Clipper's Vera Cruise Build

Clipper's Vera Cruise Build

Saturday, September 7, 2013

Positioning The Frames

With the building form finished, I could finally get to positioning the frames on the form. The frames need to be in specific positions measured fore and aft, up and down, and side to side. They also need to leveled in relation to each other and square to the building form (except the transom frame which is mounted 12 degrees from vertical).

The building form was constructed so that it's two long horizontal members were level with each other and the legs on one side were aligned with the legs on the other side. I also made every attempt to keep the form square. Readers will also remember that I had to level the form in the garage. All of that was necessary in order to make this next step possible.

The steps I went through with each frame were essentially the same, with minor variations to fit each frame's situation. First I would establish the height of the frame on the form as well as the correct distance from the front of the the form.

The long horizontal members of the building form are used to establish the height for most of the frames. Only frames 4 and 3 (and the transom frame) were different. Frames 3 and 4 were mounted on the legs 3 inches higher than the rest of the frames.

The distance from the front of the form was established when the legs were added to the building form. The frames rest up against the legs (or in notches for frames 3 and 4) which automatically set the correct distance fore and aft. Of course, part of the process in positioning the frames is to insure that these height and fore/aft measurements are correct and do any compensating as needed.

The next photos show the two different ways of mounting for height. The frame on the left is essentially mounted at the level of the horizontal members of the building form, although this particular frame is actually setting on a crosspiece between the two horizontal members. It is also mounted flush with the end of the form, establishing it's fore and aft position.


This photo shows frame 4 mounted on the leg 3 inches higher than the other forms.


All of the frames were built in such a manner that when they are mounted on the building form, the bottom of the boat will be the correct contour. In other words, the inside edge of the frame (or  the inside edge of the floor timber) is the reference point for the frame.

Once the mounting height  and fore/aft positions were established, I needed to insure that the frame was centered in the form. The form was as square as I could make it and the distance between the horizontal members was 24 inches (outside to outside). But to insure that the boat itself was centered correctly, I took all measurements from the same horizontal member.

Each frame has a given measurement from a centerline to the outer edge at the tops of the side frame members. This is where the sheer will eventually be mounted. In order to get the frames centered, I used a drop string from a measured point on the building form. A horizontal bar was clamped at the measurement points on each frame and a centerline established on the bar. This line was then aligned with the drop string.





This is why it is important that the building form be level in both directions, because otherwise the drop string approach would not work as it would be hanging at an angle in relation to the building form.

After getting the frame centered, I insured that it was level in relation to the form by using a level lying on top of the horizontal bar. In order for this to work, the bar had to be aligned to the same points on opposites sides of the frame. I used the sheer points for this.

The final step was to insure that the frames are 90 degrees to the building form when clamped into position. 

Throughout this process, I continually checked all measurements and adjusted where needed. When I was satisfied with the frames positioning, I clamped it into position. I did not permanently mount it at this stage of the process.

Each frame went through this process. The transom frame was a bit different in that it needs to be mounted at 12 degrees from vertical. This required that I rig up a different method of hanging the drop string. You can see that in the next photo. It is the two short horizontal pieces attached to the bottom of the building form horizontal members.The drop string drops from a board lying across those two short members.


The transom frame is not completed at this point, requiring two sheets of 3/4 inch plywood which I am in the process of saving for. So I have to make allowances for the fact that it will be taken back off and completed when I get the plywood.

In the next photo, all the frames have been positioned and clamped into place.


The final step in this process is to test the alignment of  the frames to each other. I did this by using a 16 foot long batten  clamped to the transom frame and then placed into position around the frames up to the forward frame 5. This was done at several points on each side and several points on the top (the bottom of the boat).

What I was looking for was any place where the batten was forced out of a natural curve by a frame being out of position. I was also looking for any spots where the batten was significantly away from the batten, in other words a low spot. You do this after the batten is clamped in position by sighting down the length of the batten and look for fairness of the curve. You can see this well in the next photo.


 As mentioned, I did this at several points on the frames. here , the frame near the sheer points is being checked.


So this process took me quite a few hours to accomplish, primarily because I made some mistakes along the way and had to go back and redo some work. But I also wanted to insure that the boat was going to be built right. After completing this process, I am satisfied that the boat will be even and the correct shape. A lot of work, but worth the effort.

This coming week, I will permanently mount the frames to the building form and then start getting the stem and frame 6 into position. I will cover that in another blog article. So until next time, take care.

Click Here To Comment:

  1. Well done! She's looking great! I admire the precision of your construction form.

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    Replies
    1. Thank you Michael. It's nice to see that other's are reading the blog. Hopefully, it is of some use to others as well.

      One thing I learned in my older career years ago was that if the base isn't right, then everything built off the base be be wrong as well.

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