Something isn't lining up...newbie needs your help

[Ryan.davis137]

Hello everyone I'm new here and I have a question regarding the building process. I'm building the prospector 16 straight out of canoecraft. At this point I have the molds cut, the strongback built, stems bent and laminated and the stem mold and station 6 attached to the strongback. Station 7 is also attached in it's respective place. It's this station that's giving me problems.

The offsets from canoecraft describe the profile of one half of the station from the centerline out as well as the depth of craft right? And being that the stem mold is centered on the strongback and runs through the center of station 7 I would need to deduct the total thickness of the mold material from the overall width of station 7 otherwise the sheer line of the half breadths would be off right? It would too wide in other words. So that's what I did; Im using 1/2" thick MDF therefore I cut 1/4" from each half of station 7 centerline. When I set a plank against my molds I notice there is a gap between the plank and mold 7, a sizable, worrisome gap that leads me to think I've done something wrong.

My real question is just this: did I booger something up by cutting the material thickness out of station 7? I feel that I should just go back to drawing board and redo it.

Sorry for the short story I wanted to be as detailed as possible. Also I didn't look on the forum for any answers before posting this so my apologies if this has been answered before.

Thank you all I'm so very appreciative of your help and advice.

[Cruiser]

The tables in CC produce a mold that is ready to go and they shouldn't have anything else deducted ... now the bow and stern sections do require you to adjust for the stem, so those do get trimmed.

I did a detailed post when I worked out how to do the lofting from tables, you can find that here: viewtopic.php?f=9&t=4658

Hopefully that covers your question.


Brian

[Ryan.davis137]

DSC03846~2.JPG

Brian,

Let me first start by saying your write up was my go to when I first started on this project; very well written and incredibly easy to follow. Your information was pivotal when I was drawing up the stem molds.

The image I included is obviously from your original post and shows the area I'm having difficulties with. The two half sized station molds, indicated with the red arrow, are mounted to the stem mold, indicated in blue. I assumed that since everything is based off of a centerline and baseline and because the stem mold is attached directly over the centerline I would need to cut these half sized molds to make up for the offset of the material thickness.

I'm probably over thinking this but I don't understand how the offsets in CC can account for the thickness of the material, considering the book recommends 3/8 or 1/2 plywood/particle board for the station molds.

Thank you for taking the time to help me, it's much appreciated.

[Patricks Dad]

You should indeed deduct half the thickness of your stem molds from station 7. I'm not sure there is a problem here however. You noted that you saw a gap between the plank and station 7 when you laid it across the forms. How big of a gap and did you lay the strip across the shaped stem (it's not shown in your picture) and station 6? A stem would tend to make whatever gap you have larger but I'm curious how large of a gap you are actually seeing here.

The design may have a concavity in the design in which case a gap would make perfect sense.

Finally, in designs I've built where a station 7 is provided (which sits along side of the stem mold), I've simply left them out of the build (they tend to be more trouble than they are worth).

More details of the problem you are seeing would be helpful.

Thanks

[Cruiser]

The CC table give you the shape of the station ... BUT when this one gets installed on your bow/stern molds, it can be either cut in half and the thickness of the bow/stern mold removed (as Randy said) ... alternatively , it could be locked in with cutout notch, which effectively does the same thing.

So, you are correct in your question "How does this take into account the bow/stern mold?" .. it doesn't ... you do, depending on the material you select for those molds.

Cutting it in half is maybe the simplest way, but it can be done a few other ways as well, depending on your equipment and what "bag o tricks" you have. I typically draw in the thickness lines for the bow/stern mold, cut roughly, sand to the lines. To attach, I use cap screws .. bore a hole with a forstner bit to fit a #8 cap screw head, deep enough to get head below the outside, then complete the hole with regular bit to let the screw part go in easily and use that to attach to the bow/stern molds.

Brian

[Ryan.davis137]

Thanks for the help guys! I was able to find why it was wrong and it's because I'm human or can't measure or maybe something called accumulated error. I ended up making new paper templates with better precision than my previous attempt(s) and checked them against my station molds and sure enough there were considerable inconsistencies. Luckily for me I only had to recut station 0 and the little half sized molds, the rest I sanded down because they were relatively close but needed trueing.

Next time I will omit using graph paper in favor of Jason Eke's instruction on lofting. One might presume this method might be more accurate/precise yeah?

Live and learn. Again thanks for the help people!

[Cruiser]

You are doing the absolute right thing in taking your time and making sure your initial setup is as good as you can get it IMO, it will save you much grief as the build progresses.

I am just in the throes of planning my next build and used the lofting info in reverse to lift the lines from a Swift Keewaydin 14, I just drew up all the stations and am going over each mold to make sure all the points make sense. I have found a few entry errors 3.57 instead of 3.75 etc, a few areas that needed some smoothing, but it will be much better to have the base mold info correct before I start modifying the design ( I am not copying the boat, just using it as a starting point).

Please start a project thread for your build and keep us in the loop, we love to watch others build when we don't have one on the go.


Brian