Glassing The Transom And Plans For The Coosa! 

The forces exerted by the thrust of the engines are the upward pull of the stern transom and downward thrust. The critical area to be reinforced is therefore upwards. In the keel of my sailboat I have made a very efficient reinforcement by layering kevlar fabric on a closed cell polystyrene support in the shape of a triangle. In your case it must be horizontal from left to right and have the vertex facing the bow. The stiffness given by a profile with this shape is exceptional. I'm not sure I've made myself clear but I don't know how to send you a drawing. You will certainly receive many useful tips. Good job and keep healthy ...

Great videos. You are my go to glass guy. I have been doing a 1972 Glasspar with a new floor, because of you I had the confidence to tackle the job. Not too sure I got it 100% correct but I have a solid floor now and I used all total boat products. Keep the videos coming.

I think creating a shelf across the transom to support the sole can offer so much structural support, you can skip adding knees. The shelf can be used to reattach the stringers to the transom. If you add seating across the back of the boat, you could re-enforce the transom with a second horizontal shelf and add storage boxes under.

I'm working with a similar situation albeit on a smaller scale. I am considering using a router to cut out the plywood around the inset with is 3/16", glassing it to the abutting board, job finished. I'm a newbie and would appreciate pro/con comment. Thanks for the excellent tutorials, you've expanded my knowledge exponentially.

I think your approach to the refit is spot on I am glad I found your channel I am also in the process of restoring a 1960 yalta craft But my little boat is no match for yours but I love it just the same keep up the great informative work thanks again

Having built a fiberglass kit boat. I have enjoyed watching several people repairing fiberglass, boats. You show us the difference between an artist and the mechanics.

I like it. I see the vision. Just a thought, suppose you come forward with the knees but keep them high enough to 1) create the joists for the flooring and 2) tie into the existing lateral stringers with a large rib/bulkhead, to create a kind of grid system, if you will. I have a 1998 Scarab 302 which started it's life as a bracket boat and they took that approach. 22 years later it's still solid.

OUTSTANDING! I commented many videos back about the power/hull dynamics being changed by moving the motors. I also said breakout the chainsaw LOL. I feel your a credit to the boating community in putting out high quality (read that as best information) on RU-vid. Glad to see you adding stiffeners to help redistribute the power/hull dynamics. That was my major concern, But I should not have feared your work Sir is AA top notch per usual. You are one of the few read that as 2 now people I would ever allow to even think about working on my boat. On a side note people who dislike your videos and not leave a comment as to why they disliked it must be your competitors or just random bots that dislike every video on this forumn. I saw nothing "wrong" in this video. why would someone dislike it? Information was spot on and the execution was excellent.

I think it will be more than strong enough. Transom thickness of 2” with 1.5” of Coosa and 1/4” glass on either side will support 400 + HP outboards. Never a problem to go overboard.

I don’t understand why no other comments have been made. 🤔🤔🤔 I’ll kick things off. Great job...she’s going to be battle ready. Thanks for providing us with your knowledge and workmanship. Much appreciated. 👍👍👍

It is possible to bend thick ply or Cousa by placing serial, parallel cuts into the material. Carried down to within 1/8 inch of the surface allows the material to conform as a flexible skin. Fill the grooves with thickened epoxy and a layer of 1708 between. Epoxy and repeat.

Your building a battleship, it’s great. The stress of the outboard will, of course, be pulling back on the top of the transom and pushing in at the bottom, so that ledger and knees are very very important.

I don't think I would worry about the knees so much as I would install 3 or more vertical ribs running from the bottom of the hull to the underside if the deck. The outboards on that huge bracket are trying to push the bottom of the transom forward and the top of the transom to the rear. Vertical ribs from the keel to the deck will lock the transom in place and fight the outward bowing of the top half of the transom.

Watching these videos are making me want to go nuts and find an old 60’s-70’s v-drive or jet hull that’s trashed, split the cap from the hull, use those pieces as plugs for a mold and then glassing a new cap and hull. Maybe its the never leaving the house thing that most of us are dealing with at the moment, who knows, I have done crazy stuff like that in the past so why not lol. Thank you for these videos, they are awesome.

I like the idea that you for the transom. I do not know if that is the way I would go, but that being said I would go your way over my way just because I have never done a transom before. So you are the expert here as far as I'm concerned. Great video.

Decent ideas. If your looking for strength. Which is obvious. Using a few layers of S2 Fiberglass will give you all the strength you could desire. It is used in aerospace composites and it is stronger than Kevlar yet conforms to curvature much more readily. Its a bit more expensive. But 10 yards of it. Wont cost as much as a 3/4 sheet of Cosa. 1 layer inbetween your cosa sheets 3 layers over the top. A few layers of 1708 on top for sanding and fairing.The rest of the S2 for tabbing in your transom and knees. After that you should be able to park a dump truck on the transom.

I used to buy the expensive tools but after my guys trashing them on jobs... I got used to buying and using Harbor Freight tools, for example... $12 for an angle grinder on sale... so I buy multiples and keep some in the boxes in case one breaks... Don't care if they fall off a ladder, deck, roof, whatever... haven't had any issues and they last pretty long... No dust collection however... But strategically placed shop vac nozzle does the trick. Very cool trick on laying up the layers... I've been doing mine one at a time on a vertical surface and trying to wet it out and get the air out with a lam roller, without the one under it moving, it has been a pain... especially after the third layer. I'm going to get a big piece of plastic and try it tomorrow if it doesn't rain...

Andy Have you considered a stack of horizontal laminations, rather than the vertical sheets you are planing? The idea is that it is more difficult to bend a piece of coosa that is 3-1/2” wide than 1” wide. This would also allow you to custom tailor the coosa to fit the entire width of the area you want to cover without having to force it to bend. I’ve had good success with the technique.

You might consider through bolting that ledger board through the transom, and through the platform brackets. That way you make the platform stronger as well as the ledger board. But if you cannot hit the brackets just through the transom would give huge added strength to the boat.

When this is finished, it's going to be unusually strong I'm sure. Thank you for all the knowledge you impart to us !! 😎

Hi Andy Great video we bought a boat 3months ago before lock down. Top notch videos 👌 IV learn a lot from watching them. I was told but seems incorrect that to repair old fiber glass you have to use epoxy but watching you fix things bloody great Keep up the great work Regards John in the UK

Capt. Andy,I agree with your plan to strengthen the transom with tying the supports from the stringers via to the Ledger through and over the keyholes what would you say adding a additional Ledger above the a few inches above the Coosa previous mentioned ledger across the entire transom that would be what my Grandpa said "Belt and Suspenders" dam britches can't fall to your ankles with your hands are full...Txs., for allowing me too throw another which you have covered I truly enjoy your Boat Skills ...

Engineer the new build so that each engine is tied to a single stringer. Don't depend on the transom to be the primary structure. I love watching your stuff, keep it up

Hey Andy, I redid my transom last winter using 1" Coosa and you can bend it. To do mine, I used reversed clamps (i.e. spreaders) to press the Coosa into the shape of the outer skin. Fortunately in my case the outer skin was/is 1/2"+ at it's thinnest (3/4"+ below the waterline). Long story short, it appears to have been very successful as the cores I drilled for the thru hulls didn't show any voids. Your work so far looks great and it brings back a lot of memories.

That would be a great 3 hr plus video lol. I could watch this boat repair all day

Yes comments work. Onto your question: it sounds like a solid plan. I guess it’s already in your plans, but I believe the support going across (to also support your new sole) is probably the key element of your new structure, so I would suggest reinforcing it generously, maybe with a cooza core so you get the needed cross section size to distribute the loads. It will be interesting to see the next updates!

Andy, would it be a good idea to put a second cross piece (similar to the ledge for the floor) higher up on the transom. It would have the dual purpose of supporting whatever you end up using as a back wall as well as beefing up the transom. Perhaps make some sort of vertical tie-in from your under floor knees to the second horizontal cross piece. Belt and suspenders sort of idea.

'Life on the Hulls' has been using some fibre Glass angle stuff to fix floors & modules in the hulls of his Cat... seems to be the same sort of application you want. I saw one guy, 'Building Wilda' made a mould to make some lengths ...

Your plans sound good, maybe even overbuilt if there is such a thing. Most people have no idea how strong multiple layers of fiberglass sandwiched over a strong filler material is actually. Main idea is to get a good solid connection to the stringers etc so that the forces of both propulsions and the sea are shared and transferee. I’m sure a marine engineer could probably cut out some weight with a good design but it’s a boat not an airplane. An extra hundred pounds of glass and resin isn’t the end of the world.

Compact router would be ideal for the keyhole wood removal. Good depth stop control, and the keyhole opening is a perfect guide for the bearing.

Hi Andy. You look happy to be getting on with the transom, removing the old rubbish is now rewarding. Great video thanks.

Ive got a 74 Allied Mistress Mk 3 (hull #1 if you believe it). Ive been fixing blisters and removing thru hulls, 8 thru hulls. 1 went back in for inboard diesel cooling, installed with 5200...I hope I didnt anger the boatworks gods in doing so.

For the knees, check your hull thickness at the transom and then where the knee will end on the bottom of the hull . My guess is your hull is thicker at the transom then it is where the knees will end. You want to make sure you don’t make a stress riser where the knee ends on thinner glass.

Hey Andy, after the 2” coosa I would grind the edges flush with surrounding area, then tape that in with a bunch of 1708. Also, I would follow that up with layers of 1708 over the complete transom, with a little window for the VIN...instead of layers of 1/2” coosa ;-)

Hey Andy, I don't know what the combined HP rating of the those outboards are, which is the main concern, however, the maximum weight put in the boat, should be taken into account. I believe by the time you put the knees in place, you should have plenty of strength in that transom.

If your center support is tied into the stringers it will basicly make a frame of the whole hull to support it.

For a second I actually thought you were using a foam roller to spread the glass initially. Also i'm working on a project where i took a swim platform and extended it from 17" to 25" (was shooting for 24 but hey i'll take the extra inch lol ) now i've come to a point where i have the two original sections glassed back together in their new positions and i am working on strengthening these connections and building up the new section of "deck" with new ribs my plan is i'm using 1.5oz csm at the moment to build a first layer of the new deck sections and glassing the two original pieces back together sort of as a "tack" then plan is to go over with Biaxial and really make it strong and build up thickness. I can get 1708 locally so this is the next best thing i can do. The plan is to use this platform as a display for a product i'm working on but this will involve cutting a rectangular hole in the platform to then put in a casing so to speak which would be molded separately using csm and carbon twill, Which potentially would cut out a good portion of the csm/biaxial i would have previously glassed in . Would you take the time to do the Biaxial cloth in this case where majority of it could end up being cut out ? Plus is there an available option to thickened resin ? something that is already thickened ?

Always learning something new and enjoying the journey with this boat Andy. Think the three knees with everything else will give you the peace of mind when completed. i.e. slight overkill but definitely worth it.. Keep up the great work..

Awesome work ,with my limited knowledge there would be nothing for me to add ...I watch and learn .I have watched %80 of your videos. I have a 98 23SR Maxum came from Florida and needs all layers (5--7) bottom coat stripped and start over and a paint job. And from watching your videos it wont be gel-coat LOL

That’s gonna be really strong. Good plan Andy.

Make the new knees be apart of the deck support, then you have little angle iron fiberglass cleats filling in between the knees....that way the transom is transfering more of the load down to the keel also

Beefing up is an understatement. You will have built a tank once you create the 3.5 inch thick transom and added the knees. How much weight will you have added to the total project? I love the project.

I'll be hitting you up for ideas this winter Andy! Going to rebuild the consoles in my boat...they are literally falling apart right now. I'm going to rebuild them then probly glass the wood over...it's a 1989 Bluefin 1900 sportsman...the ply the manufacturer built the current consoles out of has rotted...I got the boat from my dad and redid the floor last year...consoles this year! Boat ownership fun eh!? LOL

Top work as usual and I'm glad to see you are over engineering the transom, so many are built to "just" perform...

Andy, I love your videos. very informative. Thank you for sharing all the tips and tricks. This project has become a part of my Sunday morning ritual. I have to admit, I'm starting to wonder if it wouldn't have been a whole lot easier at this point if you had just simply taken a chainsaw and cut the whole transom off and rebuilt it. I admire your patience but look forward to another boat, another project. Cheers from Edmonton, Canada

Andy the layout you have in mind sounds great. On the knees I would run them forward to tie them in to a bulkhead that is connected to the original stringers.

It sounds like you have a good workable plan.

Great work as always Andy ! Your plan for the reinforcement of the transom via knees and the full width beam sounds great mate , can't wait to see it come to fruition !

I wish I had seen this before I started working on my canoe this week! I used fast hardener which I believe did not allow for leveling before curing, and now I have little divets all over my repaired areas of the canoe!

You might try using piano wire or fine guitar string on the 5200, it will slice right thru it. Great videos and thanks for sharing your knowledge.

Yep! Boy I sure wish my grinders would play guitar music too!! I sometimes protect a thin spot by sticking some thin sheet metal over it with super77. If it’s super fragile remove it later with a guitar string. Good work glad to see you using a mask when mixing esp cabosil.

Doing the wet out on the table was an idea I wouldn't have thought of, been following the Bertram Transom project to help plan out the transom replacement on my Bonito and it looks like Total Boat will be getting an order from me soon!

Really enjoying the series! Almost 16k views and no comments? Can't be! See you next week!

Ooh yes!!! Lets do some glass!!!

i recall you once saying that epoxy on glass can be tricky because the epoxy, unlike the resin, doesnt melt into the cloth so binding can be an issue. im guessing that can be overcome with sufficient squishing? i recently repaired a hole in my deck with your method of sanding a crater around the hole (tapered) then layering in alternate larger layers of weave and chop using epoxy. so far so good but...

Hi Andy. Thanks for a great vid. Your approach is so helpful for someone learning.

Could you extend those extra knees forwards to a frame? That is if there is a frame. Either way, I love that you are over engineering whilst you are in underneath the floor. Can't hurt.

Sounds like you have a good plan for the knees and horizontal support. Once all of the Coosa is in place, before you attach the knees, do you plan on installing a couple layes/sheets of 1708 from the entire side to side, covering the transom all the way to the corners? I’d love to see you tuck the Coosa entirely in place with a nice snug 1708 blanket(s).

I'm building a wooden boat and, man, I should have watched your videos earlier. I used standard weave fiberglass cloth and it was a pain in the tuchus to lay out wet. 1708 looks so much easier.

Keep up the great works and thanks again for all you do! Having this continue with "the situation" going on around us has really made my life a little less abnormal.

That transom looks great!

More great work Andy. Thanks for sharing.

Thank you for your videos Andy. I always look for them and enjoy them. Glad you got rid of the wood on the transom (peace of mind) and i like your plan for the knees and ledger . Have agreat week sir! -kao

You are the man. Thank you for going through everything with such great detail. I learn more on your channel and channels like this on RU-vid than anywhere else.

I reckon your plan is excellent.

Make sure the transom knees don't block the bolts that need to be re-installed thru the transom.

love your work, thanks Andy, sounds like you have a plan. the OCD and over kill is why i love to watch your channel. This will make this better than new, and last for eva.

IMO, your plan is excellent. It will be interesting to see. What material will you be using for the knees and sole brace?

Hey Andy, apologies for the dumb newb question but why not remove the Armstrong, revert to original setup and refit a pair of IOs? Thanks for the video so relaxing yo watch glassing and sanding. I’ll go back to fixing a lower unit now....

I would put in a single knee in the center, that should be plenty strong, but I am not opposed to over building unless weight is a consideration.

Hi There, I like what you are doing and your plan but the only thing I will change is instead of putting a support nee in the center of the transom I will grind down the bottom 2" stringer about 6" to 8" away from the transom and make that section of the boat flat and open the plug hole at the bottom center where it should be and also the flat area will help in placing the bilge pump that will be able to dump just about all the water from the bilge, Bertrams of those years had an overkill amount of glass at the bottom and removing that little piece of stringer would not be an issue. Frank

If you want to cover the ID number, take a photo of it, print it out and epoxy the copy into the final laminate. Also, you probably know this but if you do not core all the way to the edges you should fair the core to the original laminate to avoid stress concentrations. Hard spots tend to be where stress accumulates when you put force on a panel. There is no penalty for over-engineering except weight. You are probably good all the way around.

Comments are working Andy. I think you have a good plan going forward. One question, if you put a knee in the center, will your boat not have a drain plug (I'm a bass boat guy) or will you just put it to one side of the knee??

How about making the "ledger" out of aluminum C channel so that the sole can slot into it. I would think aluminum would reduce weight as well as direct any load out to the existing stringers similar to the header over a doorway transferring load to jack studs.

So looking forward to the next installment.

Progress, woohoo! What type of plastic is covering your bench or, more importantly, any tips for finding similar? I’ve struggled finding sheet plastic that isn’t folded on the roll, which then leaves ridges when unfolded and laid flat.

Yup. The only place to use 5200 is on someone else's boat. Although I did recently find a place that I would use it on my boat... Gluing rubber strips to the bottom of a gas tank.

Cant you make a cut out in the coosa board where the boat identification is and thereby extend the coosa wider without covering the id? Not ideal to make that cut out from the board but it should be possible to have it cover most of the transom that way. Love your channel!

3 knees for sure, about a foot apart will be awsome.

Hey Andy run knees fwd too that transverse beam near your feet , maybe?

Solid plan. The knees will be easy!

Speaking of which, I want to use pigmented epoxy to skim the entire canoe. Any suggestion as to how to epoxy onto a vertical surface? It would seem challenging to set up a rolling rig of some type...

I like your thoughts about the extra gussets (knees) tying into the ledge for the sole, probably overkill but anything worth doing is worth doing right.

Sounds like it will be pretty strong.

My personal favourite in the series! Good work, thanks!

Nice Andy!! Progress!! I think your knee idea is fine. Are you going to make a hatch for that back area when the floor goes back in?

Take this for what it's worth as I've never worked with Coosa. Can you pattern the hull curvature, then kerf the backside of the Coosa to match, fill the kerfs with thickened epoxy, let dry, then install the Coosa?

Looking forward to seeing the reenforcement of the transom

I'm looking into opening my own boat working shopping. From repair, painting, flipping, building boats. Can you do a video in some tools you absolutely need or if you know of tools you wish you had but don't for whatever reason. I just want to get a idea of what kind of tools are most important. Machine wise that is, hand tools are something you buy as you learn / go

Excited to see your progress! Anxious to see how this turns out.

The Coosa/glass plan sounds good.....as long as none of the Armstrong mount bolts won't interfere! ;) Are you going to run a layer of thickened/graded resin between layers or resin and perhaps a sheet of CS to fill voids/keep it solid?

I love your videos and the information you provide really helps me with my own projects. If we shouldn't use 5200, what should we use? Thanks again for all of your effort. You are helping more people than you know!!

Guessing overkill is a winner :) Looking good

Good job. Like your plan for going forward. How are you going to bend the coosa? Lots of clamps?

All I can say is you do great work and Thank you for sharing your talent.

Is there a reason you laid your glass down in order of 1,2,3,4 on the table? Would it not be easier to pick up after wet out if the order was 4,3,2,1. Just asking because I'm also redoing the transom on my 1979 24 skipjack and will be closing the I/o hole next week. I'm so happy that you are working on this boat in real time almost exactly as I am doing mine. Thank you so much, you are my go to for any and all boat projects!

Should work great and awesome level of Overkill is the to go. People look at it in the future and say this guy took it serious to the next level

I would take the knees right up under the comings like you did on the sides. Take all motor loads and spread them all over the transom. 👍

Wouldn't tying the knees into the stringers be stronger than the hull of the boat? Three large ones into the hull as planned and shorter ones tying into the top or sides of the stringers would sure be strong. But, maybe I'm just not seeing the total plan. Thanks for the video.

man, i get some many ideas,(shortcuts) by watching your vids...thank you once again!