Stock Estes Door Knob

[Jimbooregon]

Hi all,
I just ordered and am planning a Estes Door Knob build. I will paper the fins and thinking about how to reinforce the cardboard centering rings without adding a lot of weight.
Will this configuration handle most G engines? Without going to aftermarket plywood fins etc is there any other mod that I should consider? All advice welcome.
As they say here in the UK: "keep calm and fly rockets."
Cheers
James
Ayr Scotland

 

[Pinetree]

I fly mine on an F15-4.. it's built "stock" right from the package. No issues here.

 

[cls]

Yes, stock on Gs and Hs here. Used yellow glue, too. No problem! It's one stout, sturdy, interlocked rocket. I want to order another one.

Are you going to finish it white and orange? Or get the special light blue decals?

 

[Scott_650]

The original cardstock rings should be fine on G motors. If you think it needs some added stoutnesses cut an extra upper ring from like cardstock. I like to skip using the slot/notch in the middle centering and use it as a typical centering ring, that way I can do internal glue fillets the whole length of the fin tabs before installing the aft ring.

But built carefully as it comes should be fine on even low-end H motors.

 

[Rob Campbell]

You can make gussets from foam board to reinforce the centering rings. Rectangular gussets glued to the CRs, MMT, and body tube will add strength and very little weight.

 

[Jimbooregon]

The original cardstock rings should be fine on G motors. If you think it needs some added stoutnesses cut an extra upper ring from like cardstock. I like to skip using the slot/notch in the middle centering and use it as a typical centering ring, that way I can do internal glue fillets the whole length of the fin tabs before installing the aft ring.

But built carefully as it comes should be fine on even low-end H motors.

Tnx Scott, sounds great!

 

[Jimbooregon]

So reinforcing with card stock would be enough, and looking up the GSM of a cereal box seems to be fine. ?? Thanks all for your response.

 

[Gastrok]

Check these out. These are nice, but like others said, stock should be fine.

Estes Doorknob 29 mm Vander-Burn Plywood Upgrade Kit

 

[SolarYellow]

Interestingly, the scale fin thickness for a 3-in single stage Doorknob is only 3/32 inch.

 

[Gastrok]

Interestingly, the scale fin thickness for a 3-in single stage Doorknob is only 3/32 inch.

I happen to have both the stock balsa fins and Vander Burn plywood fins handy. Not really seeing much in the way of difference in thickness.

I know that in the US measurements of wood/lumber measurements are "nominal", as in, LESS than advertised. Infuriating (i.e., BULLSHIT), but so be it.

 

[SolarYellow]

Birch ply is most often produced to metric standards. Your measurements show 3mm, within likely manufacturing tolerance. Scale thickness would be 0.095 inch, slightly less than 2.5mm. 3/32 inch is 0.093 or so.

 

[Gastrok]

Birch ply is most often produced to metric standards. Your measurements show 3mm, within likely manufacturing tolerance. Scale thickness would be 0.095 inch, slightly less than 2.5mm. 3/32 inch is 0.093 or so.

OK. Just trying to show you what the actual measurements are.

I guess what you're getting at is that the Estes Doorknob is not a true scale model. No surprise there. It's Estes.

 

[Jeff Curtis]

Check these out. These are nice, but like others said, stock should be fine.

Estes Doorknob 29 mm Vander-Burn Plywood Upgrade Kit


View attachment 619652

I bought this set but wonder how much nose weight I'm going to have to add.

 

[Jimbooregon]

Thanks for the pics Gastrok, they do indeed look nice. Maybe I'll do a second knob with those fins.
I'd be interested in the added nose weight too Jeff.

 

[Jimbooregon]

Solar, I appreciate scale models too, but what would you do, try and sand 1/6th off the fins? one would have to have two for sure, a flier and a desktop queen.

 

[SolarYellow]

You can buy plywood, bass wood, balsa, and G10 in 3/32" thick sheets if that matters to you.

 

[John Brohm]

I used 3/32" balsa for the fin cores, and then faced the fins with 0.010" Styrene. Flew on an F15; was fine.

 

[Jimbooregon]

Nice build John!!

 

[Gastrok]

I bought this set but wonder how much nose weight I'm going to have to add.

I put a small amount of modelling clay in the tip of the nosecone, maybe 1 oz. I can't remember if that came with the kit or I added it on my own.

 

[jackiboi_11]

I put a small amount of modelling clay in the tip of the nosecone, maybe 1 oz. I can't remember if that came with the kit or I added it on my own.

It comes with some nose weight, not sure how much though.

 

[jackiboi_11]

Check these out. These are nice, but like others said, stock should be fine.

Estes Doorknob 29 mm Vander-Burn Plywood Upgrade Kit


View attachment 619652

I got those for my doorknob and flew it on an E20-4 with the nose weight that came with it, flew awesome. By eye I'd say it went around 500-600 if that even matters. I did build it heavy for a mid power rocket.

 

[Gastrok]

I got those for my doorknob and flew it on an E20-4 with the nose weight that came with it, flew awesome. By eye I'd say it went around 500-600 if that even matters. I did build it heavy for a mid power rocket.

I've flown my on F27-4's a bunch of times with similar results. The plywood parts make it into a tank. Mine has "landed" multiple times with a partially functional chute and come out fine.

 

[jackiboi_11]

I've flown my on F27-4's a bunch of times with similar results. The plywood parts make it into a tank. Mine has "landed" multiple times with a partially functional chute and come out fine.

yeah mine came down extremely quick with the stock parachute but it was unscathed. It was a win for me!

 

[SolarYellow]

@hcmbanjo did a pretty nice build series here:

https://modelrocketbuilding.blogspot.com/2020/05/estes-doorknob-9720-build-part-1-parts.html

 

[Back_at_it]

Hi all,
I just ordered and am planning a Estes Door Knob build. I will paper the fins and thinking about how to reinforce the cardboard centering rings without adding a lot of weight.
Will this configuration handle most G engines? Without going to aftermarket plywood fins etc is there any other mod that I should consider? All advice welcome.
As they say here in the UK: "keep calm and fly rockets."
Cheers
James
Ayr Scotland

If you paper the fins you should be fine on a G motor. As for the centering rings, You don't really need to be concerned as this model has through the wall fins so they will take the force of the motor on launch and ejection.

During the build, I'd recommend upgrading to a Kevlar shock cord and attaching the shock cord to the upper centering ring. If you choose to do this, you might want to add a small piece of plywood under the upper ring where the Kevlar attached. Since Kevlar doesn't really stretch, it puts a bit of a shock on the mounting point. Any scrap of ply you have laying around will work just fine.

Here is an example of what I'm describing.

 

[hcmbanjo]

@hcmbanjo did a pretty nice build series here:

https://modelrocketbuilding.blogspot.com/2020/05/estes-doorknob-9720-build-part-1-parts.html

Thanks for the plug Solar Yellow!
Here's the whole build from finished model to start:
https://modelrocketbuilding.blogspot.com/search/label/E Doorknob