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  #1  
Old 02-16-2017, 01:25 PM
Goliat Goliat is offline
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Epoxy on styrofoam fishing mini-cat

Hello all
i'm new here, so best regards for all readers. Lately i was thinking about epoxy on styrofoam, tiny, folding catamaran for fishing. It will be 3,4m long and 1,6m wide, with both hulls half-foldable for storage/transportation, and with solid deck also half-foldable. I already know how i will make decks, but i have doubts about half-hull. I was thinking about solid aluminium, lightweight frame made with square profiles and thin sheetmetal covered in xps styrofoam. Then i will cut it to have good x-section that will make stable and preety fast boat with outboard. And for surface protection thin and light layer of epoxy fiberglass, 2 layers of cloth should be enough.

So what do you think? Is it worth of trying? I have doubts mainly about epoxy delamination, cause i've little expirience in epoxy glassing. I heard about problems with delamination on styrofoam. Is it true?
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  #2  
Old 02-16-2017, 02:27 PM
upchurchmr upchurchmr is offline
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Styrofoam is very weak.
The glass will be fine and epoxy is required to bond to the foam, because polyester resin melts the foam.
All your strength will be in the glass, the foam will just make the shape. If you make a trial sample of glass epoxy on foam, you will find you can peel off the foam with your hands. The glass should be connected to the hull internal frame for strength.
There have been others who put a piece of plywood vertically down the middle of each hull, glue the foam to that, shape it, and then glass. Your connecting frame needs to attach to the plywood. Or the aluminum frame if I understand it will be internal to the hull.
2 plies might be ok if you will be going slow and not hitting rocks, etc.
You can always put more plies on the foam for strength

Don't use a big motor.
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  #3  
Old 02-16-2017, 05:25 PM
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Richard Woods Richard Woods is offline
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I have sketched a hinging 3.3m catamaran, much as you describe, several times but it isn't possible to keep the weight down yet load carrying up to what you can do with a monohull dinghy.

Having said that, I still try from time to time. The weight should be 40kgs or less. My current 3.3m dinghy weighs under 20kgs. 40kgs is about the max that can be cartopped or handle ashore by one person

I'm afraid I don't think your ideas will solve the weight problem and generally you want to avoid mixing too many materials, especially in salt water

Richard Woods of Woods Designs

www.sailingcatamarans.com
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  #4  
Old 02-16-2017, 09:21 PM
mydauphin mydauphin is offline
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I have also done this before. Be careful over time most foam will absorb water, shrink and it will get heavier. Believe it or not, very light wood for framing can be amazing weight to strength if you reinforce it with glass.
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  #5  
Old 02-17-2017, 06:10 AM
Manfred.pech Manfred.pech is offline
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Simple samples: https://www.youtube.com/watch?v=YfoUhLiQzyE and https://www.youtube.com/watch?v=cIkg5VmrgLk and
https://www.youtube.com/watch?v=jPCxNw37hMc and https://www.youtube.com/watch?v=ZtxeJLM3MhY
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  #6  
Old 02-17-2017, 06:29 AM
Goliat Goliat is offline
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Thx for answers.
@ Richard Woods i'm glad that so expierienced boatbuilder like you thought about it, maybe it's not so bad idea My goal is about 60 kg so maybe ist more possible

@ mydauphin xps styrofoam doesn't absorb water, i've checked it.

I was inspired for this with this article http://www.flycarpin.com/p/diy-stand...ddleboard.html. This guy made pretty little thing with just xps and epoxy, without any frame. So with proper lightweight aluminium frame it should be ok in bigger dimensions.
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  #7  
Old 02-17-2017, 10:55 AM
Ilan Voyager Ilan Voyager is offline
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I've tried 30 years ago glass/epoxy over structural Styrofoam panels for floors. My doubts were confirmed.
For 12 to 20 mm thick internal reinforcements on compounded plywood catamarans that works, the main advantages are easy to glue and no point stresses on the very thin 2.5 to 3 mm skin.
Not so light, the foam may absorb lots of resin and the glass skin peels more than easily. There is no solution, the foam is too weak.
The main problem on hulls is peeling and extreme fragility of the outer skin to puncture. The life span is very short. After one year of use they look like garbage. If you put enough fiber, that becomes too heavy.
As Mr Woods explained, catamarans are not the best solution for a small dinghy. There is far to much surface and complications for the displacement obtained. A monohull is superior for that use of fishing/hunting and rowing dinghy and can be designed easily at 3.4m long and 1.6 m wide to offer a similar stability as the catamaran with less draft. As Mr Woods wrote a good lasting 10 feet dinghy can be made in the range of 20-30 kg, goal almost impossible to obtain with ordinary and cheap materials for a catamaran of similar capacity. The amount of work is not the same also.
A proven solution that works very well is the old technology of Dacron cloth, PVC or hypalon skins over frame, descending from the Inuit kayak or umiak.
I made with a friend as holidays all purpose boat a two persons rowing dinghy dacron on wood 3 meters long 1.2 m wide that weighted about 15 kilos. It survived a lot of abuse with minimal maintenance, and after installing some polystyrene foam blocs for "insubmersibility" it ended as boat for our children and friends' children and also survived. It must be stored now in my friend's garage, we are now old survivors with plenty of broken bones pains and the children are adults with none interest in boating.
Dacron is the easiest material for skins. It heat shrinks, can be sewed, glued, painted. The flexible paints for plastics make miracles.
A very similar design to our boat http://gaboats.com/boats/classic10.html
You should visit the web site. There are some very interesting items. The designs http://gaboats.com/boats/

To give you ideas; a step further is the foldable coracle made by the old French company Nautiraid, used by the French navy and the Legion Etrangère, a lot of marine commandos in the world and several expeditions. Not light, pretty expensive but bullet proof in any meaning of the word.
https://www.nautiraid.com/fr/coracle.html
The make also kayaks used world wide, as you can take them as luggages in a plane.
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  #8  
Old 02-18-2017, 12:36 PM
Goliat Goliat is offline
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@ Ilan Voyager, after testing some xps in various matter i must said that you all are right. Type of hull described above isn't going to last very long due to delamination. During tests i've figured out one usage of xps board. It's perfect for making sandwich panel with thin sheet of alu glued both sides. With just few reinforcing bars ( also alu sheetmetal bended in c-profile) its almost impossible to break it, and it's very light. At this forum there was someone, who used sandwich made just like above, only with ply instead of alu-sheet. Board of 3mm ply-30mm xps-3mm ply in his boat glassed with thin epoxy layer withstand an adult male standing on it, with little bend, and supports for this part was splitted for about 1,4m, so it's pretty imperessive.
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  #9  
Old 02-18-2017, 02:47 PM
Ilan Voyager Ilan Voyager is offline
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Goliat. You're describing the floors made in sandwich that you can find on planes, trucks, boats etc. Just that these floors are made with PVC foam, polyethylene honey comb and other materials but never in Styrofoam. It's light but not enough for a small boat. And not enough strong on a bigger boat.

A 3m dinghy can be made in 6mm marine plywood, around 3.6 kg m2 bare, 4.2 kg m2 epoxified and painted. It will last years.

For comparison
A 18 feet sport catamaran in compounded plywood is made in 3mm marine okoumé.
A 20 feet Tormado catamaran in 4mm to 4.5 mm okoumé plywood.

That is far lighter even including the structure that the XPS sandwich.
And it's a lot less work.
Compare the surfaces involved in a 3.4 m by 1.5 m small boat for rowing hunting fishing.
The monohull uses less material and needs far less work than the catamaran which has to 2 hulls, 2 decks, arms, connections, and platform to be made.
Now calculate the weight by m2 of the XPS sandwich (do not forget the two 500 gr m2 glue lines of the skins as foam absorbs a lot of resin) and the surfaces involved in the cata. You'll be badly surprised...Calculate also the cost of materials...ouch!
I almost forgot the 3mm doorskins you can find now have cheap glue and are unsuitable on any kind of boat.

The mono has more place, good seats (on the catamaran you are on your knees on the platform), can carry far more, and can be made rough and fast if wanted. If it's properly dry stored it can be made in exterior plywood, polyurethane glued and oil painted...Dirt cheap and simple. It's just a boat for fishing, not a luxury varnished yacht for shows.

If you want to go ultralight, practical and beautiful take an dacron/wood boat and use a clear coat plastic paint. The result is astounding. You'll be sure to have the total success. The last but not the least advantage that the materials are not difficult to find and do not require expensive shipping like marine plywood sheets.
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  #10  
Old 02-18-2017, 04:38 PM
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Richard Woods Richard Woods is offline
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My current dinghy is the Duo, built from 2 sheets 4mm plywood. The WBP okoume plywood we used cost USD17 a sheet from Edensaw of Port Townsend. We built it in two days three years ago. It is used daily when cruising. I just rowed it back to our boat with my wife and 30kgs food on board.

Of course it also sails, and can be motored (although we rarely do that)

You can see more here, http://sailingcatamarans.com/index.p...sailrow-dinghy

on that page are a few videos, including one showing me lifting it with one hand into the back of our pickup truck

The most recent is this one, showing a capsize test, which all small boats should undertake.

https://www.youtube.com/watch?v=5UtDa54AJMs

That's all why I decided not to try a catamaran tender

Richard Woods of Woods Designs

www.sailingcatamarans.com
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  #11  
Old 02-19-2017, 02:22 AM
Ilan Voyager Ilan Voyager is offline
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Hi, Mr Woods. A nice little boat. Seems to be a lot of fun. So we agree that for a small boat like a tender, hunting of fishing boat, a catamaran is not a rational solution.
A remark: you got your plywood at very good price ai the Edensaw shop in WA USA. Probably made by Joubert or some Gabonese factory. You are a very lucky guy. In most parts of the USA the shipping prices will kill any desire to use WBP or marine plywood.
There is a problem in most countries of the world; no good plywood available. For example In Mexico you won't find a WBP plywood, and if imported it will cost more than 100 USD a sheet. I find only very expensive fourth rate junk unsuitable for any use even crates because it has more internal holes than a swiss cheese. So I have renounced to build anything in plywood, even furniture.
Goliat is in Poland. What marine, WBP or high quality exterior well priced plywood can he find in this country? Can he get a WBP okoumé plywood from Joubert at decent price?
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  #12  
Old 02-19-2017, 05:48 AM
Manfred.pech Manfred.pech is offline
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Quote:
Originally Posted by Ilan Voyager View Post
Hi, Mr Woods. A nice little boat. Seems to be a lot of fun. So we agree that for a small boat like a tender, hunting of fishing boat, a catamaran is not a rational solution.
A remark: you got your plywood at very good price ai the Edensaw shop in WA USA. Probably made by Joubert or some Gabonese factory. You are a very lucky guy. In most parts of the USA the shipping prices will kill any desire to use WBP or marine plywood.
There is a problem in most countries of the world; no good plywood available. For example In Mexico you won't find a WBP plywood, and if imported it will cost more than 100 USD a sheet. I find only very expensive fourth rate junk unsuitable for any use even crates because it has more internal holes than a swiss cheese. So I have renounced to build anything in plywood, even furniture.
Goliat is in Poland. What marine, WBP or high quality exterior well priced plywood can he find in this country? Can he get a WBP okoumé plywood from Joubert at decent price?
Yes, ply is a problem. Five years ago I`ve built a shed from ext. ply for wood for the fireplace in our living room. Now I have to renew the roof because the ply is rotten though it was painted every year.
My first catamaran was built from first class marine ply 1968 and it was still going strong after 25 years with another owner and I took photos.
I have still a bit of the old marine plywood and to compare it with new pieces is shocking. Today I would not dare to build a boat from ply again.

But what about a boat from Styrofoam? First you must know that the form wherein the sheets are fabricated is oiled to prevent sticking. The sheets have to be grinded for a better bond with epoxy and you need a special tool to provide little holes into the surface to get a physical bondage as it was learned from surfboards. Further on you must choose the right material. There are soft and very hard degrees of Styrofoam. The strongest sheets (Styrodur 5000) are like wood -- and they are expencive. Last not least there are hundreds of different brands of epoxy and some are bonding better. Before glueing I have always made my own tests apart from what the storytellers said who wanted to sell their brands of epoxy.

From Fingermullet http://www.duckworksmagazine.com/13/...m#.WKmhG_JK1AJ



Today I would build a boat with AIREX or DIVINICELL or??? and Polyester. May be you have read the posts of "sailhand" here Catamaran tender to replace rib? (please scroll down to 44 and the following pages). He has built a lot of boats especially his tenders and made sufficient tests. I would like to get plans from him and follow his advice. His methods are proven simple and effective and his tenders will last longer than anything built of ply or Styrofoam.

A picture from "sailhand"

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Old 02-19-2017, 05:51 AM
sailhand sailhand is offline
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hi guys I have lived on my boat and cruised for the last 13 years. I pretty much dont do marinas at all. I started out with a monohull dinghy but couldnt put up with all the shortfalls of that type of craft. Dont get me wrong I think there is a place for monohull dinghys but I much prefer my catamaran dinghy. As someone who relies on his tender for everything I wouldnt use anything else, I have had 7 people in it for short trips and regularly have 400 litres of water and my partner and I in the dinghy no problems. its not for everyone but it definitely fulfills that role for me. It gives me more than just a relatively unstable small platform with minimal freeboard that is slow to row and tragically slow to motor. If I had no other option I would go back to that but I find my tender so much better at fulfilling what is an incredibly diverse role as an auxillary vessel. I think on a smaller yacht I would have no other option and would seriously consider one of richards small monos. For a fishing role I would never consider anything other than a cat in anything under 5 metres. The added speed, stability and range is unbeatable, and trust me Ive spent a fair bit of that thirteen years fishing. My smaller mono dinghy was difficult to move around in especially with two people. The slow speed made long range forays difficult and not being self draining it was difficult to keep clean. For fishing its a hands down misere, a self draining stable deck wins, you can use a mono dinghy and most people do, but once you've had a big stable self draining deck you wont go back. I have attached some pics of my tender used for fishing if you look on the deck I have a depth sounder, three tackle boxes, 6 rods, crab pots etc and Ive still got plenty of room. For fishing its great, and as a tender its brilliant. Check out this video on youtube for more info and to see it under oars it does row quite well.

https://www.youtube.com/watch?v=_uZaIGwQZA0

My dinghy is 45 kilos and with the wheels its great on the land as well as the water, its really easy to handle. If you want a versatile boat its hard to beat!! I think you are on the right track with a cat dinghy and if you can make it demountable and light you would definitely be on a winner!!!!
Attached Thumbnails
Epoxy on styrofoam fishing mini-cat-barra-modified.jpg  Epoxy on styrofoam fishing mini-cat-tuna-modified.jpg  
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Old 02-19-2017, 11:44 AM
Goliat Goliat is offline
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Quote:
Originally Posted by Ilan Voyager View Post
Hi, Mr Woods. A nice little boat. Seems to be a lot of fun. So we agree that for a small boat like a tender, hunting of fishing boat, a catamaran is not a rational solution.
A remark: you got your plywood at very good price ai the Edensaw shop in WA USA. Probably made by Joubert or some Gabonese factory. You are a very lucky guy. In most parts of the USA the shipping prices will kill any desire to use WBP or marine plywood.
There is a problem in most countries of the world; no good plywood available. For example In Mexico you won't find a WBP plywood, and if imported it will cost more than 100 USD a sheet. I find only very expensive fourth rate junk unsuitable for any use even crates because it has more internal holes than a swiss cheese. So I have renounced to build anything in plywood, even furniture.
Goliat is in Poland. What marine, WBP or high quality exterior well priced plywood can he find in this country? Can he get a WBP okoumé plywood from Joubert at decent price?
Here in Poland i have waterproof plywood about 8USD/m2 in 6mm thickness and 1-st class.
I'm starting to draw a folding plywood dinghy, more like wide jon boat. I went to portableboatplans.com and i found inspiration there. Main goal is to transport it inside my car, i have 1,05x1,5m of open space with backseat folded. I draw roughly some 3d model, it shold have 3,3x1,4m all mounted, so it will be quite comfortable for fishing. I hope it will weight under 60 kg being made from 6mm ply.
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Epoxy on styrofoam fishing mini-cat-f_boat.jpg  Epoxy on styrofoam fishing mini-cat-f_boat_pack.jpg  
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  #15  
Old 02-19-2017, 12:33 PM
Goliat Goliat is offline
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Quote:
Originally Posted by sailhand View Post
hi guys I have lived on my boat and cruised for the last 13 years. I pretty much dont do marinas at all. I started out with a monohull dinghy but couldnt put up with all the shortfalls of that type of craft. Dont get me wrong I think there is a place for monohull dinghys but I much prefer my catamaran dinghy. As someone who relies on his tender for everything I wouldnt use anything else, I have had 7 people in it for short trips and regularly have 400 litres of water and my partner and I in the dinghy no problems. its not for everyone but it definitely fulfills that role for me. It gives me more than just a relatively unstable small platform with minimal freeboard that is slow to row and tragically slow to motor. If I had no other option I would go back to that but I find my tender so much better at fulfilling what is an incredibly diverse role as an auxillary vessel. I think on a smaller yacht I would have no other option and would seriously consider one of richards small monos. For a fishing role I would never consider anything other than a cat in anything under 5 metres. The added speed, stability and range is unbeatable, and trust me Ive spent a fair bit of that thirteen years fishing. My smaller mono dinghy was difficult to move around in especially with two people. The slow speed made long range forays difficult and not being self draining it was difficult to keep clean. For fishing its a hands down misere, a self draining stable deck wins, you can use a mono dinghy and most people do, but once you've had a big stable self draining deck you wont go back. I have attached some pics of my tender used for fishing if you look on the deck I have a depth sounder, three tackle boxes, 6 rods, crab pots etc and Ive still got plenty of room. For fishing its great, and as a tender its brilliant. Check out this video on youtube for more info and to see it under oars it does row quite well.

https://www.youtube.com/watch?v=_uZaIGwQZA0

My dinghy is 45 kilos and with the wheels its great on the land as well as the water, its really easy to handle. If you want a versatile boat its hard to beat!! I think you are on the right track with a cat dinghy and if you can make it demountable and light you would definitely be on a winner!!!!
Wow, your boat is great. That is a great construction. So how its made? Is it epoxy on xps at whole hull? Please if you can describe how you overcome the delamination problems it will be very nice and i guess interesting for all readers. 45kg is great idea, i was looking for something near 60 kg. 2 years ago i build 3x1,6m folding cat, made of aluminium, and its great for fishing, but to heavy to be also comfortable in transport/storage/unfolding. It weights about 85-90 kg. Please describe something more about your fantastic project. Big thumb up for you.
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Epoxy on styrofoam fishing mini-cat-kat.jpg  
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