How to increase Epoxy curing time?

[frastorno]

... and some more

... and some more

.. then today I started with the stringers, shaped to the hull few days ago, rechecked the hull surface for dirty spots, regrinded where needed, mixed 1/2 gallon of epoxy with woodflour (1/4) at a time, painted the hull and the wood to paste with clear epoxy, pasted the stringer to the hull.
As the stringer was a bit curved I only had to push down the 2 extreems to have it flat against the bottom hull. Some pictures:
Next steps:

1. paste the 2 lateral stringers
2. 2 layers of roving on top of everithing
3. start thinking about the floor!

any suggestions?

 

[frastorno]

Re: How to increase Epoxy curing time?

Any comments on what accomplished so far or the plan for next steps?

Was looking in e-bay.. 365$ for 10gl of Max Bond low viscosity boat building epoxy, do you know this brand? I?m currently paying over 100$ each gallon for the west system.. it would be a huge saving for me, the seller is Polymer Products, they are located in Ontario... anybody know this product?

 

[BillP]

Re: How to increase Epoxy curing time?

A large chunk of the WEST price is brand recognition. Their retail margin is double/tripple of generic epoxy. So, in reality you might be getting a little more quality for a lot more price. Generics are fine and way better than any polyester.

If using mat with it be sure it's the stitched type made for epoxy. Poly mat is different and epoxy doesn't saturate it well. Get a ribbed roller for working the fabric too.

bp

 

[BillP]

Re: How to increase Epoxy curing time?

double post

 

[frastorno]

Re: How to increase Epoxy curing time?

Thx for your input Bill, I'm only using roving and cloth tape in the corners/fillets. I'm using an aluminium roller to work the fabric... I guess I'll try to buy that stuff in e-bay then! I'm not sure I got this part: "unless you are cutting the laminate schedule so thin that every molecule of tensile strength matters"

 

[KnottyBuoyz]

Re: How to increase Epoxy curing time?

Any comments on what accomplished so far or the plan for next steps?

Was looking in e-bay.. 365$ for 10gl of Max Bond low viscosity boat building epoxy, do you know this brand? I?m currently paying over 100$ each gallon for the west system.. it would be a huge saving for me, the seller is Polymer Products, they are located in Ontario... anybody know this product?

I've used their products and they perform as advertised. I use their Ultra Low Viscosity resins for infusion projects. Their regular epoxy should work well and decent price. Check shipping costs though. Not always economical depending on where you live.

 

[frastorno]

Re: How to increase Epoxy curing time?

Thx Knotty! what is an "infusion project" the product I'm looking at is the "Epoxy Resin LOW VISCOSITY BOAT BUILDING 10 Gallon Kit" is it the one you call "their regular epoxy"? I'm checking on shipment costs and taxes (will be something between 200 and 300).. not cheap but it seems I still have a wide margin

 

[BillP]

Re: How to increase Epoxy curing time?

Thx for your input Bill, I'm only using roving and cloth tape in the corners/fillets. I'm using an aluminium roller to work the fabric... I guess I'll try to buy that stuff in e-bay then! I'm not sure I got this part: "unless you are cutting the laminate schedule so thin that every molecule of tensile strength matters"

Tensile strengths vary widely with different brands and WEST probaby IS stronger than generics. IF building where the absolute lightest/thinnest layup is needed you would go with the strongest tensile strength per lb of weight resin...to me that would be for building airplanes or vaccum bag jobs on high performance sailboats. Boat rebuild projects like being done here usually don't fall into that category and people bulk up the glass no matter what type resin is used. The ONLY reason I use epoxy for transoms, stringers, etc is for their superior gap filling, glueing and secondary bonding properties. It makes cutting, fitting and prep work easier than using polyester. It isn't a free ride though. Epoxy likes to run down vertical surfaces (stringers/transoms) or soak into foam (various composites) while waiting for it to kick...and you have to stay and babysit or end up with a dry layup with a puddle of resin. Polyester lets you vary kick times by changing catalyst ratios or hot coating immediately thereafter...which means you can make it kick immediately after glassing...less babysitting, no puddling, no dry layups.

Does that s'plain it?

bp

 

[frastorno]

Re: How to increase Epoxy curing time?

Got it, thx. I still need to find out what exactly the transportation costs are but keep adding fees.. and the margin is getting smaller so I'll probably stay with the WS.
I'm attaching below my fiberglassing schedule for the bottom of the boat, I hope it's clear enough. I'd like to fill the gap (green triangle) that goes along the external sides of the stringers, so I won't have water on the stringer sides and won't have e to drill draining holes in the same stringer (i'll drill them in the wood above the stringer that support the floor).
My question is, which material can I use to fill it? Is there any foam that will never absorb water? more wood? thickened epoxy ($$)? ANy suggestion is more than welcome.. ah.. also apreciate any feedback about the layers layout.

 

[frastorno]

Re: How to increase Epoxy curing time?

Any suggestion on the filler to use? Is it a bad idea to fill that gap? Is the layup to heavy?...

 

[ondarvr]

Re: How to increase Epoxy curing time?

What are the reasons for adding so much more material to the hull?

There are some foams that will work, but it will be costly, some of the online companies that sell the other supplies should carry them.

 

[BillP]

Re: How to increase Epoxy curing time?

Got it, thx. I still need to find out what exactly the transportation costs are but keep adding fees.. and the margin is getting smaller so I'll probably stay with the WS.
I'm attaching below my fiberglassing schedule for the bottom of the boat, I hope it's clear enough. I'd like to fill the gap (green triangle) that goes along the external sides of the stringers, so I won't have water on the stringer sides and won't have e to drill draining holes in the same stringer (i'll drill them in the wood above the stringer that support the floor).
My question is, which material can I use to fill it? Is there any foam that will never absorb water? more wood? thickened epoxy ($$)? ANy suggestion is more than welcome.. ah.. also apreciate any feedback about the layers layout.

Everyone has their own ideas and there isn't just one way that works. Here's my thoughts...Yes you can use foam but I'd use cutouts in the stringers instead. They are easy to do and can be sealed before installing.

Big $$$ and work can be saved by reducing the laminate schedule. Think in terms of total oz of laminate needed. What you are doing is way overkill on the glass for anything under 30'. As I understand it you are using combo 24oz cloth with epoxy. Example: 10 layers of 24oz (240 oz) on the transom tabs is double the bulletproof factor for ocean wave jumping 300 hp 20' outboards using standard polyester resin. The epoxy strength increase factor is somewhere around 35% depending on which mfg you believe. Do the math.

Given that you are using 24oz there isn't deviation from those multiples. For stringers use a layup of 2 minimum (48oz) to 3 max (72oz) and overlap on the hull only 6-8"...if memory serves me right glass fibers technically need 1" of overlap to retail full strength on new polyester work...6"-8" overlap is proven beyond doubt to work but there's no way to measure secondary bonding. Now consider that most epoxy glues technically can be butt jointed to retail full strength...which means a stringer could be glued down without glass and work ok. I don't know anyone who does that but it makes one wonder doesn't it? I might try it someday in an open skiff just to see. Anyway, a layer of glass under the stringer isn't needed but won't add much weight or cost. From there out use only one layer to reinforce the rest of the hull where you just want to make it stronger...24 oz here is 2x what would be fine in most cases.

One last thought. The pics on your transom show what looks like unsaturated mat tabs. It looks like epoxy resin was used with poly mat. Full saturation should show clear like it does on the woven roven. With 10 layers and epoxy you are probably ok but don't use poly mat with epoxy again if that's what happened.

bp

 

[frastorno]

Re: How to increase Epoxy curing time?

Thankyou very much for your suggestion and comments Bill!

About the filler, what is a cut out? Is it precut foam (or wood?) painted with epoxy to seal it and then pasted in?

About the laminate, I?m using plain roving 24oz, the boat was previously (very poorly) rebuilt, so mine was the 2nd grinding on the hull, making the original fiberglass a little thin in some spots, the previous rebuilt was a real mess so I wanted to grind everything out, but yes, I suspected my programmed laminate was a bit heavy.. I?ll redo the plan including your suggestion and re-post it.

About the transom, I think you are right, for those 2 reinforcement tabs (the 5 layers per side only in the corners), I used the combo mat/roven, the rest done with 2+2 layers of roven 24oz all over transom bottom and sides. The combo was reacting differently, plain roven got almost transparent while the other more white and less transparent (I laid down the piece horizontally, impregnated with a roller and than pasted to the corner of the transom to do this part). At the shop they told me it was ok for both (epoxy/poly) but they are not much used to epoxy here so I wouldn?t totally rely on that statement. The corner sounds very solid though.. should I reinforce it further?

 

[BillP]

Re: How to increase Epoxy curing time?

You want to drain water by the stringers right? A "cutout" is simply a hole in the stringer to let the water pass through. You don't need many and the strength loss isn't a factor if you don't make them too big. They need to be large enough for water to drain without crud being able to plug them up...maybe the size of a half round piece of 3" diameter pvc, etc...whatever you think that fits the stringer.

On the mat tabs...you have so much glass that they are probably ok as is but there are several ways to make up for mistakes like this. I'm assuming you have 3-4 good solid layers of woven roven there already. Take 1/4" lag bolts or #14 screws and screw them into the wood where the mat squares are...use large washers and then glass over the heads with one layer to seal them. That gives a mechanical clamp. I did it once with #14 screws where the tab bond to transom was questionable and it worked without a problem...but I don't know if they were necessary either. Another way is to drill multiple 1/4" dia holes though the tabs and well into the transom ply...then fill them with epoxy to lock the mass together.

For what its worth...several yrs ago I experimented with epoxy and poly mat to see exactly what happened. The mat took maybe 50% of what it should have. Also, when and if you ever use epoxy mat it's more fragile than poly mat and can't be worked as much before it shreds apart.

bp