Going foamless

[logan944t]

Re: Going foamless

and 2 gals of bubbles is a lot...

A lot? A layer of csm + resin in between 2 layers of marine ply--full transom width, 1 layer csm+ resin for another smaller marine ply in the center of that and then a layer ( csm + resin) back,front and sides. Sixteen oz of PB to transom to fill in holes and chunks missing and a full width tab (port to starboard) on transom bottom to fair in a thru hull hole and some thin places.

I apply resin till it becomes translucent-- no extra pouring on of resin. Besides weight --is too much a problem?

 

[oops!]

Re: Going foamless

the transom is good with that schedule....

the glass bubbles make a good fairing compound. i would have chose a different mix for the section under the transom...

but no worries....as long as the thickened resin has some type of glass in it to fill the majority of the void you are good.

resin by it self is brittle and will crack with little stress

 

[logan944t]

Re: Going foamless

the transom is good with that schedule....

the glass bubbles make a good fairing compound. i would have chose a different mix for the section under the transom...

but no worries....as long as the thickened resin has some type of glass in it to fill the majority of the void you are good.

resin by it self is brittle and will crack with little stress

Yep -- in fact I realized when I was mixing the PB for the transom bond that the cabosil should be mixed in last. That way there is plenty of resin for the chopped glass to absorb--before you thicken it.


*Edit*--Oops I think we arent understanding each other. I have used about 2 gallons of resin not cabosil. All the PB I have mixed has been resin+ csm+ cabosil+ hardener. There is no resin+ cabosil only-- anywhere.

 

[logan944t]

Re: Going foamless



This is the transom installed. Two 3/4 " marine ply coated with resin --then bonded with csm and resin. Then an additional 3/4" marine ply "stiffener" where the motor bolts in. The stiffener will be bonded to the stringers on either side. The stiffener had to be cut away from the top edge because the cap sits at an angle and there is only space enough for 2 layers of 3/4" ply.


For those of you with good eyes-- you might notice 2 bolts are missing. I drilled the holes where the motor bolts in as places to clamp with 2x4's. I buttered both the transom skin and transom blank with PB --installed it and when I went to thread the nuts onto the bolts.....the threads are stripped. I was able to drill a hole into the drain at the bottom to make sure the bottom was against the skin-- the threaded the other bolt in and clamped it across the top just as the PB kicked. Im sure the guy next door heard my language-- the bolts were new from the hardware store--but its my fault for not checking the threads before I tried to use them. My son was helping and when he started berating me for not knowing how to start a nut on a bolt --I "politely" informed him that I wasnt joking. I think thats when the benny hill theme started playing in the background as he started running around looking for a wire brush or another long enough bolt......






I was worried that there might have been a void in between the transom blank and skin in the area where I didnt have a bolt--but when I looked at the outside of the transom at some holes I havent repaired yet-- there was PB oozing out and the blank is tight up against the skin.


I PB'd the perimeter of the blank and will probably add a bigger fillet tomorrow when I glass 1708 to the transom inner surface.


Im not so sure about the HF grinder. When I was mixing the PB for the transom on my porch --about 75' away from the boat--the grinder kicked on....by itself.

 

[Woodonglass]

Re: Going foamless

Sooo... Just exactly what is your formula for making your PB? For example if you had 1/2 quart (2 cups of resin) how much cabosil would you use and When ou say csm what exactly do you mean?

 

[logan944t]

Re: Going foamless

Sooo... Just exactly what is your formula for making your PB? For example if you had 1/2 quart (2 cups of resin) how much cabosil would you use and When ou say csm what exactly do you mean?

Csm = chopped strand mat. I cut it into pieces about 1/2" to 1/4".

Lets go with 4 cups since I mix everything in a mixing container that way. I cut the csm until its about half full ( loose--2 cups +/-) then I add resin until the resin reachs the 32 oz level. I mix until the csm is saturated. I then add the cabosil until its the desired consistency---thicker for vertical --looser for horizontal. If I had to guess at the cabosil I would say 4 -8 oz (volume not weight) --maybe more. Then the hardener. Is this wrong?


The PB I added to the transom skin kicked way before I thought it would because it was in the sun. I didnt realize the transom was hot to the touch until after I had it buttered. I might have to start working after the sun goes down.

 

[Woodonglass]

Re: Going foamless

Yeah, that's really not the formula for PB when you use it for glue and filleting. What you made is more like a Structural PB.
Take a look at this...http://www.youtube.com/watch?v=N3kmr9ZctUo

PB for Glueing and filleting is Resin, Cabosil and 1/4" chopped Milled fibers. The milled fibers are pretty small

 

[logan944t]

Re: Going foamless

Ok -- should I remove the transom and redo it? Ya got me sweatin here.....and Ive watched all of those videos--that guy does good work.

 

[oops!]

Re: Going foamless

no....dont worry about it....

you were using csm strands....

the only way i would recommend grinding it out is if it was a mostly resin filler ,,,,,like 25% filler and 75 % resin

resin is brittle....very brittle to the point that if you dropped a chunk that was one inch thick....(the filler in the transom is 2 inches thick) it would shatter like peanut brittle !

 

[Woodonglass]

Re: Going foamless

Nope, it's fine but for future reference I posted the formula for ya.

 

[logan944t]

Re: Going foamless

Nope, it's fine but for future reference I posted the formula for ya.

Thank you.

the only way i would recommend grinding it out is if it was a mostly resin filler ,,,,,like 25% filler and 75 % resin

resin is brittle....very brittle to the point that if you dropped a chunk that was one inch thick....(the filler in the transom is 2 inches thick) it would shatter like peanut brittle !

No --Ive had occasion to take a hammer to fiberglass panels and the ones that I liked were the ones that were mostly resin --because they shattered and were easy to remove. The ones made right were more tenacious.

Tomorrow I will beat on the bit I have left in the mixing bucket--and see what happens....

 

[logan944t]

Re: Going foamless

Ok I beat the bit that was left in the bucket and it fractured--but stayed together for a few hits.


Today I ground down the bits sticking up on the transom and took off the clamps. I applied fillets around the transom with PB.

I rough and scuffed the whole transom, fillet and hull in front of the transom. Wiped with acetone.

I applied a 4" ( 2" on transom 2" on hull) section of 1708 on the 3 sides of the transom.

Mat goes down --cloth up?...I hope.

1708 is some of the easiest glass I have worked with. I like it a lot more than csm.

 

[oops!]

Re: Going foamless

Ok I beat the bit that was left in the bucket and it fractured--but stayed together for a few hits.
.

lol.....the structural stuff i mix....

i made a casting out of the bottom of a coffee cup to some 20 year olds i work with...they are big boys.... then i gave them a 10 lb sledge hammer and sent them to the back alley and said "go for it"
they came back 20 minits later.....huffing and puffing......
and handed me the totally intact casting.!

 

[oops!]

Re: Going foamless

Mat goes down --cloth up?...I hope.

1708 is some of the easiest glass I have worked with. I like it a lot more than csm.

yes....the matt side is allways between the substraight and the cloth...

so matt down cloth up...

the reason for this is that resin by it self is very brittle.....if you layed cloth against the wood.....you would have a resin rich layer between the wood and the thick fibers of the bi ax stitch.
this would easily fail....

by placing the matt side down.....the csm stitched to the knit bi ax is a resin soaking barrier ....the bond will be stronger.
the strongest yet would be a inital layer of 1,5 oz csm. between the matt side and the substraight

 

[logan944t]

Re: Going foamless

by placing the matt side down.....the csm stitched to the knit bi ax is a resin soaking barrier ....the bond will be stronger.
the strongest yet would be a inital layer of 1,5 oz csm. between the matt side and the substraight

Yep-- csm covered the transom blank-- it was already hardened but its there.

 

[Woodonglass]

Re: Going foamless

You're tabbing should be 6 to 8" not 2" . You are going to put a Full layer of 1708 over the entire transom and extend it out onto the sides and bottom of the hull...right???? Just like my drawings indicate.

 

[logan944t]

Re: Going foamless

You're tabbing should be 6 to 8" not 2" . You are going to put a Full layer of 1708 over the entire transom and extend it out onto the sides and bottom of the hull...right???? Just like my drawings indicate.

Yep.

It will end up being different than your drawing tho. I had planned on 2 full layers of 1708 on the transom/bottom/sides. But the sides of the boat were foamed as well. So I have to put another layer from the remaining glass on the sides to the transom and reinstall 2lb foam in between.

 

[Yacht Dr.]

Re: Going foamless

You're tabbing should be 6 to 8" not 2" .

Very important to follow what Woody is saying here..

6-8" on EACH surface .. not split into 3 and 3 or 4 and 4.

YD.

 

[logan944t]

Re: Going foamless

Very important to follow what Woody is saying here..

6-8" on EACH surface .. not split into 3 and 3 or 4 and 4.

Yep I got it--that tabbing I put on that night was more of an experiment because Ive never worked with 1708 before--in fact that night was the first time I had taken it out of the package. If I was not putting on 2 layers of 1708 --but was just using the tabbing I would have put another layer on top of the 4" that was bigger -- and then a bigger one on top of that.

The first full layer of 1708 I put on today extended on the sides of the hull 6"--and on the bottom 5" ( because of a bulkhead)

The last layer will extend 8" or 9" over that.


I plugged in my hf grinder this morning and hit the switch -- and it would only turn very slowly --then intermittently. So I pulled out the 2nd one I bought and worked away. Im thinking the brushs are gone--but Ive only used it about 15 hours total -- and its been blown out after every use.


The tabbing I put on yesterday had a white film over it today. Ive never seen this with any of the other resin Ive put on this boat --and its all come from the same can. I wiped it down with acetone after I roughed and scuffed but I was wondering why the difference--is there wax in the 1708?

 

[oops!]

Re: Going foamless

nope ....no wax in the 1708.

the white could have come form any where....atmospheric contaminants......an improperly mixed barrel of resin