is your plug supremely sacrificial?
 
That’s good to know you were able to make it work with the sharp angle of the kite. And yes, I was planning to seal both stems on this kamakazee plug.
 
It has been awhile since I posted an update, mainly because this has been a really tedious process. I stripped it up with the hardboard strips along the sides and luckily could get larger sheets to fit nicely on the bottom. That part worked beautifully and I was hoping the whole boat would go like that. Alas...

I planed all the rough edges and figured a layer or two of drywall mud would make an even smoother surface. This revealed a major wave pattern between stations along the entire hull. ~5 gallons of mud later and too many hours of sanding to count, I’m almost OK with it. I’ve done “the last touch up” 3 times so I’m going to have to call it good enough pretty soon as my epoxy and materials are starting to arrive.

Knowing what I do now, I think using cedar or pine stripping on the sides and a sheet of hardboard on the flatter bottom would work really well. I imagine it’s easier than working your way to the whisky strip and it’s a one-piece smooth material.

Here are some progress pics
 

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I've never understood the logic of making a male mold, and then not making a canoe out of it !

Even Gene Jensen, paddled his plugss before they were used to make production molds.

You've gone to the effort of building a plug, or in your case a male mold, and what will you do when done ? Will you keep it as a mold, or tear it apart ?

I'm betting you could have built a stripper hull in less time and energy. When you were done using it as a mold ? You could make a canoe out of it, or sell it to someone that would !

Sorry for going off on that !

Looking forward to the lay up schedule ! Stay at it Mike !

Jim
 
I can understand not making a finished boat out of a male mold. It lets you construct your mold from a variety of materials to save cost/work and sometimes (and with some people) there isn't desire or room for extra boats. When I did a male mold I I used a variety of scrap lumber and short cutoffs to make a strip hull; wood I never would have used for anything else. After stripping the mold I used bondo for fairing and gave it a couple coats of epoxy and wax/partall before using it as a mold. No fiberglass. After laying up the composite boat I tore the mold out (should have used more partall) and tossed the broken pieces in the fire. I had hardly any cost in the mold and not much time either since stripping was fast and sloppy.

If I'd chosen to make a finished boat from the mold it would have taken more money for better wood. More time to strip it. More time and money to fiberglass it. More work to use it as a mold. More worry using it as a mold, and a lot more time and money to finish it off after using it as a mold. And when I got done I'd have two identical boats. A lightweight one I'd paddle all the time and a heavy wood one that would sit in the garage and take up space.

I did once use a male mold and then finish it off as a complete boat. It worked great but in that case it was desirable to have two identical hulls, one that was pretty and one that was light.

It sounds like maybe saving time and work isn't working so well for Mrindy but it looks like it's coming along nicely and that he's going to end up with a nice hull. Sometimes experimenting and doing something different is its own reward. Or at least that's what I tell myself when my "simple" plan turns out to be anything but. ;)

Alan
 
Jim, I do not doubt for a minute that you’d have had a cedar strip canoe on the water by now :). I’d honestly probably be at about the same point I am with the plug, unfortunately. Though it would be a lot easier to get rid of a half-finished strip canoe on Craigslist than whatever is left of this mold when I’m done. Thanks for the perspective and you hit on some my key thoughts when I started this experiment, Alan.

It’s a minimal cost invested so far, and all I have is time during this quarantine. Maybe someone 5 years from now will read this post and figure out a variation that works or scrap their dreams of a full sheet of hardboard for a plug.
 
At least If the hull sticks to the mold ? You won't feel so bad about tearing it apart !

It seems James Moran had to dismantle a foam mold, in his book about making the Kevlar canoe.. Correct me if I'm wrong ! I tried to find his book, but I must have loaned mine out.

I understand Alan's reasoning ! It didn't cost much, so it was expedible. I know that Vacuum bagged and infusion made hulls, create a lot of waste. also. This no doubt contributes to their cost !

I guess it's just not in my genes, to do that ! :rolleyes:

The four Composites I made, for myself all came off stripper hulls, that I also finished.

I alternate between Pearl, and Black Pearl regularly, on my local rivers. ( Just Last night, I paddled Pearl) I'm glad I finished both.

A paddler can never have too many Pearls ! :eek:

I apologise for getting off topic !

I hope I can make it up to Minnesota this year, and paddle with you and your new Merlin Mike !

Good Luck !

Jim
 
No need for apologies Jim, I know you’ve got nothing but positivity and advice for everyone attempting builds and it is much appreciated! I have seen used “Moran style” plugs on Facebook marketplace, so they can be reused with a bit of refurbishing. Mine should actually be sturdier as the hardboard should stay together better than foam if I don’t seal both stems.

Being really honest with myself, what I lack in tools and woodworking ability I have to make up for in creativity and risk-taking for what I want to achieve. I’m fairly handy for your average desk pilot, but can’t hold a candle to the skills folks here have. Hopefully I can entice a few on-the-fence future builders with the occasional janky, yet light and functional canoe builds I post :)

I’m really itching to get out on the water and a bit jealous you’ve gotten the pearl out already. Would love to meet up and get some paddling in this summer!
 
Try wiggle board next time bendable plywood you can get it to bend one or both directions
 
Ah yeah, that might have worked! Just googled it. Cool that it can bend multi directionally.
 
The nice thing about using a Male mold, it's a little foregiving.

I'm trying to share a few of my mistakes, so you might benefit from them !

I had a few small wrinkles, in the release film (plastic), caused by poor tape application. They were quite visible on the inside, of the hull and needed to be scraped.

On the outside, and after several layers of cloth, they didn't show .

The main thing is to apply all the full layers to the outside, and then flip to add partials to the inside.

If you do seal the ends ? Just cut them open ! You can glass them together later ! No problem !
 
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Thanks Jim! That’s a good idea to cut open the ends. It sounds petty, but sealing the stems has been my least favorite part of the composite process.

Before my last build, I saw that you used Duck brand window shrink so I tried it and noticed a huge difference between that and the 3M brand. It was much easier to get all the wrinkles out. (FWIW the 3M brand is clearer and better for window insulation IMO)

I’ll give an update on the lamination schedule when the materials come. One other thing I’m going to try is an inside layer of 3/4 oz. fiberglass surfacing veil (mat) so the foam core has something better than Kevlar to adhere to after cured. Finding mixed reviews on whether or not it works with epoxy...tests should confirm unless someone has experience with this?
 
I’ll give an update on the lamination schedule when the materials come. One other thing I’m going to try is an inside layer of 3/4 oz. fiberglass surfacing veil (mat) so the foam core has something better than Kevlar to adhere to after cured. Finding mixed reviews on whether or not it works with epoxy...tests should confirm unless someone has experience with this?

Fiberglass mat does not work with epoxy, that's what I have always been told by the manufacturer, it does work great with vinyl ester.
 
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