DonStegall

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Back in March of 2006, Dave Norman and I started a collaboration on a composite tail for his Seeker. He had produced a tail plug and I produced molds from the tail plug. See the original thread at [link=http://www.rcuniverse.com/forum/fb.asp?m=4026463]Seeker V-tail - Making the molds[/link].

Dave and I were corresponding on Monday and he told me that the plane he finished 3rd at the 2008 NATS in 428 with had a tail he had produced from those molds.

When I made the molds, I made male molds so that I could make more sets of molds for myself or others.

Now that I know that the tail is working well on the Seeker, I'm going to make some more sets of molds for myself so I can make tails for myself and others.

I'm going to use this thread to show how I make the molds and the composite tails. I will use words, pictures, and videos posted on YouTube so that you guys can see how I do it.

Here are a couple of pictures of the male molds and pictures from the 2008 NATS.

DonStegall

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My spray rig is getting used a lot right now, so I waxed the male molds and sprayed a good coat of PartAll PVA on them this afternoon.

They'll be ready for the surface coat tonight or tomorrow morning. Whenever I can get to it.

DonStegall

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I mixed up a batch of surface coat this evening and put it on the molds. The recipe was

12 pumps of WEST 105/209 (about 11 ounces)
2 tablespoons of WEST 423 graphite powder
9 ounces of cabosil

First the epoxy was mixed. Then the black powder was mixed in. Then the cabosil was added in three batches. All was mixed using a jiffy mixer.

This provided enough for a good coat on both molds.

I always save my mixing cups until the next day. Assuming it hardens properly, I'll be ready to start laying on layers and making the molds.

DonStegall

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The surface coat hardened fine.

Even though I brushed it on as smoothly as possible, there are peaks and valleys. To get started on the cloth, I mixed up 3 pumps of WEST 105/206 and 3 ounces of cabosil and spread it on one mold. Then I laid one layer of 1.4 ounce cloth on using one pump of 105/206. Then I did the other mold using the same technique. This will be allowed to cure at room temperature because I don't want the thickened epoxy to bubble in the heat of the hot box.

Now I will have something to do anytime I get 10-15 minutes to put on a couple of layers of cloth. I will contiinue posting so you know the lay-up schedule.

DonStegall

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I've been too busy to take pictures, but I've been putting layers on the Seeker tail molds. I put the final layers on the bottom mold early this morning and put it in the hot box. I still have one more round of layers for the top mold.

Here is the bottom mold. It came out quite decent.

Having male molds to make duplicates is great. Low stress, and you can make a set twice as fast. I will be offering sets of these molds for $500 a set Ready-To-Use.

For those who don't know, this tail is based on cores cut to mimic the Vortex tail. And Dave Norman did a fine job of making the plug and putting decent tips on the tail. And since Dave came in 3rd place at the 2008 NATS in 428 with a Seeker with a tail made from the original molds, we know the tail performs well.

I have a bunch of 1/32" balsa coming in on Monday and I should have the molds ready to make a tail early next week. Tails will be $75.

DonStegall

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Here is the top mold with the final layers on it.

The layers were as follows:

Surface coat
1 - 1.4 ounce cloth
4 - 5.8 ounce cloth
11 - mat (not sure of weight - compared to 1.5 ounce from CST and what I have is lighter)
1 - 5.8 ounce cloth

I also added 4 strands of carbon fiber tow every 3 layers of mat to strengthen the molds and keep them warp free

daven

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just to set things straight, this quote is not accurate.

"For those who don't know, this tail is based on cores cut to mimic the Vortex tail."

The airfoil is not the same as the vortex and the rounding of the corners is more severe.

The square inches of area are very similar though.

DonStegall

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Sorry Dave, That was the impression I was under. It's been a couple of years since I made the molds.

What airfoil is it based on?

DonStegall

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I drill the holes for the torque rods before I start sanding and compounding the molds. If I have to patch and redrill the holes, I would rather do it before doing all of that work.

When I made Dave's molds, I made a jig to drill the holes. It is very difficult to drill a hole on a 40 something degree incline. I made the jig from MDF and sanded it until it fit. It doesn't look exactly straight, but the holes were pretty close to where they needed to be.

I drill the holes at 3/32" knowing that I'm going to open them up to 7/64". I do this so I can use a small round file to adjust the location of the holes before I run the 7/64" drill through them.

I put the jig in place and tape it down. Then I drill one hole. I stick a piece of leftover 4-40 rod through the hole and drill the other hole.

In this case I'm off to the left by 1/64" to 1/32". But it is no big deal. Not worth worrying about. I will move the right hole out some and the left hole in a little, and drill them out.

DonStegall

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And here is the top mold before trimming the edges and washing off the PVA.

DonStegall

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Dave,

You are correct. I laid part of a Vortex tail in the molds and only the first 2/3 of the airfoil is the same. The rear of the Vortex tail has more reflex.

I don't know if reflex on a tail is necessarily a benefit. So it is hard to say which is better.

But an airfoiled tail should be better than a balsa slab stab. Albeit harder to line up.

DonStegall

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Someone contacted me and asked what kind of deals I can make on copies of these molds. I know money and cash flow are a big issue for most people right now. I hate for that to be a reason to stop people from pursuing their goals and dreams.

Here's the deal. In May, I will offer a no interest 4 month financing deal. $200 up front to place the order. Then $100 every month following delivery of the molds for 3 months. For a total of $500. All I need is a credit card or debit card valid for 6 months from the time of the order. First come, first served.

You can make as many tails as you want for whatever purpose you want. For yourself, for your friends, even to sell. But you'll be competing with me.