Making new spars for a 7BCM

[s35pilot]

David, I too had to shave the forstner Bits, I used a piece of emery cloth and just cleaned uo the edge of any burs, I didn't want to try and grind tool steel or have a good way. I would say that the hole are not real snug but, they don't fall out, this also brings up a good point.
When I was talking with Ron Percy about spars, he mentioned, Just using some varnish to hold the bushing in, then I read somewhere about glueing them in with epoxy. Which do you think would be the best?
Something else I thought about was the bushings I have look like they were installed before varnishing, I cleaned a flim of varnish off the top and bottom edge. What would be wrong with using T-88 to glue them in and then do the varnishing, the T-88 would provide a good seal for inside the hole and give a real tight fit for the bushing, then when varnish is complete I would use a 3/8' and 1/4' reamer to clean up the inside of the bushings, just a thought.

[David Johnson]

Tim, I built a set one time and used T-88 to glue the bushings in. Bill Pancake later advised against it. Something about letting the wood breathe and move with weather changes. I figured he had a lot more experience than any of us around here. You should not have to ream the inside of the bushings. As to varnishing or glueing them in, your guess is as good as mine. David J.

[s35pilot]

David, when I mentioned reaming the bushing, I was thinking if they were installed prior to varnishing some residue would get inside from the spraying of the varnish, it would be to just clean up the bushing but, it sounds like I will not install before varnishing, varnish inside the holes and then just clean up for a nice thight fit and like Ron mentioned, use some varnish to lock in place. If anyone else has some advise, please jump in. Tim

[s35pilot]

Getting ready to cut the spars to lenght and the angled end cuts, pulled out the Aeronca drawing DVD and checked drawing #'s 5-146 and 5-147 for details. Here they are, I will start the layout and cutting Monday.

[s35pilot]

I wanted to add the "H" detail for the front spar, you need to pay close attention to this detail.
The top of the spar has a slight angle from where the lower angle starts to the tip. When I was looking at the old spar, I just thought it had sagged over time But, when you look at the detail closer you will figure out that it cuts.

This is where you start the tapper cut on the top of front spar. Notice that you start at the top of bevel.

Here you can see how slight the angle is about a 1/4" from the bottom of the top bevel, I used a piece of masking tape on the spars for layout, I didn't want to mark the spars all up and have to sand the marks off later.


This is the layout of the bottom cut.

I used a utility knife to score the spar on my layout line using my straight edge. I will score on all layout lines and cut just a fraction outside the line this will prevent any edges from splintering.



I layout for the rear spars, these are fairly straight forward but, again you notice a slight angle cut on the top.

I did a sample cut on a piece of scrap to see where the blade would cut from the edge of the fence.

It's a light 1" so, when I clamped my straight edge to the spar, I will set it so the cut will be a fraction outside the line. This along with the knife score will prevent any splintering, at least that's the plan.

I was getting ready to cut, when I got a call from a buddy of mine "Bob" and asked if wanted to go flying in his new (well, 2005) Waco......need I say more.

The spars will wait..........

[Shaw Siglin]

Absolutely no one will argue with that logic!

[s35pilot]

Here I clamped my straight edge 15/16' from the razor score.

You can see how it cuts just outside the score and leaves a clean cut.

Finished the first lower cut again, you can see how clean it leaves the cut.

Both cuts on the bottom of front spar complete.

I set the straight edge up for the top of the front spar cut.


This is the layout for the front spar tip angle cut.

Tip cut completed.

Here the front spar tip inserted in the tip bow bracket.

This is the rear spar tip ready for tip cut, I thought I took a few photos of the angle cuts but, I can't find them.

Tip cut completed.

Looks like a fit to me......... well, that's it for building spars, I hope this will help a few of you that decide to build your own spars, It's a lot of work but, I feel it's worth the effort.
Now, I will get them sanded up and varnished. Maybe, I will see and meet a few of you if I can make it to the convention in June.

[joea]

Very, very nice.

When you come to Middletown you are going to be giving a presentation on building spars we hope????

We cannot wait to see the rest of the airplane considering the quality of the work you have done on the spars!

Joe

[Nathan K. Hammond]

Excelent work Tim! So..... is there an "7BCM Wing Assembly" thread and "7BCM Wing Covering" thread in the future??

nkh

[CptKelly]

Ok, you have sold me. I'll take a set.

Mike

[s35pilot]

Thanks guys,
Joe, if I'm able to make it to Middletown we could talk about it.

Nathan, you should have the template very soon, I mailed it on Monday, I thought you would be covering those topics but, I'm documenting all the rebuild so....I might post a few pic's, working with wood was the easy part for me, all the rest will have a pretty steep learning curve.

I have found a guy that has a lot of experience with covering and is going to teach me on a set of wings that he will be coving soon. He said, I could work with him from start to finish, and would teach me all the tricks he knows, I'm looking forward to it.

Mike, if you decide to make your own and ever have a question, I would be glad to help but, I better leave the spar building to the guys that make them for a living.

[s35pilot]

I thought, I would go ahead and post the finishing process of the spars.


Here is the varnish I have chosen to use after reading several good things about this system(EV-400).

I emailed Nathan for some tips and here is what he said: On virgin wood, it will take 2-3 coats. The first needs to be thinned 50/50 (Catalyzed varnish/thinner) and brushed on. By making it really thin and brushing it, assures the wood will soak up the varnish and it wont flake off in 15 years.

The next 2 coats can be mixed normally and sprayed on. 1 sprayed coat would work if you're trying to save every ounce of weight, but 2 will be better in the long run for protection from rot. No need to sand between coats, because smoothness isn't an issue.

If you were doing floorboards or something visible and touchable, then you would want to sand between coats. The varnish has a habit of raising a little bit of grain.

I'm working on a way to support the spars while being varnished, I will be working on them tonight.

[s35pilot]

Here is what I came up with to support the spars while varnishing. I went to my favorite home center's plumbing and hardware dept. I purchased a few 1/4" and 3/8"X 12" all thread rods with a few nuts and washers, then over in the plumbing dept., I found a couple different sizes of tubing, 3/8'OD w/1/4"ID and 3/4"OD w/1/2" ID then in the washer area some 5/8" OD w/ 3/8" ID washers (you will see how I used them in the next few photos).
This all cost about 20 bucks

I used this one for the rear spar 3/8" wing attach holes (1/4" all thread).

I used this one for the front and rear 3/4" strut attach holes (3/8" all thread).

This one is for the front spar 7/8" wing attach holes (3/8" all thread).



After they are placed in the hole you just tighten up the nuts and rubber expands and holds them in place.



I drilled a few holes in a 2X6 I had for the all thread to slip into, after varnishing one side I can flip it over(I will need some help to flip them) , do the next and then move to a couple of other boards I will set up to let them dry.

[Nathan K. Hammond]

Tim, I'm continuously amazed!

nkh

[Jimmy Payne]

Tim,

I think I am a few years older than you, but will you adopt me?