Jayhawk

[AKPilot]

Does anyone have any, direct, first-hand experience with a Jayhawk?

I've checked out EMRR and really want one. Am just a bit nervous about laying out the cash, or scratchbuilding one, to have the fins get damaged on landing.

Lets face it, the full size version wasn't mean to land on it's boat tails/fins, like a model rocket. It was meant to go BOOM!

 

[H_Rocket]

I have three (had four - one drifted away) and they fly/land beautifully. A good starter is the Polecat 4" which is sport scale as shipped. It does not include the belly conduit for true scale, however you can add it at your leisure. It does not lend itself well to dual deploy due the long fins. It is a fantastic mid field HPR flight on an I305FJ. Recovery on a SkyAngle 44 is letter perfect for me. Build it exactly the way the instructions say, with minimal epoxy, and don't lay down big glass reinforced fillets and worst case you can repair it in about 5 minutes on the field.

 

[MarkM]

Not sure if you were looking for a high power or mid-power kit...
I have the Madcow Jayhawk. Nice kit. Flies beatutifully on G64 (only launched once so far). I reinforced the winglet/wing joint so it wouldn't break off on landing. It did require a lot of nose weight, but I have the older balsa nosecone version. The newer plastic NC does not require as much since you can get the noseweight in the very tip. Recovery on a Spherachute 30" is perfect.

There is a review (or two) on EMRR about this kit.

 

[AKPilot]

Yup, was leaning heavily towards the Madcow version, just say the warnings about the fins popping off on landing is why I was concerned.

I really like the Madcow kits. Paired up with Skinny Cow ice creams treats makes for a perfect day!

 

[H_Rocket]

Yeah, what Mark said about the nose weight.

I plan to get the Mad Cow one at some point.


One thing that is kind of fun. Lay a thin strip of wood on the trailing edge of the fins (one side top, the other bottom). Gives it a nice spin on take off.

 

[MarkM]

Yup, was leaning heavily towards the Madcow version, just say the warnings about the fins popping off on landing is why I was concerned.

So did I.
But I gave the good reinforcement to the fins and carefully weighed the rocket (after all the noseweight added) and with a 29/40-120 empty casing. My finished Jayhawk weight falls right in the sweet spot for the 30" Spherachute. Nice chutes and inexpensive for the quality, pack nicely and gave a nice decent rate. I fly on a nice, soft cow pasture so landings are soft. It's only flight was perfect and no damage at all to the wing or winglet joints.

 

[dedleytedley]

I'm building a scratch scale version of this rocket based in 1/5 scale. The wings are laminated balsa, a 5/32 core with 1mm thick balsa epoxied on either side. The winglets are made from 1/8 ply. I'm thinking about using a mortise and tenon joint reinforced with fiberglass. Do you think the m and t joint will be stronger than a butt joint?

 

[MarkM]

Do you think the m and t joint will be stronger than a butt joint?

That's the way the Madcow Jayhawk's winglets are mounted onto the main wings. So, yes..a M & T joint should be stronger than a simple flush mounted joint. You may not need the fiberglass, though; I didn't use it on my Jayhawk.

 

[dedleytedley]

Since the tenon will be balsa I was concerned the joint might actually be weaker. The fiberglass I'm referring to is Fibatape wall joint repair tape. It is an open weave mesh. I've used it on many of my builds to reinforce the body tube/surface mount fin joint. I place it from a fin tip to the root, across the B.T. out to the adjacent fin tip. Then multiple layers of glue are brushed onto it. Sanding and filling complete the fin. I've had heavy rockets land without damage when the parachute fails.
Do you know the C.P. location or the C.G. for this size(approx. the same as the Madcow)?

 

[MarkM]

Do you know the C.P. location or the C.G. for this size(approx. the same as the Madcow)?

The Madcow instructions state that the CG should be 19" from the nosecone tip. In order to fly a G motor in it, I had to add a significant amount of noseweight to get the CG to that location. If using a plastic NC, you'll need less since you can get the weight into the tip. With the balsa cone, you add the weight inside a coupler glued to the nosecone shoulder.

 

[dedleytedley]

It's good to have that C.G. confirmed. My confusion results from the C.P. library on EMRR. There is a value of 19.50? inches given by the maker for the C.P. This must be an error as a C.G. of 19.0 inches would be marginally stable at best.
When you flew yours, how would you describe the flight profile? I'm considering using the wing flaps to compensate for any possible arcing in flight. Mine will be powered by a D-12+C-6 with the motors canted toward C.G.
Attached is the drawing I'm working from.

 

[MarkM]

Single G-64 motor gave a perfect, nearly vertical flight with only minor arching. Some minor rotation (maybe a 1/4 turn). Very nice flight for a first time out. No hint of a CG/CP issue.

 

[madcow]

The CG for the Madcow JayHawk was determined empirically through swing tests and test flights with the CG behind the recommended position in various wind conditions. The calculated CP positions seemed way forward and we didn't want to have a lot of unnecessary weight in nose. We decided to try to determine the CP the old fashioned way

Hope that helps.

Thanks!
Mike

 

[H_Rocket]

We decided to try to determine the CP the old fashioned way

Does that involve a SWAG and then pressing the button from behind a pile of sand bags?

 

[madcow]

Does that involve a SWAG and then pressing the button from behind a pile of sand bags?

Ha! Yes, it does!

 

[dedleytedley]

Hi Mike Yes that does help! I can see why you added the question mark to the C.P. value. I will be mounting the nosecone fins on a freely rotating dowel 1/3 of the distance from the fin's leading edge. This should cause them to have a minimal effect on the flight profile and effectively lower the C.P.
Have you ever built a version of this rocket with angled elevators? If yes how did it fly? Ted

 

[CharlaineC]

I used to have the estes maxxi version. it flew great. The only thing I did different to the kit was to rig it to come down flat. that really helped it imop. to bad I lost it to my mother and a yardsale when i was in basic.

 

[Mike Di Venti]

I built the madcow one also
i used med-ca and 5 mins epoxy and was very careful not to use too much.
my bird came in at 18oz. painted.
I have flown it on the rms g71r and a few single use g80t
she flys fast and high on those does a little glide thingy at the end of boost.
I have had one zipper(too short delay) and the winglets came off upon landing on same flight.

I suggest you do not fiberglass the winglets on as they are the first thing to hit the ground on will break.
if you mount them per instructions, they may pop off and then you can reglue them on.

They have only popped off once so far on the first flight.
My son loves this rocket. she does like to drift though with the supplied chute but using anything smaller you risk landing damage too.

Good luck.

ps, i did post a build here on the old forum of it.

 

[Stymye]

I built the old centuri 2.6 dia version , it comes down horizontaly on a chute/yoke setup...works great and was much less trouble and effort than glassing