Installment XV in the chronicles of a Mako classic restoration
We returned the next morning eager to see how this old boat accepted her new core. The Penske core sandwich buttered with epoxy cured nicely, the clamps securely held everything in position. We removed the C-clamps and exterior 2×4 board handily. The bond between the new core and the old outside laminate skin was rock solid. Unavoidably, some epoxy ran through the bolt holes of our 2×4 clamping setup. Excess epoxy also drizzled down from the top. Thus our temporary clamp was also accidentally bonded rock solid to the inside in a few spots. It needed persuasion from the multimaster with an ecut blade to cut through the bond and free it up. We resisted the urge to tear the board free as the penske material is only a dense foam. The E-cut made a surgeon like incision which solved this problem perfectly.

This evening involved prep work in advance of the next stage, laying-up cloth inside the transom. We will lay 1708 biaxial cloth over top to the inside of the transom. To assure optimal bonding between old and new, a taper of 5:1 surface area to laminate thickness is recommended. We used a rotex orbital sander with coarse grit discs to grind the bonding area. [Beveled area pictured above, the tan area along the top of transom.] We rounded the top edges slightly and will add some thickened epoxy. Our goal is to fair any sharp edges to a smooth transition- this makes better bonding surface for the cloth.

Traces of epoxy oozed over night leaving a slight hollowing under the core bottom edge. Some epoxy thickened with high density 404 filler and cabosil remedied the voids under the core edge. With this same mix, we laid a fillet joint bead along the entire transom to hull edge. The back of a spoon or a gloved fingertip is all that’s needed to create the concave fillet. The fillet shape forms a nice easy curve for cloth to adhere, which is our next step.

Gravity brought low some epoxy from up on high. Epoxy run is an inherent problem to both bonding and hand-layup of vertical surfaces. We filled the voids along the top corners with the same blend of epoxy thickened with high density filler. The remaining thickened epoxy we spread across the top transom edge to complete a nice smooth transition- like icing on a cake.

The complex form of the top corners will prove challenging to rebuild. We have ground out taper here and still have a bit more grinding to get the correct ratio for a proper bond. Our first layup in this area will focus purely on encapsulating the transom core. We will address the gap in the gunnel in a later step. Bridging that gap will require placing some temporary mold to lay wet-out cloth over.

The final consideration before the glass layup is assuring the surface is clean from contaminants. We will cover this in the next post.

Battening Down the Penske

With Tyvek suits donned we’re ready to roll, like NASA storming down the street to capture ET (unfortunately, camera couldn’t catch TJ’s glowing finger trick) Thus far we’ve ripped out all the old rotten stuff, prepped the transom, filled the voids with thickened epoxy, added a layer of biaxial cloth, and now we’re ready to replace the core. For core we’ve cut out two 3/4″ Penske sheets, equalling 1-1/2″ total core thickness.

We mixed up neat epoxy using the standard fast hardener and 105 resin. We spread this on both sides of the first Penske core sheet to fill in any porosity. We’ll do the same to bonding side of the second Penske panel before installing it.

Just before setting the first core sheet in place, we mixed a batch of thickened epoxy. This we troweled approximately 1/8″ thick on the boat where core edges meet hull, and thinner along the inside of the transom skin. The remaining thickened epoxy we distributed evenly over the joining faces of Penske core once the first panel was in place. The thickened mix assures a strong adhesive bond.

We needed a large clamp to secure everything. A couple of boards thru-bolted with long hex cap bolts and fender washers on either end did the trick. This kept the core in place under moderate pressure until it cured. (We cut the boards and pre-drilled them beforehand.) A liberal wax application to the bolts permitted removal post-cure. Though the inside board lay against dry core, a little epoxy slop inadvertently worked in there. Plastic sheeting would have prevented the board from bonding to the core wherever epoxy oozed. This occured to us in after thought and we later needed the multimaster to pop the inside board free. The bolts passed through the entire clamp setup. We drew tight the 4 hex nuts in sequence, a few turns of the ratchet per bolt to maintain even pressure. The pressure from our makeshift clamp squeezed out any excess epoxy.

Much of the thickened mixture displaced any remaining voids along the bottom base of the core, working to our advantage. We squeegeed away where necessary. Lastly, we braced the top edges with C-Clamps (with plastic sheeting in between). This entire setup was then left untouched to cure overnight.

- Michael Reardon

We mixed up several batches of West System neat epoxy (no additives) and wet out the 1708 cloth on the table. There is a science to estimating the amount of epoxy needed to wet out cloth. We don’t make any pretenses to be scientists; our formula= mix many small batches til we don’t need anymore. We gently squeegeed it over the surface with a single edge spreader and let the cloth soak in the epoxy. Typically the cloth will become translucent as fibers soaks up and bond to the resin. This did not hold true for the biax, but more on that later.

Transfering the wet-out cloth to the transom is most certainly a messy two person procedure. An alternate method is to bring dry cloth over and wet it in place.

Once aligned, we chased out all air from under the cloth using laminating rollers and spreaders.

Notice the Biaxial cloth does not wet out completely clear. In hindsight we learned that styrenes in this “mat type” fiberglass cloth do not bond with epoxy as they do with polyester resin. (Biaxial is woven cloth one side and mat on other side.) Engineers at West System acknowledge this quirk between mat type fiberglass and epoxy in their literature. They also state it does not negatively impact the finished composite strength (from extensive testing). Yet any mat based fiberglass wetted out with epoxy will be less conformable (i.e. harder to drape over a shape) than the same mat cloth using polyester resin. Wow, who knew? Certainly not these two guys. Also, if this were a critical application where it needed to be clear, biax and epoxy should not be your mix of choice (i.e. a cold molded hull where beautiful mahogany shows clear through). Lucky for us, biax and epoxy are fine in this hidden and flat application. Henceforth though, I think we’ll stick to regular 4 to 8 oz cloth compatible with epoxy.

With the biaxial cloth in place, we’re now ready to bed in the core.

- Michael Reardon

Mixing It Up

We’ve moved the boat over to a nice clean and warm workshop for the epoxy application. 60 degree or better room temp is what we’re after. For this whole process we’ve got a wealth of resin and hardener onhand. We also have a cache of mixing pots, mixing sticks, single edge spreaders, fillers, latex gloves and tyvek suits.
The transom area received one last go over with wire brush and vacuum. (See “Preparing Laminates” for more info.) Then we wiped it clean with acetone, let it flash off, and wiped dry with a clean dry cloth. We measured out the resin and hardener into separate graduated mixing pots, and then mixed them together. (Isolating resin and hardener during the measuring process allows us to recapture overpours. An alternative is pumping from the calibrated measuring pumps, but this proves tiresome and slow for large volumes.) We added a 50/50 mix of high density filler and coloidal silica until it was thickened to a peanut butter consistency.We layered on several pairs of gloves so we could peel off a layer without interupting workflow as the epoxy becomes tacky and tools stick. We then used spreaders to fill the epoxy mixture into all sharp angles and hollows, with a fillet joint bead lining the hull to transom joint. Our goal is to ease any sharp angles for the biax cloth, which we will layup in our next step.

This first step will fill voids so that in our final bonding step, when the core is clamped in under pressure, there are no voids. Clamping will squeeze out any excess epoxy which will then be removed.We mixed several small batches to complete this step. Large batches hold heat from the resin/hardener exotherm and will surely kick before you can apply it all. Should the epoxy “kick” in the pot, you’ll feel the heat building in the mixing pot, and the epoxy balls up like chunky cookie dough as you spread it - not good. To forestall the heat buildup we could chill the resin beforehand or disperse the mixed epoxy in a flat pan, but it’s easier- with less waste- just to mix in smaller portions.

We focused attention under the transom top edge and in the complex top corner where gunwale, transom and hull meet.

Once this step was completed we moved immediately to wetting out the biaxial cloth.

- Michael Reardon

Core Strength

TJ and I have reached a major turning point - so far it’s all been destruction to this old Mako. Now we’re ready to build! After a fair amount of elbow grease cutting, grinding and chiseling out the old rotten core from the transom, we’ll begin preparations to bond in new core.
Step one - we need a template for the new core. A large cardboard box worked well for this. Matching the exact core shape is a challenge since we destroyed the old core. We approximated the shape by first clamping the cardboard sheet lightly to the outside of the transom. We traced the exterior contours for a rough, oversized shape, too big to fit inside. Then we pared away excess to fit the inside the boat. An easier approach would be to drape a simple cloth over the inside and trace it with a sharpie, but we used what we had. Matching every intricate imperfection would be extremely tedious. We didn’t sweat the details too much, any voids will be filled with thickened epoxy. We will ultimately bed our core into place with thickened epoxy, like a brick in mortar.

With a satisfactory fit of the template, we traced the shape to new core. We selected a sheet of 3/4″ Penske board. Penske, properly known as Airex PXc board, is high density urethane with glass fibers mixed in for reinforcement. A sheet of Penske is structurally strong, shapes easily and is impervious to water. Unlike traditional plywood, this core will never rot! We managed two transom cutouts onto one 4′x8′ sheet. Sandwiched together it will give us a total core thickness of 1.5 inch. To scribe the cut, we used a Festool Jigsaw. The jigsaw style seen in the picture is the barrel grip. I prefer this style to the traditional top handle for lightness and scribing blind underside cuts.
We dry fit our core cutouts to the transom. A little grinding was required on high spots. We also trimmed the top to approximate the old core height - slightly less than the outside skin.

Now, I’d like to say removing the old core came off without a hitch- but I can’t. We punched through the outside a time or two in the process and those need some touching up. A
proper patch would suffice, but we opted to bullet proof the transom with one layer of biaxial cloth. This will go in place just before the core installation. Biax, also called 1708, is great stuff for structure applications. But before you go ahead and jump on the biax train too, you may want to read on in future post to see how it worked with epoxy. These pictures show our cut of the cloth.

We used these electric shears to cut the cloth and man they’re awesome. One of those simple things that makes life so much easier. A little battery powered gadget that sounds like an electric toothbrush. You can lay the cloth over a shape and cut it out without manipulating it and distorting the weave. If you have alot of cloth cutting to do, it’s worth it’s weight ten times over for the savings on damaged cloth!

The old Mako made a trip for the the next phase. We were blessed with access to a heated building in winter! The unheated warehouse posed a problem for resins to cure. Cold temps can be overcome by very fast hardeners in a pinch, but it’s a give and take. Very fast hardener will accelerate cure in cold temperatures, but epoxy cures much stronger in temperatures above 60 degrees (the warmer the better). The cure strength is much happier in a warm workshop. Come summertime mother nature will take care of the heat for us, but for now this workshop is a blessing.

Before calling it quits for the night we did a few last odds and ends. We tried out the biax cloth for fit and made some diagonal slices to fit it into the odd corners. Next we etched the whole bonding area with a wire brush and course sandpaper to add a little tooth for bonding. We then cleaned the inside thoroughly with the shopvac. Placed a few bandaids with painters tape to show our sympathy for the wounds we had inflicted, then we filled all those old screw holes and damaged spots with thickened epoxy. Content with how things looked, we retired to our favorite pastime - standing back for a gam session with a beer in hand, talking about “what we should really do next is…”

-Michael Reardon

Transom Dissection

In our last segment, we cleared out all the belowdeck flotation foam. This boat looks and feels lighter and drier. It was noticeable when we jumped aboard. The weight loss changed the trailer balance enough that we had to re-adjust the poppets bracing the stern. Now it’s time to address the transom.

Our goal in this next phase is to cut out the wet core in the transom. We need to leave the outside skin intact to keep the hull shape - draw upon those old frog dissections skills from science class. After some discussion, we decided to also cut out the corner fish boxes. The old style boxes aren’t really big enough to store anything, they’re mostly shinbusters eating up valuable deck space. Admittedly, the heavy layup of the fish boxes added tremendous structural strength to the transom. But the stress cracks in the corner joint needed addressing regardless. We’ll build a little extra reinforcing to make up for the loss, but the end result will be alot more usable deck space.

For precise cutting we used a Fein Multimaster with HSS Saw Blade. This tool is great for digging in odd corners and angles. But for this task it lacked the muscle to power through efficiently. The beefier Fein Supercut might have torqued through this material easier. Some advantages of the multimaster you just can’t beat- it is light, easy to use, and will do things other tools simply cannot. But this isn’t one of em.

After what seemed an eternity of carving out the score lines to pop off the inside laminate, the blade of the tool heated up too much and shattered. Perhaps there is a better tool for this work.

We grabbed a tool with muscle. The Dynabrade Cut-Off Wheel cuts a 1000 times faster than any reciprocating tool, but still is easy to control. The shape is more challenging to squeeze into contours, and impossible in some tight spots. The cutoff wheel also requires a compressor with a little bit more umph to power her (21 SCFM max). Because our compressor was a little shy on airflow, the tool would bog down once the cutting edge was buried. Frustrating, but still much faster than the multimaster alone for this job.

With our cuts completed and the March night mercury dropping to hand numbing levels, we retired for the week.

The following Wednesday we began the most tedious of all tasks- removing the inner fiberglass skin and every last bit of plywood bonded to the outside skin. The inside laminate came away without too much effort. Removing the newly exposed plywood was tougher, much tougher. The wringing wet plywood was still heavy and dense. The plywood must have been a good marine grade to have held up intact while soaking wet all these years. The challenge was to remove the wood without destroying the outside of the hull. We set to the task with chisels, pry bars and some heavy hammers. But prying would certainly crack through the outside of the transom. Instead we chiseled and chipped away. It took what seemed an eternity, like “sailing from tedium to apathy and back again, with an occasional side trip to monotony.” Plywood is made of wood pieces or veneers bonded together in layers. It did not respond well to a chisel. Separating plywood bonded to fiberglass made for slow going. This job took us two complete nights of work.

- Michael Reardon

Take a load off…

After hacking away at punk flotation foam for awhile, we assessed the situation and our process. All this foam is no fun - in fact it’s hard work. This picture shows better how wet this stuff is. It’s mind boggling, since this boat has been dry for years. The boat was covered under a ventilated tarp for 3 years and then sat in dry storage of the warehouse for another 7 months or so. It’s still soaking wet! The only way to truly dry it, short of ripping everything up, would be some decent holes ontop the deck to evaporate water out. But we don’t want to wait and hope. We’re taking it all out, saturated foam gone once and for all.

This is the way to do it - after struggling for a while with big pry bars, we came across a couple of shovels in the building. Flat nosed garden spade shovels would probably work best; we used what was on hand, pointed long handled shovels. As we picked up steam the foam kept a rolling- so fast that it meant constant trips to the dumpster. And these buckets of water soaked foam were not light either. Good tunes kept us motivated as TJ scoured out foam from every corner and I trudged between bright work zone and the quiet, cold winter night darkness of the dumpster.

A few hours in and things were beginning to clean up. We shoveled the ankle deep rubble into big trash cans. Now the stringers and hull began to peak through.

The foredeck area was perhaps the one spot of the boat in good condition with no soft spots. Nonetheless, we opted to cut this out as well. We want to evacuate as much wet foam as possible. Also, as we exposed more of the stringers, we conclusively agreed they desperately needed some TLC. With foredeck extracted we could access foam, stringers and main deck installation. TJ and I also agreed it may be nice to include a foredeck locker in the rebuild. Since the deck is in good shape, we’re hanging onto the piece we extracted.

Now that looks much better. We even dug out any accessible areas below the gunwales. Any foam that felt dry to the touch on top was always wet on the bottom when we popped it out. It was particularly built up around the stringers as you might imagine. Improved design will certainly include some limber holes through the stringers to let the moisture drain into the bilge and out.

I wish we could put this dumpster on a scale - I bet we pulled out a between 500-1000 lbs out of that boat in just foam. It truly filled about 3/4 of the dumpster in the above picture.

- Michael Reardon

Foam Foam go away…

Would you look at this mess. But wait, before you do…

If you found the repair video of last post helpful, here is the final half of West System Fiberglass Repair video. The West System steps outlined here are a proven successful repair method, one of many possible approaches. In any repair, proper preparation of the repair area takes the most time and is critical to repair strength. If you have never done this before, do some research beforehand, but fear not, it’s easy when done properly.

In all fairness, this repair could be done more cheaply using polyester resins instead of epoxy. (See Epoxies, Vinylesters and Polyesters Explained) We selected epoxy because we are familiar with it, like the working characteristics of epoxy, better strength to weight ratio of epoxy and it isn’t as stinky when the stuff kicks. Any polyester gelcoat finish will stick just fine to properly cleaned epoxy (soap and water scrub to remove amines). This was a great boat made of polyester, and it will be just as good should you choose to use poly resins in the rebuild. Whichever your tool of choice, just make sure you follow the proper preparation and mixing procedures. The West System Fiberglass Boat Repair and Maintenance Manual is a great resource for exactly this type of project. Now, on with the story…

With the old deck removed, we peer into black box. What lurks below decks is cruddy foam galore. Mako filled mostly all the void areas with 2 Part Flotation Foam. This closed cell foam serves many purposes. Foremost, it adds needed buoyancy should you wish to invert the boat and make it a life raft. Additionally, the foam has structural purpose. Some boat designs seat the deck directly atop the stringers (fore aft longitudinal supports). The Mako deck instead is suspended. Smaller longitudinal supports are bonded to the underside of the deck, and the whole thing seated on a bed of foam. The foam cushion deadens shock when pounding through waves.

It almost looks fluffy and edible in the above pictures - some salty fluffernutter sandwich. But here’s the rub- all this foam is soaking wet. Closed cell foam normally does not hold water. But even this most synthetic of foam degrades with age and exposure to elements, in this case good old H2O with a dash of fuel and twist of mildew. Dead flotation foam born again into a giant sponge. Cool! Remember those eerie groans and pops the winch cable made as she was guided home on the trailer. That’s one heavy boat! If you suspect this may be a case in your boat, check the waterline. The yellow tell-tale waterline on this old girl grew higher and higher. Tall tale perhaps (sorry, couldn’t refrain from the bad pun), but I suspect there was a time or two she was floated up from the bottom of some bay. There’s alot of water in here.

So bring on the unsavory nasty task. We have to pull and rip all this foam out.

First we tried to lever chunks out with pry bars. It worked a bit, sort of like shoveling snow with a teaspoon. Occasionally we’d celebrate a particularly big chunk that would pop free. Maybe even show it off boastfully til a bigger one came along.

But mostly, the big prybars made wet, mushy pulp freed up between the stringers. (and yes, that is a big ol crack in the stringer pictured above. “Dem bones weren’t made to carry all that water Cap’n”)

We need to change tacks to make any decent progress.

Check out the pictorial of her repairs and an accompanying article in the local paper at the Ernestina website

“Off with her Head!”

Time for the ceremonial first cut - Would the person responsible for the derelict white power boat please step forward… It’s a funny feeling when you actually hold a saw over any boat with malicious intent. We’re about to make every boat owner cringe - literally cut the top off this boat. Once we do, there’s no turning back. TJ and I comfort ourselves by agreeing, “well, we can’t make it any worse!” So here goes nothing - we grit our teeth and plunge in. See, it’s not so bad. Just like a friendly dentist visit Our basic plan with this cut is to leave a flange of at least 4-5 inches of remaining deck. The flange will provide area needed to tab the new fiberglass deck into. Check out the West System repair video to get an idea of basic fiberglass repair principles…

We will return to the flange of remaining deck at a later date to prep it for laying in the new deck.

The Sawzall rough cut through the old polyester fiberglass deck handily. This reciprocating saw is a great cut anything tool but beware - if you plan on keeping stringers and all intact for re-use, be careful in the depth of cut. Or you may unwittingly cut through stringers and other structural members unseen. It was challenging to contour the 90 degree corners with a Sawzall. If you plan on re-using the deck later, a jig saw will make a consistent, cleaner cut at a controlled depth, thus it may be a better choice.