In the Groove

[Quetzalsailor]

I have a pair of rabbets, in wood, whose edges are thoroughly chewed up. When finished, the pieces will be painted. There is no 'draft' in the grooves ('draft' in the foundryman's sense; the sides of the groove are parallel). In the interests of function, appearance and simple perfection, I wish to recreate the original clean sharp edges of the groove. The grooves are about 6' long, vertical and in pieces which cannot be relocated for work; additionally, the groove is 1 1/2" from an adjacent shape and dies up into an end feature. The microclimate surrounding the grooved wood has been made temperate for work but the components will be exterior when put back in service.

My thought is to place a wood form into the groove which is rendered suitably non-stick, say, by packing tape, and fill out the missing wood with filled epoxy. After cure, pop the form out and sand the surfaces of the filler to adequate perfection.

Is there an easier, better way? Better material? A hitch in the material choice? One objection to the epoxy is that the surrounding wood is a far larger portion of the epoxy-wood finished component, thus any expansion or contraction due to moisture or temperature will tend to separate the two materials. There is no opportunity for 'encapsulating' the wood.

[Tim]

How about using a piece of UHMW sized to fit your rabbet as your "form"? Epoxy won't stick to it, and it's smooth and clean.

[Hirilondë]

I use UHMW plastic for clamping blocks all the time. It may take a rap with a hammer to release it, but it comes off clean. I have also used pieces of wood wrapped in waxed paper. Even so, it would be so much easier to do that with the doors standing on edge and the rabbeted edge up. Why can't they be removed?

[Quetzalsailor]

Great suggestions re: HDPE. I shall look into acquiring some. I, too, use waxed paper for releases, also polyethylene film. Another good one is the yellow bags from IKEA; dunno what the material is. Ordinary grocery store plastic bags are not so quick to release. I don't know what the plastic is in that smooth thin packing tape; the advantage to it is that it's sticky, thin and smooth.

I routinely use ordinary cheap duct tape when I don't care about smooth and have the ability to use a scraper and heat gun to get it off. Ditto 3M's masking tape. Both are more of a failure plane than a release surface.

Trust me, re: removing the pieces; think 'Sword in the Stone'.

[Hirilondë]

Great suggestions re: HDPE. I shall look into acquiring some.

You will find it quite expensive for this application. I only use scrap cut offs for clamping blocks and such.

[Zach]

Anything of the right dimensions with a piece of mylar packing tape will let you get by. Put a slight draft angle on the piece so it will pop out, and make it taller than it needs to be so the epoxy can't lock it down. (I just goofed on a router table plate... Used cotton fiber as a thickener instead of cabosil... whoops, never coming back out!)

If you are looking for UHMW, check around for plastics distributors and see if they have scrap pieces and off-cuts. My portlights on Pylasteki will be MR10 Lexan (10 year scratch resistant... same stuff they use for windows on sky scrapers) as I didn't mind the wait for pieces of scrap from across the country to show up... Same overall cost as UV stable polycarbonate by the sheet.

I have an account with Piedmont Plastics, but pretty much just open up the yellow pages and see who will talk to you about scrap pieces. Anything made of polyethelene will work. Use a router to make the pieces, and pass a torch by them to take off the machining marks, if there are any... Don't saw it out and expect it to be easy to take loose.

Zach

[Quetzalsailor]

I had not realized that the thin packing tape is Mylar. No wonder it does well!

Dad's engineering career at DuPont found him next to the newest plastics before they ever made the market. He had, in about 1957, samples of some of the first mylar sheet: clear, thick, wide, strong sheet, but brittle. He made a sail for his kayak out of the stuff but soon found that there was no available suitable glue. He joined the sheets with aluminum grommets. Hard to arrange draft anyway, so he did not; and the sail would never have been willing to roll up.

I have not yet got to the filling part of the job, but soon.

[Zach]

Yeah, packing tape is awesome, particularly if you put a coat of wax on top of it...

I use it alot for making fiberglass risers for bedding in hardware. Still have to hammer the cleat or whatever loose, but easier than gluing it down forever and always.

I made a router table earlier this week, and dropped my phenolic drop in plate into the recess, waxed it... and smushed it into some epoxy/cotton fiber... That sucker isn't going to come out in this lifetime... Neat way to get a flush mount though, I smushed it down with a straight edge so its level with the top. Now I think I'm just going to have to hinge the whole top... fence and everything. (Not a fan of hands and knees to get down and unclamp the motor... to change bits or adjust height.

[Quetzalsailor]

I built a router table base years ago (about 1972(!)) using parts sawn out of a wartime wood piano (all wood, frame and all, painted green). It mounted a Craftsman router with 'c' clamps and had a clamped table arranged so that the work passed between the router base and the clamped table. The third side was the table base itself and the fourth side was held by a sprung stick. I could make quite complex, but small scaled mouldings with multiple passes. Mouldings for a harpsichord made from Virginia red cypress, picture frames of walnut, etc. You're bang on about having to grovel to change tool setups!

I have, at various times bolted a specialized base onto the router base. Lots of aluminum to drill and tap. Pretty easy. One simply has to weigh the cost of building a particular jig and tooling with the ease of making some part, with just how perfect you want some part and how many times you want to make it perfect.

Anyway, back to the groove. I made up slightly thinner temporary strips, taped them with Mylar packing tape, and filled the broken edges of the groove with west's 105 and microfibers. Done yesterday, I went up this morning with my tinknocker's vicegrips and waggled a strip enough to know that they will come out without event. Pictures to follow.

[Zach]

Update on my router table.

A 3 pound maul banging on a 4x4 with it upside down did not unseat it. 2 pops with a dead blow it fell out, with some minor cracking around the corners.
I'm tickled. grin.

Yeah, jigs make life so much easier if you are doing a lot of something!

[Rachel]

Yeah, packing tape is awesome, particularly if you put a coat of wax on top of it...

I use it alot for making fiberglass risers for bedding in hardware. Still have to hammer the cleat or whatever loose, but easier than gluing it down forever and always.

Somehow I'm not getting this - yet it sounds interesting. Would you mind elucidating?

Thank you,

Rachel

[Zach]

Rachel,

If you have a cleat with a flat base you tape mylar packing tape to the bottom.
Wax the bolts.
Scoop out some epoxy thickened with cotton fiber and some cabosil.
Plop it down where your hardware will go.
Set your cleat or whatever on the pile of goop, sliding the bolts in through the holes.
If its not overly heavy, or has a lot of surface area... that is all you need to do, aside from wiggling it a bit to burp out the air. Heavy stuff just wedge it up from the middle to however thick the pads needs to be.
Take a plastic spreader, smooth off the excess around the edge.
Pack extra in where ever there is an air pocket around the edge. You are going to pull it up later... so air pockets in the middle will be fixed. (Scratch off with sand paper, use a spreader and fill up to just above level (if you like to work...) or just a hair low and let the sealant fill the low spot.
If you want a semi-quasi fillet, you can wrap packing tape around the edge, covering up the goop.

The wrap around afterward is more for doing stuff overhead. The fellow I learned this trick from used it to make a wedge for shaft struts, aligning the shaft to the stern tube with the bolts loose. Taping around the strut up to the hull, then packing the tape area full of cotton fiber thickened epoxy. I'm not sure if they left a side open, or used an empty caulk gun tube. (They sell them... dollar or two each.)

Its massively strong stuff, and you have to hammer/pry the part off... even with the packing tape.

For packing tape removal, a razor blade will scrape most of it. Goo gone will take off the adhesive, as will WD40. (Dish soap will clean up the wd40...)
On the metal cleat side, a razor blade does a pretty decent job... but its easier if your sander has a piece of worn out 60 or 80 on it to take off the plasticy top... spray it with wd40 and come back in a bit. Acetone and thinners will take it off too, but you have to wet it down a few times and rub the rag a bit to get all the smudgy stuff off.

Cheers,

Zach

[Zach]

I should add...

Big boats don't have anything on deck that is flat enough on the underside to get a good seal with just sealant. It's all welded on plate... so you have to make the deck fit the part, thats all bent/warped from welding. (Flat to the eye when mounted on deck, but would rock if you set it on a flat table. On a glass boat, its not such a big deal... a wooden one, you snug the bolts down all the way tight and it acts like a shear smushing the wood (and in my case, glass sheathing...) inviting disaster when the water gets in. A lot of work boats weld the bolt heads to the plate, so that the sealant and weld keeps things dry. When the sealant fails... and it does... its not serviceable.

It also comes in handy if you are fitting something that is already welded together, with mounting foot pads that don't match the curve... like stainless hand rails and such. One of those arrows in the quiver to get a marine surplus item to work on a boat other than the one it was designed for...

Zach - Water leaks worst nightmare. Wait... those are my worst nightmare... grin.

[Rachel]

Aha, I still didn't get it until I read the second part. Now I see what you're doing - thanks!

I've seen a variation on that done when rebedding a keel to a boat (C & C 33-ish type). Only with no extra stuff around the outside - just epoxy to make two perfectly mating inner surfaces, then take apart again once cured, and then re-mate with sealant.

Rachel

[Quetzalsailor]

A followup to the beginning portion of this string.

The groove in question is seen in this pic, looking up along the jamb of an 150 year old double hung window.

This shows the window reassembled with the new gib door closed;

the second with the gib open.

(And, why if you can only upload three pictures, does the website tease you with the next opportunity and then thumb it's nose at you after you've attempted to upload it?)

This window originally had, in 1857, a sill and a bit of wall outside with a raised panel on the inside. Perhaps around the turn of the last century, the bay window in the dining room below was replaced with a much larger bay and this window was cut down into a gib door (gib window; terminology varies). The original sash remained, the original shutters and the under-panel were put in the barn. A bi-parting gib door was made whose design I did not like and which did not work well. I made the new gib door using the original under-panel and made a matching panel for the exterior. I repaired the window frame, and new parting strips. Sash weights are now hung with fuzzy braid dacron. Following post shows a detail of the repaired groove for the parting strip.

Crossover technology...

It all went back together yesterday. Time to get down and start recommissioning Q!

[Quetzalsailor]

Detail of the repaired groove on the right jamb and the new parting strip.

[Rachel]

(And, why if you can only upload three pictures, does the website tease you with the next opportunity and then thumb it's nose at you after you've attempted to upload it?)

I haven't used the uploading feature enough to know (yet), but does it perhaps have a cumulative size limit? Say, 400k or something? So it invites you to keep uploading and then when it sees the first photo that puts it over that amount it gives you the thumbs down? (Or is it always at photo #4 no matter what....?)

Thanks for the photos - those are neat windows.

Rachel

[Tim]

I've increased the number of attachments in a single post to 10 from 3.

Individual maximum file size for each attachment remains at 256K (per photo).

[Chris Campbell]

Very nice work and a lovely window, Doug.

My only question - is a gib door where you pass the jenoa in and out?