New Scale Model Build-Navaho

[hornet driver]

I can only say this after following this thread. we're not worthy

I have to second that feeling! Ya know, at first I was a little worried about the angle on the canards. But, after seeing the entire assembly and their placement I don't think they will have much -if any -affect on the pitch after launch. Nice way to pull the booster away. I'll put that idea away in my little bag of tricks for the future. --H

 

[JumpJet]

Last images for tonight! One image shows the rear top of the booster and how the top tunnel joints up with the rear of the model. The other shows the front top of the booster. The top front tunnel part has a straight taper so I needed to sand the bottom edges of the sheet balsa to get them to come in a little, plus I added a top sheet of balsa cut to the proper angle to get the parts to come together correctly. I found a great use for one of the half round wood dowels found in an Estes Saturn V kit that are used for the conduits. It now serves the same purpose on my Navaho.

I still have lots of sanding and final shaping before I can begin the finishing process.

John Boren

 

[JumpJet]

The last two days has been spent joining the two major parts together with a servo release system. For this I used an old Vortac Bomb drop mechanism. The image of the bomb mounted to the bottom of an airplane wing gives you an idea of what the parts look like. The part that would normally attach to the bomb is now attached to the booster while the release mechanism that would normally attach to the wing of the airplane is now installed inside the wing of the Navaho. A small servo will simply use a short pushrod to activate the release. My plan is to release the model in flight about two seconds after thrust burnout. I’ve been waiting a long time to see this model in the vertical position.

To help keep the model stable on the bomb release I have added a carbon fiber rod shapped to fit inside the socket head screws that attached the wing to the body. These black pointed items can be seen in one of the photos.

I still need to pre-finish all the surfaces on the booster before they are attached permanently, so hopefully in the next couple of days I can start adding the primer to the booster.

John Boren

 

[mpitfield]

The last two days has been spent joining the two major parts together with a servo release system. For this I used an old Vortac Bomb drop mechanism. The image of the bomb mounted to the bottom of an airplane wing gives you an idea of what the parts look like. The part that would normally attach to the bomb is now attached to the booster while the release mechanism that would normally attach to the wing of the airplane is now installed inside the wing of the Navaho. A small servo will simply use a short pushrod to activate the release. My plan is to release the model in flight about two seconds after thrust burnout. I’ve been waiting a long time to see this model in the vertical position.

To help keep the model stable on the bomb release I have added a carbon fiber rod shapped to fit inside the socket head screws that attached the wing to the body. These black pointed items can be seen in one of the photos.

I still need to pre-finish all the surfaces on the booster before they are attached permanently, so hopefully in the next couple of days I can start adding the primer to the booster.

John Boren

Wow such a talented builder...amazing build to follow!

 

[thobin]

I built one of these in the way back but it wasn't a tenth as nice as yours. It didn't fly very well ether, I still have the glider portion somewhere but the booster died upon impact. This was before I knew about CP. :confused2:


Yours however is a work of art and I cant wait to see if it will fly!


TA

 

[JumpJet]

I built one of these in the way back

Any pictures of your completed model? Can you explain further how it flew. Did you have your motors set at an angle or were they inline with the booster body tube?

John Boren

 

[thobin]

Well it made a complete circle and KERSPLODED on the ground! The booster motor was inline, just offset all the way towards the center of the rocket and glider. I would have canted it a bit now if I had to do it over and spent way more time in working out the CP & CG.

This is all that's left, the booster & NC has long since been turned into another rocket. Not quite as awesome as yours.


TA

 

[JumpJet]

Thanks for the images. So it pitch towards the glider side, " UP Elevator" and looped right into the ground?

That's pretty much my biggest fear for mine as well, of course it could pitch down and destroy itself just as easily. Since I made all the surfaces scale in size there simply isn't very much in the way of fin area on the rear of the booster, at least not compared to all the area the winged portion has.


John Boren

 

[thobin]

Thanks for the images. So it pitch towards the glider side, " UP Elevator" and looped right into the ground?
John Boren

Yup.


TA

 

[aerostadt]

Nice pictures, TA! I don't think I saw you launch that one, but I like the glider. I know that I won't make a model as good as John's. I don't have the time, patience, talent, and laser cutter, but I keep thinking and dreaming in the back of my mind of making the simplified version. (I think there is computer work and research involved in John's work and I don't have that either.) So, it sounds to me that we are saying that the simplified model wants to pitch towards the glider side. Thus, would angling the booster thrust on a simple model in the opposite direction help the model to fly straight up?

 

[thobin]

Ya I built and launched this when I was much younger, it was a long time ago 25 or so years.

TA

 

[Cookie the Dog's Owner]

This is all that's left, the booster & NC has long since been turned into another rocket. Not quite as awesome as yours.


TA

Give yourself some credit, that's a pretty nice model of a Navaho sustainer you came up with.

 

[JumpJet]

The majority of the build is now complete. Been sick as a dog for the past week, great way to spend your vacation so I never got to work on all my airplane projects that needed work! The winged portion still needs work on both vertical stabilizers before being permanently being glued in place as does the two small canards up front. Besides this only other major thing will be the addition of the two rail buttons.

There is still plenty more to do before the final paint is applied which includes the radio installation but nothing real demanding from this point forward. I will have to perform final balance on both the glider as well as the completed stack before test flying sometime this spring so for the most part this build is complete until then.

Not sure how many more posts I will do on my Navaho until it’s test flight so if you have any questions please fell free to ask.

You may notice a small piece of wire sticking out the left Ram Jet exhaust. This is used to activate the bomb release so I can get the stack apart when the RC system is not turned on.. I will locate it in a less obvious place at a later date.

Total weight of model stack as seen is 23.8 ounces at this time.

John Boren

 

[thobin]

OOOG! That look good! Get lots of flight video.


TA

 

[bill2654]

That is a work of art man!

 

[mpitfield]

Hi John,

I am sure it is mentioned somewhere but I can't recall, why are the fins on the booster slotted on the aft end?

BTW, this has been a fantastic build to follow, and I have said it before but it must be said again, you are a master builder and your attention to detail is inspirational.

 

[JumpJet]

The only answer I can give you is because the real one had them. I believe they are for holding the rocket on the pad as the motors come up to preasure but that's only a guess on my part.


Any body know where to purchase a pair of REAL CHEAP 29mm aluminum screw on motor retainers. I really don't want to spend 60 bucks on this model just to hold the motors in, and before anyone mentions the Estes ones they won't fit plus they would look out of place on this scale model.

John Boren

 

[mpitfield]

Any body know where to purchase a pair of REAL CHEAP 29mm aluminum screw on motor retainers. I really don't want to spend 60 bucks on this model just to hold the motors in, and before anyone mentions the Estes ones they won't fit plus they would look out of place on this scale model.

There is talk here about using 3D printing to make retainers. I am not sure if they are having any luck but if so it does open the door for scale building as far as adding something on the rocket that looks like it should be there, assuming it can be painted or printed in the correct colours. Price may also be an issue. My favourite retainers are the expensive ones, Giant Leap Qwik-Lok Slimline retainers, by far the best ones I have used.

 

[JumpJet]

Those Giant Leap retainers look nice but I still don't wish to spend 60 bucks for two of them, plus another 100 bucks for the ducted fan system is getting way to expensive for this model. It’s looking more and more like I am going to use a threaded insert between the motor tubs and simply use a large washer and bolt to hold the two motors in place.


I used our rapid prototype machine at work when developing the 24mm and 29mm retainers for Estes. It worked just fine for a prototype but if you plan on flying that model over and over again I don’t believe the parts are going to hold up over the long run


John Boren

 

[TomSmith58]

John
You were right. This looks awesome. When do we see final paint?

 

[JumpJet]

When do we see final paint?

Probably the night before the Model is turned in for judging. :smile:

If all goes as planed, I hope to fly it in the next three months, in grey primer. "IF" if flies, I will then finish with color and other details over the following weeks. Hopefully by late April or May it should be completely done and waiting to be turned in for judging in July. Hopefully my concept model will fall into this time line as well.


John Boren

 

[TheAviator]

I'm glad I finally caught this thread. Great inspiration for rocket and airplane work here, John.

Just a random though here, won't the pair of ducted fan units and associated hardware rob a good deal of altitude/glide time? I know you said Mission Points, but I don't think 5 mission points is worth 5 ounces of weight, especially when it might affect the lateral CG negatively. Personally, I'd throw a parachute on an R/C release into the exhaust ducts, but that's probably paranoia talking.

 

[JumpJet]

Five points could be the difference between first and third place. The RC gear to control the model down is only about one ounce, if I go the ducted fan route then I would be adding 3 to 4 more ounces. If this model goes up only 200 feet, separates, booster comes down on it's chute and the wing portion comes down in a controlled manor and lands 10 seconds later , I would be in heaven.

John Boren

 

[TheAviator]

Fair enough. Is there a test date?

 

[JumpJet]

No test date scheduled right now. I've got some detail work to do on the tips of the rudders I've been putting off for a month now plus I don't like to fly when it's cold. I would say April would be a good time frame for it's first test flight.

John Boren

 

[TopRamen]

She's a Beauty!!!:clap:

 

[CarVac]

PML HAMR's are 25 bucks each in 29mm and have the nicest machining quality (particularly, good knurling) I've seen from all the various brands of retainers.

For the really cheap ones, you could get old-fashioned snap-ring Giant Leap Slimline retainers, which work great and are your cheapest option; just don't forget your thin-bladed flathead screwdriver.

 

[powderburner]

To Doctor Boren:

Maybe a crazy thought here, but if you are already planning to test-fly while unpainted this might be do-able:

If you are concerned about stability of your "stack" during boost, you could enhance it (that is, cheat) a little by adding some auxiliary fins at the rear end of a spruce stick temporarily tacked (taped?) to the side of your booster. If the whole mess flies well, you could then take intermediate steps by shortening the stick and/or reducing the aux fin size. This could demonstrate enough inherent stability to do away with the auxiliary device completely for a final series of tests.

I'll be quiet now....

 

[JumpJet]

you could enhance it (that is, cheat) a little by adding some auxiliary fins at the rear end of a spruce stick

Why that would be cheating and I'll have none of that. If you knew me better and some of the RC airplane and rockets things I've come up with, I never play it safe. I do however end up with a lot of stuff to burn in the fire place, but I have fun doing it.


John Boren

 

[GuyNoir]

Why that would be cheating

Cheating is bad. . .

I do however end up with a lot of stuff to burn in the fire place, but I have fun doing it.

Fun is good . . .