Restoring a Mirror Dinghy

[pdr]

Hello

I thank Michael Storer for all his info on line. I have some specific questions for my project about how much epoxy to use.

My project is an old mirror sailing dinghy (possibly about 30 years old - #36265) and have stripped the hull which was flaking off. It came with a set of brand new sails and I would like to restore hull to be light to keep racing as an option (it was fast in its day!).

The hull has some weak spots where ply has been cracked. All seams need to be re-taped and there is a small section of rot on transom extending 10 cm around the side.

I have read about the wet on wet method and would like advice on whether I should do 3 coats of bote-cote epoxy over hull and sides, or just re-tape the seams and fill/tape weak points and then paint with 2 pack poly.

I have seen one blog where they used matting over 80% of hull for extra strength when epoxying. Is this overkill or a good idea? I can't tell how weakened the ply is as have never sailed a mirror before, but don't want to risk stepping through the bottom from above.

For the patch on transom I am planning to cut a new piece to fit and do a joint around the side.

Main thing I suppose is how much bote-cote and tape / matting to use to strengthen the hull vs adding weight.

I used fibre glass tape as a kid, but have not used epoxy before. I have read about the bag method and this looks efficient. Although to get it out from the mixing cup and onto the surface and spread quickly from there looks fastest. What is recommended?

Any assistance much appreciated.

Paul

[PAR]

Don't use mat with epoxy. It doesn't add strength, but does add a lot of weight, mostly from the high resin content, typical of mat laminates.

Don't apply epoxy all over the outside. If you have just a taped seam boat, that hasn't been encapsulated, then you're really just wasting you time and lots of goo. The only time you want to fully coat, is to encapsulate the whole of each boat part. If you can't do this, which is the case in repairs and restorations usually, you're best advised to seal only the seams (if necessary), make adhesive (epoxy) type of repairs, but skip the coating stuff.

As a rule, "weak stuff" needs to be cut out and replaced. You'll use epoxy for the glue, but that's it, don't smear it around. The "pastry bag" technique is handy for making fillets, but you will not be doing this. If it was me, I'd replace the whole of the transom, renewing the planking/transom seam in the process. If you do this, then encapsulating the new transom piece would be a good idea. The fully coated transom would then be bonded to the planking, the same as the original.

[pdr]

Hi, thanks. So far my thinking is:
- re-tape the seams using epoxy for glue and epoxy suitable tape
- patch the weak areas by drenching in epoxy and covering with cloth (its not rotten so don't think I need to cut out)

I am still thinking about the transom,
- I can either glue patches onto solid timber, or
- get the whole old piece off and start again, as you suggest

I have attached pics of transom and two weak areas on either side forward of the centreboard case.

196458
196459
196460

[MikeyRoberts]

Hi Paul,

I think Par has the right idea - just tape the chines on the outside and paint the hull in two pack paint. As for the weak spots in the ply - I don't think you need to worry about putting your foot through it - wouldn't your weight be carried by the frames and the floors inside the boat?

The transom damage seems minimal. My slapdash approach would be to slap some thickened epoxy in there to patch it up.

Mike

[pdr]

Hi Mike!

Thanks for confirmation of general idea to only re-tape the seams and then paint, except for the minor repairs.

The floor of the Mirror is the hull - no boards. I turned boat over and found evidence of a thin crack from inside. When I sanded back, I uncovered a previous fibreglass patch, so imagine that was the approach followed before. So my plan is to work from the outside, fill and then strengthen the general area with cloth/epoxy, and blend that in.

I have cut out a bit more on the transom now, so I think it needs a bit of ply epoxied in. For the bit on the side I will be re-taping on inside as well to replace that taping which had come off.

Thanks guys, for your help, now I have next weekend to get to work!

Paul

[vk4]

PDR<

Agree with PAR, :2tsup:

1, tape chines and seams as required

2, cut out transom rot and epoxy in a new piece of ply glass both sides + 50mmall round

3, cracked spots, i would sand and glass & epoxy patch +50mm all round,

Areas where you have added glass , fair with epoxy and microballons.

Sand hull and use epoxy & microballons to fair the hull then 1-2 coats of epoxy, sand & paint.

any weight gain will be minimal measured in ounces.

Jeff

[pdr]

Hi Jeff

Thanks! I understand your approach uses more epoxy to achieve a nicely fared hull, before painting. This is different than just taping the chines and painting. PAR had indicated that painting on epoxy or "encapsulating" the entire hull was a waste of time on a repair, as it wouldn't cover the entire wood surface. As I do need to make some repairs on the hull, applying epoxy and sanding seems the way to get a really smooth finish, where required.

I will need to investigate further about the microballons, hopefully they know about them at the boat shop.

Thanks again, to you, PAR and Mikey for advice

Paul

[cookiesa]

Microballoons is a fairing mix added to the epoxy, light and easy to sand. Mix to the consistency you want (peanut butter is the usual start point, add more or less from there!) In places where runs are an isue you can add some high strength glue powder to help prevent sagging (not usually an issue on a dingy you can turn)

[pdr]

Thanks for explanation about microballons. Yes, they had the fairing mix at the boat shop so I picked some of that up yesterday (Sat) with the epoxy, paint, gloves, tape, rowlocks, new sheets and some very light cloth. Did patching when I came home from the shop. Today (Sun) re-taped the chines and joins. Despite advice to the contrary I also used epoxy and the light cloth (not mat) to go over bottom of hull. The ply had copped quite a weathering (been upside down to the elements for past 15 years, and much of previous paint and tape had peeled off leaving about half of the ply unprotected), so I like to think that I have now strengthened it and made it waterproof. Anyhow, now I know about the joys of smearing goo around and smoothing out air bubbles. (May come in handy one day for the bigger boat of my dreams). I will shave off edges and sand tomorrow evening, hopefully before it sets really hard. Then next weekend will fill with that fairing compound and sand again....

[cookiesa]

It isn't going to hurt! I prefer to sheath all exposed areas. If nothing else you have protected the timber when beaching.

Ahh yes, fairing and filling... welcome to my world lol, have fun! There is nothing you can't fix without some poxy and sanding lol

A cheap source of gloves is safety shops, eg Australian Safety, Blackwoods etc. Usually around $15 for good quality, good fitting! gloves (Examination gloves etc)

[vk4]

PDR<

when you do the fair/fill of the glass, use a wide plastic scraper to spread the filler, .

You need to fill the glass , and leave just enough filler so that you can not see the glass.

you will then have enough coverage for sanding, beware of sanding the chines do these by hand,.

Jeff

[pdr]

Jeff

Thanks, just read your post ... makes sense now. I am learning things along the way. Maybe some other novice who reads this may benefit. The ply had uneven "valleys" where exposed sections had weathered more. After I sheathed it, it still had inherited some of this uneveness. On Fri afternoon I sanded the epoxy that had covered the glass to even out some of the "mountains" with 120 grit, and then on Sat morning applied the fairing mix. I was surprised how quickly one little tub of filler mix (microballons ?) disappeared to make the peanut butter consistency. Initially I think I was too liberal, but after the second mix I was more frugal in targeting the "Valleys". Could have done with a wider spatula / piece of ply though. On Sat afternoon it was already hard, and so started sanding back, but 120 grit did not make much impression. Today I bought loads more paper and it was the 60 and finally the 40 grit that made the impact (but without getting into the glass cloth and I am taking care not to go through the tape on the chines). I will now move to finer grit sanding to achieve the desired smooth finish before painting. The bottom feels much firmer than when it was just wood alone. Hope to paint undercoat next weekend, after I sand down and glue back the rubbing strips underneath ... and then expect to sand some more between coats ... aah, the the zen of sanding! One can meditate for hours. I plan to apply paint with a 75 mm wide, 5mm nap roller. Have also been trying to breathe some life into the old fittings (cam cleats and mainsheet block. I have soaked in hot water and then in a strong mixture of household cleaner used in showers to remove the calcium build up. Partial success achieved, with metal looking shiny now and parts begin to move again and respond to their springs. However, some cleats still jammed, so have left them in to soak some more.

[pdr]

My project has now been for a sail.

204788

My three children were delighted at the experience - so much so that we shall be sailing again this week end. The mirror dinghy is a real classic and a pleasure to sail. The gaff rig was a bit fiddly to get up. The main wire halyard seemed to be too thin and kept slipping off the block at the mast head and jamming. So I had to tilt the boat over and free. Apart from that all went well. I last sailed a dinghy about 25 years ago! Where has the time gone. Anyhow, thanks for all your tips during the restoration. Best, Paul

[cookiesa]

Looking great!

Like the tip on the calcium build up soak, must give that a go thanks.

It is amazing how hard epoxy sets, I had a patch once I left for about 6 weeks due to other commitments........ Learn't never to leave it that long again!

[vk4]

Looks really good:2tsup::2tsup::2tsup:, nice job of restoration.:2tsup::2tsup:

You could replace the wire halliard with 3 or 4mm spectra rope , or look at the pulley sheave and reduce the side clearances.


Cheers

Jeff

[8387mike]

Hello Paul,

Good looking Mirror but I think you stole my paint scheme:D I bought a mirror from up your way (Hillarys) about 2 weeks ago off ebay (#45000 something), got it very cheap with a trailer very happy:2tsup:.

I haven't had the chance to get into getting all the old paint off to see what the wood it like:oo: I have noticed that the gunwales in one spot have rotted so they will replacing any idea on what timber to use?

The hull has been painted on the inside and the fibreglass tape is lifting so once stipped I will have to epoxy and tape again.

Next big question is the gaff has areally bad bow in it how can I straighten it?

Look forward to your replies.

Mike