Structural Reinforcements and Hull Repairs on my SJ320 (Raceboat Refit Ep3)

[@Anthony-rp1qc]

Liking your channel, very straight forward and informative with great British whit and charm.

[@RefitandSail]

Thanks very much, I appreciate the comment

[@Sonnell]

Nice vid, many useful info! Just a note, from physics point of view: When strengthening the hull, the strength will come from the perpendicular part of the glassing (to the hull) not the parallel, so it does close to nothing if you make your foam wider, or even this vide. It is always the perpendicular part that will resist. So the higher you make your foam, the stronger it will be.

[@RefitandSail]

Indeed, absolutely right. But by having a wider stringer I’m spreading out the reinforcement, the resistance to flexing over a wider part of the hull.

[@Sonnell]

@@RefitandSail That is also true!

[@chrismiller29]

I disagree. The wide stringer is effectively a foam cored section of hull. The inner face of the new lamination provides the stiffness. I did wonder why not put foam over the whole area so the whole panel is stiffened?

[@deancleavesmith]

Thanks George, amazing simple approach to fix the flex in the gelcoat.

[@zapcat4194]

Very good episode. I garnered all sorts of tips that are now safely logged away in the old brain box. Keep up the good work...👍

[@RefitandSail]

Great to hear!

[@nickwalters5380]

Loving your work. I'm a wooden boat kind of chap, although most of my actual work is carpentry on metal gin palaces. Your attention to detail makes me happy.

[@jong.5508]

George, Yes!, another outstanding episode! I love watching the sanding, the gluing, the glassing, and all of it. The flow-coated results are just beautiful. George, you indeed are the Presenter, the Director, the Cameraman, the Soundman, the Producer, and you're terrific at all of them. Refit to Sail is my favorite KZbin channel. Love every part of it. The sound effects when you're suiting up are fabulously funny! Your new breathing kit, hood, and hose are impressive, and I'm glad you have them now. What wonderful work you do. Thank you!

[@RefitandSail]

Thanks for the lovely comment, pleased you are enjoying the series.

[@sproket168]

Bloody excellent. Great video mate

[@RefitandSail]

Thanks 👍

[@philipwright7186]

Nice job. Glad you went to the effort of grinding away the outside of the hole to refill beyond the aperture, I'd say that makes it much stronger than a simple plug. Thanks for sharing your knowledge.

[@giorgoskaradimas6438]

Awesome content! Really like the race boat series videos, since I’m an offshore racing sailor myself (after watched all the Lottie series). One of the top channels for refitting sailing (and not only) yachts! Keep up the good work mate! Cheers from Greece!

[@RefitandSail]

Thanks very much, stay tuned, more to come 😊

[@fritsvdwielen]

thanks for the great videos George. I'm learning alot, hope to buy a boat myself some day. (sent a beer, or two, enjoy!)

[@RefitandSail]

Thanks for that, it’s appreciated!

[@37grandsoleil]

Thanks George , again a fantastic video and it makes my day every time you put a new one one you tube channel

[@derekfawell2853]

Don’t worry George - the sanding will satisfy me until Mads gets into the real stuff!

[@RefitandSail]

Haha, that’s good.

[@buzzkillington3354]

This is an awesome boat it looks so modern inside and out for a boat from the 90's, im really enjoying this series. im a big fan of air fed masks they're so much more comfortable than having a tight fitting face mask on for hours

[@RefitandSail]

Stephen Jones was always a bit ahead of the curve, looks more modern both inside and out compared to other 90’s boats.

[@thisismatu]

These SJ320 videos are fantastic! It's somewhat similar to my boat (FG28e), and I've already picked up a few good tips for future repairs and maintenance. Keep the videos coming! PS: I strangely enjoy the sanding parts, even though they're not that fun in real life. :D

[@RefitandSail]

Pleased you are enjoying the project and the sanding, I think people enjoy the sanding because they are not the one doing it!

[@boatMatthias]

The sanding shows very nicely how the filler disappears from the non-crack areas

[@davidrichards-67]

Great job !!! Id be so nervous about damaging the laminate when cutting into the gel coat cracks !!!!!!!

[@sailawayteam]

Great minds think alike. When I bought my boat, adding similar stringers was one of the first things I did (different class boat though).

[@RefitandSail]

Off camera I added a further central longitudinal stringer but it was in such a tight spot filming was going to be difficult. I prob should have mentioned that in the vid.

[@sailawayteam]

@RefitandSail by the way, to me the existing stringer looked a bit unprofessional, could it be a later addition done by previous owner? The paint instead of topcoat also points to that. Weight saving in that spot seems hardly worthwhile in a boat with such a classic and nice interior 😁

[@RefitandSail]

@@sailawayteamI’m confident that the other stringer (the whole structure in fact) is as built when new, some of the laminating is a little less tidy than ideal but laying up a hull with woven glass is never as neat as using csm, but the strength to weight is much much higher. Csm needs a lot more resin to wet out and you need a lot more csm to get the strength. Agree that it’s a shame it wasn’t coated with gel on the inside though.

[@ronkluwe4875]

George - great work and from the pattern of the gelcoat cracks (very visible after you ground them out) it looks like the hull was oil canning under load. The extra stringer is just the fix for that. Just found your site and am now a subscriber.

[@RefitandSail]

Thanks

[@ezequieldiaz1950]

Buen trabajo Capitan !!! Saludo desde Argentina !!!

[@juanenriquezmartinez6864]

Many thanks for your amazing videos I have a lot to learn!

[@vingreensill]

Great vid George. Learned heaps.

[@richarddavies-scourfield8413]

Great video as usual! Didn't notice a fillet between hull and foam before glassing. I use and epoxy fillet or a triangular section foam fillet to ease the ninety degree angle. I know biax is pretty forgiving over tight angles.

[@RefitandSail]

Well spotted, I decided not to use a fillet there, the biax glass happily formed a radius between the two without needed any additional material in there.

[@pauld9530]

I love how the boat has the long windows in the cabin. Pretty good visabilty

[@RefitandSail]

Yeah, I like them too. Need to replace those windows at some point. I think one of them leaks and the tint is faded. Will look cool in a darker black tint

[@albertofourie3294]

Great episode! Even enjoyed all the sanding!

[@RefitandSail]

Thanks

[@topc9858]

Usually, epoxy is hard and a lot of work to sand. Your epoxy looked easy to sand.

[@RefitandSail]

The harness of an epoxy based filler is dependent on what is in it. A silica based filling medium is very hard to sand while micro balloons are easy and you get everything in between.

[@gohanovago2288]

I love the build - awesome bost

[@Manny_Akamotakis]

the mask does look like a game changer, nothing worse than fogging up. another outstanding series,, one of my fav youtubers.

[@RefitandSail]

Thanks

[@jackdbur]

There are covers that attach to your vacuum cleaner for grinders & concrete surface grinding diamond wheels work great on fibreglass. 😊

[@RefitandSail]

Yes I have bought and tried them, they are ok but restrict how close you can get into corners and I found that they made the tool much more bulky and harder to handle.

[@churchofthegreenflipflop2436]

You should create your own t-shirt with the slogan 'This is a Dremel, it's not a Dremel - it's a Bosch' . . . 😀

[@RefitandSail]

Am I really that repetitive haha, maybe a good idea but only if I get sponsored by Bosch tools

[@noversis5361]

Funny thing though is: Bosch bought Dremel in 1993

[@nroose]

Would love to see you do the gelcoat some time if you can!

[@kbbarton1]

I real like the interior layout of your SJ320, and I'm envious that you can probably stand up all the way throughout the cabin! When you were fitting the additional stringer, was it because of the type of glass fiber you used that you didn't have to make a fillet along it on the hull with thickened epoxy?

[@RefitandSail]

I did consider it a fillet was necessary but decided the glass would be happy making its own internal radius there. Saved a bit of weight too.

[@ELCADAROSA]

Great work, George! And others have said, I enjoy your humour! Even if unintended! Remind us again why you don't use Silicone unless you absolutely, positively have to, please?

[@RefitandSail]

Thanks, pleased you like the vids. Silicone is not overly adhesive (which can be a good thing) but mostly I don’t use it as it can’t be painted over easily, and if it gets on a surface that you may want to paint some day it can cause no-end of problems. It’s cheap but unless you are using tons of sealant there are generally better options in my view.

[@ELCADAROSA]

@ , thank you!

[@vladaslitvinas5392]

Great insightful video, as always! :) Did you consider doing the reinforcement stringers along the length of the boat, in a grid-like manner?

[@RefitandSail]

I did consider going for a smaller but grid format stringers but decided that it would be better to put an intermediate as per the originals but I’m sure both options would have worked. If I’d though about it I could have vac-bagged the new laminate to reduce weight but it will make minimal difference

[@kencoutts2051]

Health and safety your own , later years it will come back on you.

[@RefitandSail]

You are absolutely right… I’m normally pretty careful but when videoing and concentrating on capturing what I’m doing and talking and doing the job I then forget the ppe…. I’m a man so struggle to multitask!

[@damonkennard6154]

Really enjoying the SJ320 content. Lovely boat. You mentioned she was one of perhaps five models you were interested in, what were the others out of interest?

[@RefitandSail]

Hi and thanks. Given my relatively small budget I also considered mg335, jenneau Sunfast 32i, x332, contessa 33, beneteau first class 10 (probably with a modified rig) and a few others but nothing ticked as many boxes like the sj320, I was lucky to find one that was affordable. With a bigger budget there are new boats that would definitely have tickled me

[@alexmcintyre5720]

What type of sanding pads did you use to remove the epoxy barrier coat from the hull Great informative videos

[@RefitandSail]

Mirka abranet 80g

[@basilismavrogiorgis4343]

Hi George. Nice boat indeed your new acquisition. With regard to stiffening the fore bottom I wonder why you didn't wet the foam frame with 105+205 epoxy resin and hardener mixture.

[@RefitandSail]

I don’t use west 105 epoxy as I have a preferred alternative. However the foam was fairly well wetted out with the very runny epoxy and silica mix that stuck the initial piece of foam to the hull and the additional layers to the first. This was then glassed over using vinylester resin as a compatible product for both polyester and epoxy.

[@ceirwan]

Its quite possible that the paint was added by a previous owner, I've owned boats from that generation that don't have any internal flow coat in the locker spaces. It can be disconcerting to see sunlight through the Hull laminate when the boat is out the water!

[@RefitandSail]

Possible I guess

[@LagleSailingTeam]

What do you think about ultrasonic or electromagnetic log transducer with countersinking thru-hull, so that transducer is completely flat with hull. How would you do it? I was thinking, removing fiberglass exactly the thickness of thru-hull flange (using checking board and test fitting thru hull to get it exactly right), then installing it, then use thickened epoxy to fill up around the flange low areas and sand very carefully (not to sand too much into the thru-hull itself). Or are there thru-hulls available that would be specially made to flush install? Something like Forespar Flowtech valves?

[@RefitandSail]

Airmar (who make the majority of transducers for the main instrument manufacturers) do make a flush mount transducer housing and I considered buying one but in the interests of time and cost and the extra effort required I decided not to fit one for the minimal benefit they offer. To fit I would have to do I as you say and remove the material needed to fit the flush mount flanged fitting and the hull is not super thick so I would have ended up laying up some additional glass (more weight) on the inside of the hull. That may be a future mod/upgrade but my time and my funds to get this boat on the water are limited so having to prioritise.

[@robtoujours]

Hi George, Looks like the paint in the bilge was added later as in the video it looked like there was already a layer of white gelcoat under it? Didn’t look like the usual brown/semi-transparent bare glass you’d see. About the through hull fill, aren’t you doing it the wrong way around? The primary bevel should be on the outside as the water is pressing inwards. I believe there is a specific formula for the thickness of hull vs width of bevel as well. I am sure it’s strong enough the way you did it but eg in the west system guide to fg repairs its primary bevel on outside and sealing layers on inside.

[@RefitandSail]

Hi, thanks for the comment, there was no gelcoat under the internal paint, the grey coating was directly on the laminate. It may be it looked a bit white due to light reflection or you could see the exterior white a though the semi translucent laminate, its fairly thin in this area. The the hole, it’s generally recommended to go for a 12:1 taper/bevel around the hole, you can think about it like a scarf joint in two sections of timber being joined. Sometimes you can’t achieve this due to surrounding structure so I end up doing more of a grind on the opposite side and lay up more glass there to make up for it. I really don’t think it makes much difference which side the taper is made and the glass laid up, getting a good bond is more important an that is significantly easier if working with gravity rather than against so the primary repair was done on the inside and a small amount of glass on the outside.

[@timdhines]

Thanks George! I need to do same hull hole repair on a thick 25mm fibreglass hull. Would you do half and half, grind down 12mm inside and out then glass? Also do you start with smallest circle of glass and lay up bigger ones or other way around? Cheers.

[@Wysiwig99]

Biggest patch first, then getting smaller and smaller. Make sure that before you need to taper off towards the perimeter when grinding back. That way you don't have to do as much filling and sanding after glassing over

[@timdhines]

@Wysiwig99 id heard littlest patch first so that each patch has original hull to bind to. With biggest patch first only that one single patch is against original hull and is single point of failure.

[@Wysiwig99]

@@timdhines I know, it's somewhat counter-inuitive, but that's how it's being done.

[@spikeypineapple552]

Thanks for the video. Could you help me understand something that confused me on my recent contessa refit binge watch? What does the layup of the hull look like? (inside to outside) On the inside you have 'flowcoat', to make it pretty. Then some sort of balsa/nomex sandwich, which is glassed either side, then gelcoat, barriercoat, then antifoul? What you've gone back to here looks like gelcoat, but the contessa didnt have that nice white, you just put barriercoat straight on top of what looked like glass.

[@RefitandSail]

The contessa has no core material, it’s all solid laminate, same for the hull of the sj although I think there is some coremat in the topsides of the sj. So on the contessa it will be flow/gelcoat on the inside, glass laminate (mix of woven glass and csm), gelcoat and then barrier coat and af. That said there was no gelcoat on the contessa before I removed it as part of the osmosis repair. Also be aware that builders sometimes use clear gelcoat below the waterline so it may not be white like it is on the sj.

[@knickebien1966]

1:27 For once we see George using a respirator.

[@RefitandSail]

When not on camera I am pretty good at wearing the ppe, but when filming it sometimes slips my mind as I’m doing the job, and talking, and filming and there are only so many things my man-brain can do at one time

[@jonathanblanchard6480]

I like what you show and tell, but know of stringers as fore and aft, and mils as thousandths of an inch.

[@RefitandSail]

Yeah, I prob should have used the term frame for the reinforcement I put in but tend to think of them as a transverse stringers when they are not full length. I’m at that funny age where I use both metric and imperial measurements which can confuse the hell out of other people who are older/american (imperial) or younger/european (metric).

[@bodywood]

Hi George you said the whole hull is going to get a epoxy barrier coat. When you do that do you take the hull back to glass layup

[@bodywood]

You had the keel media blasted but if you was going to take the hull back to glass I suspect you would have done that at the same time. As you didn’t I guess you are doing a barrier coat over the existing. Would be interested to understand to options on that.

[@RefitandSail]

The barrier coat will be applied over the gelcoat, there is no need to remove that and get back to the glass in this case.

[@dadzilla007]

A question, why do you grind the taper on the inside? It seem countertutive to me, as if the taper should be outside, pushing the patch to the hull.

[@RefitandSail]

Hi, thanks for the comment, The taper is just about creating sufficient surface area for the bond between old laminate and new so tape on the inside or the outside (in the case of this repair I did both) makes little difference. Also, think about it this way….. what’s stronger?… the laminate I have just laid up to repair the hole or the relatively thin plastic skin fitting that was there…

[@secretsquirrel6124]

I take it doesn't affect the class rules putting in extra rigidity?

[@mickey1299]

Interesting you fitted the skin fitting before you epoxied the hull George . Is there any money in doing this , or is it something you would recommend with a racing hull ? . I ask this , as my theory would have been , it's better to do this the other way round , so the actual hole itself gets a layer of epoxy . Another point is the foam itself . You didn't show pre-wetting of either the foam or hull with resin before applying the filler/glue so to speak . I've heard you should soak at least the foam , to get a good bond . Just to be clear , i'm not talking about the actual fabric layup , because i'm pretty sure you did do this , just likely off camera .

[@RefitandSail]

Hi and thanks for the comment, my plan is to put the epoxy barrier coating over all repairs, filler, etc on the hull so when it comes to sanding and repainting the hull in future years I can sand it back until the barrier coat is just starting to be visible. With the transducer housing fitted in the (front) hole it has had a skim of epoxy filler to fair-in the flange to make the boat as slippery as possible, makes sense to coat that along with everything else with epoxy barrier after the fill and fair. When gluing the foam in place the thickened epoxy was very runny on purpose so that it would be able to soak into the surface of the foam, which is do because I mixed up loads and still only just had enough. The foam is closed cell so will only absorb so much anyway. I could have wetted it all over with unthickened resin I guess but went with having a very runny mix as a time saver.

[@mickey1299]

@@RefitandSail Ah got ya . Thanks for clarifying those George . Yes i do understand drag and making the hull as slippery as possible , but this is an area i may have to visit some time soon . Though not so much with a racing eye !

[@MaxPivovarov]

It's not stringer (stringer is a longitudinal element of a ship's hull) but frame (frames are ribs that are transverse).

[@RefitandSail]

I try not to get too bogged down in terminology on the channel but you are largely correct although I tend to think of frames as stiffening members that run from the sheer-line to the lowest point of the hull while the new one I fitted was only short and reinforcing the lower part of the hull so I normally use the term longditudinal or transverse stingers.

[@SV_Sienna]

Would it help to transfer loads better and eliminate „hard spots“ when the sides of the stringers would be tapered a bit as well, or would this weaken the stringer to much?

[@RefitandSail]

I don’t think that would add much, it’s the tapering of the glass that is needed so that you don’t have multiple layers of glass laid up that suddenly stop like the end is a shelf and then the thinner laminate of the hull could hinge on that edge.

[@nigellucas560]

Re barrier coats, is the hull low moisture? Asking as I did my impala with six coats after sanding a couple of areas that were surprisingly high around skin fittings. Ten years later still dry.

[@RefitandSail]

Moisture is low in most areas but localised higher spots. It appears to have had a barrier coat from new. The first job was to strip the bottom when it was still warm and I have left the hull to breathe since then so it can dry as much as it’s going to in uk atmosphere. Hoping to get it coated next week if the weather allows.

[@pironiero]

do you have any opinion on inboard well for outboard engines? like melges and ft10

[@RefitandSail]

it can be a good option for smaller boats and sports boats but they can also be problematic with fumes into the boat. Much easier and cheaper to replace an outboard than an inboard.

[@kencoutts2051]

I like the roundal doors it's like watertight doors

[@RefitandSail]

Yes, make me think I’m in a nicely appointed submarine 😂

[@andrewlaming]

What are you using thats making the filler pink? Is that just colloidal silica in epoxy?

[@RefitandSail]

the pink filler is Nautic Watertight epoxy. 1:1 mix - super easy to use and easy sand but will sag if you put too much on.

[@andrewlaming]

@RefitandSail many thanks. Enjoy your videos,.very useful.

[@0drat]

This is probably s stupid Q but can you make stringers longitudinal as well? Is there a reason why stringers that work across the beam at any one pt are preferable?

[@RefitandSail]

Yes, you can have longitudinal and transverse stringers (and bulkheads) that add structure into a boat although many new boats will have a pre-moulded then bonded in matrix that does the job of stringers and bulkheads as I have which is the more traditional (and frankly better) way to build a boat but it’s also more expensive which is one reason many manufacturers now use a bonded in matrix

[@skyd8726]

Personally I'd call anything crosswise either a full bulkhead, or anything less a "frame". Stringers run fore/aft.

[@RefitandSail]

@@skyd8726technically I think you are correct.

[@skyd8726]

@@RefitandSail Grew up in Gurnard, building & sailing boats & dinghys, father was a shipwright.🙂 Once again, really loving that interior layout on the SJ design! The only thing that bugs me is the door into the head. Why have it opeing into the saloon? Weird!

[@peterb9038]

Hi George, , what are you calling this project?

[@RefitandSail]

The name of the boat of the name of the project. At the moment it’s my “raceboat refit” but the oats name will be revealed in a future episode that is already recorded.

[@SuperGardenshed]

why an additional transverse stringer and not a longitudinal between the existing stringer and the bulkhead?

[@RefitandSail]

I felt, having looked at the unsupported hull area that a transverse stringer (or frame as I have been corrected) would better resist flex over a larger area. But both would have worked I expect. Off camera I added an another centreline stringer but it was in an area further forward and access was limited to work let alone film it.

[@SuperGardenshed]

@@RefitandSail more than one way to skin a cat! you've got a good tough boat, looking forward to seeing how you improve it.

[@RefitandSail]

@@SuperGardenshedindeed, I think the internet tends to feed people “this is the way to do it and any other way is wrong” the reality is, as you say, “many ways to skin a cat” although I have not personally tried that activity 😂

[@waterbuoy9121]

Do stringers not run fore-aft?

[@RefitandSail]

Not when they are transverse stringers I guess. I try not to get too bogged down in their terminology in the vids, it’s a structural reinforcement that resists flexing that is not a bulkhead so it’s what most folk would call a stringer.

[@chrismiller29]

@@RefitandSailframe on a wooden boat?

[@waterbuoy9121]

I had thought frames, ribs or maybe even floors - all of which are tied together by stringers?

[@RefitandSail]

@@waterbuoy9121yeah, frame is probably the more common term for what I put in but because it did not run from the sheerline down I think of it as a transverse stringer but frame is probably the term I should have used .

[@johnstott1431]

You do great stuff. But this is a frame not a stringer. Frames go transversely and stringers go longitudinally.

[@RefitandSail]

Yep, absolutely, you are not the only one to correct me on this although I think I I call it a transverse stringer which is a term I have heard others use too. I try not to get too bogged down in their terminology. Thanks for the comment 😊

[@jonasjohansson9060]

I am not convinced that the cracks are from slamming..To me, it looks more like damage from supports?

[@RefitandSail]

I’m pretty confident they are, it’s a bit far forward for cradle pads. Not saying it can’t happen, definitely seen that when a yard hand has not checked where the internal structure is prior to shoring a boat.

@RefitandSail Hi! My boat has slightly dent areas around the two forward support arms. Should I take off the load (with additional temporary supports) and install stringers there?

[@chrismiller29]

@@RefitandSailagree with slamming. Boats like beni 40.7 have similar issues, but worse as the internal grid delaminates.

[@RefitandSail]

If it’s a permanent dent/deformation that does not pop out then it could be from the original build. The manufacturer may have put the hull in a cradle when the laminate had not fully cured so it sagged a bit on the cradle pad. Seen that often and it’s not somthing to worry about. If it is a flexible spot then maybe it needs some reinforcement but without seeing the boat it’s really impossible to advise.

[@RefitandSail]

@@chrismiller29agree !

[@PiggyBank-s5f]

You need to wear that expensive mask you bought it does not work in the box you only have two lungs