Upscale H powered 4" diameter Interceptor R/C rocket glider

[burkefj]

I saw a picture of Tom Beach Long back in sport rocketry with his 4-in upscale interceptor and I always loved that picture. I actually got to meet him a couple of times and see that model in person and it left a real impression on me.

Back when Estes was closing out their Cosmic Interceptors I bought a ton and designed an R/C gliding version of the standard Interceptor that I kitted and it flew really well.

Taking what I've learned in my upscales I'm going to attempt a 4" version of that model using BT-101 and designed for the 29mm H-13 motors with rtf weight target around 32 oz rtf. The original was 38" long and 2" diameter and 21" wingspan, but I scaled the length/surfaces by 1.63 which is a good scale for meeting weight for the H-13 so the diameter is slightly larger than would be required.

Length is 62", wingspan 35" I've included a pic of the kit I used to make and the 3-d rendering of my openrocket mass balancing model which doesn't include the wing tips or cockpit. I'm planning on stacking 9mm depron and shaping the nose cone by hand, with a carbon rod to the nose tip for strength and then melting out a bit of the center to put the nose weight. This will glue to a 1/16" ply ring which will in turn glue to a bt-101 coupler 3" long where the receiver and battery will be velcrod in place. Fingers crossed this will work out, it whould be about the same size as my Space Transporter America upscale for length and wingspan. Wing is upsized for glide compared to the original Estes Interceptor of course but the theme/feel/markings will be there.

I know Jack Hydrazines(his handle on trf etc) may work on a 3-d printable cone in this size that I might use later if it will meet the weight requirements. Right now the tapered part of the cone is sized to 12.63" long and the weight of the cone with nose weight should target about 3.9 oz, so if the 3-d printed version can hit that it should work fine. I ran the body tubes longer than my scaled kit because this nose will not have the long straight section attached, it will be part of the body tube if that makes sense.

If you doubt the Interceptor can fly, here is the old kit version...

 

[neil_w]

Beautiful.

 

[burkefj]

Got the wings done and assembled and all of the tail parts motor supports cut out and the nose cone pieces that I have to glue together just waiting on the tubing from a rockets now to make more progress..

 

[burkefj]

Stacked the 11 pieces of 9mm depron and laminated them using 3m-77 spray adhesive. I installed a 9" long piece of 3mm carbon rod in the nose to support it for any landing load, and glued a 4" diameter 1/16" ply plate at the base sized for the BT-101 OD, the coupler will glue to this. I drilled a 1.5" hole in the ply, and then drilled and installed 3 3" long 3mm carbon rods into the ply plate and down into the foam cone to support the coupler/plate to foam. I then melted the foam out of the ply hole to about 3" deep to allow me to get nose weight further forward as needed. This new 9mm depron is super to work, nice and dense, didn't chip, I was able to use my belt sander with 240 belt to shape it almost down to final size and then hand sanded with 320 to finish it. Now to work on the cockpit. I think I'm going to cover it with white self adhesive vinyl to protect it. 12" long only 1.7 oz. Shoulder/coupler is .7 oz, sim says I need 2.5 oz additional so a 3d printed cone could be 4-5 oz and work.

 

[burkefj]

Cockpit made up of 3 mm depron plates and showing the back end of the cone with the melted out section for the nose weight.

 

[burkefj]

I covered the nose cone with white self-adhesive vinyl and heated it and pressed it into the foam structure and then added some hand cut vinyl trim markings I'm pretty happy with how easily this went together and how good it looks, the cone is the one thing that mentally prevented me from proceeding with this for many years...

 

[burkefj]

Little more progress on my 4-in diameter radio controlled interceptor theme rocket glider, one wingtip pod in place and painted. I'll have to wait for the other side until I get the body tube and slot the tube and install the wing. The nose cone is placed at about the right overall length of 61 in. Added some vinyl accent trim to the wing and some panel lines on the wing and stabilizers using a sharpie pen. The rest of the decals are on the way from sticker shock.

 

[tab28682]

Looking good!!

 

[burkefj]

My entire life has led me to this, which could mean my life has led me to complete failure 32.2 oz rtf with an H-13 loaded.

 

[burkefj]

Maiden was a success, I did have flutter induced by the wing tip pods and some wing flex I'll have to work on, but no damage and glide was pretty good

 

[burkefj]

I talked to Bob Parks about how to stiffen the wing, he felt it was likely due to wing flex and the spars being too far back. I had been a bit concerned with the flex in the wing but it was similar to what I had done on my space transporter america and i was really trying to keep the weight down.

I took his suggestions(that were several options) and did what I could without completely ripping the wing out and starting over. I grooved, glued and taped 2.5mm spars on the top of the wing right over the bottom spars in both places and also put 2.5mm spars just behind the leading edge of the wing. I now can't flex the wing at all, it still has a bit of twist but hopefully that's ok.

It did add 1.25 oz and I needed to add .5 oz in the nose to compensate so I'm at just under 34 oz which will also slow the model down somewhat, hopefully get to re-fly it in a week and a half and test it out.

 

[BABAR]

Still always amazed a bird with that long a beak can glide.

that larger version makes it a whole lot easier to see the flight!

 

[tab28682]

Still always amazed a bird with that long a beak can glide.

that larger version makes it a whole lot easier to see the flight!

You actually get a little lift from that long beak.

 

[burkefj]

I usually model it as about 1/2 the diameter contributing as a flat plate-ish....

You actually get a little lift from that long beak.

 

[burkefj]

With the wing stiffened the flutter problem is fixed, flight 2 was perfect:

 

[burkefj]

Another beautiful flight today, saw a little flash and poof at the end, turned out the H-13 had burned completely through the casing almost all the way around the base, torching the motor mount, but fortunately not destroying the model or preventing glide recovery, I'll pull out the carnage and insert another mount, hopefully Karl will warrantee it.

 

[bibbster]

Great flight! Bummer about the damage, but you'll have it back in shape in no time! And maybe a couple new motors to boot!

It's really tempting to build one of those.

 

[burkefj]

Fixed the rear end. Was able to get my razor saw in and cut the three foam centering strip remnants out, then used a heavy round wood rasp to get rid of the foam/glue next to the body tube inside, made a new motor mount and fit it in rotated slightly to be offset from the previous glue areas and glued it in. Since I think I was a little nose heavy, I cut off 1" from the nose cardboard coupler and glue it in the back end of the body tube to reinforce the inner burnt bit and move the weight back to the tail, I think it will move the cg back about 1/4" which isn't too much in this size model.

 

[tab28682]

“I hate it when that happens!”

Glad to see damage was minor and easy for you to make right.

Just out of curiosity, what is your total quantity of H13 motors expended to date?

I doubt many are being used in conventional rockets, so I am guessing you have to be the number one user of these things……

 

[burkefj]

I've got over 40 H-13 flights and I've got another 10 on order... Plus three demo flights on the newer g12 ST single-use that led up to the h13..

“I hate it when that happens!”

Glad to see damage was minor and easy for you to make right.

Just out of curiosity, what is your total quantity of H13 motors expended to date?

I doubt many are being used in conventional rockets, so I am guessing you have to be the number one user of these things……

 

[burkefj]

Another nice flight on the 4" diameter R/C Interceptor rocket glider on H-13 power.

 

[burkefj]

Another H-13 flight, #5, on the R/C Interceptor

 

[burkefj]

Here are two of the three great flights from this weekend at the tri cities washington!

 

[Crawf56]

Great stuff!

What receiver battery are you using with these large models?

 

[burkefj]

Same battery 1s lipo and servos that I use in my smaller models

 

[burkefj]

Some great photos from Jim Wilkerson

 

[burkefj]

Jim Wilkersons photos shot at Sodblaster IV

 

[burkefj]

I decided to revisit this one just for fun, I wanted to re-do the wing with my newer 9mm depron and sandwich it with a layer of 6mm for the main wing and re-do the spars and spar location to be stiffer and further forward, and do full length ailerons instead of barn door type. I decided to make the wing pods removable for transport. On the original the wing sometimes had a weird flutter while under boost due to all the pod mass aft of the 20% chord line and the bending/twist behavior of the original wing. Pulling vertical or doing a roll ususlly stopped the flutter but I added reinforcement to the original wing and changed the shape and size of the pods which seemed to fix it, but I had my spars spread out which isn't ideal. Moving the spars more forward helps the bending/twisting response. I also changed the servo location to be more centered on the surface instead of the inboard end also to help avoid any control flex and mount them vertically into a pocket in the wing.

 

[burkefj]

Wing and tail done, just waiting for tubes and decals. The new wing is slightly denser foam and laminated to 15mm thick and is much stiffer in flex and twist than the reinforced single layer 9mm depron wing. The new wing is only about 1/2 ounce heavier. I think a good tradeoff.

 

[John Kemker]

Any chance you make it into a kit?