it's very common in joinery to glue up multiple boards. even if they come as a solid plank cutting them into sections and re-gluing releases the internal stress. If you look at a table or something like that from the endgrain you can usually also see they place the boards alternately heart-side up heart-side down and so on across the board. this is because when boards cup , which wood naturally does, they cup away from the heart side, but alternating them causes the warp to equalize so it doesn't bend out of shape.
thise chairs were made for indoor use and they [probably used hide glue. You can clean up the surface and use carpenters glue or even elmer's school glue, or if it was a true restoration you can still use hide glue. The rest of the joints will also give as well as the glue in the spindle holes if it is hide glue and left tot he elements. You might protect it from a light rain with paint but if you leave them to the elements too much they will be a pile of little boards after the glue comes apart.
you can glue them up and clamp them or dowel them or drill holes and drive nails or screws and hide the heads. you can see some separation on other boards further toward center as well. Those are nice chairs. I like how the spindles are bent and not overly large, just enough wood was used to give them enough strength. I can understand you dont' have a lot of space inside for them and they are nice to sit on on the porch. I dont' see anything wrong with using them for as long as they last. You do have a little cover and you could always put a little plastic over them if you know its going to rain. If you are nostalgic about them then the porch isn't the place to store them whren it's raining. If you aren't so in love with them, and if you plan to just use them up then I'd say go ahead and glue the little edge, give them a paint job and they will last a little while longer. or you could restore them and keep them inside if you wanted to.
maple is a nice hard wood. it has good strength and long strips can be bent and laminated. it isn't' the most rot resistant lumber so it isn't usually used outdoors a lot.
if boards are jointed or planed to have a good fit. a common way to join them is to apply glue to both pieces and put them together and just squeeze them and slide them against each other a little , then leave them to sit. often things like glue blocks are done that way and not clamped. If you rub too much you can squeeze too much glue out. but this is common practice. it's called a rub joint. If you look under old furniture you will often see the glue blocks and you may notice some are shifted because they got bumped after they were applied and before the glue dried.
this is also a way of using up lumber. since with this method you dont' need to start with wide planks. but it isn't uncommon for tabletops to be joined, usually they are. some have veneer to give the appearance of a full board but if it were actually a table made of one board it would also be susceptible to warping so it is usually made of pieces and it wasn't necessarily because the boards came as narrow planks.
in the factory they would probably cut all the lumber to the same thickness but use it as they could so the width of planks may vary. they would place it in a large frame and clamp all the boards together with glue until dry , then the next step would be to cut the shape of the seats out of these boards.
if one joint gave way the others might not be too far behind, the moisture is getting into the glue and it isn't waterproof glue so it just lets go. even if you paint hem , if you let them get rained on a lot the water will get in but the paint will help slow the process.
I had a little ornamental table, I had mean to restore it , when we moved in it found its way to the porch and it needed some veneer work. it wasn't long and the veneer all let go for the same reasons. I felt a little disheartened because I had meant to do the piece better than that. then I found the exact same table in nice shape in valu village for 30 bucks and I scooped it up and thought wow that was the easiest restoration ever
last summer I found a whole lot of spindles for an interior staircase. they are beautiful and in a craftsman style. I need porch posts but the issue with them is they too are glued up from pieces in the same way so they just wont' take the weather. I keep thinking if I could wrap them with epoxy coated string or something maybe they would hold together but I am probably better to just make new spindles. I have a huge pile of rough cut 2x2 and my plan is to cut them square with a slight taper and use those instead.
from a preservationist point of view. those are probably glued with hide glue, you can clean it off and use more hide glue. the beauty in using hide glue is that unlike most modern glues it can be taken apart and put back together. So that would be the way to go if you considered them valuable and worthy of restoration. In reality those likely aren't worth much money especially like that and they are yours to do with as you like.
chairs have a lot of geometry and they can be tricky to clamp sometimes lots of clamps can be used or sometimes you can make plywood jigs and things to clamp against.
if you like the clear wood oil or poly would probably protect as well as paint but that isn't restoration it is just having fun and destroying them but maybe you are right to just enjoy the last couple years out of them.
I've got a wooden rocker that was kind of nice.. same thing it was out on a boulevard and I felt sorry for it lol... it just had a plywood seat someone stuck on it. I found a leather padded seat cover with tie straps from some other piece of furniture and i found it comfy and I didn't worry about leaving it out, no one would steal it and it's comfy to sit and rock and watch people walk by. same thing it could be restored yea but it isn't worth a lot of work.
about them would be appreciated.
