Best Resin To Use With Coosa On Your Boat Project?

This transom replacement is something that's been really weighing on my mind and with it being such an integral part of the boat I thought it might be wise to actually see which resins are going to give the best results for both bonding as well as laminating. Up to this point the way I've utilized Coosa has been for the most part in 'non-critical' applications, and given how important the transom is I want to make sure this thing as strong as possible!!
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[@beefcakes27]

Andy, bravo..! You just did a ton of research in a tidy video for so many out here. Thanks so much for saving so many, time and expense...!!!

[@jnewts1]

As always , great work Andy ! A big thumbs up for all the effort you got to to bring us all this info .

[@captainjayc9217]

Thanks for the test. I used epoxy mixed with filler to glue two Coosa boards together to repair the transom of my boat. Glad that this was a right choice because I had no idea.

[@johnsauls4983]

Just bought 2 sheet of coosa replacing the soft deck in my boat. Rewatching several of you videos

[@sjp52047]

Excellent comparative analysis. It does show that you do have a choice. It's not like their is only one way to do it. Very cool. Regards, Solomon

[@ninney794]

Andy. I dont know if you already have a video about this but, I'd love to here how you got into boats and acquired all of your knowledge. I think that would be a good one for all of us that follow your channel! Hope to hear back soon 🙂

[@donb4386]

Still love the audio at the end. I hope you continue to use it even when this young lady is in college.

[@duanemiller5606]

Didn’t just hit the like button, I also hit save. This was a very good example of how the different products work.

[@MVSweetwater]

Andy I always look forward to your videos and love the content. After seeing today’s video I totally wanted to do a parody of testing various leather gloves when peeling apart coosa panels.

[@CheersWarren]

Nice job, as a polyester advocate for most applications where you understand about prep , structure and proper application like you and I do I agree use the fast to work with , fair priced and plenty strong enough for project quality polyester resin . Cheers Warren

[@kuzz7919]

Thanks Andy your insight is always helpful !!

[@davidcarr4464]

Andy something you may or may not know. The Coosa "regardless of its thickness" has 2 layups of woven roving in them. 1/4" thick Coosa has 2 layups of woven roving and a 1" piece of Coosa has two peaces of woven roving in it. So two 1/2" peaces of Coosa laminated together is stronger than a single peace of 1" Coosa because the two 1/2" peaces now have 4 peaces of woven roving in it. I hope that makes sense. Just something to think about when you order your transom Coosa.

[@Richard-nb4iv]

Great video! learning something new every time i watch.

[@tartansailor]

Thanks for a very informative video. Cheers, Richard

[@Captain_kinz]

I have always used in the past, polyester resin, and two sheets of 1.5 ounce chop mat. The mat helps with bonding, the coosa absorbs some resin, when I sandwich the mat between the coosa I place a bunch of weights on it from the center out until theres squeeze out all the way around and let it kick off. Its worked awesome so far. The coosa doesn't need to be sanded before hand. Cut a key hole on the last one and it was bonded all the way around perfect. Love coosa for transoms. Recently have been messing around with pvc foam boards for good screw retention on floors etc. Interesting core materials available now a days..

[@SCFoster]

The thickened 5:1 epoxy between sheets is the way I went with my SeaRay 380 transom. Given the curve of the transom, I had to kerf cut the Coosa, so the thickened epoxy was rolled and squeegeed into the vertical cuts. Really messy job. Thanks for doing these videos. You're doing what engineering firms do to determine the best approach to construction methods.

[@eddiezalewski5764]

Great info Andy! If I was using Coosa on my project, I would sand the snot out of them, to get some good tooth, and use the thicken epoxy to bond them to the hull, and and together. I remember something about epoxy is one hell of a glue. I totally agree that the polly for glass work would be the best! Or maybe even VinylEster. (Polyester and Epoxy’s illegitimate child😂)

[@jasondavis6746]

Just bought 3 sheets of coosa blue water for my transom! Let the fun begin!!!

[@markmusso7959]

That’sa big help. I just changed my mind from poly to the 5-1. I’m going to be removing my cuddy cabin which means I will have to rebuild my gunwhale cap and sides to put on bolsters. I will finish it with poly but I’m going to use the epoxy to stick them together!

[@pezpengy9308]

ivebeen thinking of making a new rudder for my boat with this coosa stuff so this is really timely.

[@arturpracht3154]

Thanks for this test👍

[@steverichardson6920]

Hi Andy, if you look closely, with the thickened 5:1 the coosa looks to be made up with definite layers and it is one of those layers that has failed, the bond is chemically stronger than the coosa itself which in my book is as good as it gets 👍 the only caveat is that on the larger transom surfaces can you maintain the layup quality/consistency 🤔

[@Ken-xm1rf]

I was impressed! I didn't think that the epoxy would create a strong enough bond to rip a layer off the coosa. I know it will with plywood, but plywood is really porous. Thanks!

[@seanlathbury5410]

Just thinking out loud here....Project Farm is a KZbin guy that does a very disciplined testing of various products. It would be interesting to see a joint project with you two guys.

[@tedgraves6366]

Always informative!

[@nicholasvangreat260]

Thanks Andy! I’ve been wondering how the best way to do a transom, knees, etc and you just gave me that insight and reassurance I needed with your test samples - this is by far best test methods for Coosa I’ve ever seen on KZbin- thank you! I do have a quick question though; if you were to do stringers by combing Meranti Plywood or Douglas fir to sandwich them together, would you still use the 5:1 epoxy with cabosil or 1708?

[@markwentland3147]

Thx Andy this helped me , I'm doing a deck recoreing on my sailboat, i was wondering if you can thicken Polyester resin possiably ? thx

[@borismartinez6475]

I did two transoms, my friend's boat and mine, we used a material similar to coosa board, physically almost the same, but half the price, we layered a one layer of stranded mat 1.5oz and glued it against the fiber on the boat with cabosil, then we put one layer of 1708, covering the material and about 4 layers of 1708 on every bend, starting with 2 inches wide, then 4, then 6, then 8, we used 1.5 inches material, we used, polyester in my friends boat and vinilester in mine, so far so good, each boat has a platform bracket and one outboard.

[@sandydaugherty458]

I agree with Brian Navalinski: vacuum bagging could produce fewer voids and a more uniform thickness. It might work best on a sample with cloth in the join.

[@Twelvestonestacking]

thank you .... i been learnt!!!! goodonyas!

[@DesmoProfundis]

@Boatworks Today, I loved this video... it was kind of a "Project Farm" vid. I don't know if you've watched any of that KZbin channel but if you haven't, you should. It's all about pitting products like this against each other and seeing what works best.

[@justhusqy5616]

I have to apologize for how hard I just laughed when you separated the 5:1 lol muther....

[@johnpayne3197]

thanks informative post for us not in the boat building fraternity,

[@Micington]

Thanks for doing that experiment. I don’t have to do it now. Could you do a video on vinyl ester resin. Have you had much to do with tanks? I’m doing a 25ft Bertram up as well and I’m turning the hollow stringers into fresh water tanks! What do you think?? Haha

[@gregorywest2029]

How was the coosa preped proir to the application of epoxies, sanding with coarse or med paper? thanks for the videos , keep them comming.

[@PrivateUsername]

Thanks for the very informative vid Andy. Also, @13:53 Use those camera settings from now on please :)

[@brianhof7599]

I thought the main reason to add cloth between Coosa was to add retention ability to retain screws. Great vid as always.

[@russudvp]

Great information

[@MrOne925]

Excellent video! Was wondering: In your opinion, is the Coosa bonded with thickened 5:1 epoxy the strongest composite you've worked with thus far?

[@chrislangdell117]

I liked the sheer strength test. Good information. As far as professional boat shops go. All Cosa transoms I have seen are Laminated with a 5 to 1 epoxy and a layer of Glass. On your first laminate the most impressive method I have seen is they layered a fresh layer of chop strand mat to the old transom. Let that cure and then cleaned off wax and scuffed up. Then they layered cosa to it. It gave them fresh glass to laminate too. The CSM. Had more tooth than what was there originally. As far as mechanical Bond. If it were my boat. I would probably take the time to cut 1/8 th inches groves into my cosa boards laminated faces for a deeper mechanical bond. Used to do that with plywood transoms and west system. By wetting out both plywoods with straight resin mix. Then sandwich laminated them with Thickened epoxy using microspheers and silica.

[@christophere5130]

I know old thread… use of all epoxy or both p&e? Thanks

[@bunyipdan]

Left me wondering if perferations might have improved Interlaminar tensile strength for the coosa pannels, sorta like what some foam pannels have?

[@hudson8865]

Thank you.

[@sailingcitrinesunset4065]

Nice video

[@dannyjones3840]

Im sorry Andy, but I lmao when you smashed your hand on that first piece lol.

[@jeremyrainman]

You should think of partnering with other channels, like Beyond The Press to run tests when you do videos like this. They've got all kinds of great ways to set up tests with instruments.

[@sprinkhole58]

Did you clean the surfaces before bonding? Asking as I didnt see it in the video and *might* change the results. AND I am think that you would be using a cleaner on the actual application... meaning your actual results will have experined additional chemicals/processing. As others have noted - the Coosa seems to absorb the epoxy. Perhaps it would also absorb the cleaner too? Might be something to check against (test cleaned vs non)? Thanks again Andy! Glad to see you back at it!

[@tstrandv123]

could you demonstrate epoxy infusion technique and the pros and cons about that?

[@xOLDGUYx]

would you ever consider building a outboard engine swim platform bracket using coosa ? i'm changing a Boston Whaler from jet to outboard

[@ninehundreddollarluxuryyac5958]

Why thicken the epoxy? Are you going to be joining these in a vertical orientation? Can the sheets be bonded while laying flat, and if so, would you just use epoxy without thickener? Does the thickener add strength to the epoxy, weaken it, or have no effect?

[@BrianNavalinsky]

Coosa is a good choice, but whichever resin you use or laminate schedule, bag it and vacuum infuse it. Take it to the next level.

[@bricemcbride8869]

Hi Andy, even though the thickened epoxy may be plenty strong as a bonding agent between coosa sheets, wouldn't the 1708 add strength to the transom overall aside from just bonding the coosa? I would think it would result in a stronger transom to withstand the other forces put on it from the bracket and engine weight and torque.

[@geneduclos4003]

Hey Andy! Hope you had a great Memorial weekend as well. This comment/question is in reference to an older video you presented several years ago entitled, "Gelcoat Buffing And Care." Awesome video BTW. I'm presuming that Gelcoat is Gelcoat, but then again, I'm a newbie when it comes to Gelcoat. We've recently purchased an RV with a Gelcoat coated roof that doesn't look like it has ever been maintained. It's rough/pitted, oxidized, and looks like it's peppered with mold spots. My thoughts are to strip and redo. What do you think would be the best path to take, and do you have any videos where you've done such a drastic repair? Thank you.

[@rodbrandon8598]

Hey Andy, I really enjoy your channel, and concur with most of your conclusions. I know you were attempting to conduct a simple test for demo purposes but fear the process was flawed and led to false conclusions. Such a test should include proper bonding process materials prep.

[@rodbrandon8598]

In all cases, before bonding, the Coosa should have been solvent cleaned (e.g. Acetone, 2 rag method), abraded (80 grit or coarser), dusted off (vacuum or compressed air), and then tacked off again with solvent (in the case of poly, with styrene, which will "activate" the surface of the cured poly resin in the Coosa, to more of a primary rather than solely secondary bond). Had the proper prep been completed, the poly bond would have proven as strong or stronger than the Coosa, which is as good as a bond has to be. Though one can argue that the epoxy bond was stronger (and we already know it will likely be about 20% stronger than poly, under ideal lab controlled conditions, for "standard" resins) without any prep, that is just bad practice and should not be done, EVER, else an unknown variable could cause the job to fail catastrophically, and present a dangerous situation or at least a costly and time consuming otherwise avoidable repair, regardless which resin is used. The other issue is catalyst / hardener. The strength of the epoxy bond is dependant on the hardener used vs ambient conditions. For example, if a faster hardener is used than temperature conditions dictate, then the bond strength can be far less than poly. Using epoxy in uncontrolled environmental conditions can be very tricky, especially when the temperature swings wildly over the curing period. For example, if one attempts to use a certain brand of epoxy that has to do with a compass point that relates to the direction the sun appears to set, and the fast hardender, with a 20 C (68F) ambient temp, the bond will be a dismal failure. Another factor is the poly resin catalyst. For optimum secondary bond, the poly catalyst should be around 1% at 25C (75F). (You didn't mention in your test what percentage of poly catalyst was used.) Any conclusion from the test shown, that "epoxy is better than poly" is a false conclusion. Completed properly, a polyester bond will be at least as strong as the polyester FRP bonded, and quite frankly, any increase in bond strength is to no avail. While one may attempt to argue that the epoxy bond may overcome process error (as introduced in your test) the flip side is that an epoxy process error (too fast of a hardener for conditions) can produce even worse results yet. For any FRP repair, proper prep and process is of utmost importance; anything less for a structural application like a transom is just bad practice.

[@tstrandv123]

is for example a boat hull very resistant to water and glass fiber osmosis that is built with epoxy infusion?

[@mikeyadrick5154]

I have had good luck with 5:1 epoxy(West Syst). There is a youtube video out with a contractor replacing a transom core and Mr Coosa gets involved and they use West System--5:1!----------Mikey , in Sequim

[@mattrogers5036]

Have you ever used corebond? I think it’s made by Arjay industries. I’m curious about the working time advantages the manufacturer claims for it.

[@joelbrown4110]

It appears that the epoxy is actually penetrating the Coosa subsurface vs. the poly. It may be just a matter of viscosity and a slow hardener may add some more time to penetrate further.

[@coffeefish]

Epoxy is good at adhering to things. Poly is not.

[@SteelDoesMyWill]

I love when Andy tests stuff, but this seems like a waste of time. Anyone that works with resins 'should' know that the secondary bonding qualities of polyester are squat compared to epoxy (Andy did say that). Was this video the result of a viewer question? I missed if that or what the origin reason of this test was...

[@johnduncan9749]

I would drill some small holes in the coosa so the resin can penetrate into the coosa, just between each layer. Are you going to lay them up flat on a table or add each layer in the transom as you go?

[@mvp_martinez9104]

I have to do a 1999 Grady white outboard transom. I am going to use Coosa how much 5-1 do I need will I need more then the 1 gallon? Should I get the 1 gallon kit or the 4.5 gallon kit It’s a 7’11 foot transom

[@theoldbigmoose]

Hope you could give a little insight into the intrinsic differences of 5:1 and 2:1 epoxies? What you have observed as the intrinsic and meaningful differences?

[@sufferedenuf]

I've been using 2:1 epoxy and would love to see a comparison to 5:1. Thank you

[@hagn7350]

Will it be a stronger bond if you have holes in the coosa like a foamcore have?

[@markkurtis8637]

How would this compare with standard laid up glass panels?

[@faykos9267]

Which side of the 1708 let go? Was it the biaxial side that let go on the polyester sample?

[@rodneywillard4341]

The glass in between May help you with your over all thickness?

[@aarongreco6328]

I like to thin out my resin with acetone and soak the coosa like you would with wood. Then glass them together normally

[@natekowalczyk5130]

I would have like to see how vinyl ester resin would have held up

[@MrJimmyAbbott]

I think you did video comparing plywood to coosa. In your opinion is the cost of the coosa worth it? (Transom project)

[@joshmosley5864]

Being that the weak point is the coosa itself, would you consider reinforcing with screws?

[@djmjr77]

Would have been curious to see thickened poly in that test!! I bet some poly peanut butter with cabo and chopped fiber would have done much better. Great vid, cant wait to see the transom get some love ;)

[@coffeefish]

Poly is a bad adhesive. It always has been and it always will be a bad adhesive. Not sure that adding fibers or thickeners will change anything.

[@rodbrandon8598]

@@coffeefish Not true! Depending on the application requirements, poly can be a great adhesive, and far better than needed to meet the application needs. What's more, in less than ideal conditions (variable temperature during cure time) the bond strength of epoxy can be less than poly. For every application, one must evaluate the pros and cons of ALL options, and the importance of each to the end result, to determine the "best" solution.

[@tillkoerber8429]

Thanks for your videos. How long did you let the resins cure? I believe the 2:1 epoxy will take longer to reach full cure and should ultimately have the highest strength.

[@j.c187]

This is exactly what I wanted to see for my upcoming project.

[@GrantSR]

Did you get a battery for your calipers yet?

[@michaelberroteran3467]

A true test is to wrap the exterior of the coosa broad with glass with 1708 and woven or just woven glass by itself... at the same time gluing the 2 pieces together.... then try to pull them apart at that point.... I believe you will find the results to be quite satisfying...

[@z_actual]

In a sense this is exactly what we should expect, the poly will separate at the glue line, the epoxy will not. And it follows that these traits are transferable to plywood or timber in exactly the same way. Ultimately for knees and the like you would be advised to have mechanical fasteners for the most assured joint properties.

[@davidkoba]

What an expensive test! As a poor person I appreciate you putting out this content.

[@Bryster51]

Looks like you did not rough sand for better adhesion

[@tomwood6989]

I think coosa has a "bonding board" it has holes in it to allow the resins to penetrate and bond better

[@wadeprivott5750]

Should try with 1.5 oz. mat. Needs binder on both side?

[@BackyardBoatworks]

Agree. 1708 is single sided. 1708 here is not the correct glass to use.

[@turner593]

why no Vinyl-ester ???

[@rlwilson29325]

Great vid but you should have tried VINYLESTER... I use it with coosa and find it penetrates deeper than epoxy because of lower viscosity. Price is the midpoint between polyester and epoxy and it works fast like poly.

[@kenr4137]

Any issues 3 years later? I was told by multiple local marine guys to use vinyl ester on my coosa transom

[@atruefreethinker1944]

Hey Andy, since you fabricate big and small boat parts, why don't you fabricate a connection from vacuum to your jig saw and other tools out of fiberglass to free up your non-tool hand?

[@yatessmyrna]

I worked for Owens Corning die cutting insulation for stoves and refrigerators for one day. That is all it took to itch all over, and I quit. I can't imagine sanding fiberglass and getting the dust everywhere.

[@richardmondor1360]

Andy, drill a few holes in one panel and use the 5-1 thickened making sure it squishes into the holes...bet you wont be able to separate them....let me know how it works out.

[@BlastedKat]

Interesting, what size holes?

[@joebrenner4428]

They probably only use the polyester to laminate the Coosa.I am planning on laminating for the transom also but I am more concerned about scarfing.

[@jakeramirez6096]

Try to score the mating surfaces to give more of a bite

[@GrantSR]

At about 10:50 you can see that the objects were in focus until your face became visible in the shot, then your camera focused on your face instead. So, if you want to show something to the camera, up close, make sure your face isn't in the shot.

[@michaelsimpson9779]

Interesting tests, good to see the variations. I think the destructive testing was not really representative of any real world failure scenarios though. The chiseling apart of the test pieces introduces a wedging progressive peel mode of failure which isnt really going to give you a good tensile or shear strength indication. Also, the uncontrolled release of energy at the point of failure was a bit dangerous, esp given that you have fresh broken sharp composite edges. You really dodged a bullet there.

[@bobw222]

It's almost as if the 5:1 actually sinks into the Coosa a ways.

[@alexnagle575]

I want to see a test with some 404 filler!

[@edrymes3653]

Perhaps you should be safe as well otherwise we'd be tuning in to Boatworks Today with Stumpy Miller. Seriously, great video. It's always helpful seeing products/methods go head to head.

[@the_saint_1]

First one.. YEY!!!

[@trentyoung1135]

Hope your hand is ok.

[@paulkube3901]

Consider either 1708 soaked I resin bedded between graded cabosil thickened to take up voids; or thickened with chopped fiber? Also....remind me which epoxy resin is more "flexible", and do you believe that may have made a difference? TIA

[@ianherdis7438]

It may be best to start off with a layer of glass laid up with epoxy onto the existing transom. Then the next layers have a good fresh layer to bond to.

[@VT1100tbo]

Was it a slow hardener or fast hardener you used? Coosa clearly becomes stronger if the epoxy allows time to penetrate far into it. As long as the glue joint lasts and the Coosa gives, you have a strong bond. The more you can make the Coosa stay with the glue, the stronger the overall strength will be. Then use the slowest hardener you can get, so the epoxy will take the longest time to penetrate the Coosa. Nice to see some tests, but use gloves next time, it takes a bit of beating.

[@randallrice6314]

I love the videos and I watch them. You really need some better music!

[@blcouch]

If only there were some way you could protect your hands while doing tests like this.

[@fg146]

Interesting! Makes me wonder what would happen if you prepped the Coosa with 40 grit and cleaned it well first.

[@alan-sk7ky]

yeah i was thinking that, scuff up with 60 grit, clean with acetone maybe 'prime' with straight epoxy (5-1 appears to be it!) then in with the filled/glassed.

[@boatworkstoday]

As part of the final thicknessing from Coosa it's run through a big drum sander before being sent out so it already has sanded faces :-)

[@coffeefish]

The epoxies adhered so well that the Coosa board tore apart. I think that if the surface was better prepped, you'd see the exact same result. Adhesion with the epoxy was excellent, hard to improve on that.

[@thomassheppard2690]

I'm wondering if drilling holes every few inches through the Coosa would give the epoxy more grip - somewhat like an epoxy peg or bolt.

[@backyardrebuilds4068]

Watch your digits 😉

[@yepyep340]

I love you man! I will ship you all the reciprocating saws you want! I sugest a Milwaukee sawmill! I dont give a shit wich one thay are all weapons!

[@yepyep340]

SawZall stupid G.D. auto correct!!!