Fiberglassing over balsa wood

[riggerman]

I am building a John Stark GP-12V3 12 cell tunnel hull a Dumas 7.5 sprint abs cowl will not work for this application so im carving one from balsa as per instructions . Painted balsa has no resitance to any sort of impact so i was thinking covering the cowl with 2 layers of 1.5 or 2.5 oz fiberglass cloth with Pacer finishing resin and once the inside of the cowl is sanded down to a 1/4'' thickness maybe 1 layer of cloth and resin on the inside of the cowl any suggestions would be welcome.Regards Andris Golts.

 

[Jim Caldwell]

My experience is those weight of cloths just add a finishing surface not impact resistance

because the fibers are so thin. You can tear 1 layer of 6.0 oz. and epoxy with your hands like a piece of paper.

 

[SayMikey]

My experience is those weight of cloths just add a finishing surface not impact resistancebecause the fibers are so thin. You can tear 1 layer of 6.0 oz. and epoxy with your hands like a piece of paper.

Soak the balsa with thin ca after you have it to shape,thin ca weeps in deep and hardens the wood. After that one layer should be fine..........Mikey

 

[Don Ferrette]

My experience is those weight of cloths just add a finishing surface not impact resistancebecause the fibers are so thin. You can tear 1 layer of 6.0 oz. and epoxy with your hands like a piece of paper.

I'm gonna have to disagree a bit with this one. When laid over a balsa core it will add some surface tension strength. Also the resin will wick into the coarse grain which will improve the impact resistance over just plain paint as the cured epoxy will act like a hardened "shell" on the outer areas of the balsa. Granted it won't be as tough as a glass weave cowl but it will be stronger provided the layers of cloth are done in one resin application so it does not form "layers" & the resin is thin enough & a slow cure to allow for good penetration into the grain.

Tear a piece of cured 6oz. epoxy impregnated cloth with your hands like a piece paper? I'd like to see that.

 

[Terry Keeley]

Hey Andris:

Why not make a plug from the balsa and make a mold, then you can make a nice epoxy-glass part?

 

[Jerry Wyss]

When I made "one off" parts in the past I shaped regular ol styrene white foam (styrofoam) bandsaw it to

a good rough shape, glue the bottom to a 3/4" thick chunck wood (wooden stake) grab it with a vise

and go to work on it with a wood rasp, block of 36 grit, 80 grit (you get the picture)

"Light weight spackle" any big problem areas or thin it down with water and paste the whole dam thing

and finish shape that. Now at this point you can use Terry's method and make a cheap mold out of it with

"reinforced plaster" (you'd have to work out a surface finish to seperate from mold) or you can layup

epoxy glass right over the plug you just made.

Either way, it's allot of work if your doin' it the first time, thats why most guy's (i would imagine) look

for a suitable existing cowl that'll work or adapt.

Be advised, 2 or 3 layers of the fiberglass cloth you mentioned are gunna be perdy thin and twisty though

for like a 7.5 tunnel cowl.

 

[Jim Caldwell]

Don,

Try it, surprised the heck out of me too.

 

[Ron Saxvik]

When I made "one off" parts in the past I shaped regular ol styrene white foam (styrofoam) bandsaw it toa good rough shape, glue the bottom to a 3/4" thick chunck wood (wooden stake) grab it with a vise

and go to work on it with a wood rasp, block of 36 grit, 80 grit (you get the picture)

"Light weight spackle" any big problem areas or thin it down with water and paste the whole dam thing

and finish shape that. Now at this point you can use Terry's method and make a cheap mold out of it with

"reinforced plaster" (you'd have to work out a surface finish to seperate from mold) or you can layup

epoxy glass right over the plug you just made.

Either way, it's allot of work if your doin' it the first time, thats why most guy's (i would imagine) look

for a suitable existing cowl that'll work or adapt.

Be advised, 2 or 3 layers of the fiberglass cloth you mentioned are gunna be perdy thin and twisty though

for like a 7.5 tunnel cowl.

Here is a good article on "lost foam" fabrication in the West System "EpoxyWorks" magazine.

http://www.epoxyworks.com/

 

[puckstermi]

Sorry to jump in but I have a question. When reinforcing wood with fiberglass should the wood be sealed with WestSystem epoxy and let cure first then when fully cured sand and then glass the areas of concern? Or do you glass the naked wood? Curious as I am almost done with my Whiplash build and want to reinforce the front sponsons and some critical potential impact areas as I am going to paint the boat. Thanks guys, your expertise is very helpful.

 

[RodneyPierce]

Im also working on making a custom cowl for my whiplash sport 20 hydro. Interesting topic here. Im just planning on carving it from foam, then over laying it will glass, and using the foam as a plug if you will for the cowl. we will see what I come up with :huh:

 

[Ed.R]

I'm thinking of the same thing but for a Dumas Eagle hull , later on though . When making the part would you use west system with fiberglass mat or fiberglass resin with the mat ? I was just going to use west systems .

The first couble of layers of mat would be heavier then finish with a lighter like 1 oz . Would this be correct or not?

Ed

 

[Jerry Wyss]

Sorry to jump in but I have a question. When reinforcing wood with fiberglass should the wood be sealed with WestSystem epoxy and let cure first then when fully cured sand and then glass the areas of concern? Or do you glass the naked wood? Curious as I am almost done with my Whiplash build and want to reinforce the front sponsons and some critical potential impact areas as I am going to paint the boat. Thanks guys, your expertise is very helpful.

When you prepare a hull for a crash generally you add too much weight. Wood framed / sheeted hulls are the toughest

hulls on the water and its only necessary to have good glue joints without alot of puddles of epoxy in every cell.

Its great to seal with epoxy but scrape off every bit excess resin to keep the weight down.

When the top deck sheeting goes on I thicken the resin with a product called "cab-o-sil", you can thicken the epoxy

to the consistancey of "Vasoline", popcicle stick a thin layer on all the ribs and bulkheads an such, position the sheeting,

take it off and you can see where the structure has hit and missed. Dab on some more everywhere the frame contacted

and just a little more where it didn't quite touch, it dont take alot to make a good joint. The advantage of the thickened

epoxy is that you dont have any running excess resin puddling where you cant get at it to scrape it off.

Cab-o-sil can "tick off" the epoxy perdy quick if left in a cup while working. Spread it out on a doubled sheet of aluminum

foil taped down on the table , spread the epoxy out to about 1/8th to 3/16ths thick,, it will give you much more time to work.

JW