N motor rocket

Rebuild

Update 2008:

The flight in 2008 gave me a chance to rebuild the bird.
I will build it the same as the last time since it worked good then.
I am going to clarify some of the methods used with more photos.

Nosecone electronics:

The new nosecone electronics package will be all new so it deserved it's own page.
Nosecone details

Temperature logger:

I wanted to put a temperature logger inside the fin when I built the first fincan.
But since it was my first high performance bird I didn't want to complicate matters.
I used this rebuild as a chance to add the logger.
The core of this is the MAX6674 Thermocouple-to-digital converter and a thermocouple sensor.
The data would be stored in an RS232 data logger I built that has 16Meg of data storage.
So the plan is to trim the nomex honeycomb to accomodate the circuitry and battery. I will 'dead bug' style mount the MAX6674 and a PIC to convert the data to RS232 data my logger is happy with.
The battery and logger will be removable and get inserted from the inside of the airframe before flight then removed after flight to download the data.

Circuit-Dead bug style

You can see the thermocouple going to the fin edge on the left, I cut a 1/2in long slot to the edge for it to get glued into.
On the right you can see the connector for the logger and the second cutout for the battery.

Logger installed

Once I had all the permanent electronics installed I carved away the nomex honeycomb for it.

Honeycomb trimmed

I glued the honeycomb onto the core G10 and potted all the builtin electronics in epoxy.
I then made foam plugs and glued them into the openings to keep the epoxy from vacuum bagging out.
After vacuum bagging the carbon on the outside and trimming I located the plugs and trimmed the openings.

Openings trimmed

Half way in

I would then cut a slot in the BT before mounting the fins.

Leading edge:

I added 4 layers of 5.7oz carbon fiber to the leading edge of the fins before attaching them.
Here is one in the vacuum bag.

Bagged fin

Fillets:

I thought I would add some details as to how I do my kevlar fillets.
I do two fillets at a time, on opposite fins.
I used Cotronics epoxy, Duralco 4461-IP.
I mixed up 30grams resin and 9grams hardner.
Once mixed I used a small acid brush to brush a small amount of epoxy where the fillet goes to get it wetted out.

epoxy brushed on

I then added 2grams of Kevlar pulp to the epoxy and mixed this till wetted out.
It is very thick so just work at it, it will wet out.
Once all wet out tap in all down into the bottom of the cup so you can divide it in two

Ready to divide up

Now split it in two and put half on each fillet and work it out

Applying fillet

With your thumb and forefinger touching, smush down the kevlar so it makes a uniform ridge down the length of the fillet.
This helps to distribute the Kevlar evenly.

Pushing excess ahead of fingers

See the ridge

Once you are satisfied it's distributed evenly smash down the ridge with a finger so it's flat.

Smoothing out

Now place a strip of release fabric along the length and smooth the fillet out to a nice shape.

Shaped with thumb

Once the epoxy dries peal off the release and there is your fillet.

Nice fillet

I then put 3 layers of 4oz S-Glass tip to tip. It used ~62g epoxy

All glassed

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