Stringer repair or replacement? -How to fiberglass stringers and over plywood-

Plywood is just one of those materials everyone uses on their boat. In this video I will show you the proper way to do a fiberglass layup. Using some MDO I had in the shop, and is my preferred plywood for any boat project. Its light and once sealed semi waterproof (road signs and billboards were made from MDO) Fiberglassing plywood is a lot easier than you think!! And this technique applies to all fiberglass repair, or your own boat restoration project.
This type of repair can be applied to transom repair, or to replace the stringers on your boat. Even fiberglassing the bulkheads in your boat, really anytime you need to fiberglass a 90 degree angle.
You will need some 1708 fiberglass and some chop strand matting to do this layup. It is crucial that you round over the top edge. Fiberglass does not like to bend at 90 degree angles. I really prefer to use a structural repair putty like total boats or hull and deck because I don't have to mess around with silica, which is very toxic to our lungs.
If your using laminating polyester resin make sure you cure it with gelcoat, please don't use the PVA. I explain why in this video!
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[@williamnichols8227]

A metal spoon works good for fairing those inside edges. I like a soup spoon because they're round. You can put the acetone to it after and it cleans off easily.

[@HoldFastMarine]

This is the only reason I like social media!!! I would have never thought of that!! Amazing yup. I’m pinning this!!

[@williamnichols8227]

@@HoldFastMarine I can't take credit. A friend of mine who's been glassing for years told me to try it. I probably wouldn't have thought of it either.

[@avelitosan]

I've been using yogurt containers for years and I have so many of them

[@HoldFastMarine]

That’s a good idea.

[@mhansl]

Don’t expect the “magic” folding chop strand if you use epoxy. The binders only dissolve in polyester.

[@HoldFastMarine]

Exactly.

[@kylemacarthur3177]

I know this is an older video, but I was under the impression that TotalBoat's polyester structural repair putty required gelcoat with wax to cure. However, after applying it to the stringer, you put polyester resin and fiberglass on top of it. Does the resin act like a curing agent, making the gelcoat with wax no longer necessary? Very informative video, BTW.

[@HoldFastMarine]

First off thanks for the kind words. The TB putty does need wax OR gelcoat with wax to cure it. However because it is covered with layers of glass it allows it to cure. No different than putting pva or a plastic bag over it. I’d recommend using hull and deck which contains wax if you’re worried about it. For the fiberglass you’d need to apply gelcoat over it or use finishing resin for the last layup. Does that make sense to you? I tend to go off the rails after a few bourbons 😂

[@TriPham-sn9jj]

The city mill sold fabric fiber glass like fabric is very good

[@philelmes6967]

Could you suggest a way to attach a piece of 18mm marine ply to an existing solid and sound fibre glass deck. The ply is acting as a sacrificial piece to attach a single seat jockey console. I dont want to screw into the existing deck, hence the ply.

[@HoldFastMarine]

I’d have to see the project to give you the best advice I can.

[@johnvgig]

Extreme newbie. Did you mix a hardner to the resin's before application? Did you mix a hardner to the structural putty?

[@HoldFastMarine]

All resin has some kind of “hardener” epoxy has a ratio, one to one, 5 to one. And polyester resin like we used in this video is a liquid Hardener that you mix according to weight or volume.

[@berntout3697]

Radius all sharp edges with 35 grit sand paper

[@samdavies8564]

Would this type of thing work for a trolling motor mount? I have a Boston Whaler SS. My transom trolling motor doesn’t clamp well due to the layout of the boat. Thinking about adding a bracket on top of the transom in the corner where the transom connects to the gunwale.

[@HoldFastMarine]

Yes, it absolutely would work!!

[@ChainsawSquirrel]

epoxy resin is better over polyster resin , epoxy resin is waterproof and better bond

[@HoldFastMarine]

Yes it is better. However for the amount I use not cost effective. Epoxy is a great choice for repairs you’ll never see. On a hull you want to stick with poly, unless you plan on painting your whole boat. Epoxy is 5 times as expensive and a lot more of a pain to work with.

[@0718dm]

I wet out 1708 before whenever I can. ...Peal Ply for curing.

[@HoldFastMarine]

I do the same. Makes it a lot easier to apply. But it is impossible to film lol

[@chiboreache]

4:09 no need for measure it by fingers legs or marks on the cup - just buy a digit scales 😉👍

[@HoldFastMarine]

I have one. It takes far too long to get it out, calibrate it and then use it. It’s all about speed at the shop!

[@chiboreache]

​@@HoldFastMarine i have two, one for jewelry, the other for the kitchen - both works like a charm, zero waste! turn on and go i can mix resin just a few grams, to glue something at size of a pen or buckle on boots 👌

[@tony7713]

Thanks, I am restoring my first boat, and I have no clue what to do

[@HoldFastMarine]

Your welcome!

[@mikefishhead]

The dollar stores carry 1 oz plastic shot glasses 25 per bag

[@HoldFastMarine]

Awesome

[@brandonmonroe7050]

If I was building a waterproof box like an aquarium would you need to caulk the corners? What type of caulk would adhere to the fiberglass? Is it even necessary?

[@brandonmonroe7050]

I think you just answered my question with the structural repair putty

[@HoldFastMarine]

I don’t know why you’d be making an aquarium out of wood, but make sure you layup many layers of 1708 in the corners. Water pressure and weight is pretty strong!!

[@ryancobb369]

@@brandonmonroe7050 check out king of Diy he the best for aquarium videos here's what your looking for kzbin.info/www/bejne/bHenhpmdodqlpNU

[@ryancobb369]

@@HoldFastMarine size and price a lot of larger aquariums are made of wood.

[@SconHeadVideos]

How long do you leave it to dry before you add the second layer? Also, can you overlap pieces of the fibre glass when the original layer has almost cured?

[@HoldFastMarine]

A few minutes or a few days. Doesn’t matter as long as you’re using laminating resin. Always use laminating resin for these applications and then cure it with some gelcoat with wax.

[@9NailzGarage]

Awesome video, helped me a lot! Thank you!

[@HoldFastMarine]

Thank you for watching! It means a lot to me!

[@stevequate1797]

It sure if you read comments but got question, I’m building a little shallow water catamaran style flat deck trolling motor boat to get me to some of my fishing spots since my 21’ center console was stolen few weeks ago saving up for a down payment and not spending 5,000 on a kayak that I wanted too much. I Incorperated hydra plane style front sponson, attached to a pontoon type hull. Wanted it to look kind cool so figured let’s play. I hv my sponson pontoon both sides build outta heavy cardboard, then cut a 1/8” plywood will be glued to top and bottom of pontoon, 1 cost of resin hardens it a little bit. I going 3 layers thick, 2 coats of gel coat to finish off. But befire gel coating I am pouring in 2lb floatation foam in each cavity of pontoon sponson, a lot of bull sharks on Texas coast line crossing a ship channel not taking a chance. Anyway I talked to a glass man in Fort Worth he told me to cost the plywood with resin like I did cardboard, the. After cured use the cut glass fiberglass then woven, then cut glass again. I never have had a lot of success with the cut glass, coukd t I use 3 lavers of the woven fiberglass? Woukdnt it be just as strong, there isn’t going to be any high speed passes with a 74lb thrush minn Kota trolling motor. I am layering 1st layer in quarters, top let cure bottom let. It’s then one side the other side o relapsing 3” or so, the. Good sanding, to keep smooth surface as I can get, then I am dividing pontoon into 3 equal parts long ways, and wrapping all way around let cure overlap 2-3” wrap middle section all way around overlapping 2-3”, then the front part all way around, overlapping. I really wanted to go do last or 3rd layer, back to front 1 piece on top overlapping 6”, 1 solid piece but each pontoon(2) of them would require 4 -12’ lengths and multiply that by another 4 which is 8 gonna run into money. Doin it correct Isn’t woven as strong as cut glass? My question

[@HoldFastMarine]

You need less layers of woven compared to 1708. Im having a hard time envisioning what your trying to build, but you need layers. Chop and woven or woven and 1708.

[@roghoff1959]

Lose the music

[@HoldFastMarine]

Care to elaborate?

[@DominiqueFleming-cd9wc]

Where can I get the fiberglass mat and 1700 08

[@HoldFastMarine]

Hamilton marine or fiberglass supply depot

[@mulletoutdooradventures6286]

Water infiltration into the wood? How? You just glassed it and if you did it correctly will never occur. The purpose of glassing is to prevent water from reaching the wood 😂.

[@HoldFastMarine]

So when someone runs a screw into the wood without sealing it? Would water get in then? How then do transoms rot out, they are glassed properly? And the purpose of fiberglass is not to keep water out, it’s to gain strength. Even coosa which is technically waterproof needs glass to strengthen it. But I appreciate you watching the video.

[@mulletoutdooradventures6286]

Believe me I totally understand. I own a 72 no stringer sea Bird that is purely balsa and glass and am currently restoring a 68 DUO. Sure if you put a hole in it or is not totally sealed you'll have issues but only in those areas. And if glass is the strength why is there wood? Why not just glass? Wood,any wood, rots. It needs protection. If water can get to it then it will rot. I understand that yes the glass reinforces the wood but it is also waterproof. If glass wasn't waterproof then how do boats float? Not trying to be a dick. When I'm laying glass over wood my main concern as is most is to protect the wood. The bonus is that the glass does reinforce everything. If that wasn't the case you'd have to seal the wood before glassing (when you precoat you seal). Transoms rot because holes get drilled for motors, caps are installed and more holes are drilled. Then you add trim tabs and transducers and zincs. Transoms don't just rot. Floors don't just get soft. Either it wasn't done correctly or after market add ons caused issues. If I'm wrong then my boats are unicorns and the guys who make Viking are the worst boat builders of all time. Like I said I'm not trying to be a dick it just is what it is. I do appreciate the structural putty idea and will be trying that on where my floor meets the sides.

[@richardseagraves2343]

@@mulletoutdooradventures6286 Please do your homework - polyester resin is not waterproof, water does penetrate the glass through osmosis. The other issue is that polyester is not a glue and does not bond to wood like epoxy and allows water to penetrate, hence the rot problem. Thousands of "fiberglass " boats are built using poly with wood components, and many survive for decades - but epoxy wil do a better job - why not build the boat with the best and appropriate materials, you go through basically the same steps? I continue to be amazed at how poorly informed many boat repairers are when it comes to the wood/epoxy issue. Many are self taught or learned from people who really don't unerstand the fundamental differences in the chemistry between epoxy and polyester. Many of the horror stories about epoxy problems arise because the mechanics don't know what the hell they are doing.Can you imagine the house fires or other failures that would arise if electricians were self taught- the probem in the boat building and repair industries is they have no codes or standards to follow. From what I havs observed, the boat repair industry is shameful, many repairs are being done by mechanics with little or no training and it may take years for failure to occur, long after the check has dried.

[@paulbriggs3072]

West System did a survey of epoxy fiberglass over wood and plywood boats that were up to 38 years old and were still in good shape. NO polyester fiberglass boat over wood that old is still in good shape. Much polyester fiberglass was put over end-grain balsa for decks and roofs which are thoroughly rotten inside now. Polyester resin fiberglass has NO PLACE over wood members of any kind. The adhesion is at best 60% of epoxy, and the long term durability outdoors is a guaranteed fail caused by trapped moisture. It's epoxy or nothing.

[@HoldFastMarine]

So an epoxy company did a survey where as the conclusion was epoxy was the only thing you should use. Gotcha. So. The reason balsa core decks and “roofs” got water infiltration is because of the boat owners. I am currently standing on a 1977 Calvin beal where the bulkhead; original isn’t even remotely rotten. Yes it’s being replaced with coosa, and I am 100% pro composites in boats. If wood is to be used, then we use mdo like in the video and decore the non papered places and bla bla bla. Every boat is made from poly resin. There is a reason for that.

[@paulbriggs3072]

@@HoldFastMarine Polyester resin fiberglass in boats is indeed the most widespread due to its cheap cost. But polyester resin suffers from osmosis, and it is well known that older polyester resin fiberglass boats suffer from widespread rot of all kinds in their various encapsulated wood members. The internet is loaded with videos of ripping rotted wood out of old fiberglass boats. This is due to the inferiority of polyester resin. (Its bond strength is also significantly weaker). Using polyester resin to cover wood in any fiberglass boat is asking for trouble down the road.

[@HoldFastMarine]

Out of curiosity what your boat shops name?

[@GTILOUD]

​@@HoldFastMarineI just want to fiberglass the inside of a subwoofer box to better seal and for better airflow eliminate standing waves. What kind of resinn should I use, any tips?

[@HoldFastMarine]

Polyester resin is your best bet. It’s inexpensive and easier for you to use.

[@samuelcooke502]

Great video man!! Thank you!

[@HoldFastMarine]

You bet!

[@sailingdev]

no need to wet over the putty after applied?

[@sailingdev]

also, I'm going to reinforce my dinghy RIB, the back is plywood and I want to add supports (screw it in) then do what you did here, how much I should go into the dinghy hull with the glass from the edge? since I'll need to sand all the gelcoat I want it to be as little as possible without losing strength

[@HoldFastMarine]

No need to wet over it because the putty should still be soft. I can’t really tell you how to do your project without seeing it.

[@terryharris2092]

be good if showed how to cover the ends,

[@HoldFastMarine]

Thank you terry!! That will be coming up in another video!!

[@MrJoeylisto]

Rev chem makes the one oz size cups!

[@HoldFastMarine]

Thank you!! Just ordered some!

[@MrJoeylisto]

Your very welcome

[@hawkhatcher]

Thank you

[@HoldFastMarine]

Welcome