Questions on North Coast Rocketry SA-14 Archer Build

New to the forum so just want to start with saying hello and letting anyone interested know that I was into model rockets as a kid, using Estes A & B size kits. Haven't done it in 35 years and bought a NCR Archer kit a couple weeks ago after finding it on eBay. Been surfing a lot to get up to speed.

Anyway, I have a question about the kit. It looks well made and easy to put together but one thing bothers me and that's the fact that it wants me to install a bulkhead with a center-mounted eye bolt in the coupler tube. This would end up having the delay charge ejecting the payload section instead of the nosecone, which would probably fall off on its own. It later goes on to instruct attaching the shock cord from the motor tube's forward center ring to the nosecone, somehow bypassing the bulkhead.

My intention is using a single 36" parachute so I am going to leave out the bulkhead, glue the coupler to the main body tube and rivet the other end to the payload section. I was also going to drill a couple 1/16" pressurization holes into the payload section.

This may all sound silly but I wanted to ask if I'm missing something before I get too far along.

Why don't you just use plastic rivets or a few small screws to secure the nosecone to the payload tube?

rocketgeek101 said:

Why don't you just use plastic rivets or a few small screws to secure the nosecone to the payload tube?

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Is there a benefit to that technique versus riveting the payload section?

Sounds to me like there is a typo somewhere in the instructions. A lot of mid power rockets have a "payload" section. The shock cord will connect the lower section (booster) to the eyebolt on the bulkhead which is connected to the payload tube (upper section). Now if you want it to be a nose-blow design, simply leave the bulkhead out, glue the two sections together using the tube coupler, and attach the shock cord to the nose.

atomichead said:

Is there a benefit to that technique versus riveting the payload section?

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Well, there would be less volume for the ejection charge to pressurize, and the nose would still be removable so you could launch payloads.

Hello,
Mid and high power rocketry are done a little different then estes. Having the payload section deploy is about standard for single deploy. Nose cone can be screwed or riveted on allowing future access. The bigger the inside volume the more ejection charge you need for recovery deployment. the shock cord would attach to the bulkhead in the coupler. Also I am not sure on this but I think I remember something about the motor mount being an odd size and having to be changed on the NCR kits. I am not sure on that maybe someone who has built the kit can answer that for sure.

Hi,
Built one of these a few months ago. The bulkhead goes in the coupler tube and not the nose cone. Also, if you have not gotten past where you can do it, put something around the wire anchor for the shock cord. The wire does a great number on your bodytube if your delay is off.

With regards to odd sized motor mounts, the old NCR kits used to come with 28mm engine tubes. The new ones come with standard 29mm tubes.

Less volume makes good sense so I'll go that route.

I think I must have gotten one of their newer version kits as the motor mount fits 29mm no problem and it has plywood centering rings versus the plastic ones I've read about in reviews.

I believe the tube diameter on the kit you have is 3", while the Estes North Coast was 4".

Adrian

There is a mistake on an older version of the instructions. The shock cords both attach to the eye bolt, not the nose cone. That has been corrected in later versions of the instructions. You can download an updated version from the Apogee site, if you need further clarification.

If the nose cone is loose, you can friction fit the nose cone in place by putting tape on the nose cone shoulder until it is tight.

The current version of the NCR Archer is 2.64" OD - the older versions were based on a 3.9" diameter tube.

Have fun with the kit!

Matt

I just finished my Archer build, its the newer 2.56" w 29mm Motor. I went with a Baffle/eyebolt installed about 7" down the main tube. Plenty of room for the motor, and for the 36" chute and shock cord. I went kevlar from baffle to bulkhead, then the elastic cord that came with the kit from bulkhead to parachute. Hoping to launch on a AT F40-7 at MDRA in July.

Here it is finished:

https://www.rocketryforum.com/showthread.php?35812-NCR-SA-14-Archer-(K-76)-Gallery&p=552801#post552801

Changing my design to attach to the nose cone instead, ordered new payload tube from Matt/Apogee. Gonna fly it in July at MDRA, see how it goes, taking both setups to see which way I like better.

ManofSteele said:

There is a mistake on an older version of the instructions. The shock cords both attach to the eye bolt, not the nose cone. That has been corrected in later versions of the instructions. You can download an updated version from the Apogee site, if you need further clarification.

If the nose cone is loose, you can friction fit the nose cone in place by putting tape on the nose cone shoulder until it is tight.

The current version of the NCR Archer is 2.64" OD - the older versions were based on a 3.9" diameter tube.

Have fun with the kit!

Matt

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Pretty nice when you are able to get your answer from the kit designer. Thanks Matt.

Thanks for all the help and yes, hearing from the designer is pretty cool!

Now I have another question: What type of screws do you use to secure the nose to the payload section?

I used a string from the nose cone eye to the inside end of the screw in the bulkhead. Then taped the nose cone to make a tight fit in the payload section and put a couple of vent holes in the payload section.

atomichead said:

Thanks for all the help and yes, hearing from the designer is pretty cool!

Now I have another question: What type of screws do you use to secure the nose to the payload section?

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I don't use any screws - just tape to friction fit it. The loads are generally not high enough to cause problems. You can add a kevlar lanyard from the eyebolt to the nose cone, leaving an extra 12" in length to allow payloads to be inserted into the payload section.

Matt

So tape and a length of Kevlar for the nose sounds good. Still have a few questions:

I've cut the steel cable short so that it doesn't go past the main body tube in the hopes that this is less likely to cause a zipper than the Kevlar (sounds good in my head). A 9" x 9" Nomex blanket will be use.

Should the parachute be attached to the Kevlar?
Should the parachute's attachment point be offset slightly from the eye bolt?
Should the Nomex blanket be down as close to the motor as possible?
Should the parachute be installed on top of the coiled/bunched Kevlar line?

Thanks for all you help... Don

1) The cable should not extend past the tube - that will make it much less likely to zipper.
2) I usually attach the parachute to the eyebolt, unless I am flying eggs, then I attach the parachute about 12" down from the eyebolt on the elastic.
3) Yes, put the Nomex as far down the tube as possible (though it likely doesn't make a big difference).
4) Yes, put the cable/kevlar/elastic in first, then the parachute. When the nose comes off, you want the line behind the parachute to help extract the parachute.

Good flying!

Matt

atomichead said:

So tape and a length of Kevlar for the nose sounds good. Still have a few questions:

I've cut the steel cable short so that it doesn't go past the main body tube in the hopes that this is less likely to cause a zipper than the Kevlar (sounds good in my head). A 9" x 9" Nomex blanket will be use.

Should the parachute be attached to the Kevlar?
Should the parachute's attachment point be offset slightly from the eye bolt?
Should the Nomex blanket be down as close to the motor as possible?
Should the parachute be installed on top of the coiled/bunched Kevlar line?

Thanks for all you help... Don

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Thanks again for you help Matt. So looking forward to getting this model in the air!

Okay, almost ready to fly and I have yet another question.... I plan to use the coupler as an e-bay in the future but in order to access it, it has to be removable. My question is will it work to use 3 or 4 rivets to hold it in place instead of epoxying it? I'll be using single-use engines so it has to survive the deployment charge.

You could use a couple nylon buttons, or tape it so its tight, theres hardly any force acting on it, if it does happen to seperate, all of it will be held by the shock cord.
I flew mine a couple weeks ago on an F50-7, super straight flight, Fins whistled! guessing about 900ft or so, but ejection charge blewout upper baffle plate (too thin plus kevlar only shock cord) came down nose cone on parachute, lower sustainer floated to the grass. Only a little mud on the fin! Its now repaired and ready to go again! I epoxied a CR over the blown baffle plate with an eye bolt in it, and added about 12 feet of elastic nylon to the kevlar.

Thank you for the thread. I just ordered the kit from Apogee and this was very VALUABLE information....

I, too, just got a copy of this kit. Even though this thread is dated, still some great information. Can't wait to get mine up in the sky.

Pics, or it didn't happen, right? Cesaroni G88 Smoky Sam. Home made 30" elliptical parachute. PERFECT flight!

FYI, I built my archer with nosecone separation. Just a simpler build (no bulkhead + eyebolt, just shock cords to nosecone). Works fine.

Banzai88 said:

Pics, or it didn't happen, right? Cesaroni G88 Smoky Sam. Home made 30" elliptical parachute. PERFECT flight!

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How about one "up close and personal" like? I'm sure it's ready for it's close up Mr. DeMille.

K'Tesh said:

How about one "up close and personal" like? I'm sure it's ready for it's close up Mr. DeMille.

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Whoops, forgot that one!