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All plascore honky dory

Posted by blakejd 
All plascore honky dory
December 04, 2015 06:56AM
Hello everyone this is my first post and so its a bit of an intro as well as some initial questions. I'm planning on building a Honky Dory this winter in my little shop and after pricing out the price of quality marine plywood vs shipping of plascore I'm considering just making the whole thing out of plascore. I know its been done but my searches on the site haven't come up with too many specifics. Sandy suggests plascore of 1/2 inch for the bottom and 1/4 inch plywood for the sides. Initially that seemed good but then I saw where another forum member make his boat with 1inch and 1/2 inch respectively. A little about my intentions. I will probably be rowing primarily on the Arkansas river when flows reach levels where rock hits are less likely but being the river that it is they will happen. Of course I will be putting it on many other western desert rivers as well. I know that there is no single right answer and it seems that materials for glassing the boat (fiberglass, kevlar, etc) are probably as important as the thickness of the plascore. I have no boat building experience so I'm kind of thinking this one will fall into that initial learning experience/ how far do I want to take this hobby. Thanks so much for the replies.

Re: All plascore honky dory
December 04, 2015 12:39PM
I've never used 1/2" inch Plascore. Always 3/4" inch. Jeremy Christensen built a Briggs with 1" inch Plascore for the bottom. Jeremy did a fabulous job. With that boat Jeremy earned his internet monicker--dorylad. The only problem with that boat was. Well. It was a Briggs. Back to Plascore.

The stiffness of any core material (that is covered both sides with glass) increases as the square of the diameter, while the weight increases only a little. So thin Plascore doesn't make much sense.

Larry Hedrick built an all Plascore boat (I've rowed it) that was an HD with an additional 2' feet added in the middle. Larry treated the Plascore like funny-looking plywood and attached it directly to temporary chip board, trapezoid shaped formers. I think he pre-glassed one side only before attaching to formers but I'm not sure. You could contact Larry through this forum. He reads it occasionally. He is lhedrick on the forum.

I've built all Plascore too but I do it differently. I build a plywood plug, somewhat like a concrete form. Then drape 4mil visqueen over the plug and then attach the Plascore to the plug. There are lots of photos under the one man Rowdyak section of the plans login area.

You don't need expensive plywood for the plug. You can use ordinary AC 1/4" lumber yard plywood. To get AC to bend onto formers in the front section of the HD boat, where it bends the most, you would have to wet it over night with wet rags. With more expensive plywood you wouldn't need to wet it. I use AA Marine Fir, which isn't good enough to build boats with anymore. But it works well for plugs. $48 dollars a sheet with shipping, at the lumber yard. AC is more like $27 a sheet. And that they have in stock. Once wet AC plywood bends like a noodle. Attach it to the formers and walk away for 24 hours. Then drape it with visqueen.

Pre-glass your Plascore panels on the inside surface only. Then lay the Plascore on top of the visqueen, on top of the plywood, and fasten it in place with drywall screws that go through a scrap of plywood, through the Plascore and into the plywood of the underlying plug. Now glue the edges of the Plascore panels with epoxy putty.

Wait a day. Pull all the square fasteners that temporarily held the Plascore. Now that the edges are glued you don't need them anymore. Round off any edges (where the chine meets the bottom, for instance) with a big and extra course horse shoer's rasp. Glass up the outside. Here's a note on cleaning up edges with a horse shoer's rasp. I use this tool a lot. It's powerful, key tool for me, in various contexts. I always--or nearly always--wrap the end of the rasp with duct tape, which raises the end of the rasp. Then it's easier to keep the rasp cutting only any high spots, without scratching any good-surface fiberglass below the high spots.

Pull it off the plug. The inside is already glassed. Straighten the hull. Use putty and fiberglass tape over all inside joints.

Now it's the same as a plywood covered hull, from there on out.

For a 15' foot boat I'd use 3/4" Plascore for the bottom. For a 17' foot boat I'd use 1" inch Plascore for the bottom. 3/4" for the sides.
Re: All plascore honky dory
December 04, 2015 12:46PM
How to finish exposed Plascore edges has come up as a topic in the past. You can manually round off the edges slightly with a horse shoer's rasp, slobber on some putty and then glass it with 3" inch fiberglass tape.

I bought a 3/4" high speed steel trim bit for my router and then ground its edges so they were chamfered top and bottom, so the flat part was about 5/8" inch. Put the router upside down in a home made plywood router table with a notched straight edge surrounding the bit, so only 1/8" of the router bit stuck out past the straight edge. Then I ran the edges of some Plascore seat top panels past the bit.

That slightly gouges out the edge of the Plascore while still leaving the top and bottom surfaces. Which made it possible to neatly glue on veneer like edge strip ripped off a 3/4" inch fir board. It was a fair amount of work. But it worked. The horse shoer's rasp and 3" tape works just fine. Most Plascore edges get buried so it's not an issue anyway. But for benches and seat tops where the edges might be exposed, you can finish them off neatly if you want. One way or the other.
Re: All plascore honky dory
December 05, 2015 06:08AM
Thanks for all the info. So I'm guessing for the "plug" form I am essentially making a honky dory hull out of AC plywood and then building the plascore hull over the top. If that is correct it raises the question. Should I be downsizing the plug to keep the dory's end sizing accurate or should I build the plug to the dimensions of the original honky dory and build the plascore boat the 2-3 inches larger? Lastly and perhaps most importantly before I order plascore I want to be sure I understand. You would recommend 3/4 plascore for the entire hull of the honky dory?
Re: All plascore honky dory
December 05, 2015 11:51AM
Ok. This still warrants further discussion.

I build on top of a plywood plug because that is my way of designing a new boat. It's not clear it's needed for building an existing, already designed boat. Most builders make 1/4" inch Meranti plywood sides (eventually covered inside and out with 4oz to 10oz glass). Those panels attach (with my method) to temporary chipboard trapezoid shapes that can be thought of as temporary boat ribs.

Then you pull the front ends of the side panels together at the stem. Then you pull the rear ends of the side panels together around a transom. At that point there is still no bottom but it looks a lot like a boat. At that point you can see the shape of the hull. Then you add a bottom panel that could be plywood or Plascore. Glass it up, add seats, paint it and call it a boat.

You can make side panels with 3/4" inch Plascore instead of 1/4" inch Meranti plywood. Just think of it as funny looking plywood. Follow the instructions as per plywood. Larry Hedrick built his Rio Verde that way. That method works just fine.


I like to build over a plywood plug when building a new design because it's the same as working with a full size model. I get to see what the boat looks like during the form-making process. I adjust and re-adjust widths and side angle repeatedly. Until it looks right. I build it upside down but I often roll it over to right side up so I can look at it. Stare at it. Then make some more adjustments.

When it finally looks right I drape light 4mil Visqueen over the plug and then put the Plascore on top. I'm not sure it makes sense to build that way for a boat like the HD where you already know the dimensions. In that case you might be better off to build the way Larry did--just thinking of pre-glassed (on the inside surface only) Plascore as funny plywood.

You are correct. If you build on top of a plug you end up with a boat that is slightly larger. That's a good thing. Yes 3/4" Plascore every where.


So. Ultimately you will have to decide for yourself. One final note. Jason Cajune builds drift boats differently than I do--without the temporary shaping ribs. He knows the dimensions of his side panels AND the dimensions of his bottom panel in advance. He has a convenient way of cobbling the whole thing together with a few 2x4 side to side stretcher bars. That's fabulous. Quick. Convenient. I'm not in any way knocking it. Jason builds some of the most beautiful boats ever made. But you cannot build the Honky Dory that way. The HD stays wide far closer to the front end of the boat than most other boats. And then bends in too sharply to build without using temporary rib-like formers. I like that shape. The HD doesn't knife into waves (like the Briggs). The HD climbs right up, as if it was walking up a ladder. The extra width close to the front end makes it climb like that. The HD has to be built around temporary formers because of its sharp up front side bend.

Because of its (wide) width and because so much of that width extends so far forward the HD is a unique boat. There is no other commercial boat or blueprint plan set like it.
Re: All plascore honky dory
December 09, 2015 05:59AM
Ok as i was thinking through things I realized that 5 sheets of plascore is going to come no where near enough if I'm decking the boat in the grand canyon/Briggs style. I'm guessing another 4 sheets will be necessary. So call it an even 10 sheets. Anyone who has built one able to confirm this? Also, maybe its a bit of paranoia but looking at the stations the top deck of the boat is going to be close to 78" wide. This is great but looking at the pics on this site of honky dories don't look nearly wide enough for a 6'2 dude to sleep perpendicular on the deck. I'm thinking I'm just paranoid but hate to waste money because I'm misreading things.
Re: All plascore honky dory
December 09, 2015 04:36PM
I'm 6 foot 3 and set up my last boat so I could put a small tent on the deck. I don't really see that working out trying to sleep on the perpendicular line. I found it was a waste to time for my tent set up even though there was just enough room. The only place I would sleep on the deck anyway is in the grand canyon in July. As one who does not like that kind of heat I will never run the grand in summer again.

Plascore is a problem for sure. My last order I got something like 20 sheets with several being 5X10 foot. I sold off a bunch as time went by. Shipping is such a difficult thing, we just have to eat the high costs.

If you are going to do it I would go with 1 inch on the bottom and don't hold back on the glass. I would go with 2 layers of 17 ounce triaxial glass and toped with 1 layer of 10 ounce to smooth it out, or 4-5 layers of 1 ounce plain weave if you can't get axial. I have found that a plascore boat is so light as compared to a wood boat there is no reason to cut corners on the bottom and chine where the rocks are. The plascore is hollow, so, park the boat, it's floating, then the river drops and your boat sinks down onto a sharp rock and it can poke through the glass if it's not think enough. The more fiber the less chance it will poke through. How do I know this, because I have had to patch holes and cracks on a 3/4 inch bottom with 1 layer of 17 ounce triaxial kevlar covered with 1 layer of 10 ounce plain weave glass. Another layer of 17 ounce triaxial glass wouldn't have added enough extra weight to make any real difference when you consider a loaded grand canyon boat with 2 people is 1500 pounds. An extra 50 pounds of epoxy and fabric is nothing.
Re: All plascore honky dory
December 09, 2015 04:40PM
You sure cannot sleep on a Briggs perpendicular at 6'2" in height. Consider a hammock? Maybe sleep parallel to the center line on a paco pad?

Re: All plascore honky dory
December 10, 2015 02:04PM
The boat I'm working on will be something like 88" inches between the oarlocks. Is it really that much? I'm still in Chicago. Still. What ever it is you could put an aluminum frame cot sideways to the long axis. And sleep like a baby.

On a Deso trip 3 years ago I only brought an air mattress. The water was so high we ended up sleeping on the rocks half the time. That was not good for my old man's back.
Re: All plascore honky dory
December 10, 2015 06:20PM
Mattress huh? Thats living in style. Which is what boating is about in the first place. "strong back" is under construction and plascore order is complete!
Re: All plascore honky dory
January 17, 2016 01:15AM
So the boat is underway. However a few hiccups and problems of already occurred. Anybody has suggestions for the best solutions to these problems that would be fantastic. First I didn't realize when cutting in joining the plascore that I would be 8 inches short of the 16 feet for my hunky-dory. Is this 8 inches a negligible amount? Perhaps I should join on another 8 inches to the end and then fiberglass that small section. The other hick up is that I managed to use too much epoxy when fiberglassing my my plascore. Being that it's the first sheet I'm guessing that it's OK to simply Sandown the excess epoxy and continue on more carefully with the next couple layers. Final question how do you go about determining layers of fiberglass? If I'm building a decked dory I assume the interior needs only one-two layers of lighter glass but for the exterior how heavy and how many? Do you need to glass both the bottom and sides with equal amounts or is it common to have say 2 layers on the sides and 3 or even 4 on the bottom? Thanks.
Re: All plascore honky dory
January 17, 2016 07:50PM
Many of the builders who participate here use fancier layups involving stitched bi-axial and tri-axial this and that. I won't go there. I'll let them chime in.

I try to keep it simple. I use what ever fabric I have on hand. I've used everything from 3oz to 12oz in various widths. Right now I have a half a roll of 3.5oz 38" inches wide.

On a wide bottom I make overlapping diagonal rows in opposite directions, building up 4 layers on the outside bottom. 6" inch and 3.5" tape over the chine builds that up to 7 or 8 layers thick over the chine.

On Plascore I do 2 layers on the side. Inside and out. Same for the deck. 3 layers inside bottom.

I don't build over plywood any more. But when I did I used less glass than that.

RE> " eight inches short " ............ add some more Plascore and glass it up. It's better to get what you want.
Re: All plascore honky dory
February 28, 2016 02:37AM
Well I'm laying the fiberglass on the bottom and looking forward to putting everything together on the temporary ribs when I realized I may have another hiccup. I built the bottom with two 4x8 sheets of plascore and then attached "wings" to the sides of those to accommodate for the area where the bottom would be wider than 48inches. The problem comes in that the transom is supposed to be cut from the aft end of the bottom and it looks a little tight to get that piece out Of the sheet. Has anyone who's built the honky dory confirm that there is enough material there?
Re: All plascore honky dory
February 28, 2016 02:50AM
I'm out of town, poking a cell phone. Gonna see and photograph at least one ptivate, historic fly collection cool stuff

Had a boat design dream last night. Gonna make a cupped pear shaped fiberglass depression that becomes the rowing unit. With adjustable foot pegs, sliding seat and wood/fiberglass wings for oar lock pins. All as a unit. Drop that onto and into the decked boat. Close my eyes and I can see it.
Re: All plascore honky dory
February 28, 2016 11:07PM
Good feedback. I am going to keep bulkheads to a minimum. I've been on boats that had too many small compartments. Then it is a puzzle figuring out how to fit all the coolers and dry bags. Seems to me you only need enough 2 keep the deck from sań£ging. I might still do a pop off deck too. I did that on my little one man and it worked just fine.
Re: All plascore honky dory
February 29, 2016 05:42AM
Thanks for the great info. I ordered 10 sheets of plascore figuring that 4-6 sheets would be eaten up building decking and hatches etc. The whole project is at a bit of a standstill right now with my recent wedding and a new position at work but I'm hoping to glass the bottom and attach everything to the temporary ribs in the next few weeks. Once I get it looking a bit like a boat I will try to post op a picture of progress. On a side note George the rep from plascore was passing through town and stopped by to say hi and take a look at the project. Gotta say that the customer service from plascore is pretty damn nice. He seemed to be impressed with the quality of my joints between sheets which made me feel a hell of a lot better about the quality of my amateur work.
Re: All plascore honky dory
November 16, 2016 03:38AM
Well I'm finally at the point of glassing up the bottom of the boat after a long hiatus that involved, marriage, laying hardwood floors and many other home renovations. So now after glassing up the sides I realized that I somehow either purchased 52 inch wide glass or was shipped the wrong thing. Either way what I have doesn't cover the bottom and definitely doesn't overlap the chine. So I will have to overlap each layer with multiple pieces to completely cover it. Question being are there any do not's? I figure I have a few options.

option 1: Lay the glass right down the center stem to stern with gaps on each side and then add a couple short strips of glass to cover the bottom and chine over lap on each side.
option 2: offset the layer to one side so that it overlaps the chine on one side and then add a thicker strip to the opposite side and then reverse the process on the second layer.
option 3: Sandy had mentioned above laying the glass at an angle overlapping the layers. If I do 2 layers in opposite directions this should create an X of overlapped fibers through the bottom of the boat.

Any ideas of the best way or warnings for theses methods. I'm sure they would all work but if i'm gonna do the work I would prefer to do it the best way.
Re: All plascore honky dory
November 22, 2016 03:54AM
Thanks tungsten. I got her mostly glassed up nearly running out of epoxy. I went with option 3 from above to create an angle for the 2 layers. That heavy biax really sucks up epoxy and has a tendency to bubble up and or not absorb epoxy. It left me with a lesson well learned and a fair bit of repair/touch up before moving on. Hoping to get it taken care of before christmas so I can get her flipped and get to the fun part of designing the inside of the boat.
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