JeffR

Tabbing in bulkhead, advice on cloth

Recommended Posts

Pulled my chainplates this season for inspection and found the main bulkhead had mostly rotted due to water getting into the end-grain of the plywood over 35 years. 

I'm pretty far along on the rebuild.  Laminated 2" thick hunks of marine ply to replace what was rotted.  Wrapped them in 40z cloth with WEST Epoxy and then fit them to the boat.  I initially shot Six10 into the small gaps where they meet the deck and what was left of the original bulkhead and then built wide fillets using filled WEST.

Next step is to tab these to the hull and deck to transfer the loads.  Boat is an S2 9.1 that is raced. 

I bought a roll of 6" 1708 Biax tape with mat to do the tabbing but then started reading a lot of other websites and read a lot of advice to not use 1708 with Epoxy resin, just wastes resin.  The suggested alternative is just Biax cloth with no mat because the epoxy has such good adhesive properties.

What to the collective minds of SA think?

 

IMG_3234.jpg

Share this post


Link to post
Share on other sites

I'd just use 17 Oz biax. Unless you specifically request it, the mat (the 08 in 1708) is held together with a styrene soluble binder and there is no styrene in epoxy.

Biax doesn't have the crimps of woven fabric which is the main reason for having the mat layer - to level the surface for the next layer.

In actual fact, on a boat that size I'd probably use a lighter weight of biax to ensure good "drape" around the fillets.

I'd also drill through the cured flange and bolt the whole thing together with some machine screws just to add a bit of mechanical strength to the bond to the plywood. Seal the bolt holes by brushing some epoxy in them. You can see how I did it in the attached pic - sorry but it only shows at the bottom of the starboard bulkhead by the chainplate - I had them every 8".

Interior.thumb.jpg.5bd9f6a3ef86ad704e33316deba59ee3.jpg

Share this post


Link to post
Share on other sites
42 minutes ago, JeffR said:

Pulled my chainplates this season for inspection and found the main bulkhead had mostly rotted due to water getting into the end-grain of the plywood over 35 years. 

I'm pretty far along on the rebuild.  Laminated 2" thick hunks of marine ply to replace what was rotted.  Wrapped them in 40z cloth with WEST Epoxy and then fit them to the boat.  I initially shot Six10 into the small gaps where they meet the deck and what was left of the original bulkhead and then built wide fillets using filled WEST.

Next step is to tab these to the hull and deck to transfer the loads.  Boat is an S2 9.1 that is raced. 

I bought a roll of 6" 1708 Biax tape with mat to do the tabbing but then started reading a lot of other websites and read a lot of advice to not use 1708 with Epoxy resin, just wastes resin.  The suggested alternative is just Biax cloth with no mat because the epoxy has such good adhesive properties.

What to the collective minds of SA think?

 

IMG_3234.jpg

Agreed..... unless the mat is specifically made to use with epoxy, and says so, DON'T use it with epoxy because the resin will not bind to the fibers. Unlike woven cloth, mat is stuck together with goo, and the goo needs to be compatible with the resin.

Because epoxy is a very good adhesive, it's the best (IMHO and others) resin to use for this kind of work. What you're doing is creating a secondary bond to the inner face of the hull laminate, which I can see you've ground out nicely (I'd go a little wider but no deeper) and for that you need the best adhesion you can get.

The heavy fiberglass cloth does not like to bend. The biax is a little better in this respect, another possible solution is to take regular 18oz cloth and cut strips of it diagonally, so the strands are at 45 to the joint you are overlaying. This is easier to get to "drape"into the angle, and is strong also.

I've gotten very addicted to using peel ply. Holds the cloth in place better, gets bubbles out easier, comes off clean and neat with no less sanding. (admission..... sometimes I still have to sand it to a good finish).

Hope this helps, looks good so far

FB- Doug

Share this post


Link to post
Share on other sites

100% of all the replacement bulkheads I have ever installed have been tabbed in place with layers of chop strand mat. 

Unless the boat was built of epoxy or vinylester resin I used polyester as the plastic. 

In Fifty years of doing so, I have seen zero failures. 

  • Like 1
  • Downvote 1

Share this post


Link to post
Share on other sites

Thanks for the feedback.

FWIW the boat WAS built with vinylester resin.  The bolt holes are already isolated from the plywood.  I drilled 1" holes, filled with high density filled epoxy and re-drilled them for the 5/16" bolts.  There is no reason to bolt the plywood together.  I laminated it with WEST and it is so solid you can not split the 1/4" pieces I trilled off.  I use WEST for everything because it is what I am used to and it has never failed me.

My question really comes down to using biax with or without the attached mat. 

This

https://www.jamestowndistributors.com/userportal/show_product.do?pid=1441&familyName=1708+Fiberglass+Cloth%3A+17+oz+Biaxial+3%2F4+oz+Mat+Back

or this

https://www.jamestowndistributors.com/userportal/show_product.do?pid=97480&familyName=Fiberglass+Cloth+-+17+oz+Biaxial

Share this post


Link to post
Share on other sites
34 minutes ago, Gouvernail said:

100% of all the replacement bulkheads I have ever installed have been tabbed in place with layers of chop strand mat. 

Unless the boat was built of epoxy or vinylester resin I used polyester as the plastic. 

In Fifty years of doing so, I have seen zero failures. 

I have - the one in the pic - the glass had started to peel away from the ply - hence the replacement.

Share this post


Link to post
Share on other sites
19 minutes ago, SloopJonB said:

I have - the one in the pic - the glass had started to peel away from the ply - hence the replacement.

I think adhesion with mat is vastly superior to adhesion with cloth. As for polyester, vinylester, or epoxy?? Each soaks well into wood, stops the soaked wood from rotting, and fails miserably of the rest of the wood is allowed to rot 

  • Like 1
  • Downvote 1

Share this post


Link to post
Share on other sites
2 hours ago, Gouvernail said:

I think adhesion with mat is vastly superior to adhesion with cloth.

There are some who agree with that view, myself included.  When removing the tabbing and fiberglass from my boat, the cloth or roving cleaved off more easily than the mat. 

On the other hand, there are also some who say this only applies to polyester resin and not epoxy.  IDK.  But when I am laminating over old glass, I always use 1708 for the first lamination.

Another reason to use 1708 in my opinion is that the mat backing holds the bi-axial fibres in place when cutting or placing the glass.  When cutting or placing non-matt backed ones , I've found the fibres tend to pull and distort.  Taping the edge helps as does using one of those pizza wheel style fabric cutters.  but 1708 is just so much easier to work with and you'll get cleaner edges.  Slight weight penalty I suppose, but IMO a small penalty to pay 

Share this post


Link to post
Share on other sites

I also like 1708 because of the clean edges when cut. The stuff I have works fine with epoxy.

Share this post


Link to post
Share on other sites

I must admit I love the looks of glass tabbing accomplished with something like 10 oz cloth tape 

but

( and this is a Kardashian sized but)

The tape can easily bee peeled off, sometimes peels on its own, and paints over glass cloth always seem to flake off. 

 

Also... I like ken to do whatever looks just on he the rest of the insides so it dies not look “worked on.”

  • Downvote 1

Share this post


Link to post
Share on other sites
8 hours ago, Gouvernail said:

100% of all the replacement bulkheads I have ever installed have been tabbed in place with layers of chop strand mat. 

Unless the boat was built of epoxy or vinylester resin I used polyester as the plastic. 

In Fifty years of doing so, I have seen zero failures. 

Gouvernail: so secondary bonds have worked OK w polyester resin? Any hints on prep etc?

I am planning to install extra floors in my 30-footer (beef up). PU foam as core, some 5-6 laminates of 450 csm  + roving.  Suggestions?

Share this post


Link to post
Share on other sites

You will not find me down playing the fact there is added  security in using epoxy. If your surface prep is lacking, , the epoxy Might help mitigate the “not as good result.”

but

it is easy to have a surface to which nothing else will stick well.,

if you grind PROPERLY,  New polyester will stick very nicely to old polyester . 

 If your surface preparation sucks the best epoxy in the world won’t stick worth a damn . 

 I don’t mean to be pompous or elitist or anything of the sort but this is my simple answer .  Either the following mean something to you or does not . 

The surface must be thoroughly  abraded was 16 grit or perhaps a paper as fine as 24 or 40 grit. The dust must be removed and the new materials properly mixed and applied.

 

I hate to be a jack ass but if I have to explain the previous paragraph you need to have someone there standing by you to inspect your work when you do the job

Share this post


Link to post
Share on other sites

1708 biax to start with.  If you have a decent shop in the area you can order 1708 "tape" rather than a chunk off a full width roll(I stock 12, 10 8 and 6 for myself).  If they have multiple widths, I'd just start with your widest width and step down in 2" increments, if they charge more for getting that, just buy the widest tape you'll need and cut pieces from that.    It's much faster to work this way, and cleaner edges too.  I wouldn't use straight biax when going over something old, the mat helps conform and it fits nicer.  Dry fit your pieces, and cut darts from the edge as needed to get it to drape and overlap nicely with no wrinkles.  It's much nicer to do this dry but can be done wet in a pinch.    1708 is epoxy compatible, the mat is stitched rather than held together with binder, I'd work with the same resin as the hull there myself, it's faster and easier than epoxy but if you're familiar and comfortable with epoxy and not the former then stick to what you know.    It's such a small repair that the difference in resin cost because of the mat absorbing it isn't a big deal, if you were building something new it'd be different. 

If the original hull layup is 1.5oz mat and 24 oz roving, I'd finish with a 24oz roving to match perfectly, or flip a piece of 1708 mat up if the inside is mat finished and you don't want to mess around with buying extra materials(not acceptable from a shop as far as I'm concerned, but better than leaving the distinctive patter of the 1708 showing completely). 

I'd also get a cheap melamine shelf for 9$ from the store or a scrap of laminate counter, I like to wet out the mat side with a single roll of resin before applying, holds in place better, wets out nicer. 

 

Whatever you decide for your biax layup, buy a pair of these:

https://www.homedepot.com/p/Milwaukee-Jobsite-Offset-Scissors-48-22-4040/205218098

 

They're only 18$, and beat even the 200$ straight bladed shears the fiberglass warehouses use in my opinion.  Both for how clean the cut is, how easy they are to use even at the tips for darting and length of time between sharpening.  You'll find dozens of uses for them around the house after too.   They have small serrations on the one blade but not the other, so you get a clean cut but the glass doesn't side down the blade or bunch up on you so you get perfect neat edges.  They are also safe for acetone so if you get resin on them because you had to cut a dart wet or add some extra material just throw them in your solvent bucket along with the rest of the tools. 

The offset handle means you can trace a pattern and cut on a flat table with your fingers away from the surface and disturb the fiberglass a minimum amount, and the ruler on the side is handier than you might think.  Hold it up to where you need to cut a dart, cut the dart to the exact length and apply. 

 

 

Optional:  https://www.fibreglast.com/product/Bristle_Roller_01105_A/Supplies_Tools_Rollers_Squeegees

 

These are the bomb when you are doing repair work.  The bristles are flexible and will work around edges where a metal air roller will not, even if you have a little lump near an edge because you ended up with a slightly wider repair than you expected when you were grinding and hit an old lump outside the original repair area. they will force the fibers down around it and avoid air pockets.   Handy in around inside corners too, the bristles will conform at the end.  Can't be torched off like a metal roller and are a little pricey but worth it. 

 

Last thing I do is to put on a pair of bring green large nitrile gloves as the first layer, then a couple pairs of XL blacks overtop(large fit tight for me).  Occasionally swap outer layers as you work, they won't slide onto sweaty hands easily but will slide perfectly over other gloves.  Less important with epoxy since it doesn't dissolve them, but it leaves you with a final clean  pair of gloves on for cleanup, and if you see green you know it's time to reglove.

 

 

Share this post


Link to post
Share on other sites

Thanks for the great response jgb

I have more than enough of 6” 1708 tape.  My plan was to stagger them so they naturally taper.  I was planning on 3 layers to be safe.  Do you think 2 would be enough.?

im not worried about making it match the original layup. The builder mixed all sorts of cloth in different places. I slapped paint on it after tossing the old mildewed carpet hull liner. The boat nots pretty inside. 

Share this post


Link to post
Share on other sites

What is the distance as measured between red arrows?   The width of the tabbing from the plywood to the edge of the original tab along the hull? How thick was it?

How easy are the chainplates to remove?    That's not a job I'd want to do with them in place for a lot of reasons. Only one of which is that they're going to be all kinds of irritating, but also because if water gets down them I want it to stay off the wood entirely and on the outside of the glass, they are good sources of condensation too.  Typing the following took longer than doing the whole job should, lol. 

 

Not being able to see more or knowing what kind of strain they are under, or see most of the rest of the boat, this is what I am thinking I am seeing(and yes it may be obvious but I want to confirm we're exactly on the same page):  The right hand side is a prexisting bulkhead that has glass on it, the new plywood is a block you've set in place, the left hand side is the hull and the upper part of the image is the deck.   For next time I wouldn't bed the block against the hull in rigid filler, I'd use a foam tape for that, and then fillet over it. 

Here would be my workflow if it were my boat(and this is really guesswork, I deal with powerboats all day long, and I know what kinds and what directions of loads I'm working with(big outboards on transoms mostly). Not sailboats, and poly not epoxy, only time I use epoxy is for thruster tubes where it is specified by the manufacturer, there they specify the layup then as well).   A general rule I use is to build the same thickness as original, if working in 1708 where it used to be 1.5/24oz mat and roving or same plus one extra layer if using 1.5/24 oz again.   It's hard to go wrong with that, sometimes it's excessive but on something this small weight isn't an issue, but failure would be unpleasant.   If it was just mat before, you can do that again, no sense dealing with fussier materials than you have to. In that case substitute vinylester for epoxy, and the layers of mat for the 1708 in the following steps, following the same rule of thumb of same thickness as original plus one layer.

Preparation

-Buy a few yards of full width 1708.

-Remove chainplate.

-Grind plywood and glass again with a 36+grit 3m Cubitron II disk(they have pointy grit and leave a way more aggressive profile, that plywood doesn't look ground), until the edges of the plywood are flush with the edges of the glass, it looks like the plywood is protruding at the bottom, it doesn't need to be dead flat all the way, just taper the plywood down to the glass if needed.   Vacuum it well with a brush end on your vacuum hose.   I would solvent wash with Acetone, but that's a big no-no if you've only got paper towels, it can contaminate the bond with what's used to make the towel.  I use satwipes(presaturated and packaged rayon pads) for this, they are certified and contain nothing to contaminate this.   I usually do this the day before so I can be fresh and not itchy and the work area is perfectly dry. 

-Dry fit full sized 1708 to cover the plywood all the way to the hull, the deck and well out onto the rest of the bulkhead, next piece 1" smaller.  Dry fit strips to go from bulkhead to deck, long enough that they also overlap the original fiberglassed bulkhead as well, dry fit the hull-bulkhead ones as well, plus some short ones for the notch around the hull deck joint, they'll have to be skinny to avoid the bolts.  I don't have a good sense of scale here, which is why I'm asking for the distance in red, 6" as a starting size seems narrow, how wide is the original tabbing from the bulkhead to the edge on the boat?   I'd like to see at least 3 layers staggering down in size as a good general purpose thickness, but I don't find the 1708 fun to work with less than 4" across, it always seems to want to fall apart then.   Tape plastic masking a few inches beyond the edge of the areas you are working, below the repair area tape a bit of old cardboard or cheap paper towels on top of the plastic a couple inches farther down from that taped edge to absorb run off(not important if you do it every day, but eyeballing resin quantities accurately enough takes a while).   Take a big piece of cardboard to put under your work area/tools, but just over the edge of the plastic, tape it's other edges to the boat.   Measure your resin and hardener into a 3 batches(aim for two batches to do the job the third is in case you are short) in mixing containers but don't mix them together, set them just outside your work area so you don't know them over.  With polyester I typically pre-measure 1-1.5L batches depending on temperature and work size(or 1 gallon if we're doing big stringers with 2 people, but since catalyst is fast to measure with the squeeze bottle, and very hazardous I don't pre-measure it(also because I may reduce catalyst slightly in subsequent batches if I find myself racing the gel time).

Work:

Mix your first batch, pour it in the paint tray.   Wet the bare plywood with resin, let it soak while you make fairly wet filler(just stiff enough not to slump much) with your resin of choice, make enough of it for the later fillets, you'll just add a bit more filler when you get there to stiffen it for the overhead one.  Lightly wet the glass on the existing bulkhead area(I find this always helps with avoiding air underneath, but the key is LIGHT, you don't want too much resin under there, your'e just trying to get it to the bottom of any pits or texture.  Butter up that seam between the plywood and bulkhead one last time, scrape down the seam with a plastic spreader(the square yellow ones from wet or a cheap bodywork one from your local autobody shop)

Have the first 1708 mat up on your prep board, lightly resin the mat side, then apply it to the repair area.  Wet it out more generously, then apply the second layer of 1708 to it, wet that out.  Air roll both layers until happy, use the plastic scraper to collect any resin that runs out and put it back on the prep table, leaving that around the edge of a repair is ugly and not helpful.  Pull outermost pair of gloves and put on new ones(so still 3 per hand) and take a deep breath for the fun part is next!

Next start on the deck to hull, same procedure, apply slightly stiffer filler to the right angle between deck and bulkhead, fillet it(doesn't have to be a perfect fillet but the better it is the easier your next job is, no more than 10-15 seconds of fussing with it though), lightly wet the mat side up of your strip on your board, lightly wet the surface of the deck and apply the first(widest) strip, wet it out.  Apply the next strip to it, wet that out, apply the next strip, wet it out.  Air roll the whole lot.  Dry your (already mostly empty) roller by lightly wetting out the first of each of the little strips and the parts of the boat they'll be applied to, use this now quite dry roller to VERY VERY gently pick up any excess resin from the air rolling at the bottom of the current strips, to avoid it being under the hull-bulkhead tab.   Next apply the little strips by the hull deck joint the same way.(now pull off outer gloves and go down to two pairs and take another breath or two to relax and check over the repair area so far, it's easy to get too focused and miss that you've nudged somewhere or touched something or have resin leaking, hair on fire etc). 

Last: lightly wet the hull with resin, apply filler to the right angle between hull and bulkhead, fillet it same as before.  Fully wet out the whole 3 layer patch on your board, mat side up, smallest strip first, largest strip last.  Pick up the whole wet mess with two hands, press it into place along the top edges on the hull side of the joint, and kind of pat it into place below that a bit with your other hand, ignore the curling over bit that will go on the bulkhead for now.  Then get your once again almost empty resin roller(not the air roller) roll gently down from your hand to stick the patch in place on the hull until you have it well enough in place you could remove your hand from the top(but don't let go yet).  Put down the roller, switch hands, use your other hand to press the top of the bulkhead side of the material in place, I usually start with the edge of my hand(little finger side) right near the fillet, then kind of roll my hand and the material against the back of my hand into place.   Holding it in place with the back of that same hand, use your other hand to grab the resin roller again, roll the material out, starting from the fillet, rolling towards the centerline of the boat along the new bulkhead tab, working from top to bottom.  Now air roll it, clean up any excess resin on hull side of repair with plastic scraper, clean up where it overlaps onto new bulkhead glass with dry resin roller as before(If you didn't get it dry enough before this point just grab it with your hand and slide down the roller pushing the resin off).  Check for any ugly areas, touching up with the air roller.  Clean your resin roller with your hand one last time, gently roll the entire thing with the almost dry roller to pick up any excess resin.  If I were working with polyester I would then apply a final layer of 1.5 oz mat over the whole thing to blend it into one almost seamless repair, and provide a sacrificial layer for later grinding/sanding).  For epoxy I guess I'd just leave it be then fill and sand. 

Cleanup

Pull off second pair of gloves(one pair left), grab your solvent bucket, clean your tools and leave them to soak in the solvent bucket, wipe up any mess where it shouldn't be, or spills, set mixing containers to drain into roller tray, pile paper towels/rags, any mess onto the big piece of cardboard you taped down at the start.    Remove your last pair of gloves so you don't get resin anywhere on the way out.  Roll cardboard up and go throw it away, then get your resin/solvent etc buckets outside the boat, do one last look over, if you see anything wrong, dip a cheap chip brush in your tray and gently tap it on the problem area(don't drag it like painting).  If nothing wrong, leave things draining into the tray(no sense risking a spill on the way out), get out of the boat, out of your suit and go have a well earned cup of tea(or a beer if it's the end of the day).    I prefer to work wet on wet the whole way for something this size.  It saves time(and nobody likes paying by the hour for wasted time) I don't like the whole fillet, let it set, sand it, glass an area, sand it, etc method some people seem to use even on small jobs like this though it definitely has it's place on big jobs.  

 

 

 

img.jpg

Share this post


Link to post
Share on other sites
3 hours ago, jgbrown said:

Typing the following took longer than doing the whole job should,

Polyester bonds well enough to polyster or plywood as gouv says, nice of jg to write you a workorder. Never got that when I worked as boatbuilder :)
But you say the pieces of plywood are wrapped in epoxy/glass... if so, I would stick to epoxy for the rest.

I prefer to wet out the fibre outside the boat, roll it on a pvc pipe, put in bucket and transport to boat.
If you never did any of this stuff, practice it first outside, couple of scraps will mock the situation easy.

Share this post


Link to post
Share on other sites

The original tabbing extends 6" down the hull on either side.  The distance between the red arrows is about 8"  The way the original bulkhead was constructed appears to be they first glassed in 5/8" veneered plywood to make the head enclosure on port side and wet locker on the starboard side (pic I posted is inside of wet locker, only place they glassed over that plywood).  It looks like used one layer 1.5/24 on each side.  Then they came back and added another 1/2" of plywood on either side of that in the area I am replacing.  The tabbed that in the same way.  So they had 4 layers of 1.5/24 total.   If I do 2 each side of the joint I'll have about the same total cloth thickness, 3 is extra.  They only used thin woven cloth to tab the bulkhead to the deck (little load there). 

I am planning on removing the chainplates before tabbing.  I fit them when I glued my pieces in place so I knew they would fit.

Everything has been recently sanded with 40 grit and wiped with acetone using cloth rags.

Here's an wider shot to see the scale of things.

IMG_3230.jpg

  • Like 1

Share this post


Link to post
Share on other sites

FYI One of the first references I found on line was this article. 

http://epoxyworks.com/index.php/replacing-damaged-bulkheads/

I considered using G10 like they did, I have used it for other projects. I really dislike cutting, drilling and sanding that stuff and wanted to be close to the same thickness of the original bulkhead so I used the plywood.  Instead of 5/8+1/2+1/2+several layers of glass I glued up 4 layers of 1/2 plywood.  My pieces ended up about 1/8" thicker after I glassed over them with the 4 Oz cloth.

The Evenlyn-32 in the article should have very similar/slightly greater loads to my boat.  I see the tabbing they put in place only extends about 4" either side of the joint and was 2 layers of 17oz biax with mat. 

That project looks well done and apparently held up well.  That is where a lot of my plan came from.

And thanks again to everyone who has responded.

Share this post


Link to post
Share on other sites
8 hours ago, LeoV said:

Polyester bonds well enough to polyster or plywood

I have seen the polyester/glass sheathing on a Thunderbird hull peeled off from transom to bow in one sheet simply by grabbing it at the corner of the transom and walking forward.

I've never seen an epoxy sheathing come off without tearing apart the substrate.

For the small difference in cost of the resin for smallish jobs, why take the chance?

Besides, epoxy doesn't stink like poly.

Share this post


Link to post
Share on other sites
18 minutes ago, SloopJonB said:
9 hours ago, LeoV said:

Polyester bonds well enough to polyster or plywood

I have seen the polyester/glass sheathing on a Thunderbird hull peeled off from transom to bow in one sheet simply by grabbing it at the corner of the transom and walking forward.

I've never seen an epoxy sheathing come off without tearing apart the substrate.

For the small difference in cost of the resin for smallish jobs, why take the chance?

Besides, epoxy doesn't stink like poly.

 

Although I am in the epoxy camp myself, take Gouvernail's words above..... "never seen a failure using poly" Even though I have seen failures similar to what you describe, it -can- work well.

Personally, the safety and easier/more reliable mix of epoxy make it worth while for me. I hate the smell of polyester resin and hardener and I like liver cancer even less.

-DSK

Share this post


Link to post
Share on other sites
35 minutes ago, SloopJonB said:

I have seen the polyester/glass sheathing on a Thunderbird hull peeled off from transom to bow in one sheet simply by grabbing it at the corner of the transom and walking forward.

I've never seen an epoxy sheathing come off without tearing apart the substrate.

For the small difference in cost of the resin for smallish jobs, why take the chance?

Besides, epoxy doesn't stink like poly.

It's slow to pour and measure, slow to work with, smells wretched, and to my mind actually harder to get right(slow hardener, fast hardener, mixing ratios by squirts of a pump or measured cups...  Pour volume of poly in container, divide volume poured into 1L if less than 1L mentally, squeeze catalyst bottle, squirt and mix.  Much faster and simpler to my brain(familiarity)  I can't even smell poly anymore, but epoxy still stinks, something about it smells slightly rancid and turns my stomach.  I have peeled out epoxy repairs(from both ply and fiberglass) without major fuss and replaced them with poly... It isn't a magical cure for  bad installation(the plywood was unscuffed, and the glass was sanded but not ground with a coarse enough grit).

However, I would not switch materials in the middle of a project, especially from a familiar to an unfamiliar.  So sticking with epoxy in this case is an excellent plan. 

 

4 hours ago, JeffR said:

The original tabbing extends 6" down the hull on either side.  The distance between the red arrows is about 8"  The way the original bulkhead was constructed appears to be they first glassed in 5/8" veneered plywood to make the head enclosure on port side and wet locker on the starboard side (pic I posted is inside of wet locker, only place they glassed over that plywood).  It looks like used one layer 1.5/24 on each side.  Then they came back and added another 1/2" of plywood on either side of that in the area I am replacing.  The tabbed that in the same way.  So they had 4 layers of 1.5/24 total.   If I do 2 each side of the joint I'll have about the same total cloth thickness, 3 is extra.  They only used thin woven cloth to tab the bulkhead to the deck (little load there). 

I am planning on removing the chainplates before tabbing.  I fit them when I glued my pieces in place so I knew they would fit.

Everything has been recently sanded with 40 grit and wiped with acetone using cloth rags.

Here's an wider shot to see the scale of things.

IMG_3230.jpg

Ah that image is very helpful. 

Thoughts: at 1.5/24oz x2 per side gives you a total of 3 oz of mat, 48 oz of roving per side.  Two layers of 1708 will give you 1.5 oz of mat(it's actually closer to .75 oz than .8) and 34 oz of cloth.  3 layers would give you 2.25 oz of mat and 51oz of cloth.  Yes biax is slightly stronger in most uses than woven roving, but remember my general rule of thumb of same thickness if replacing 1.5oz/24oz with 1708?  You'll have .75oz less mat, and 3 oz more cloth with 3 layers, and be pretty close to original thickness.  I wouldn't skimp.

For the wet locker side I'd proceed as suggested above, for the visible face sides, I would do the following: grind the new plywood, and sand a perimeter of an inch or two so onto the existing bulkhead, to a line defined by masking tape.  Skin the visible sides with one layer of 1708 rather than the two on the forward side(If you were working in poly I would just skin it with a couple layers of mat on this visible side).   Remove the tape you used to make the defined line on the visible side, retape it with 3 layers of 2" tape, the last layer secures the plastic masking down the bulkhead with paper towel absorber.  Cut your 1708 big enough to just overlap 1/4" or so onto the masking tape dry.  When wet it will cover slightly farther.  After the glass cures to a green cure stage(not wet but still soft) you can then careful and neatly cut that edge with a metal ruler/straight edge and a snap blade knife, breaking the tip off every section or two.  Do not miss the window to knife cut that edge. 

 

 

 

 

Share this post


Link to post
Share on other sites

Just a thought on the Evelyn 32 build: we hit a sandbar under sail. Had to haul out to see the damage. The keel joint dropped about 6" at the front. I dunno if you want to work to ultralight standards.

Share this post


Link to post
Share on other sites
20 hours ago, fucket said:

I also like 1708 because of the clean edges when cut. The stuff I have works fine with epoxy.

All biax is stitched together.  Most biax with attached mat has loose mat stitched to it, not bound with styrene.  1708 (with or without mat) is fine with epoxy.  Biax tape takes  a decent curve (you can pre-bend it over your knee) and does not squirm around as much as woven tapes. I love it for tabbing. You can lay it down two layers at a time, then apply a third /fourth layer while the first is still green. Squeegeed surface is quite smooth & requires minimal filling or sanding before paint. Builds fast, and the 45/45 biax has nearly ideal force distribution properties for this app.

done

Mat is fine too. Even more thirsty for resin than biax. Selveged woven tape is probably my least favorite for this job. You get sharp nubbly edges, bends for shit.  Available in greater range of widths, tho.

When laying multiple mat-backed biax, I like to wet out the work surface first with slightly thickened epoxy, then push the first tape into it & wet out v. liberally with a chip brush.  Squeege it pretty good, but leave the surface evenly wet.  Then lay the second tape & don't slop on any additional resin: just go at it with the brush and two squeegees. You might be able to fully wet it out from beneath, just pulling up epoxy from the first layer.  If needed, brush on a little more resin anywhere that looks dry. Then squeege some more.  You can get nice lean resin ratio if you push hard -- and unlike cloth, biax stays put while you work it. :) 

Share this post


Link to post
Share on other sites

Diarmuid, looks like a very similar repair.  Is that 6" biax tape?  How many is that?

Share this post


Link to post
Share on other sites

Diarmud - how is the mat held together within itself if not with a binder?

The sheet of mat may be stitched to the biax but it has to be held together as a sheet.

Before I knew about the binder thing I epoxied some mat and it stayed very white.

Share this post


Link to post
Share on other sites
3 hours ago, JeffR said:

Diarmuid, looks like a very similar repair.  Is that 6" biax tape?  How many is that?

Jeff: that's three layers of 6" wide 1708 + mat, which as far as I can tell is about equal to ~6 layers of 10oz woven in finished build. Did it as 2/rest/1 as described above.  It's remarkably neat to work with: you can get a beautiful tapered edge into the adjacent surfaces with minimal mess. The Albin Ballad just bolted its major bulkheads to factory-installed tabbing on one side: no glue, no 'top hat' tabbing on the second face.  Which is mostly fine: as Gouv notes, even secondary polyester-polyester bonds using mat or chopper gun can be stupid strong. But as long as I was taking the things out anyhow.... I cleaned up the factory tabs, glued the bulkheads to them with thickened epoxy, then added this biax tabbing to the inside faces. Then I put the 3/8" thrubolts back in. :D If this tabbing were the primary support, I'd add one more layer of biax for 4 total. Might even do 2 layers of 8" topped with two of 6". 

3 hours ago, SloopJonB said:

Diarmud - how is the mat held together within itself if not with a binder?

The sheet of mat may be stitched to the biax but it has to be held together as a sheet.

Before I knew about the binder thing I epoxied some mat and it stayed very white.

Jon: The mat is not a 'sheet', but just random strands thrown down & stitched along with the flat roving layers on 1/4" centers:

1708 tape

You can see it all shaggy & loose along the edge, & the arrow points to a loop of mat fiber I just unpicked with a fingernail. No glue of any kind holding it together, so it wets out perfectly.  The thing that doesn't wet out perfectly is the stitching thread, which is likely polyester.  It means your biax repair is kinda visible & you should plan on painting it.

  • Like 1

Share this post


Link to post
Share on other sites
15 hours ago, Diarmuid said:

Jeff: that's three layers of 6" wide 1708 + mat, which as far as I can tell is about equal to ~6 layers of 10oz woven in finished build. Did it as 2/rest/1 as described above.  It's remarkably neat to work with: you can get a beautiful tapered edge into the adjacent surfaces with minimal mess. The Albin Ballad just bolted its major bulkheads to factory-installed tabbing on one side: no glue, no 'top hat' tabbing on the second face.  Which is mostly fine: as Gouv notes, even secondary polyester-polyester bonds using mat or chopper gun can be stupid strong. But as long as I was taking the things out anyhow.... I cleaned up the factory tabs, glued the bulkheads to them with thickened epoxy, then added this biax tabbing to the inside faces. Then I put the 3/8" thrubolts back in. :D If this tabbing were the primary support, I'd add one more layer of biax for 4 total. Might even do 2 layers of 8" topped with two of 6". 

Jon: The mat is not a 'sheet', but just random strands thrown down & stitched along with the flat roving layers on 1/4" centers:

1708 tape

You can see it all shaggy & loose along the edge, & the arrow points to a loop of mat fiber I just unpicked with a fingernail. No glue of any kind holding it together, so it wets out perfectly.  The thing that doesn't wet out perfectly is the stitching thread, which is likely polyester.  It means your biax repair is kinda visible & you should plan on painting it.

 

yes, I like the loose mat but not the stitching. And peel ply neatens everything up but not so much that part.

I generally use a thickened mixture, bonding filler plus some microfibers, and try to do the fillet and the tabbing in one job. You want to provide some support to the hull over an larger area to prevent a hinge effect along the bulkhead. The mat bonds well and provides strength along all axis; one problem with using woven tape is that 50% of the fibers are not adding any strength.

FB- Doug

Share this post


Link to post
Share on other sites

When I did my bulkhead (well documented on this site) I tried using the heavy biax shown in the post above but I could not get it to wet out with West epoxy, probably due to the issues mentioned in the posts above.  

I ended up with multiple layers of 6 oz cloth tape in various widths which would both wet out nicely and conform to the fillet at the intersection of the hull and bulkhead.  Many years later no issues, except that I initially painted over the epoxy with gelcoat.  After 3-4 years the gelcoat started peeling off the epoxy so I got rid of it and painted over it again with epoxy paint. 

Share this post


Link to post
Share on other sites

I used 10 Oz cloth tape for the bulkhead in the pic I posted. Worked great for a small boat.

For a boat getting past 4 or 5 tons disp. I think I'd use heavier fabric - 12 or 17 Oz biax.

Share this post


Link to post
Share on other sites
5 minutes ago, SloopJonB said:

I used 10 Oz cloth tape for the bulkhead in the pic I posted. Worked great for a small boat.

For a boat getting past 4 or 5 tons disp. I think I'd use heavier fabric - 12 or 17 Oz biax.

Because of original glass weight I wouldn't use anything except 1708.  It will give almost exactly the same weight of glass, but will be stronger than original.   Mat is a real benefit when doing repair work, it conforms down to the surface much better.  I've seen straight biax have more resin pockets under it unless the surface is ground totally level(hard on a 24oz roving surface). 

 

Share this post


Link to post
Share on other sites
17 hours ago, jgbrown said:

Because of original glass weight I wouldn't use anything except 1708.  It will give almost exactly the same weight of glass, but will be stronger than original.   Mat is a real benefit when doing repair work, it conforms down to the surface much better.  I've seen straight biax have more resin pockets under it unless the surface is ground totally level(hard on a 24oz roving surface). 

 

That's the lovely thing about peel ply. You can moo-oosh the cloth/resin underneath the peel ply and get a much tighter lay-up, no air bubbles, no pockets of resin, and it keeps you from sticking your fingers in it to see if it's cured yet.

My fiberglass working skills are nothing great but the peel ply takes it to a much higher level.

-DSK

Share this post


Link to post
Share on other sites
6 hours ago, Steam Flyer said:

That's the lovely thing about peel ply. You can moo-oosh the cloth/resin underneath the peel ply and get a much tighter lay-up, no air bubbles, no pockets of resin, and it keeps you from sticking your fingers in it to see if it's cured yet.

My fiberglass working skills are nothing great but the peel ply takes it to a much higher level.

-DSK

Interesting, I must admit I've never used it.  Is it compatible with polyester or is this an epoxy thing? Out here things are pretty old school.  The other shops that do fiberglass were pretty amazed by 1708 for example...Then the idea of buying it in precut widths was absolutely mind blowing, right up there with and respirators instead of bandanas :mellow:.   Then again when I watched one use a 24'x24 block of fresh cedar, round the edges a bit and glass it in with only mat completely blocking off the bilge and mount a pair of I/O engines too it I guess it should be expected. 

Every winter we toss around the idea of building a vacuum bagging rig for doing stringers, and then get busy with the winter projects and back burner it until the next winter, and stick to hand laying it, and rolling it out with a combination of metal and bristle air rollers. 

Share this post


Link to post
Share on other sites
16 hours ago, jgbrown said:

Interesting, I must admit I've never used it.  Is it compatible with polyester or is this an epoxy thing? Out here things are pretty old school.  The other shops that do fiberglass were pretty amazed by 1708 for example...Then the idea of buying it in precut widths was absolutely mind blowing, right up there with and respirators instead of bandanas :mellow:.   Then again when I watched one use a 24'x24 block of fresh cedar, round the edges a bit and glass it in with only mat completely blocking off the bilge and mount a pair of I/O engines too it I guess it should be expected. 

Every winter we toss around the idea of building a vacuum bagging rig for doing stringers, and then get busy with the winter projects and back burner it until the next winter, and stick to hand laying it, and rolling it out with a combination of metal and bristle air rollers. 

I think it's an epoxy thing..... takes off the blush and leaves a nice surface when you peel it.

Can one use peel ply with poly resin? Anyone?

FB- Doug

Share this post


Link to post
Share on other sites
2 hours ago, Steam Flyer said:

I think it's an epoxy thing..... takes off the blush and leaves a nice surface when you peel it.

Can one use peel ply with poly resin? Anyone?

FB- Doug

Oof, good question.  My guess would be No, because Peel Ply is polyester fabric (isn't it?) & seems likely to dissolve in styrene, like polyester resin does. But maybe not.

 

Share this post


Link to post
Share on other sites
44 minutes ago, Diarmuid said:

Oof, good question.  My guess would be No, because Peel Ply is polyester fabric (isn't it?) & seems likely to dissolve in styrene, like polyester resin does. But maybe not.

 

Why would you want to secondary bond with poly anyway ?

 

Share this post


Link to post
Share on other sites
2 hours ago, ScowVegas said:

Why would you want to secondary bond with poly anyway ?

 

Consistency(same glass weights and same materials as original eg 24oz roving 1.5 oz mat) simplicity, cost, speed, control-ability of cure time, able to gelcoat as part of the process.  I'm sure there's a few other reasons too, but those are the most common reasons we don't use it often(pretty much just for bow-thruster tubes). 

 

Share this post


Link to post
Share on other sites
23 hours ago, jgbrown said:

Interesting, I must admit I've never used it. 

Your life is just about to change. You will not believe how much time NOT sanding you can do using peel ply. It leaves a lovely smooth surface and prevents all those horrible loose strands of glass that poke you. It also absorbs excess resin leaving a stronger finished product. How can you NOT use peel ply if you are in the repair industry?

Seriously, it doesn't have to be the composite store supplied special stuff. You can use nylon not polyester, though I've used both. I've just gone to a fabric store and bought the cheapest woven/rip stop nylon (1.5 oz or stronger) they had on sale. Neon colours are good because they tend to be cheap and make you not forget to remove them later. White is not so good that way.  Using this I've vac bagged foam/glass panels that are 8'x8' in one shot. 

Get yourself some lightweight nylon cloth and try out a few square feet of it on some roving or mat or 1708 layups and see for yourself.

 

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, Zonker said:

Your life is just about to change. You will not believe how much time NOT sanding you can do using peel ply. It leaves a lovely smooth surface and prevents all those horrible loose strands of glass that poke you. It also absorbs excess resin leaving a stronger finished product. How can you NOT use peel ply if you are in the repair industry?

Seriously, it doesn't have to be the composite store supplied special stuff. You can use nylon not polyester, though I've used both. I've just gone to a fabric store and bought the cheapest woven/rip stop nylon (1.5 oz or stronger) they had on sale. Neon colours are good because they tend to be cheap and make you not forget to remove them later. White is not so good that way.  Using this I've vac bagged foam/glass panels that are 8'x8' in one shot. 

Get yourself some lightweight nylon cloth and try out a few square feet of it on some roving or mat or 1708 layups and see for yourself.

 

my cousin, who makes some interesting carbon stuff (mühlecomposites.com.br) has used umbrella nylon cloth as peel-ply with pretty good results.

Share this post


Link to post
Share on other sites
1 hour ago, Zonker said:

Your life is just about to change. You will not believe how much time NOT sanding you can do using peel ply. It leaves a lovely smooth surface and prevents all those horrible loose strands of glass that poke you. It also absorbs excess resin leaving a stronger finished product. How can you NOT use peel ply if you are in the repair industry?

Seriously, it doesn't have to be the composite store supplied special stuff. You can use nylon not polyester, though I've used both. I've just gone to a fabric store and bought the cheapest woven/rip stop nylon (1.5 oz or stronger) they had on sale. Neon colours are good because they tend to be cheap and make you not forget to remove them later. White is not so good that way.  Using this I've vac bagged foam/glass panels that are 8'x8' in one shot. 

Get yourself some lightweight nylon cloth and try out a few square feet of it on some roving or mat or 1708 layups and see for yourself.

 

I can see using peel ply if you goober the epoxy on with a brush.  My experience has been that by the time I've finished with the spreader and lay on the peel ply, it won't thoroughly wet out because of the relatively low resin content.  Mostly tiny air pockets with some wet out at the fibre peaks.  Maybe I"m just using it incorrectly, IDK.

Another issue I have with  peel ply is much the same as vacuum bagging -  it really prefers to be applied on a flat surface and is more difficult to work in corners or inside edges

Share this post


Link to post
Share on other sites
2 hours ago, Zonker said:

Your life is just about to change. You will not believe how much time NOT sanding you can do using peel ply. It leaves a lovely smooth surface and prevents all those horrible loose strands of glass that poke you. It also absorbs excess resin leaving a stronger finished product. How can you NOT use peel ply if you are in the repair industry?

Seriously, it doesn't have to be the composite store supplied special stuff. You can use nylon not polyester, though I've used both. I've just gone to a fabric store and bought the cheapest woven/rip stop nylon (1.5 oz or stronger) they had on sale. Neon colours are good because they tend to be cheap and make you not forget to remove them later. White is not so good that way.  Using this I've vac bagged foam/glass panels that are 8'x8' in one shot. 

Get yourself some lightweight nylon cloth and try out a few square feet of it on some roving or mat or 1708 layups and see for yourself.

 

We'll give it a go, so far none of my suppliers had a version that they thought was poly compatible, but I'll be calling one on the mainland next week to see.   To be honest we don't really have many loose strands, when wet out consistently and properly rolled a mat finish should appear nice and evenly fibrous with no shiny resin spots, and no dry areas.   Work flow is typically: Grind, fill, glass and gelcoat.  For finished surfaces two mats or a mat and a veil cloth on the outside(depending on original layup) add short strand fill(If it's air rolled nicely enough you can fill right on the mat without lumps and bumps which saves time), grind @ 80 grit, final fill, light sand and finish.     Like I said, things are old school around here.  1708 was mind blowing for other shops, nevermind stocking pre-cut widths to lay up stringers faster.  We'll experiment with it on something simple, but for complicated repairs with limited work space and lots of curves and angles, I'm not sure if I'd be comfortable rolling blind, I could see benefits on flatwork though(eg modifying hard tops, outside part of leg hole replacement, around here they typically cut a bit of plywood to fit in the hole(no scarf or even a rabbet) stick it in place and slap it with mat until full, then grind and call it good.   I'd be interested in picking your brain about vacuum bagging sometime if you've got a bit of time to kill, I've been curious about using it to build panels, and thought about experimenting for a few other things besides. 

Here's a photo of a cut out from a 1-1/4 thick layup.  alternating mat and roving.  If I remember correctly, it was around 40 layers 1.5/24oz.  It's hard to see the fiber well in a photo, but the layers where it cut right along a strand of roving show up white, you can see they are reasonably straight and consistent, with even fiber distribution, I'm not sure how much better peel ply would make that. 

 

20180504_172727.jpg

Share this post


Link to post
Share on other sites
On May 1, 2018 at 4:59 AM, JeffR said:

The original tabbing extends 6" down the hull on either side.  The distance between the red arrows is about 8"  The way the original bulkhead was constructed appears to be they first glassed in 5/8" veneered plywood to make the head enclosure on port side and wet locker on the starboard side (pic I posted is inside of wet locker, only place they glassed over that plywood).  It looks like used one layer 1.5/24 on each side.  Then they came back and added another 1/2" of plywood on either side of that in the area I am replacing.  The tabbed that in the same way.  So they had 4 layers of 1.5/24 total.   If I do 2 each side of the joint I'll have about the same total cloth thickness, 3 is extra.  They only used thin woven cloth to tab the bulkhead to the deck (little load there). 

I am planning on removing the chainplates before tabbing.  I fit them when I glued my pieces in place so I knew they would fit.

Everything has been recently sanded with 40 grit and wiped with acetone using cloth rags.

Here's an wider shot to see the scale of things.

IMG_3230.jpg

Nice job on prepping the work site.  I would have papered off the louvers too but I'm a bit of a nut.

Share this post


Link to post
Share on other sites

Peel ply is strictly a surface modifier for the last few layers. It won't improve wet out of a thick laminate that.

I confess I've never used peel ply on mat or with polyester resin. But I'd bet nylon won't stick to polyester resin. 

It should improve the finished appearance of even mat - and maybe you can skip the "final fill" stage. Just be aware that cheap fabric store stuff might have a residue behind which could impede bonding or painting - so just wipe it down before further bonding or gelcoating/painting.

Vacuum bagging seems scary the first time you do it. But I build big 8'x8'+ foam/glass panels with stuff from Home Depot and the fabric store (cheap as shit nylon for peel ply, polyester cushion batting for the bleed/breather layer, HD 4 mil builders plastic for the bag, and HD butyl tape to seal the bag. For building flat and cored panels its almost essential - but for repairs I don't use it much. Pump was about $250, vaccum gauge was off the shelf, resin trap was a mason jar with a few holes punched in the lid and a vacuum in/out hose.

These guys (who I trust) say you can use their nylon peel ply with polyester resin. Good description of the process too.

http://atlcomposites.com.au/icart/products/123/images/main/CP00500 Peel Ply.pdf

Here is very good shot illustrating the difference between a peel plyed surface (on the right) and a regular wet out surface (on the left). The excess resin filling the weave leaves a very nice finish with minimal sanding required. 

140504_478m.jpg

Share this post


Link to post
Share on other sites

I recalled tonight that I had used nylon peel ply (the proper stuff, actually bought from ATL Composites in S.Africa) with polyester resin. Worked fine.

Do roll out your laminate first, then apply peel ply, and then a squeegee to smooth out the laminate underneath.

Share this post


Link to post
Share on other sites
10 hours ago, Zonker said:

I recalled tonight that I had used nylon peel ply (the proper stuff, actually bought from ATL Composites in S.Africa) with polyester resin. Worked fine.

Do roll out your laminate first, then apply peel ply, and then a squeegee to smooth out the laminate underneath.

This might be getting a little off topic, but have you used vacuum bagging for stringers/tabbing at all, how does it handle in inside corners?  Does it have sufficient pressure to bend plywood?  My main interest would be if we could use it to fit core to the curve of the transom from the inside without requiring the use of bolts and clamps.  If it's fast enough we could go with thinner layers and still get a better/faster result, and I could then play with it for other purposes as well. 

Share this post


Link to post
Share on other sites

Peel ply works with poly, if you finish with mat then not much improvement. Well rolled (pro tip, get small mohair or solvent resist rollers and the right size air roller) mat is pretty clean, can always use veil. Mat has a binder, even when stitched iirc, and some binders are styrene soluble and some are epoxy soluble. When the binder dissolves (takes a little time) then the mat drapes bettah and absorbs more resin. Std mat doesn't dissolve in epoxy, hence lack of clarity, but it will stick to it fine just not as workable.

Ditto on Vegas re: epoxy for repairs, sticks better, stronger and easier interior wise, can use unbacked biax, just add a layer of 6 oz cloth for bedding maybe then avoid all the extra weight + low strength for mat. Also if 45:45 cloth catches 0:90. Tape has a selvedge edge that can be a nuisance so it may pay to make your own, up to you. Air roller is yr friend. Use enough resin to see through, roll out the fresh layer dry to soak up the excess then wet to clarity, repeat, finish with peel ply to reduce sanding and porosity, as noted, always wash with alcohol or water between coats. Stay clean, especially in b stage.

Share this post


Link to post
Share on other sites

No haven't used vacuum bagging for stringers and tabbing but lots of high end builders do (Cookson, Goetz etc) regularly.

Inside corners are easy if you leave enough pleats in the bag so that it can get into the corner.

I suspect it would easily bend a plywood or of course slit core to a curved transom. A flat transom would be super easy. Don't forget you get ~14.7 lbs/square inch clamping pressure if you go to full vacuum. That is a lot of clamping pressure. Only limitation would be making sure transom doesn't have any holes for air to get in, and if using plywood, the bending radius.

Share this post


Link to post
Share on other sites

Nothing sticks to polyethylene, polypropylene or nylon without some serious love & caring.  

Beyond surface finish of using peel ply, the other two advantages are removal of excess resin & very little surface prep for further bonding.

Share this post


Link to post
Share on other sites
3 hours ago, Zonker said:

No haven't used vacuum bagging for stringers and tabbing but lots of high end builders do (Cookson, Goetz etc) regularly.

Inside corners are easy if you leave enough pleats in the bag so that it can get into the corner.

I suspect it would easily bend a plywood or of course slit core to a curved transom. A flat transom would be super easy. Don't forget you get ~14.7 lbs/square inch clamping pressure if you go to full vacuum. That is a lot of clamping pressure. Only limitation would be making sure transom doesn't have any holes for air to get in, and if using plywood, the bending radius.

Interesting.  I think you've given me our new winter project :-).  I keep a queue of free/cheap old hulls for the winter, they usually need everything and are where I experiment with new products and procedures and let people practice things they need to improve their technique on.   If it works well then we carry on, if not and it's not worth fixing we can tow them to the dump.  If everything works well I can usually get most of my money back in the spring.   Some are very successful and we start to stock/use them.   Some are really, really not.    

Almost all the transoms are curved, usually on the order of .75-2" over the width of the transom.   We typically build a jig on the outside to maintain the shape when bolting or clamping.  A lot of boats the curve is actually flattened out by the time the transom is rotten enough they bring it in, we use a portapower and a 1/8-1/4" aluminum brace to get the curve back to shape, with the deck, then cut the curves into a pair of 2x10s or 12s.   Any thoughts on how you would maintain the curve so the transom fiberglass didn't flatten out towards the plywood when you apply the vacuum instead?    No air leaks, I insist on adding a unit to the inside before we start any re-coring, after grinding out the delamination.  Too many boats have large areas of delamination in the first layer, and the transoms are usually swiss cheese with holes gooped up with whatever was close to hand by owners/shops over the years.   That first layer gives everything a solid foundation and avoids any chance of a missed hole. 

 

 

Share this post


Link to post
Share on other sites

I'd use the same 2x10's on the outside - but don't know how you could easily secure them without making a huge project out of just that. Is the transom flexible enough that you could push on the inside and temporarily bond to the curved 2x10 on the outside? I'm thinking hot melt glue or something with decent short term bond strength. Apply some blue tape to transom then the hot melt glue so it doesn't leave residue on the transom. Otherwise your current system might be better.

A used vacuum pump runs about $200-300. Look for used HVAC recovery ones. Robinair and Gast are good brands. Even something small on the order of 3-4 CFM is enough for the jobs you will do. I prefer oiled pumps for their higher vacuums. They use a special vacuum pump oil; it is slowly used by the pump. Have the pump outside the shop or run a hose from the exhaust; they spew an oil mist.  https://vancouver.craigslist.ca/rds/tls/d/new-air-conditioning-gauges/6584526612.html  

The West System free book is a good introduction to it. http://www.westsystem.com/wp-content/uploads/VacuumBag-7th-Ed.pdf.  Pay particular attention to how to pleat the bag on page 19 (bitter experience is this is where bags leak a lot). You don't need a full vacuum for most jobs; too much vacuum can suck too much resin from a laminate and leave it resin starved. Try for 14-15" Hg to start on your gauge.

Start with a basic flat laminate on some waxed formica or coated MDF, about 12" square, just to try it out. You'll find out how long it takes to apply the bag, chase leaks etc. Have everything precut before any resin is mixed. Then try it with a core - glass/core/glass; all in one go. Make sure your resin has a decent pot life. Only then graduate on to repairs inside a boat.  My first piece was small, second was about 8" x 3', then 3' x 3' and so on.

 

Share this post


Link to post
Share on other sites

We use peel ply all the time with VE resin when infusing or vacuum bagging, its not just an epoxy thing. It is also not a substitute for proper prep for secondary bonding. While there are those who think they can just peel it off and proceed with secondary bonding but that would be a mistake. It does serve a useful purpose of keeping the laminate free of environmental contaminates if left in place until you are ready for secondary bonding but that's about it, you still need to prep the area by grinding/sanding but it will be easier. A couple of years ago we had to completely tab in a structural grid in a 36ft racing sailboat because it had been installed with plexus to a carbon hull that had only been peel plied. The grid was glass/ epoxy, the hull carbon/epoxy, the bond of the plexus to the grid was fine, the failure was to the carbon. We employed the design office who designed the boat  to spec the laminate schedule for the repair and we used a toughened epoxy for the tabbing and all the tabbing  was vacuum bagged. Double bias glass without mat was used for all tabbing except the ring frame ahead of the mast which was tabbed with double bias carbon. The fabric weights and number of plies which varied by location, as well as tapers were all specified by the designer. The spec was for a 65% fiber fraction  and this was achieved by weighing the fiber stacks and using only the amount of resin required , wetting out on a table with squeegees rather than rollers and rolling up and then unrolling into place. The vacuum bag just compacts the laminate without removing resin. I think if one were to consider vacuum bagging for tabbing or other purposes it may make sense to infuse instead, it is really a much lower stress proposition and much cleaner.

  • Like 1

Share this post


Link to post
Share on other sites
On 5/9/2018 at 10:26 PM, Zonker said:

I'd use the same 2x10's on the outside - but don't know how you could easily secure them without making a huge project out of just that. Is the transom flexible enough that you could push on the inside and temporarily bond to the curved 2x10 on the outside? I'm thinking hot melt glue or something with decent short term bond strength. Apply some blue tape to transom then the hot melt glue so it doesn't leave residue on the transom. Otherwise your current system might be better.

A used vacuum pump runs about $200-300. Look for used HVAC recovery ones. Robinair and Gast are good brands. Even something small on the order of 3-4 CFM is enough for the jobs you will do. I prefer oiled pumps for their higher vacuums. They use a special vacuum pump oil; it is slowly used by the pump. Have the pump outside the shop or run a hose from the exhaust; they spew an oil mist.  https://vancouver.craigslist.ca/rds/tls/d/new-air-conditioning-gauges/6584526612.html  

The West System free book is a good introduction to it. http://www.westsystem.com/wp-content/uploads/VacuumBag-7th-Ed.pdf.  Pay particular attention to how to pleat the bag on page 19 (bitter experience is this is where bags leak a lot). You don't need a full vacuum for most jobs; too much vacuum can suck too much resin from a laminate and leave it resin starved. Try for 14-15" Hg to start on your gauge.

Start with a basic flat laminate on some waxed formica or coated MDF, about 12" square, just to try it out. You'll find out how long it takes to apply the bag, chase leaks etc. Have everything precut before any resin is mixed. Then try it with a core - glass/core/glass; all in one go. Make sure your resin has a decent pot life. Only then graduate on to repairs inside a boat.  My first piece was small, second was about 8" x 3', then 3' x 3' and so on.

 

Thank you, good food for thought.  The transoms are always flexible with the core removed, typically by the time the owner notices there's a problem the transom has flattened out significantly and is distorted to one side or the other(usually consistent with prop rotation).  So we press it back out to shape with the porta-power and a semi flexible aluminium bar anyways, then cut the 2x10 so it's on edge and 90 degrees to the deck(basically a bevel and a curve at the same time on both), this makes alignment easier.  I know online they often show doing it from the outside, and there are other shops who will here but I've never liked cutting through the hull all the way around like that when you can simply cut out the tabbing on the inside, and make your cuts in the deck instead or split the hull-deck joint since usually by this time the (often not even resin coated) wood they use to back the joint has rotted away and the boat is able to take on water and move.   I've seen a few signs of failure on ones done from the outside, and the curve is never the same.  Gluing might be possible, it'll be a good experiment, maybe have to score the first couple layers of plywood or go more than one unit first.  I've already got one in mind for messing about with this in the winter.  I have a boat in need of some hatches in the settees, I'll probably see if the customer wants to pay for materials and let us use that as the first flat pieces in exchange for free labour.   

2 hours ago, Steve said:

We use peel ply all the time with VE resin when infusing or vacuum bagging, its not just an epoxy thing. It is also not a substitute for proper prep for secondary bonding. While there are those who think they can just peel it off and proceed with secondary bonding but that would be a mistake. It does serve a useful purpose of keeping the laminate free of environmental contaminates if left in place until you are ready for secondary bonding but that's about it, you still need to prep the area by grinding/sanding but it will be easier. A couple of years ago we had to completely tab in a structural grid in a 36ft racing sailboat because it had been installed with plexus to a carbon hull that had only been peel plied. The grid was glass/ epoxy, the hull carbon/epoxy, the bond of the plexus to the grid was fine, the failure was to the carbon. We employed the design office who designed the boat  to spec the laminate schedule for the repair and we used a toughened epoxy for the tabbing and all the tabbing  was vacuum bagged. Double bias glass without mat was used for all tabbing except the ring frame ahead of the mast which was tabbed with double bias carbon. The fabric weights and number of plies which varied by location, as well as tapers were all specified by the designer. The spec was for a 65% fiber fraction  and this was achieved by weighing the fiber stacks and using only the amount of resin required , wetting out on a table with squeegees rather than rollers and rolling up and then unrolling into place. The vacuum bag just compacts the laminate without removing resin. I think if one were to consider vacuum bagging for tabbing or other purposes it may make sense to infuse instead, it is really a much lower stress proposition and much cleaner.

Ouch... Anybody get fired over that one?  I make a habit of checking grinds before glass, sometimes out of sight out of mind and not getting itchy appeals to people enough to cut corners that should be cut.  Is most of the equipment usable for both processes? 

Share this post


Link to post
Share on other sites

Yes, vacuum infusion and vacuum bagging are pretty similar except with infusion:

- use much thinner (lower viscosity) resin for infusion

- you need a resin distribution media in the bag stack; sometimes special fabrics with vertical through channels to help resin flow

- the learning curve is very steep and unforgiving with infusion. You can throw away a big piece if something goes wrong

- your vacuum has to be perfect. VB allows small leaks if your pump is big enough to overcome them and still get a decent result. VI + a leak = resin stops flowing

I know a lot of Aussie builders have taken to infusion in a big way and none want to go back. But I think they were all good at vacuum bagging first and VI is a logical next step.

  • Like 1

Share this post


Link to post
Share on other sites

Thanks for all the advice.  Got it done this weekend.  Happy with results.  Now it's time to put the rig up and go sailing!!

IMG_3268.jpg

  • Like 2

Share this post


Link to post
Share on other sites
5 hours ago, JeffR said:

Thanks for all the advice.  Got it done this weekend.  Happy with results.  Now it's time to put the rig up and go sailing!!

IMG_3268.jpg

Hard to tell from photo, did you get glass across under where the chainplate will go?   If not I would at least resin coat the wood, and the holes for the bolts.  Have fun sailing!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now