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P22 construction & modeling


wkisting

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Well, a careless mis-step resulted in the destruction of my previous P22 model (the one that "Joe" built), so I'm rebuilding a model of the P22... this time out of 3/32" Birch plywood, scaled up 50% from the plans to yield a model that should be about 30" long.

Anyway, I was cutting out the bulkheads, and a question occurred to me as I thought about building the real thing... the bulkheads in the plans show slots in Bulkheads #2 and #3 that are located to allow the CB trunk to pass through the bulkheads. My question is this: Would you normally cut out those slots BEFORE assembling the hull (in real life, not talking about models here), or is it better to assemble the hull and then cut out the CB spaces from the bulkheads AFTERWARD? (Note: I'm not talking about the CB slot through the hull, which I know Charlie cut later with a router... I'm talking about the CB slots through bulkheads #2 and #3 for the TRUNK to pass through).

It seems like it would be easier to cut the slots in the bulkheads before assembly, but then again, once they're cut, they might not line up perfectly and then you would have troubles with a mis-aligned CB, no?

Thanks!

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I cut them after the boat was assembled- I wanted the intact bulkhead during the beginning work.

Really wasn't that hard to cut them- jig saw down to close to the hull and a hand saw from there down.

Besides- you won't know EXACTLY how thick the CB trunk is until you finish the centerboard, so you won't know EXACTLY how wide to make the slots.

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Greg,

Sorry if I wasn't very clear... Originally, I (well "Joe") built a model directly off Graham's blueprints, which are drawn to a scale of approx. 3/4" = 1 foot, yielding a model boat that ends up being about 16.5" long, so when I upscaled the drawings by 50% (on a copying machine) it increased the model's size to about 25" long now. (Not sure how I got that 30" number... must have done the math wrong in my head as I was typing that last post).

In any case, no, I didn't mean I was building a 50% or 1:2 scale model... 11 feet long, WOW! That would be cool though.... hmmmmm.....

Actually, this model has been a real pain... I'm using 3/32" thick birch plywood, which is MUCH stiffer than the balsa I used originally... it makes it VERY hard to glue the stations in place. They keep popping apart (from the torque of bending the sides) before the glue can cure. Ugh. I've been at it for 4 hours now (just gluing!) Hopefully, the glue will cure with no more mishaps during the night. I'm about ready to give up... I think it would be easier to build the real thing at this point! :)

Anyway, I'll post a pic or two when I get her looking ship shape. Joe's not helping with this one, so no action photos I'm afraid.

P.S. Thanks Charlie... I didn't even think about the thickness issue. I'm convinced your way is the way to do it.

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Forgot to mention... when I stepped on the previous model of the P22, in balsa, I had laid it on the floor near my desk. I thought I was stepping onto a book as I felt my foot hit it... it was VERY solid and started to lift me off the ground, then CRACK! By the time I realized what had happened, I had split the boat in half forever. :(

The cool thing is how darn solid it was though... I mean, just think about that: it momentarily lifted my body weight! The model was only built from 1/8" balsa! Guess it's true what the say about the tremendous strength of a well-designed stitch-and-glue structure. I was impressed even as I kicked myself for crushing it.

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Depending on the boat, absolutely. Stiff matt board would do a good job of making frames, as would foam core. I've modeled tack and tape boats using thin cardbaord and tape- it's absolutely amazing how stiff a structure becomes once you add a deck too.

Of course, the paper ones are throwaways- to make one to have for later really wants wood.

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Charlie,

Later meaning for display on a wall or for use as a selling tool? A really nice looking model should prove good for that. I guess the paper ones would never look really nice. I have been thinking of getting Payson's model making book.

Thanks for the advice :)

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Greg, Sure, paper would work, but as Charlie mentioned the wood ones last and last... well, um, until you step on them. :(

Ray, ooops... I meant to say that "Joe's" workmanship was so strong. Really, I was just an onlooker on that first model. I've apologized to Joe for the slip. ;)

Dale, your model looks great. Smart move using the 1/64" birch. I used 3/32" birch for this second model because I was afraid the 1/64" would be too flimsy to yield a fair curve... what a bad idea... the 3/32" birch is so stiff it has been a real ordeal getting it to bond to the stations without popping apart. I finally succeeded, but only after resorting to the ever-messy glue-gun. Fortunately, all the glue will be hidden under the floorboards of this model, as it is big enough for a detailed interior.

I'm gluing up the V-section of the bow now... laying it panel-by-panel using 1/32" birch (MUCH more flexible) just like the real boat would be built. When it's finished, I'm going to fiberglass the bottom with some 3/4 oz. fiberglass (hobbyists use it to 'glass their RC airplanes, etc.) to make sure the model never pops apart.

This time the 3/32" birch model is SOOOO much stronger than "Joe's" balsa version... I'm sure I can step on this one (maybe even jump on it) without crushing it! So in that regard, it's idiot proof. :) I'm thinking of casting a small lead keel out of fishing line weights. Any reason that wouldn't work?

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Hmmm... I was going to ask about this by starting a new thread, but maybe it fits here since this is the "P22 construction sequence" thread after all....

I've been reading Reuel Parker's _The Sharpie Book_... what a great read. I'm really attracted to the round-stern sharpies... gives them a neat little bit of flair and hides that semi-atrocious-looking "flat-panel" stern that tends to give sharpies a cruder look than comparable round-bilged "yachts". So I got to thinking....

<<<<open can of worms here>>>>>>

...how hard could it be to modify the P22 to accept a round stern? The plans show the stern just rising above the waterline at the extreme rear, so theoretically (using my crude makeshift theories, that is) couldn't a guy just add about two more feet to form a nice round stern? The addition would be (essentially) completely out of the water, so it shouldn't affect sailing as long as it wasn't so heavy as to force the stern down lower than designed, right? It would make a handy way to enclose that stern rudder to protect it from backing into a dock or whatnot... or is this just a really, really bad idea? Reason I ask is maybe I should play with the model I am currently re-building to see what she would look like (?)

Okay, that's my bad idea contribution for the day. Done. :)

P.S. On the other hand, I could just do what Chick did on his P22, and paint rounded corners on the transom to create the illusion of contour... a very clever (and much easier!) way to break up that flat-panel look of the sharpie transom.

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Wes,

Show us pictures of your model as it progresses.

Personally, I think it is generally a mistake to modify a designers important things like hull design. Modify the small unimportant stuff but not basic stuff like hull design.

Build Reuel's sharpie if you want round stern.

I also have and like Reuel's book.

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Dale, You're probably right... although I wasn't technically suggested a modification to the hull, just to the stern... sort of a "false round" so to speak, which would wrap outside the rudder assembly. Not sure it would actually modify the waterline shape, except to the extent that it might be heavy enough to force the stern down a bit more than intended per design. But yes, I think your sentiment is probably still correct... better not to mess with the perfection that is the P22. ;) I was just kicking around the idea as we boat people tend to do.

So the model is advancing nicely now that I finally got all my glue joints to survive a full night of curing without popping off the mold. Here's today's progress in pictures....

Man, the 3/4 oz. glass wets out oh-so-nicely (on the downside, it also snags incredibly easy... even the plastic squeegee was too coarse, had to switch to a brush!). Maybe I'll use it on the full-size princess... let's see, that would mean about 16 layers for adequate thickness, plus maybe another layer for abrasion resistance. :)

In retrospect, I'm kind of glad the accident happened to destroy the previous model (although Joe is still peeved at me)... this model is much more accurate to the true shape... built exactly according to the steps which the real P22 will require for completion. After two run-throughs, I think I could build the full-size boat in my sleep. Certainly, the real boat should be less frustrating than it was trying to get this model to hold the proper shape long enough for glue to cure.

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Greg,

When the plans are drawn up as nicely as Graham's (with all bulkheads and side panel diagrams drawn to the same scale), it's easy... just photocopy the relevant diagrams to whatever size you like, then cut them out and trace them onto balsa or birch ply. The cutting is the tricky part, but with a sharp dovetail saw I was able to cut out each of the pieces pretty quickly, cutting slightly outside the lines and then planing them down the last few sixteenths to the pencil edge with the block plane. If you use 1/64" as Dale did, I think you might even be able to cut out all the shapes with a sharp, heavy-duty scissors, which would be much quicker and just as accurate, with a lot less effort required than I expended to cut the shapes out of 3/32" birch.

Pretty straightforward. No great experience required. I've never bothered to model a boat before, but now I really see the value it lends to understanding the "big picture" and visualizing how all the steps come together. It would certainly be a great help to a first-time boat-builder, but even for someone who's built a few boats (like me) I think the effort that goes into modeling will save mistakes later on the actual build.

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Hmmm... I don't know guys... I was playing around with some cardboard to see what a round-sterned Princess would look like.... it looks pretty dang cool and wouldn't be hard to execute, I don't think. I might end up building this model as a round-stern prototype. ;)

Here's a couple teaser photos...

...notice that Joe stopped by to check on the progress.

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Hmmm... drew up a linesplan for a round-stern... pretty cool looking... ends up stretching her to about 24', with about 1' 9" added to the hull, though I drew her with a bit of abrupt lift starting from the original transom.

All I need now is someone to dare me to try building her. ;) Probably couldn't bring myself to do it though, since the round stern would be pure affectation, and add weight to no purpose. Still....

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Wes:

Seems to me like I read once that in order for a boat to plane, the transom chine has to have a sharp edge. You have that drawn in the vertical plane, but I don't know if the rounded stern would create enough drag to keep you down. I have an 18' paddle jon, where the stern slopes up aft just like the bow does. In fact, it's a mirror image. Put a motor on it and she won't plane. Crank up the motor and she just squats more.

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Howard,

I think you're right. I've just been tinkering around with it a bit. The easy solution, if I were to actually modify the full-size boat, would be to incorporate a round stern that doesn't touch the hull bottom at all. I think it is called a "pinky stern" if I'm not mistaken... but essentially, it could be built so that the round extension is entirely above the waterline. The hull would still end (sharply) at the original transom, then a concave section would rise up sharply (along the original transom) for the first few inches, then curve outward and back to close off the underside of the round stern. Not only would this avoid modifying the waterline, but it would reduce the total weight of the added round-stern, making it easier to compensate by shifting the lead ballast forward (probably only a couple inches at most would do the trick... maybe less).

Ultimately, as a dedicated sea kayaker (who values lightness and performance), I probably couldn't bring myself to actually modify the boat. For one, Graham's boat is gorgeous as it stands. I think it would be neat to give it a little extra flair with a round-stern (set her apart from other P22's and all that), but of course I question the wisdom of adding perhaps 100 lbs. of additional weight (in plywood panels and 'glass) to create a rounded stern which would probably offer no functional advantage except helping to avoid shipping a wave in following seas. Aesthetically, I like it because the round stern breaks up that "flat-panel" look of the stern which, to me, always gives even the nicest sharpies a bit of an institutional or home-built look. Then again, it does have a sort of charm all its own, too.

As I noted above, I really like what Chick did on the original P22... painting a radius on the corners of his transom so that it virtually eliminates the bluntness of the flat-panel appearance. I'll probably end up going that route... but I like to toy around with ideas and maybe if I toy around long enough, an exasperated Graham will throw his hand in with a beautifully-planned round-stern modification! :) (Kidding, Graham, of course.)

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