Shadow forms constrution Question

Greetings to All

Ok I am about to taken the plunge and build a Triple Crown.
Photocopies of the forms done and cut out,ready for transfer to 6mm mdf. Balsa wood strips cut, Construction table made and building board ready.
Now here is the question>>>>

How do I determine how much extra material to leave on the shadows for attachmnet to the building board??

It would make sence to me if I just ensure all the “gunwales” line up ?(edges of each form )This would make the deck line level and the hull would curve according to the form shape. I did a check in the US1M constrution guide but found no reference to this.

Thanks in advance


I take your question to mean how much extra material to add to deck sides of frames to allow for support on building surface? As long as the frames are lined up according to the plans, it doesn’t matter that much.

Ok so if I add 2 inches to the deck side of each form this will line everything up. As you said as long as I put the shadow forms at the right location the hull should turn out correctly.


Jeff - look at your plans. There should be some sort of “datum” line (or even the waterline) which lets you get the height off the building board identical for each section (which will change depending on hull design)

You can take the section that is the largest and measure up from the board to that “datum” line. Too much is better than too little and will allow you to get your hands inside the hull if needed - as the sections will be higher from the board.

Some use a string at the height and align all templates with it. When Jack Ronda built his MultiONE, he drilled and inserted two arrow shafts the lenght of the boat through all of the templates to keep them properly related in height to each other.

Again - check you plans or templates for a line of general reference that should appear on each template section.

Dick and John
thanks for the info :slight_smile:
The plans I am using does not show a datum line nor do they show a measurment . After looking at the plans a bit more ( and photos of the boat) it looks like the deck line is level right down the length of the boat. SO I am going to do the shadows so all the edges line up at the same hieght. Heck if it doesn’t work out I can always adjust the shadows later for the second boat.

I guess this is the problem when you get plans off the net not all are really complete with lots of measurments. Nor do all have a manual for constrution like the US1M does.

Has anyone every developed a manual for constrution of the IOMs ?? This might be tough as there is so many different hull designs out there. I will be using the US1m manual (at least for info) and help from those oneline when I do the IOM Triple Crown ( take this as advance warning for lots of questions).


Jeff - if you haven’t cut your templates yet, and they are “nested” like my sample attachment … or … if they are “stacked” on top one another, you can add your own reference line for shadow setup anywhere the line will cross all the templates. Just remember to draw it perpendicular and at perfect right angles to the vertical centerline on the drawn templates.

Hope you understand - if not email me and I’ll try to explain further.

Download Attachment: [ F02sm.jpg]( Lemke/200459203527_F02sm.jpg)

Ok I see what you mean now. The triple crown plans did not have this line. So I have done what you suggested and added my own .

So simple of a idea it is no wonder I never thoght of it



Having mulled over the same problem as you in deciding at what height I should have the gunwhale strip above the building board, I decided that I would need to get inside the hull at the later stages of planking,so the height was decided by the room required to get my hand in. Another thing I did was to penetrate each shadow/frame with short lengths of 1/4" dowel and use them as anchorages for rubber bands which held the planks in place until the West cured. I planked my Kite hull in cedar which was relatively stiff and needed spring clamps and rubber bands to twist the plank onto the transom and bow plate. Excess length is needed for this operation.
Good luck with your TC



Glad you caught that Jeff !

You now will have a reference line the corresponds to all the templates. Just need to decide how “high”** off the building board you want the tallest one. Measure from board to the line and you will know how much to add on to raise the next template so the reference lines match. This will insure the gunwale, deck and keel (rocker) are as designed.

Good luck with the build ! It’s a lot of work, a lot of fun and a lot of self-satisfaction.

EDIT: **added ** See Ralph’s post just above regarding need to get inside hull during construction.

Also a kayak building tip: If you run into problems as noted by Ralph, and are using a stiff wood, you can sand down the thickness to help make it easier to put the needed twist in the strips. Most kayaks here are built with 1/4 inch thick strips, but I have see some that wind up at just a bit thicker than 1/8 inch in the compound bend area of the kayak!

Hope you have subtracted plank thickness from the shadow profiles.