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A Pathfinder build project post, November/December 2021
Quick note – posting this today because iv’e had to take down this week’s post for an edit.
This is the follow-up post to my tools review in which i talked about the tools that i have bought and used on the project so far – in this part i am going to talk about the second side of the build which is the aspect of handling lots of ‘glue and screw’ operations in ply-epoxy construction. As with my tools review i’ll take this as iv’e done it up to the stage i am at – which is a planked hull , coated on the inside but not yet coated and glassed on the outside.
1.Glue station. Iv’e used Epoxy Resin in the past on several projects and my experience with those projects is that it’s very easy to accidentally get epoxy everywhere including on clothes, tools and other bits of the build so on my project i first determined to build a glue station where i would keep all of the in-use resin and hardeners, all of the glue and filler powders and all of the consumables. I would strongly suggest to anyone who is building a ply-epoxy boat or is planning to build one that they have separate benches for ‘clean’ work such as marking out and cutting out, something like a glue station or glue bench but then if space is tight, as it is with me, that they cover whatever bench they are going to use when gluing up components….i use a large sheet of plastic (tanking membrane) to cover my usual workbench when i am doing a glue job on the bench.
I took a look at the Gougeon brothers (West System) book and that suggested building or converting a trolley/bench like structure so i had a search on local buy/sell sites and Ebay to find something suitable : what came up best was a simple and cheap janitors cleaning trolley that i could easily convert with the addition of a small mixing bench which i added on one side. The photo below shows my glue station in it’s normal state and everyday set-up – a small amount of glue and hardener ready to use (top left) kitchen containers full of microfibres, high density filler and low density filler (other additives i use less are on the bottom)….then a pot full of mixing stocks, a box full of heavy grade Nitrile gloves, mixing pots and the brushes that i use when i’m applying lots of glue. My larger tubs of additives an the main cans of resin and hardener live elsewhere in the workshop and my usual routine throughout the build is to top everything up on the trolley as a regular Sunday job….the usual day i clean and tidy the workshop.
My everyday set up with the glue station.
2. Epoxy handling and storage. I buy my glue (West System) in 5kg cans – when the first batch came the hardener came in 200 Gm cans and not the usual 1 litre size…i actually found the smaller cans much easier to work with because i mix my glue by weight and i found it much easier to pour small amounts of hardener from the small cans. On the same note whereas i store my main resin cans on the cool/cold workshop floor i transfer some to a 1 Litre Nalgene style drinks bottle to work from…..this morning was near to a frost out there and the 1 litre container is warming up inside the boat tent because i’m going to be gluing later on. Now (winter) i have moved all of my resin and hardener inside because the workshop is far too cold.
3.Mixing – i don’t use the West System epoxy pumps but mix directly by weight , there is a small amount of density difference between the resin and hardener such that the exact mix ratio by weight is actually 5.19 : 1 (fast hardener) although the technical data does say that there is an acceptable range of mix ratio between 4.8 and 6.2 : 1. I actually mix at a standard 5 : 1 but if i am a tiny bit over with my resin weight it doesn’t seem to matter. As an example lets say i mix a 100 gm batch of resin with 20 gms of hardener the true weight should be 103.8 gms but an acceptable range would be 96 gms to 124 gms. For those who like measuring in a graduated container it can be more difficult to measure volumes of slightly viscid liquids like epoxy because it can be difficult to determine exactly where the meniscus is : i did an experiment with a graduated container early on and i found that my measurement was out by nearly enough to be outside the acceptable mix range .
As a side note the slow hardener density is slightly different again and the actual mix by weight is 5.36 : 1 and a side note to my side note is that yes i do have a calculator near my glue station for when i mix larger volumes and especially when i am using slow hardener. The smallest weight/volume i ever mix is 15 Gm’s of resin – therefore 3 Gms of hardener and i use an accurate kitchen scale that will measure to the nearest gram. My most common weight of mix is in the 40-60 gram range except for when i was gluing the long plank edge to stringer joint when it was commonly 150 Gms of resin.
For mixing i tried, but didn’t get on with, the West System plastic mixing sticks preferring instead simple wooden tongue depressors which i only use once and dispose of ; i did try dropping them in methylated spirits to clean them but found it more expensive and wasteful of time compared to just throwing them away and using new each time. One main feature of my mixing station by the way is that it has a large PVC fabric rubbish/linen sack on the side and anything i dispose of like gloves , mixing sticks and used glue containers go straight into a bin liner inside the sack.
4.Cups and containers. Early on when i was making the frames i was usually only gluing one at once because i didn’t have the space to handle and glue 2 at once so i usually only had to mix 40 or 50 grams of resin and for that i used simple plastic yoghurt pots that my partner saves for me. For slightly larger quantities i use disposable clear plastic or wax paper drinking cups and only use the larger graduated containers for jobs where i need more than 150 mls/gms of mixed resin. Iv’e only used large amounts of mixed but non thickened resin a few times such as when i coated the inside of the boat in stages and when i do that i tend to pour the mixed resin into a paint tray because it’s far easier to pick up the resin on a paint roller that way…..just a quick side note at this stage ; that it’s been very hard to source West System hollow foam rollers in 3 inch size this year and that’s the size i find best for working in the small spaces between stringers.
5.Gloves and glove technique.
I’m lucky in that i can buy ‘gloves’ or ‘gloves’ locally ; the Nitrile gloves that the town chemist (pharmacy) sell are quite thin and tear easily – much better are the heavier duty ones that the local farm/pet/veterinary supplies sell. I can feel the difference as soon as i put on the thicker gloves now and i know that they won’t tear like the standard ones do, for example when i run my finger down a fillet joint. It’s worth learning how to de-glove properly without smearing resin on the inside of your wrist – the trick is to grab the palm of one glove with the other, tear that one off and only then pinch the remaining one between finger and thumb to peel it off. I also usually finish a session by wiping my hands and tools with methyl alcohol (methylated spirits in the UK) and then wash my hands with detergent and water.
My glove technique can seem a little wasteful on gloves because i glove-on to mix and apply my glue and then usually dispose of that pair of gloves, then i try and do the dry work such as setting the screws without gloves and then put a fresh glove on (or fresh pair) to spread the glue, run the excess into a fillet etc and clean up.
6.Resin, hardeners and additives.
I only have direct experience with West System and a small amount of experience assisting on a different build that used SP systems resin and additives – both use 5 : 1 ratio of resin to hardener and as far as i know they’re not compatible systems except that there is no objection that i have heard to using SP systems glue powder rather than West Systems microbibres and/or high density filler in gluing jobs. How much……? i bought a 5 Kg can of 105 resin and 1 kg of 205 fast hardener at the start and that was plenty enough to allow me to build all of the frames, the centerboard , bow spine and so on – i only really started to get through a lot of resin when i fitted the stringers and frames ; one long plank , which is essentially the length of a plywood sheet, i found took 150 gms of unmixed resin and i was often gluing several planks a day.
What to buy….my opinion and suggestion only for anyone setting up a build project is to buy 5 Kg of resin but to buy both slow and fast hardeners ; i made a mistake in only having fast hardener early on which caught me out when i had a big glue job start to set before i’d got all of the clamps on. That much resin plus hardener would be plenty enough to do a lot of the early work with ans then buy resin in 5 kg lots as the work progresses. I bought one each of the medium sized tubs (around 800 Gm) of microfibers, high density filler and filleting blend as i already had some low density filler in stock. At the end of this year as i finish the hull construction iv’e got through most of the microfibers and high density filler but not used much filleting blend – i think because iv’e tended to finish most of my frame to hull joints and plank joints with a high density fillet.
I have used a 5 meter length of 200 gm cloth because i faired and glassed, and faired again, the centerboard and i used up the remaining cloth to coat the cockpit floor – i do intend to coat and glass any high wear area such as the working and sleeping space forward and all of the cockpit seats……right now on the actual project i’m getting everything warm and dry ready to run some 150mm glass tape down the first of the joins in the bunk flat boards.
NB…..Have several rolls of kitchen tissue around the place !
7. Glue storage and glue control.
This morning, as i write, we had the first frost of the year and my planned job today was to fillet around the outer edge of one of the forward bunk/sole boards. The overnight temperature in the workshop was probably only 4 or 5 degrees C , ditto the structure of the boat, that meant having to warm up my container of resin by standing it in warm water for an hour or so and running the space heater inside the tent that forms my boat cover. Several hours later , at the warmest part of the day, but with the tent all sealed and the heater on the fillet joint is just starting to gel – it’s almost too cold to do any glue jobs now and i’m just about to pack the glue and hardeners into a dry crate and bring them inside the house to store.
Earlier this year i had the exact opposite problem as i only started the main construction phase just as it got a lot warmer here – then, i had to keep the resin on the cool granite workshop floor so that it didn’t go off so fast when i mixed it. I also had to plan my glue sessions to either do them first thing in the morning or as the last job of the day ; my early mistake as i mentioned above was in not having slow hardener available and only using fast hardener. Later on i bought slow hardener and that made it far easier to work with the full plank gluing operations.
A side note on glue application is that when i now apply mixed resin to a long joint i use a disposable laminating brush and with the additive mixed resin ever so slightly on the sloppy side – not so runny that it runs out of the joint but just enough to brush out on the plank.
8. Masking up and cleaning up.
When it’s feasible to do so i will mask up a joint with masking tape and leave that in place until iv’e shaped the remnant glue and filler mix into a fillet joint – this was especially so when i was gluing the frames and the bow girder to the bottom board and masking up made the job significantly cleaner and saved a lot of post glue clean up time. I do try to run my joints and fillets clean but there is always some clean up to do afterwards, this was notably so when i was gluing the planks to the frames and the underside of a joint would sometimes catch me out as it tended to be under my eye line and i learnt to walk around to the opposite side to see where glue was being expressed and come back over that run with a mixing stick and often a gloved finger. When i did the long plank joints and applied my glue with a laminating brush i finished by dropping the use brush into a container of methylated spirits and later on washed the brush out…..i found i could get several uses out of a brush that way. As i said above i tend to finish any glue operation by wiping off the tools that i have used with methylated spirits…..the most common tools being my ratchet screwdriver and my battery drill.
While doing my best to work as clean as possible iv’e still had to do a lot of post-cure cleaning and tidying of the epoxy joints and fillets ; i keep several rolls of different sandpaper grades in stock starting with 40 grit and running down to about 120 grit for this stage. I just happened to also have a whole load of wet and dry paper from an old project and bags of triangular (Delta) pads for an electric sander so i often used that to get into a difficult corner. My favourite sanding tools though are still the simple wooden blocks i made – some are left with a square edge and some shaped specifically for my common size of fillet.
A semi industrial vacuum cleaner and some soft sweeping brushes are essential.
At the end of the ‘final cut’ of the last coat of resin i both swept and vacuumed the whole boat out twice using a soft paintbrush and a stiffer nylon detail brush to clean out all of the joints and corners…..after that i wiped out the whole boat with warm water and a small amount of detergent.
9.Just a note on epoxy fillets…..this boat, unlike the Wharram catamaran that i finished doesn’t seem to rely on structural epoxy fillets for strength but i have filleted all of the frame to board joints, the joints along the girder and all along each plank to frame joint. Mostly that just neatens the whole build and i think should prevent any water ingress along a joint. My fillets then are mostly just the same mix as in the joint sometimes bulked out and made a bit dryer with some more high density filler – there are a few joints where iv’e done a larger radius fillet , the join between the cockpit floor and sides for example and just recently where iv’e filled and filleted the bunk flat boards into the side planks.
I’m clearly not an experienced builder and i did run into some of the well known problems in using epoxy resin in a difficult outdoor (covered) setting – early on i nearly lost control of the glue when i put together all of the lamells for the centerboard and it was a huge rush to get the clamps on before the glue gelled. My mistake there was not realizing how warm the evening was and that the timber had been out in the sun all afternoon….and that i hadn’t thought to buy some slow hardener. Later on in the project i tended to think much more about which hardener to use and to be much more prepared to get the glue on and clamped up and the various fasteners in.
I did have several episodes later on of getting an Amine epoxy ‘blush’ and i note particularly later on in the year when i was trying to finish my working day by applying a coat of resin to a plank run say. I think sometimes i didn’t have enough heat inside the cover as the resin was setting and when i did make sure to have the fan heater running before and after applying glue one of the big ‘blushes’ (all of one side inside) went waxy by the next morning because the fan heater failed….i think now that it must have packed up soon after i left the job as it wasn’t running when i went back to check on it before turning in.
That particular error took a long while to correct because i had to sand back that coat quite aggressively and i found that standard dry sandpaper clogged up almost immediately and i had to revert to wet and dry paper used with warm water and some detergent ; by the end of that day’s work my fingertips were so sore that i could hardly type that week’s blog.
I had intended to talk about the fasteners that iv’e used especially where iv’e taken some different approaches to the plans…..i’ll come back to that in the last of the 3 tool and consumables review posts.
Cheers all , coffee break is over and i’m off to do some filling before running some glass tape down a join.