JEM Watercraft

Just managed to get everything in time for Xmas holidays and started marking out last night. It's slow going with lots of remeasuring and adding/subtracting dimensions to use as cross checks. Was somewhat bleary when I finished at midnight .

Question No 1 - and I'm sorry if this is in the instructions - what degree of tolerance is allowed on the dimensions and particularly the QA dimensions. Reason for asking is that on the QA1 dimension for the rear deck I am about 3mm (1/8") over but have no idea if this is acceptable. Should be 200.9cm, getting 201.2cm but I can't find any errors in the reference lines or elsewhere. (Plus I refer to drawings a lot in my work and feel lost without a +/- something).

I imagine the deck is not as critical as some other areas but having a tolerance to work within will give confidence that I'm being accurate enough without wasting time being too finicky.

I've settled for an exterior ply, ordered on spec, but am not very impressed with it. It is marketed as hardwood but the back appears to be pine and the exterior veneers are very thin. I am confident it will still make a reasonable boat but it will cost some time in needing TLC. Density is not too bad - worked it out to about .44 specific gravity (somewhere between quoted figures for Gaboon and Hoop pine).

Time to go and work on question 2 now.....

That small amount your off shouldn't impact anything. You have about +/- 6mm. I draw the dimensions with a high level of precision so builders can get a detailed as they like.

+/- 6!!!!?

WoooHooo - full steam ahead!

Thanks Matt.

I try to get within + or - 1mm with the QA measurments in QA sheet 2. These I believe are critical to the fairness of your hull.

Thanks for that tip Mick, every bit helps.
Have finished marking out the dimensions on sheet 1 and pretty happy so far - most were within a mil and the deck panels can be trimmed a bit to fit if needed.

Drawing the curves has taken a lot of time as I don't have a good set up for this type of thing. Luckily Santa's elves are working on some new sawhorses so the assembly stages will be a little better.

Next stage should be to cut the drawn pieces, trim and then use them as templates for the rest. Too late to make noise now so it's instruction reading time again. Won't get much done tomorrow even though I'm on holidays - someone who is going to work has left a list of things that need to be done before Christmas .

Good going Bob. Sounds like some good drawing if you're just 3 mm off. I just started lofting my Laker this afternoon and only managed to finish laying out half of sheet 1 before family business interfered. Hope my lines are as close as yours. (I might be slow, but I do poor work). Keep up the good work and keep us posted.

Bruce

Bruce, Yes it's hard to get a lot done in one go. Much of mine so far has been 10 minutes here, 20 minutes there. I reckon Mick could do the whole thing in 20 minutes blindfolded with one hand tied behind his back and a beer in the other while holding the pencil in his teeth

Spent some time last night unfolding my glass cloth and putting it on a roll to avoid developing permanent creases. With a tent pole through the tube it hangs nicely in my overhead rod rack.



Did the first cut this morning and very happy with 2 things:
- High quality of cut and lack of tear out using the metal cutting jigsaw blade means I can cut very close to the line and only need a few strokes with a plane in some spots then a quick rub with some old 60 grit belt stuck on a piece of wood.
- Very few voids in the ply (so far), in fact only 1 small slit that may be a joint between 2 pieces of veneer. The outer veneers may be thin but I think it's going to be good.

That is a novel idea on getting rid of the creases in the glass when they ship it folded up.

The last build I was lucky , they shipped it rolled up and not folded , like they normally do. Then after a few days of having it lay over the boat and smoothing it out before I make it a permanent part of the boat.

I knew there was a reason I keep the tubes the last shipment was wrapped around , Thanks for the insight on that. The more folks that are making wood boats , the more information there is out there , including helpful hints all of us can use.

Chuck.

Chuck, I was lucky too - had the glass all rolled up before thinking about how to store it safely. If you stand it on end it will slip down and bunch up. Laying it down makes it prone to damage. My shed is a junk heap and anywhere other than the rod rack would have been disastrous. Note the plastic sleeve around the glass - would become filthy in no time otherwise.

Just learnt lesson No 1 - for curves that must match always use a template. I used a template (from front deck drawing) on the upper coaming but the flexible batten method on the lower. Ended up with a different curve on the end of the lower. It is only between the last 2 defined points but is significantly different. Will trim out the inside and fill the outer with wood flour/epoxy as it will be under the upper coaming and almost invisible anyway . Should have expected this as I have drawn plenty of curves over the years and know that at least 1 more point is need to control the shape of the end segment.

Made some progress over the last few days and have some questions while my dinosaur PC loads pics onto Image Shack.

What do most people think about material for the cockpit coaming? Do you use the ply as per plan or go for solid timber? Is the solid timber difficult to do?

When glassing the hull is it necessary to cut the glass cloth at the ends or can it be made to conform right to the stem and stern?

Should hatches be cut out after glassing? If so then how are the edges treated - just sand and varnish or recoat with epoxy first (or even glass)?