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

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John Kemker said:
How about a "builder's kit?" You supply the Depron parts and we supply body tubes, etc?
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Still too big, I tried selling an H kit of my aurora clipper but just not enough interest, part of the issue is cost of motors per flight..
 
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I came too late in the morning to see this amazing rocket launched at sod blaster, but I saw the pictures later! I like how you take rockets like the X15 and interceptor that were not meant to fly and make them fly!
 
John Kemker said:
So just document it and sell the plans in PDF form. I'll buy one from you.
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The issue with these large upscales I'm doing is I'm making them as large as possible to just barely meet the vertical launch and boost weight of around 30-34 oz rtf, with 32 the ideal. The motor weighs 7.25 ounces, the electronics and nose weight around 4-4.5 ounces so your airframe weight is only around 20 ounces, The body tube and couplers add up to 8 ounces, so you are down to 12 ounces for everything else plus glue and decals. You don't have any margin for using whatever you want. If you add just an ounce or two in the tail end it requires about 60% of that in nose weight and it won't work, so you must use what I did.

2nd Nobody is willing to purchase the large sheets of 9mm and 6mm depron from rcdepron.com because shipping is expensive. But that's what you need, you can't just substitute any crap paper covered flite test or adams ready board or insulation foam and be light/strong enough.

If you have an R/C club do a group order and get a box of each, I've done 11 of these upscales and have only used about half or less of the 9mm sheets.

The best I can do is post the openrocket, it has the fin and wing shapes, you may need to tweak the fin tabs to fit, the fins are straight 9mm with no carbon, the wing is 9mm in two halves taped and glued, then the main wing center section without chines is laminated on the bottom with a single piece of 6mm using 3m-77 spray adhesive. I tapered the trailing edge of the lamination at the elevon cutout so it is back to 9mm and use a single strip of 9mm for the elevon. I added a 2.5mm spar on the top and bottom of the wing as far forward as I could groved/glued/taped with blenderm tape, and another set 1" behind that top and bottom. If you use 3mm spars it will add almost an extra ounce. Note the exact weights and locations of the rail buttons with t nuts, small mass allocations for added glue and decals, servo extension wires, weights of the servos, receiver with adapter wire, flight battery, nose weight and nose components, BT-101 lightweight tubing and short pieces of couplers, it is all there exactly as used and in the exact locations. Exceed any of those by a few grams and you will be overweight. You can look at the build pictures of how I built the cone here and what it weights, right now the built up cone with nose weight and shoulder is 4.3 ounces. No other tubing is near light enough.

Use a 7.75" long piece of phenolic pml 29mm motor tube, you can glue the foam strips/fin tabs directly to it and they won't melt, I tried many brands of paper tubing but the H-13 gets so hot it causes the glue used for the paper roll construction to shrink and make it impossible to get the old motor out even after cooling and using a razor blade to scrape off the paper motor label beforehand.

I cut and slotted a 3' piece of 4" pml tubing, removed a section and glued it back together so it would just fit inside of the BT-101 I got from Erockets, it is the longest 24.625 piece. I use that to support the tube and a piece of angle aluminum to pre-cut the slots for the wing and tail. You will need to finish slotting the main tube after you glue it together with the 3" piece of coupler making multiple passes. They only sell a 6" long coupler, a 3" long piece was all I needed for the main joint since the wing supports it, and it weighs almost 3/4 ounce just for that, the two tubing sections weigh 3.55 ounces each. I used a 2" long section for the nose cone shoulder since it saved .2 ounces.

I used a dubro adjustable length control horn for the surface and reinforced both sides of the foam elevon with .03 styrene strips an inch square glued on each side of the surface, and a 6" length of stiff enough pushrod wire to move the servo weight forward. The servos are simply glued in from the bottom of the wing in a pocket cut out. Use a good quality metal gear servo I used digital type that weigh 12 grams each.

The design is built stiff enough and meant to fly on the flight loads of the H-13 single use motor, you can't just stick in a higher thrust motor and expect it to survive. It will boost to 1000' on a vertical boost, so make sure you have altitude waivers for UAV in place and waiver for not having RID on board if you are not flying at an AMA FRIA site. It will glide for about a minute and a half, so purely a sport flyer. You can see if you were to start making things heavier to survive a larger/higher thrust motor with associated added nose weight and your glide time goes down rapidly.

I put the rail buttons on the top of the model so I don't land on them, and used packing tape to protect the bottom of the tube from landing dirt/water. There is no paint on the model. Trying to paint a model this big assuming it won't melt the foam will add 1-1.5 ounces so don't do that.

I only use 3m-77 spray for laminating and bob smith super gold+ for adhesives, don't use epoxy or for god's sake hot glue, they are too heavy and are not needed.

Of the four upscale Aurora Clippers I sold, only two finished them, and only one has flown theirs. Aerostadt on here scratch built one from pictures/dimensions but the Aurora Clipper has much more margin for weight tolerance than this model, he did a good job replicating exactly what I did.

It's not the only way to do things, but I've done 11 of these upscales and they have all worked well, so take advantage of my learnings is all I'm suggesting.

I'll update it when I get finished if the weight changes at all. CG location is overriden just for the wing to match the carbon rod weight and reality and the CG shown is correct as measured from the nose assuming all distances and wing shape/location are copied exactly. Do not use the openrocket for flight stability as it is not correct for aircraft purposes, it is only used for mass balancing. I use other methods and hand tossing of subscale models for CG determination.

If you want to try something from scratch, build an 18mm or 24mm version first, get the CG and placement of wings/tail figured out, then simply scale things. Use my Openrocket template as a guide for how to place things beforehand with actual weights and placements and components with a known cg location to minimize nose weight needed. Move the wing forward or backward if needed to get CG correct with minimal nose/tail weight. In this case to meet weight, I had to move the wing location more rearward than on the subscale models simply because weights are different. As you build update the openrocket simulation with glue and actual component weights, you'll be surprised how things add up quickly. Make the model as large as you can so you can trim out the CG shift of losing 3-4 ounces of propellent. The more the relative cg shift the more up trim you need and the more draggy it will be and less glide time. Target a built weight ahead of time of around 30 ounces ready to fly assuming at least 1 ounce of glue needed, and you will probably wind up with a final product around 32-33 ounces.

If you need nose weight you can use a larger flight battery, however I only use a 500mah 1s battery for all my models regardless of size for simplicty and it has never failed to give enough current/voltage to run any of my models. You can place the battery and receiver in the middle of the model to reduce extension wire lengths and help reduce voltage drop under load and access via a hatch, but if you do that, you will need to replace that receiver/battery weight that was up in the nose with dead weight, so in the end you only save the weight of the servo extensions, maybe 14-20 grams, and may actually wind up heavier, in all the models I've done I've tried short wires and nose weight versus long wires and things in the nose and the long wires always won for overall weight. If you are building a tube model it is easy to have the nose come off to access battery/rx and add/subtract nose weight and you don't have to cut a hatch, just simpler.

You can add some stiffness before or after to wings/tails with packing tape but you have to be careful with added weight as on large surfaces things add up.
 

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With some effort one can build the up-scales from Frank's threads, but it does take some determination. I have built and successfully flown the large Aurora Clipper, the Orion Star-liner, and the Colonial Viper. I have also tried my own large Concorde design, but it got away from me shortly after take-off and crashed. I was able to look at the threads and surmised the techniques that were used to build the models. In some cases I actually held up a ruler to the monitor screen and made some measurements. I then asked Frank later some of the dimensions to make sure I was close. I think it you go back and look at these threads, I think the question and answer exchange is also included in the threads. There is a large number of posts to go through, but it can be done. At one point I bought a large box of Depron from a dealer that was going out of business that Frank told me about. That was a life-time supply of low-weight Depron that I am still using. I think of the large models the Aurora Clipper is probably the most straight forward to build. I flew my 3-inch diameter version successfully again last Saturday. I think I have noticed that Frank is now advocating a BT-80 or 2.6 inch diameter design of the large (H13) Aurora Clipper to move the rtf weight from about 31 oz down to about 26 oz.
 
aerostadt said:
With some effort one can build the up-scales from Frank's threads, but it does take some determination. I have built and successfully flown the large Aurora Clipper, the Orion Star-liner, and the Colonial Viper. I have also tried my own large Concorde design, but it got away from me shortly after take-off and crashed. I was able to look at the threads and surmised the techniques that were used to build the models. In some cases I actually held up a ruler to the monitor screen and made some measurements. I then asked Frank later some of the dimensions to make sure I was close. I think it you go back and look at these threads, I think the question and answer exchange is also included in the threads. There is a large number of posts to go through, but it can be done. At one point I bought a large box of Depron from a dealer that was going out of business that Frank told me about. That was a life-time supply of low-weight Depron that I am still using. I think of the large models the Aurora Clipper is probably the most straight forward to build. I flew my 3-inch diameter version successfully again last Saturday. I think I have noticed that Frank is now advocating a BT-80 or 2.6 inch diameter design of the large (H13) Aurora Clipper to move the rtf weight from about 31 oz down to about 26 oz.
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Yes moving to bt-80 b
For the clipper allowed lighter cone ans rubing and thus more tolerance for weight bloat due to equipment or heavy handed building.
 
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Here are the removable tip pods with carbon guide posts and styrene tubes in the wing tips, there is a magnet in the wingtip and pod under the red vinyl to help secure them. I may just remove them for the first few flights to see how the wing stiffness is first before flying them.IMG_20240324_102652882.jpgIMG_20240324_102702703.jpgIMG_20240324_102712174.jpgIMG_20240324_102716541.jpg
 
rcktnut said:
You need to come here with that for a demo: https://midwestwarbirds.com/
We've done rocket demo's the crowd just loved them. The RC guys would really get a kick out of that Interceptor.
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I'd love to attend more in person, but 31 hours from Oregon is a bit much for me. Even colorado is 21 hours...a lot of the launches don't have very good landing areas for foam based rocketplanes, this looks nice, my local field is a sod farm so you can recover in bare feet:)
 
Got the servo pockets cut and installed one the other will have to wait till the tubes arrive and the wing is inserted into the slotted tube. Put a few decals on the pods as well.IMG_20240325_153610383.jpgIMG_20240325_153559294.jpgIMG_20240325_153655403.jpgIMG_20240325_153713762.jpg
 
burkefj said:
I'd love to attend more in person, but 31 hours from Oregon is a bit much for me. Even colorado is 21 hours...a lot of the launches don't have very good landing areas for foam based rocketplanes, this looks nice, my local field is a sod farm so you can recover in bare feet:)
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Thought I'd try, did not know where you lived. That is quite far away. One awesome interceptor you have there.
 
While waiting for my tubes and couplers I made the nose cone, took about two hours to laminate, shape it and cover with vinyl, turned out nice, 2 oz 11.5" long. Carbon rod in the nose tip for strength and 3 short pieces in the thin 5 ply base plate to make sure it locked into the foam, the base plate has a 2" hole and I melted a 4" deep recess in the foam for moving nose weight forward just need to glue on the short coupler piece for the shoulder IMG_20240326_171243627.jpg
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421867-8f16b0b54b7b4a0f1209774eca46cf65.jpeg421876-efac29bad4c720d7a5c4d52af80b335e.jpeg421875-4a3b9d09cbc19753af70cc51e5914477.jpeg
 
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aerostadt said:
Nice looking nose cone! Did you shape it from foam? I am thinking that this Interceptor is pretty heavy.
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Laminated 9mm sheets shaped using a belt sander and hsnd tools, only 2 ounces, weight ready to fly with H-13 will be 33-34 oz only similar as my other big ones
 
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Nice looking models! I like the model with the 3D pods better, but I am sure that it takes more work to make the 3D pods. I don't think I will attempt a 4" diameter model until I get more experience with the H13 under my belt. I am concerned about the extra drag of 4" diameter versus 3" diameter and also the extra weight. Also, if I ever attempted this, I would think about using a vendor for the nose cone. I recently used Boyce Aerospace for my Double Shuttle nose cone and I am very happy with the result.
 
aerostadt said:
Nice looking models! I like the model with the 3D pods better, but I am sure that it takes more work to make the 3D pods. I don't think I will attempt a 4" diameter model until I get more experience with the H13 under my belt. I am concerned about the extra drag of 4" diameter versus 3" diameter and also the extra weight. Also, if I ever attempted this, I would think about using a vendor for the nose cone. I recently used Boyce Aerospace for my Double Shuttle nose cone and I am very happy with the result.
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At the boost speeds the drag is more wrt the wing and tail surfaces, and the real issue is the weight, I've done 5 or six with the 4" tubing and they boost about the same at similar weights to 2.6" and 3" tube designs. I don't know if a printed cone that big will meet the weight limits, but you can ask them to estimate before you have them print one, I would not go heavier than 3 ounces for the cone at 11.5" long and 4" diameter, you don't need a base and only need a 2" shoulder, you want the nose weight to go as far forward as you can.

Frank
 
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burkefj said:
Maiden went great just a bit of boost downtrim for the second flight.
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Sweet flights!
Was curious with your Space Shuttle models (or any of these), does it work to run a scale Shuttle-like approach? As in, come in steep to keep the speed up and the angle of attack relatively low, then flare late for a flat glide to touchdown? Or are these models too lightweight to flare like that?
 
ReynoldsSlumber said:
Sweet flights!
Was curious with your Space Shuttle models (or any of these), does it work to run a scale Shuttle-like approach? As in, come in steep to keep the speed up and the angle of attack relatively low, then flare late for a flat glide to touchdown? Or are these models too lightweight to flare like that?
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You can do more damage with a fast ground speed catching on the ground ir runway mat, I find its better to just come in slow and plop down, and have reduced forward momentum, they are so light vertical decent speed isn't very fast anyway. If you had heavier wing loadings what you describe might help, my little X-15s for example I try to keep more energy till I'm very near touchdown.
 
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