First Build Results, Questions for Second Build

A year ago I had begun designing a layout style, all composite, marsh boat for duck hunting. Here is my design in Delftship that I kicked out to a large format plotter.



I began building the boat using plascore as my core material. I originally intended to use kevlar in my layup, but later decided not to. Here is the completed boat, please excuse my lack of finish quality...I'll explain why that is in a bit (as well as the kevlar decision).







The boat turned out great, but a little heavy (180lbs) at 13'10" length x 48" bottom x 60" beam. I discovered that the resin was leaking through the Plascore sheathing into the cells. I contacted Plascore and they made it right by sending me all new material (the correct product) for free including freight. However, I was so far into the project that I decided not to use the kevlar as it is very expensive and I knew I was going to build another boat. Thus I decided spend the least amount of time required to complete it (hence the crude finish work). I had to at least get it out during duck season.

You can see from the way the boat sits in the water that I've lost a considerable amount of displacement due to the rake at the stern. The next build will be a true planing hull and a lot lighter due to:

• I've had practice with hand layups, thus using less resin
• Plascore sent me the correct product
• I have more funds for this build as I have leftover materials and I don't need to purchase more material from plascore.

So questions for my next boat build...

• My original layup used 12oz biaxial tape for the seams (inside and out). Would it be feasible to use 5oz kevlar tape instead?
• With payload being crucial, does anyone have any hull design suggestions that might increase performance. Notice the mud motor, would a tunnel hull be better?

And before anyone asks...yes, we killed ducks.



Thanks in advance for any constructive advice and feedback.

 

Whoa !

Looks good. Any secret weapons like a dog boarding ramp ?

And be careful with Kevlar. Its plenty strong in tension and abrasion resistant but it also wicks water and is very tediuos to work with and repair. So tediuos that you normally burry it under a thin layer of eglass

Sglass is one level up from eglass. You might investigate . Sglass is a bit rare so it doesnt come in a wide variety of cloth weight. Carbon is also a good choice.

Fiberglasssupply . com is a good contact

http://www.fiberglasssupply.com/pdf/reinforcement/KnittedFabrics.pdf

 

There's no dog ramp as I don't have one. However, my buddies do. Their dogs like me as they only get short retrieves. I thought about getting a dog, but decided to let my friends pay the chow bill. I will say that the side compartments are very nice. I can fit three cased shotguns and more in each one (though I just keep one in there ^_^). It's nice having things out from underfoot when motoring in the dark.

I agree on the kevlar, it was to be covered in glass for the purposes you mentioned. I know it's difficult to sand making repairs tough. What I really need it for is breaking ice (we crush it) and need something very rock solid for this. I have been buying my stuff from Raka. I know they have a limited selection of S-Glass, but will check with fiberglass supply. Thanks for the info.

 

Hmm..Ice breaking. Id go glass or sglass. Kevlar is just so difficult to repair.

It is possible that you design your kevlar ice smasher strips, pads to be easily removed .

As in ...cover your cured and faired eglass chine seams with non stick brown Mylar tape. Laminate kevlar with a thin layer of glass ontop of this Mylar coated hull surface, , let cure...then remove, trim up and refit to your hull with sikaflex or similar.

This is how we fabricate seasonal dockline chafe guards on the shear clamps of supeyachts.

 

Use PE strips on the outside. They will wear, but are replacable.

Also, saving on the seams will not get the boat substantially lighter. You will need to look at the total package to save considerable weight.

 

Hmm...what is PE

Polyethylene

 

If there's one thing I've learned about being here is that everyone has an opinion (right or wrong) so I'll share mine hoping that it's not too erroneous. I read the plastacore web site and see they tend to advocate Kevlar, so I can understand why you might be persuaded to go in that direction. With a rather small project like this one the cost shouldn't be prohibitive, but I would ask you what benefit could you expect to realize in terms of weight savings when making this switch?

Personally I don't see the cost / benefit ratio being in your favor, so I'd like to hear your rational and or expectations.

As to the hull design might I suggest making the run aft to the transom flat as I've shown. This should give you better performance then your current design by increasing floatation, decreasing draft and improving speed.

While a tunnel hull might seem a viable option your use of a longtail sort of negates any benefit that might be derived from such a drastic change in hull design. Not to mention that it increases surface area, increases build complexity, increases weight over your current design, and increases draft all of which would prove determental to your service requirements.

MM

 

The weight savings would help because we frequently pull our boats over one levee to access another pool in the marsh (they're divided up into sections). This can be pivotal in the day's success. We also have to hand launch onto shallow rivers at times. I will admit...duck hunting is the dumbest thing I do voluntarily.

I completely agree. I had planned to change the design to a full planing hull.

Now that you mention it, the idea of a tunnel hull with a longtail does seem silly. Had I a surface drive or an outboard things might be different.

As to the kevlar debate, maybe I should have specified what my original layup was to be.

Inside: 6oz glass + 12oz biax tape + 6oz glass
Outside: 6oz glass + 12oz biax tape + 5oz kevlar + 6oz glass + graphite hot coat​

On the first build, I substituted the kevlar with 6oz glass. I had already purchased the kevlar but didn't use it. As I said, I already knew I was going to build a second and saved it for that.

My thoughts on the tape are this. I currently have on the boat roughly 50 yards of 12oz biaxial tape. I'm no math whiz, but one would think that 50 yards of 5oz kevlar would be lighter than 12oz biaxial. Every pound matters.

I am curious of the fact that everyone seems to say glass would be better than kevlar. I know you're concerned about this from a repair standpoint but I will say that I had a 14' four rivers polyester boat that crushed ice and didn't need repair. However...I was always nervous about it. Regardless, I always planned to have a layer of glass over the kevlar.

I know I may be over-engineering my boat, but I figured go big or go home (and sit around drinking beer). If I'm going to try and make the lightest, most advanced and feature rich boat possible; I shouldn't skimp on materials. I guess now the question is, what would be the most ideal (screw cost effective) layup you can think of? Don't forget that this is stitch and glue...

 

Duckboats and flatsfishing boats are similiar in that they must be super quite...no wave slap on the hull form to scare away the fish.

Why a blunt, over hung bow ? They are noisey...gurgle and slap.

 

Keep in mind that replacing 6 oz glass with 5 oz aramide does not have a weight advantage. The aramide will take more resin.

 

I get the idea about saving weight but in my previous post I was thinking of the weight difference between the two types of tape material, especially considering you mentioned this being stitch and glue type construction, or at least that was what I inferred from your description.

My thought exactly.

Since we all know boats are a compromise lets examine your lay-up schedule with an eye toward minimizing it's weight without sacrificing too much strength.

You listed your lay-up as

Inside: 6oz glass + 12oz biax tape + 6oz glass
Outside: 6oz glass + 12oz biax tape + (-5oz kevlar) 6oz glass + 6oz glass + graphite hot coat

If I wanted to keep this Ultra light I'd consider
Inside: 12oz Biax + 6oz glass
Outside: (#1) 12oz Biax + 12oz Biax or (#2) 12oz biax + 6oz glass

(Since I'm NOT an epoxy guy this would be about my mimimum lay-up using polyester resin)

Actually if this were me I'd probably use 50" wide 1oz matt and 1708 biax and forget the tape except for tabbing in bit and pieces.

With all of the bulkheads, flooring, seating, decks and compartments that have been added you've dramatically increased the total interior surface area and rigidity of the hull but at a considerable weight gain. BTW It's a beautiful piece of handy work! But on the other hand you have to ask yourself is it ALL absolutely neccesary? In other words is there anything you can leave out or simplify in order to save weight?

To me the most beautiful thing I can design is invariably the simplest most elegant solution to a problem. This might be a case where the KISS principle can be applied to good effect.

Now I have a question...do you have any good recipes?

MM

 

The marshes we hunt don't typically have big swells that push against the boat all day. That's a problem for guys in big-water layouts. The flat blunt bow was so that I could tie down more gear on the front and push over vegetation. As for fishing...I fly-fish.

My favorite is Gumbo, but the girlfriend really likes it when I cube up the duck, brine it in saltwater for 24 hours (pulls out blood). I season it like a steak then skewer it with bacon. Cook it over charcoal with a little bit of mesquite, glaze with BBQ sauce mixed with a little olive oil. Must be eaten fresh, and the neighbors fight over it.

 

I have several questions about the boat.

• 1) Can you describe in detail the construction method you employed?
  2) Do you have any pictures detailing the build?
  3) How did you treat the edges of the core material?
  4) Did you take advantage of Plastacore's Kit Cut?
  5) When you used the term tape in your previous posts what exactly are you referring to?
  
  50 yards of anything seems like a lot...unless we're talking 6" wide rolls, so I want to get an idea of exactly how you went about this build.
  
  6) Would you be adverse to using wider material which would allow you to skin the interior and exterior of the hull in one continuous lay-up?

What I'm looking for is a way to increase the strength and decrease the weight over your previous method.

I once helped a friend finish out a 25' hull he built using 2 layers of 1708 biax on the outside and 1 biax on the inside with a 3/8' balsa core. To be honest I thought he was nuts but it worked, so who am I to say how lite is too lite...lol.

MM