Thread: Another OZ MK2 PDRacer build in Sydney "Wood Duck"

Ye gods and little wee fishy beasties...

The sanding is all finished - plus the first swab-down to get rid of must of the sanding muck - and I was nearly at the end of my tether by then. I've started removing the old blue tape, too, which is of course proving to be a bit intractable; it has been on there for many many months, however, so no surprise there. In fact, parts of it are coming off more easily than I imagined they would. Where the tape has to be removed with a sharp paint scraper, I've sanded most of it away doing the gunwales, so there isn't much left in those strips except gum.

I have photos:

1. Port side panel half-finished using the 80-grit paper (photo from a previous post, for reference)





2. Port side - sanding back of previous paint complete. Note the increase in plywood areas showing, compared with photo no. 1 above





3. Starboard side, sanding finished. As with the previous snap, notice the increase in areas of wood showing through. I hope that the undercoat is going to blanket them sufficiently. Another thing to observe is the spots in the middle bottom of the side buoyancy tanks: I have no idea at the moment what might have caused the hull to pop out at those points. Otherwise, you would expect that the spot patterns on both sides would be pretty well symmetrical...





4. Stern transom, rubbish finish deleted. Both dark patches are wood peeking out through the abraded high-build, Plus a small amount of high-build roller stipple left in a hollow to the right. These marks are directly over the centre-stiffener what are glued to the inside of the transom


Run, dont walk, to my Flickr account, where in breathless admiration - or summink - you can marvel at the wondrous wonders that Flickr serves up to us mere mortals. Well, I marvel at 'em anyway... A bit... Well...



OK. Milestone past - albeit a completely unnecessary one. Urk. Never doing that again. Good grief. Anyway, things can only progress, fingers X-ed, as long as I hold focus and don't try to rush.

Phew...

I think I might let things dry out until Wednesday, and start the undercoating then. And give my poor elbow a rest, to boot.

Originally Posted by AlexN

9:30 am - here we are, off the jig at last. Paulownia is very flexible timber. This is going to be interesting with respect to the mast...

Overall, this seems to be quite successful. There was a lot of glue on the undersides of the chinelogs, where I could get at it. ROS for them, but only one side of each, not two .

Photos:

1. See, there was tape on there. Didn't believe me, did you?





2. And there was quite a lot of it, too...





3. The resilience of the Paulownia has made the timber spring back somewhat from the jig shape - but not so much that it will snap when I glue the chinelogs onto the side panels...





4. Placed on a side panel to test-fit - not exactly the same shape, but close enough to be able to be bent again easily. Paulownia is very flexible. Note that the jig has been totally dismantled, including all the tape.





Back to the sawing now, I suppose. With the heavy duty snout protector on...

[QUOTE=Boatmik;909522]Howdy Alex,

Alex,

Think back....waaaay back to this early post! Given the natural springback of the chine log after releasing it from the jig, do you think this behavior dismisses a recipe for precision in the jig itself? Also, would there be any merit in deliberately "overbending" the chine anticipating or compensating for springback? Or is that just another case of unnecessary "overthinking"?

To put it short--Would you do anything different with chine bending next time?

Thanks

Bob

Howdy Bob,

When we built the prototype Mk1 OZ Racers I broke one chinelog and it looked likely that boats around the world would use a very wide variety of timbers. So we included the section on the simple lamination to get them in approximately the right bend.

One of the advantages is that it teaches people building from the plans one of the fundamental methods of proper boat building - it also shows them how simple it is.

It is possible that with care a light timber (and also flexible timber) like Paulownia might be able to be bent without lamination. But it is safer for the plans to cover lamination.

Best wishes
Michael.

Originally Posted by BobAshley

Alex,

Think back....waaaay back to this early post! Given the natural springback of the chine log after releasing it from the jig, do you think this behavior dismisses a recipe for precision in the jig itself? Also, would there be any merit in deliberately "overbending" the chine anticipating or compensating for springback? Or is that just another case of unnecessary "overthinking"?

To put it short--Would you do anything different with chine bending next time?

Thanks

Bob

Hi Bob,

That was a blast from the past ;).

The short answer is...I would probably do it again, and I don't think I'd bother exaggerating the curve to allow for spring-back. But I would be a lot quicker at it, having already done it once, having worked out the jig, and still having the door with the bottom curve drawn on it ;).

The verbose, rabbitting-on answer is: I don't have experience of how the stipulated timber in the plans (oregon) would have reacted, although in MIK's instructions it did seem to hold its shape. I know that I had a somewhat wild time with the oregon that I used for the sheer clamps, even with the shallower curve (which is why MIK says to laminate it from thinner strips).

Reflecting back I would say that building the jig certainly helped; exaggerating the curve might have helped with the spring-back; but in either case the end result would have been the same with the paulownia. In a sense the jig was precise because I didn't know quite what I was doing (balsa is much easier to bend that oregon or even paulownia), but looking back the jig really wasn't that hard to flange up. I'm used to making jigs though - I'll make one at the drop of a hat. In fact, with the metalworking that I (used to) do (before the boat ;) jigs are (were) almost always the order of the day - and they have (had) to be a good deal more precise that the chinelog jig.

That still doesn't answer the question, though. I don't think it matters one way or the other using paulownia, but if using a harder timber such as oregon (the irony here is that paulownia is a "hardwood" and oregon a "softwood" - both, in my opinion, highly misleading, overly simplistic and unecessary terms) I would definitely go with the jig. I'm trying to think what would happen if one tried to use 19 mm square paulownia and bend it in one hit straight onto the panel. It would probably work OK, but the glue-layer in the laminated version would make for a stronger element in some respects.

One caveat here is that paulownia dents very easily, and using it as chinelogs isn't the greatest idea: in fact, the chinelogs both have a layer of glass cloth (extending up from the super-soft poplar lite-ply bottom ;) where they are exposed in the cockpit to help resist the inevitable thumps they'll get. But I had a lot of it, and as I had limited amounts of oregon, that's what I used. At least, without going back and looking at what I wrote sixteen or so months ago, that's what I remember.

I'll be a craven chicken and leave it to MIK to make any further pronouncements regarding exaggerating the jig for oregon ;).

I'm sorry that my reply was so rambling - it really reflects that I was trying to justify my short answer.

Cheers,
Alex.

Originally Posted by Boatmik

Howdy Bob,

When we built the prototype Mk1 OZ Racers I broke one chinelog and it looked likely that boats around the world would use a very wide variety of timbers. So we included the section on the simple lamination to get them in approximately the right bend.

One of the advantages is that it teaches people building from the plans one of the fundamental methods of proper boat building - it also shows them how simple it is.

It is possible that with care a light timber (and also flexible timber) like Paulownia might be able to be bent without lamination. But it is safer for the plans to cover lamination.

Best wishes
Michael.

Thanks Michael. Just took a quick glance at the plans. Referring back to my original question about needed/unneeded precision, and keeping in mind expectation of some inexact degree of chinelog springback, it seems to me that the simple jig in the plans (curved line of spaced screws) would be no less effective than Alex's "enhanced" jig. The goal seems to be less a matter of achieving a precise bend than simply seducing sufficient bendiness early to resist breaking later.

A kind of crafter's foreplay.

bob

Thanks Alex for a thorough explanation of your chinelog jig rationale. It gives more context. The added bits about hardwood and softwood and Pauly's proclivity to dent easily is interesting too.

The appearance of "complexity" appears to be just that and nothing more. Given the context of what stuff you had on hand and your practiced ease with jig building, your set-up really is simple. It just looks more complicated to an observer who has neither that particular grab-bag of jig-building goodies lying around, nor possessing a past packed with this specific set of experiences.

Thanks!

Bob

Originally Posted by Boatmik

Howdy Bob,

When we built the prototype Mk1 OZ Racers I broke one chinelog and it looked likely that boats around the world would use a very wide variety of timbers. So we included the section on the simple lamination to get them in approximately the right bend.

One of the advantages is that it teaches people building from the plans one of the fundamental methods of proper boat building - it also shows them how simple it is.

It is possible that with care a light timber (and also flexible timber) like Paulownia might be able to be bent without lamination. But it is safer for the plans to cover lamination.

Best wishes
Michael.

What he said .

Sorry I didn't see your post, Michael, or I wouldn't have prattled on.

Cheers,
Alex.

Haven't you finished that flamin' thing yet? Maybe you should have started with something basic as your first boat

Richard

Hia Grumpy. Have you finished your build yet? Managed to finish Snipefish hull except for protection strip and skeg, so not finished then!

Alex, how are you. Sail sewn? I have lost track a bit.

daddles how does this two sheet rowboat compare to the searowing boat designed on your thread?

Another two sheet rowboat design- "Big Guide"

Got lots of rocker, flat bottom, almost same beam.

Apologies Alex for thread drift, you have amazing stickability.

Brian

Originally Posted by BobAshley

Thanks Alex for a thorough explanation of your chinelog jig rationale. It gives more context. The added bits about hardwood and softwood and Pauly's proclivity to dent easily is interesting too.

The appearance of "complexity" appears to be just that and nothing more. Given the context of what stuff you had on hand and your practiced ease with jig building, your set-up really is simple. It just looks more complicated to an observer who has neither that particular grab-bag of jig-building goodies lying around, nor possessing a past packed with this specific set of experiences.

Thanks!

Bob

Hi Bob,

Regarding the "grab-bag", I generally grab what is first to hand! That's what makes jig-building so much fun :).

Cheers,
Alex.

Originally Posted by Daddles

Haven't you finished that flamin' thing yet? Maybe you should have started with something basic as your first boat

Richard

Daddles! Great to see you mate! I trust that you are feeling well .

Well, I have finished - the paint stripping (probably should have used paint stripper!).

Hope to start painting again in the next day or so when things have dried out a bit - the workshop is a bit of a swamp at the moment . In fact, a frog has even taken up residence in there... It croaks every now and then.

Basic - like a small balsa model? <snigger>

Cheers,
Alex.

Must be spring Daddles is out of hibernation!

Originally Posted by keyhavenpotter

Hia Grumpy. Have you finished your build yet? Managed to finish Snipefish hull except for protection strip and skeg, so not finished then!

Alex, how are you. Sail sewn? I have lost track a bit.

daddles how does this two sheet rowboat compare to the searowing boat designed on your thread?

Another two sheet rowboat design- "Big Guide"

Got lots of rocker, flat bottom, almost same beam.

Apologies Alex for thread drift, you have amazing stickability.

Brian

Hello Brian!

Long time no squeak! Actually, it's a bit spooky, I was thinking about you and Richard in the same context just yesterday (clinker-built boats). Weird.

Still haven't sewn up the sail, I've lost my bottle on that one somewhat! Once I've got the painting put to bed I'll re-visit it. I may have developed some courage for it by then.

I don't know about stickability - "pig-headedness" might be a more accurate term!

Cheers,
Alex.

Originally Posted by m2c1Iw

Must be spring Daddles is out of hibernation!

Hi Mike,

That makes two of you - or perhaps three if you add Brian . But it is autumn over there in Blighty so perhaps he will be going into hibernation .

Cheers,
Alex.