build a fiberglass bbsb

J

josh adams

New member
I am new to the site and wanted to say hi to everyone. I have been toying with the idea of building a all glass bbsb. As of rite now my plan is to build a plug out of very light plywood. One plug for the bottom and one for the top. The two problems I have come up with while rolling the projects around in my head are attaching and sealing the two halves together and i want to use no wood so there is nothing to root or delaminate. I built and glassed a Gator Boats Duckhunter a few years ago so i do have an idea what I am getting into, but I am no expert by any means. Ant thoughts or suggestions would be greatly appreciated
 
If the plywood is "very light" it may not allow the glass to come off and will tear, or it may warp under the weight of the glass and resin leaving a really messed up hull.

If you check out photos of other two part boats you will see that the top shell goes over the bottom shell like a slip fit. You will then either use resin or 5200 to glue the two pieces together.

Two part hulls have been around for decades, so they should not be a problem for any one these days.
 
If you check out photos of other two part boats you will see that the top shell goes over the bottom shell like a slip fit. You will then either use resin or 5200 to glue the two pieces together.
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The other style you will see in production boats is a flange. Each hlaf will be molded with a flat flange around the perimeter. The two flanges are then mated together and glued or bonded.
 
Welcome to the site Josh!!! Sorry I can't help on your idea of a build, but if ya try it, show lots of pics. Good luck on your build.
Dennis
 
Josh, you need to build the plug as one piece. Build the boat as you normally would and strengthen everything to handle the pressure of the fiberglas layup for the molds. Molds will be think and alot of heat will be in place during the process. Weak thin plug will only mean one thing warping. (For example the plug for the UFO layout boat weighed almost 500lbs when we were done before splashing the molds.) Once complete you splash the hull mold first. then build up the chine about 1/8" all the way around and feather the build up into the deck nicely and then splash the deck mold. Remember no undercuts unless you want more than 2 molds. The key is the Molds will only be as good as the plug work. On a Side note, by the time you get done with this project it would be cheaper to buy a boat thats already being manufactured im sure. the plug and molds will take some time and money to do them right. I would be glad to walk you through the process if you wish to talk call me 937-418-7207 or pm me. Good Luck Tony
 
Josh,
what Tony is describing is the method for making a mold, which allows you to make more than 1 boat. It sounds like he was making a production mold. When I went through the process, the mold we made wasn't nearly that thick. I built my plug the same way you would build the KARA (pine frame and laminate decks, finished with polyester resin. It worked fine for 7 or 8 boats. You can also use the plug to make a single boat by laying the glass on the outside. The boats won't be as slick on the outside, but they will be serviceable. He's right that you just build the plug as a normal boat and then create a bottom half/top half mold or one-off boat. Joints can be filled with either of the materials mentioned. I will stress the point that you can't have any edges that are undercut!

>
| bad
>

..\
| | overlap ok
/

\
.> flange, ok
/
Also, make sure you put a mold release agent between the components if you want to separate them later! We used PVA, but that may have changed (it's been 10 yrs since I did this).

_______________/ <--fiberglass layers
_______________/ <-- gel coat
_______________/ <-- pva
_______________/ <-- mold or plug

Feel free to contact me if you have questions. Have fun!
 
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Josh, If you build the plugs as you said, seal them up with epoxy , coat them with PVA which acts as a release agent then lay up your final parts over what is known as a male plug, The work of fairing the finished parts is minimal when compared to making a female mold. After all it is a duck boat not a yacht so fairing should be minimal. The female mold process is like building the boat twice, maybe more so. Use a good quality polyester layup resin and some coremat between the layers for stiffness without weighing a ton.
 
Two questions: what is meant by "no undercut edges"? and what is coremat? is that like the roven woven mate or something else? Thanks again for all the suggestions

Josh
 
Josh, think in terms of shape. If you used a cone as a plug, it would be fairly easy to get the molded cone off the plug. If you used an hourglass shaped plug, you wouldn't get the molded part off the plug in one piece. That's the simplest analogy I can come up with.
 
uNDERCUT IS WHEN YOU HAVE NEGATIVE DRAFT ON A MOLD . THE PART WILL BE LOCKED IN THE MOLD . THE TOP OF A MOLD HAS TO BE BIGGER THEN THE BOTTOM TO ALLOW THE PART TO CLEAR THE MOLD ON ITS WAY OUT. THINK OF AN ICECUBE TRAY .AND COREMAT IS A MATERIAL THAT IS USED BETWEEN LAYERS OF FIBERGLASS TO STIFFEN THE PART. COERING CAN BE FOAM , BALSA , IVE EVEN SEEN PLYWOOD USED. I LIKE DIVINECELL FOAM CORE . IT COMES IN MANY THICKNESS BUT NOT CHEAP BY AND MEANS . I CAME UP WITH A GREAT WAY TO CONNECT MY HULLS TO MY DECKS WITHOUT HAVING THAT UGLY FLANGE . ILL POST SOME PHOTOS FOR YOU
 
100_0065.jpg
The parts are made in the mold and dry . Then i put a 4 inch triple layer of once and i half mat around the sheer of the hull and put the deck on top and clamp together . The parts are joined together before they come out of the molds to eliminate any distorting . The deck holds the hulls shape and the hull holds the decks shape . After a dry time i just pull the molds off the part. After cutting the flange away im left with a clean line and a finger grab all around the boat. The sketch is rough but it was better to see then on a boat . Im left with a good inch and a half of marriage all around .
8ftpondbox.jpg

 
100_0065.jpg
The parts are made in the mold and dry . Then i put a 4 inch triple layer of once and i half mat around the sheer of the hull and put the deck on top and clamp together . The parts are joined together before they come out of the molds to eliminate any distorting . The deck holds the hulls shape and the hull holds the decks shape . After a dry time i just pull the molds off the part. After cutting the flange away im left with a clean line and a finger grab all around the boat. The sketch is rough but it was better to see then on a boat . Im left with a good inch and a half of marriage all around .
8ftpondbox.jpg
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Rick did you set up beside us 2 years ago at Tuckerton I believe I remember seeing this pond box there?
 
This is an excellent subject ...thank you all for the info...Now just out of curiosity has anyone done this process with a kara hummer design...not to steal the thread ..if you feel thats the case please pm me..otherwise post em up here as part of this thread..I'm planning on a couple of hummers this summer and would really be interested in this process... thanks ..
 
This is an excellent subject ...thank you all for the info...Now just out of curiosity has anyone done this process with a kara hummer design...not to steal the thread ..if you feel thats the case please pm me..otherwise post em up here as part of this thread..I'm planning on a couple of hummers this summer and would really be interested in this process... thanks ..
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Chris, It can be done with any boat you build. The reality of it is the costs are high to do it right if you want a glass boat. I know guys can cut corners and do reverse molding but the reality of it is if your glass boat isnt properly built it wont last very long. Proper thickness, stringers support etc etc. all play a role in molding using fiberglass. For a 1 or 2 off boat I think you would be money ahead to build 2 wood ones. Woods cheap. composites are expensive.

I am looking for a couple new boats to add to our product line up, one being a 2 man sculler and a modified sneak similar to a BB3 but want it 16-18ft in length and just dont have the time to build one and prep it for molding. If someone out there is looking to build one of these and wants a glass one, I would be very interested in making a deal with them to finish the plug for molding and building the molds the right way and giving them the first boat in exchange for the rights to produce them and sell them.
 
Tony that was me at tuckerton and you are correct about the price of composites . getting worse to .
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Amen to that and I thought so. My supplier(most use the same company) continues to raise prices atleast 6% every 6mths. Its unfortunate because it has forced me to make the first price incease ever on our products.
 
Christopher,
I took the KARA design, cut it off at one end and extended the cockpit back to the last rib, creating a transom. I also raised the bow a little to help keep it from spearing waves, increased the heightthe transom, and angled the combing in slightly to make it easier to pop the deck out of the mold. Then a buddy and I made a mold from that and we have made at least 8 boats from the mold (a different friend borrowed the mold for a while and I'm not sure how many boats he made, so probably closer to a dozen).

Here is a picture of the final product.


View attachment boatside.jpg

Here is the basic frame I built...same dimensions as the Kara, and same construction technique (I'd built 2 karas prior to this build)

View attachment boatframe2.jpg

We made these boats back in '02 and all of them that I know of (I have seen/hunted with 5 of them recently) are still going strong. I hunted mine a TON for the first 7 years, but going back to grad school has really put a damper on my hunting the last 2 seasons.

I had one problem dealing with the place where I later added a drain tube for a plug. I used plumber's putty (the 2 part epoxy) to seal it in and apparently that weakened the polyester resin, so one morning when I was wiggling the plug to make sure it was tight prior to hopping in the boat, the entire chunk around the drain tube broke out. I had a geiser about 6" high shooting into the boat. Luckily, we just dumped my gear into another guy's boat, put mine back on the trailer while I hunted and I fixed it that night.
 
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