Overlap Cuts

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January 1st, 2005 HAPPY NEW YEAR!		Before I start using up any more lumber I first need to cut the overlaps in each of the connecting rib parts before I epoxy them together. Here is rib-2 that I have cut the overlap joint out by using my router. The connecting piece of wood was much easier to cut out than the rib cut itself. I would highly recommend that you gather some scrap pieces of wood and practice before you actually start making your cuts onto rib pieces.

January 1st, 2005		In this picture you can see how both pieces of wood fit together ready to be epoxied. More importantly for you to notice is how I used straight scrap pieces of wood and clamps to set the depth of how far I would route out the wood. Cutting the rib requires two scraps clamped to set the "left-right depth" movement as well as the "up-down depth" movement for the cut. The piece of wood that connects the top of rib-2 to the bottom of rib-2 only required the left-right "fence" set up because the overlap cut will go completely across the wood piece. If this description does not make sense try looking at additional pictures below to understand the cuts.

January 1st, 2005		The picture on the left shows another picture of the fences I made using the scrap pieces of wood. The other picture is a close up picture of the router but I am using to cut a smooth even cut in the wood so both pieces of wood fit nicely together.

January 1st, 2005		Here is a picture of the top and bottom of rib-2 to give you an idea of what the cuts ended up looking like
January 1st, 2005		Finally all overlap joint cuts are made and I can now assemble the rib together. The rightmost picture show a side profile of the rib and how the overlap joints connect all of the parts together.

January 1st, 2005		Here are the parts I made earlier (in December 04) neatly arranged and labeled by the rib it belongs to. How nice it is to be organized! The paper on top of the rib parts is one of the blueprints for the hovercraft. It is draped on top just because it was a convenient place to keep it where it would not get damaged. That's known as a organized excuse to leave it there!

January 16th, 2005		Since I am still learning to use my router I thought I would try a new method to remove wood for making the overlap cuts. These two pictures show how I used a 1/2 inch forstner drill bit (its a flat drill bit) to cut most of the wood out. My plan was to remove 90% of the wood with the forstner bit and then use the router to clean up the remaining 10%. Since 90% of the wood was removed by the time I took to piece to the router, I only had to apply very light pressure to "shave" the remaining wood and get it exactly where I wanted it cut to. This seemed to work out very well and I have pictures to prove it! ;-) Even if the router cuts are not exact it wont really matter because the epoxy will fill in any voids and/or imperfections. Remember that the epoxy (when cured) is stronger than the wood itself. The only reason the entire craft isn't made from epoxy is 1) it would be too heavy and 2) it would cost too much! These are two good reasons to only use it where you need it. Just tell 'em I told you that!

January 16th, 2005		The first picture here (far left) is how I used my table saw and standard table saw blade to gradually notch out and remove the wood in order to make half of the overlap joint. Again, I cut 90% of it out and used the router to clean up the remaining 10%. The picture on the right (or is that left-right) is the router performing the cleanup.

January 16th, 2005		Here you see how the overlap joint is fitted together after the router cleanup has been completed.

January 16th, 2005		Here is another picture of the joint together for final assembly. Success!

January 23rd, 2005		I used the same method as I did above to cut/notch out the wood in the bottom of rib 3. When most of the wood was removed I used the router to "clean up" and give it that professional look. Remember...only you and I know that this is my first time making cuts like this. Everyone else who will see it will think a real pro did it. Its a good thing that this internet thing wont reveal our little secret!

January 23rd, 2005		Again...using my homemade router I perform the cleanup.

January 23rd, 2005		The cuts are now clean and fit together like closing doors on an elevator.

January 23rd, 2005		More success!!! This time instead of just celebrating one of the joints fitting together I celebrate the entire rib 99% complete. The 1% I still need to finish is to cut the excess wood that you can see in the close-up picture on the right sticking out of the bottom. This needs to be trimmed flush with the bottom of the rib and in its place will be the small "triangle" pieces that were cut earlier. Other than that the picture on the left show the rib complete and ready for epoxy.

January 23rd, 2005		Just for the record, two of the ribs have the overlap cuts made to them. Here they both are appearing for the first time in all their glory!

January 23rd, 2005		Lastly, (for today) I thought I would throw in a picture of the water bottles I am collecting. The plans suggest putting them on the inside of the sealed hull to aid in floatation in the event you start taking on water. For this size craft the plans recommend about 60 1 gallon bottles to insert in the hull before the craft is fully skinned and sealed. The nice part of this is that you will not be able to see the water jugs after the craft is fully assembled. The bad part is that you will know that your craft is made up of water jugs. The only thing left is to add duct tape and name the craft after Tom Sawyer. I have only collected a little over 30 jugs so far so I am half way to collecting what is needed for the craft. I may decide to go with an alternative method for emergency floatation if it is cost justifiable but I don't know what that method will be as of today. Luckily I still have a fair amount of time to think about it. Suggestions anyone????

February 4th, 2005		This is rib 4 where I am again marking where I need to cut for the overlap. I use the "L" square to make sure my vertical pieces are at 90 degrees . I also use my smaller square to make sure the far right and left pieces are square before I made my marking. Both of these pictures were taken after I made the overlap cuts. I am showing them to you with my above description so you have an idea how I made sure I had 90 degree angles where the should be. Imaging what the craft could look like after it was skinned if the angles on each rib was different.

February 5th, 2005		The overlap cuts continue. The picture on the far left (rib 5) is how I went about marking the proper angle that the blueprints indicated. Fortunately I have a $5 tool with a gauge that tells you exactly where to angle the wood to create the specific angle that you need. Unfortunately the blueprints only specified measurements in inches and not angles. All hope was not lost for me. I simply brought out my "L" square and a few rulers and did it the old fashioned way. My parents were right.. the stuff you learn in school you really do use later in life! Once I had the angle I needed, I traced on the horizontal rib pieces and the angled vertical pieces where I would need to cut to make the overlap. If you look closely to the image on the left, the vertical wood is only laying on the horizontal pieces.

February 8th, 2005		These are picture of rib 5 after I made the overlap cuts. A thing of beauty Eh?

February 11th, 2005		Finally, all the ribs have the optional overlap cut made to them. I think this will really help keep the frame bonds stronger when I epoxy them together. Don't forget what I said earlier that a friend of mind does not have the overlap joints on his craft and he took an 8 foot jump over a dam and did not damage the craft. Maybe he was lucky that nothing broke on his frame but chances are that you wont be putting that much stress on your frame as he did. If you have the time to make the stronger joints, I would recommend doing them just because you never know. On the other hand I am not as experienced with the strength of epoxy bonds and the stresses placed upon them by minor crashes and normal driving/flying. Others seem to do just fine without the overlap joints.
		Here is a good picture of another type of hovercraft making a landing after a jump. Major cannon ball splash!!
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