Initial Frame Fitting Part 2
Thursday, January 22, 2015
In the previous article I showed how I fit the frame parts together. I neglected to show what the end result of the two parts looked like. Here is that photo.
The remaining steps of fitting the frames involves making the gussets. Remember, these are plywood reinforcements that cover the seams between the side and bottom frame members. On my boat, these must extend 6 inches onto each frame member. So I measure up from the bottom piece the required distance and draw a line for reference. The same is done for the bottom frame member.
Next, using poster board I create a template that matches the contours of the bottom and side frame members and extends to the previously drawn reference lines. A little bit of cutting and drawing and eventually you end up with a trapezoidal shape representing the final shape of the gusset.
The gusset should extend diagonally across from the inside edges of the frame parts to form a diagonal brace. Transfer the template outlines to the appropriate thickness plywood and cut them out and sand to final shape.
This diagonal brace on the gusset will leave an area on the inside of the frames where there is no wood. The gussets will be attached to both sides of the frame (generally), so this open space between the gussets should be filled with a filler block for added strength. I’ve heard that these filler blocks are not absolutely necessary in some cases, but I think the added strength and better appearance is worth the extra effort.
The filler blocks are a trial and error process. You start with a board the same thickness as the frame parts and large enough to fill the area that is open between the gussets. One edge needs to be straight. This can be done on the belt sander. Lay this edge against the inner edge of one of the frame parts (side or bottom doesnt matter). Mark and trim the wood so that it matches the second inner edge of the frame. Make sure the filler block will be large enough to fill the entire open area under the gusset. Lay one of the gussets over this area in its final position and draw a line for the diagonal. Cut and sand this line and adjust as necessary until the part fits correctly.
The part will be some form of triangle after this is completed. It should be the same size as the open area between the gussets. When the gussets and filler blocks are latter glued to the frame parts, they will form a nice solid and strong connection at the frame joints.
You should mark all the parts with identification so you know where they go later during final assembly. I simply identify the frame number, the part type (gusset, filler block, etc) , and which side of the frame they go on. Ideally the parts are symmetrical and it doesnt matter which side they go on, but this isnt a perfect world so better to keep their locations correct.
The final step in this process is to add a brace across the open end of the frame. When the frames are mounted to the building form, they will undergo quite a bit of force as other parts are added to the structure. The brace insures that the frame doesnt get forced out of the correct shape during this process. The brace will be removed later once the boat has been turned over.
So those are the steps that I use to initially fit the frame parts together. With some variations, this is the same process I used for all six frames.
This coming week I will be finish sanding all the frame parts, filler blocks, and gussets. The reason for this is because all of these parts will be coated with epoxy resin after final assembly. This is to protect against moisture. Finish sanding them beforehand ensures that they will have a relatively smooth finish after the resin is applied. It also makes applying the resin easier.
Take care and I hope this article will be useful to someone in the future.
Subscribe to:
Post Comments (Atom)
0 comments:
Post a Comment