XP-2 Rocket Glider

I need some help.

I signed up for a contest to be held in March by DARS, the Dallas rocket club. It will be my first contest aside from the informal "make it up as you go along" afairs my club sometimes has.

I already have my C egglofter built. I will be using George Gassaway's 2 minute egg plan. It has flown once in an eggloft competition my club held. The high winds did not help and I am glad the egg was in a balloon!

For the C Rocket glider, I have chosen the XP-2c plan on the NAR site. It was designed by Al Nienast. From what I have read, it will probably not be all that competitive in this day and age but I am intrigued by the swing wings and want to give it a try. I tried rounding up some of the material I did not have at the LHS today but I have some questions about the design I do not understand. I am hoping y'all will clue me in.

I have attached the PDF so you can see what I refer to.

1. Span: the plan says 30". I assume that is from wingtip to wingtip. Is it measured along the actual wing or is it the flat projection of th dihedral angle?

2. It says: "each wing swivels on a balsa axel sandwiched between two 1/16" balsa wing brackets." On the next page, the brackets are shown to be 1/8". WHich is correct?

3. The launch lug is sandwiched between the boom and and separator strut. The instructions say "5.32" I.D. alum. tube" That sounds like I could make this an L3 project by shoving a 98mm casing in the launch lug! I bought some alum. tubing that would fit over a 1/8" rod. Is that OK or am I missing something?

4. The rear "horizontal" stabilizers are shown at the bottom of page 1. What does the vertical line between "1/2 stabilizer" and "- 1/16" balsa" represent? does the tail have a dihedral also?

5. What is meant by (airfoiled on bottom)? That text appear just below the text mentioned in 4

6. Does this thing have a vertical stab.? Wouldn't it need something in that axis? If so, is it just a copy of the horizontal?

7. page 2 indicates that the pivots are TT5. Is that just another way of saying BT5?

8. Is a TT5/TT20 adapter ring the same as a centering ring for BT5 tube in a BT20 airframe?

I am not going to be disappointed if I do not win or place. I just want to take part and do the best I can. Can you offer any help?

View attachment xp-2c.pdf

I can't say anything about the other questions...but the launch lug to me is a typo, I read it as 5/32" thinwall Al tubing...I would suggest a scrubby to clean/polish the rod before launch, 5/32" tubing is a close fit on a standard rod.
rex

Rex R said:

I can't say anything about the other questions...but the launch lug to me is a typo, I read it as 5/32" thinwall Al tubing...I would suggest a scrubby to clean/polish the rod before launch, 5/32" tubing is a close fit on a standard rod.
rex

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Duh!

That makes sense now. I would not be surprised if the tubing I got was 5/32. I just kept poking my 1/8" rod in tubes until I found the smallest one that fit.

THanks for the tip on the scrubby. THat might be helpful.

also,(now that I think about it) some brasso, a pipe cleaner, and a dremel works nicely to polish the inside of the tubing (and give a somewhat looser fit). I've done that to 'wear in' drive shaft bushings.

(Note - I am posting here, a copy of a message I also posted in the Whirl-A-While Copter model thread)
https://www.rocketryforum.com/showthread.php?t=18079


I have made some event-specific tips pages for a few NARAMs. NARAM-46 had B Rocket Glide and 1/2A Helicopter. Here are two links from then, from a copy of my now-gone AOL website which had the NARAM-46 tips pages:

Copter page:
https://homepage.mac.com/georgegassaway/GRP/AOL/GCGassaway/contest/helicopter.htm

R/G Page:
https://homepage.mac.com/georgegassaway/GRP/AOL/GCGassaway/contest/rocket_glide.htm

BTW, here is a link to Tips pages I did for NARAM-50, which is on my current website:
https://homepage.mac.com/georgegassaway/GRP/CONTEST/TIPS/event_tips_1.html

You should check out the links to other events that the upcoming contest may have. Also, definitely check out the General Competition Tips page as well as the Certified engines page and Vendors page.

Also, here is a link for plans to several of my contest model designs. It includes a C sized version of the Stiletto Slide Wing R/G. Also, a link there to a special page with info on how to build an A sized Rotaroc, when I made a crude “kit” for local club members to build.

https://homepage.mac.com/georgegassaway/GRP/CONTEST/ContestPlans.htm

For C Rocket Glide, I would suggest the Stiletto-C. And for Copter, the Rotaroc-A.

- George Gassaway

JAL3 said:

For the C Rocket glider, I have chosen the XP-2c plan on the NAR site.

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Why isn't this thread in either the contest forum, or the rocket boosted glider forum?

kj

kjohnson said:

Why isn't this thread in either the contest forum, or the rocket boosted glider forum?

kj

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Because I wanted maximum exposure to ask my questions. When I continue these 2 threads with builds, I will move them to the appropriate section. At present, I am trying to ID components and make sure I understand the plans.

JAL3 said:

Because I wanted maximum exposure to ask my questions. When I continue these 2 threads with builds, I will move them to the appropriate section. At present, I am trying to ID components and make sure I understand the plans.

Click to expand...

Seems like you'd get better responses from folks that fly contests and gliders.. but whatever. I stopped trying to figure out how things work on this forum a long time ago.

Back to the issue at hand.

1. It means your wings are 15" long. Don't overthink things.

2. I'd go with 1/8". The XP-2 was part of a series of plans in different sizes. It was probably left over from a common drawing.

3. Rex is right.

4. That line is the root edge of the fin. It is the same shape as the stab and wing tips.

5. Airfoil the stab, but put the high point on the bottom instead of the top. Acts like adding up elevator to bring the nose of the glider up.

6. See 4.

7. Yes for your purposes. As long as the pivot rotates freely. You may need to peel a layer from the inside of the CR5-20. (There is such a thing as Telescoping Tube that fits over a regular sized tube and that can have the designation TT-5 ).

8. Yes.

It's been a long time since I've built one of these. Most folks have gone to a slide wing of some sort like the Stiletto that George linked. Pros of that are lower parts count, and less finicky construction and deployment. You lose some of the geek factor though.

kj

You can buy tubing that slips over BT-5 from Balsa Machining Service.

I've had very good luck with slide wings on all sizes from Micromax to B. I've recently learned that you can reinforce the dihedral breaks on the wings with plywood so that they are strong enough for discus launching--this might be useful for bigger Rocket gliders. Tip launched gliders are also reinforced with fiberglass over the dihedral breaks, though just the plywood is enough for the smaller ones.

kjohnson said:

Seems like you'd get better responses from folks that fly contests and gliders.. but whatever. I stopped trying to figure out how things work on this forum a long time ago.

Back to the issue at hand.

1. It means your wings are 15" long. Don't overthink things.

2. I'd go with 1/8". The XP-2 was part of a series of plans in different sizes. It was probably left over from a common drawing.

3. Rex is right.

4. That line is the root edge of the fin. It is the same shape as the stab and wing tips.

5. Airfoil the stab, but put the high point on the bottom instead of the top. Acts like adding up elevator to bring the nose of the glider up.

6. See 4.

7. Yes for your purposes. As long as the pivot rotates freely. You may need to peel a layer from the inside of the CR5-20. (There is such a thing as Telescoping Tube that fits over a regular sized tube and that can have the designation TT-5 ).

8. Yes.

It's been a long time since I've built one of these. Most folks have gone to a slide wing of some sort like the Stiletto that George linked. Pros of that are lower parts count, and less finicky construction and deployment. You lose some of the geek factor though.

kj

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I very much appreciate the answers. They help and I should be moving this thread soon and transforming it into a real build thread. I started work tonight on the copter and am waiting on a few things from Semroc to start this.

Thanks again.

Zack Lau said:

You can buy tubing that slips over BT-5 from Balsa Machining Service.

I've had very good luck with slide wings on all sizes from Micromax to B. I've recently learned that you can reinforce the dihedral breaks on the wings with plywood so that they are strong enough for discus launching--this might be useful for bigger Rocket gliders. Tip launched gliders are also reinforced with fiberglass over the dihedral breaks, though just the plywood is enough for the smaller ones.

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Can you explain discus launching for me?

You grab the wingtip and fling the rocket into the air. The longest flights are typically obtained by spinning, to maximize the energy transfer--just like throwing a discus. Not only does this place a lot of stress on the dihedral joints between the wingtip you are holding and the fuselage, but you typically need to use a carbon fiber boom to prevent the fuselage from snapping.

Not only are flights longer than conventional javelin style launches, but launching is much easier and less stressful on the body.

Zack Lau said:

You grab the wingtip and fling the rocket into the air. The longest flights are typically obtained by spinning, to maximize the energy transfer--just like throwing a discus. Not only does this place a lot of stress on the dihedral joints between the wingtip you are holding and the fuselage, but you typically need to use a carbon fiber boom to prevent the fuselage from snapping.

Not only are flights longer than conventional javelin style launches, but launching is much easier and less stressful on the body.

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I can just see the middle aged guys from my club trying that! :no:

NAR does not have enough insurance! :surprised:

Lloyds doesn't either! :lol:

Thanks for cluing me in. :wink:

Here is another question.

I understand the basic shape of an airfoil. How does one go about choosing the high point on the upper surface and the point of curvature on the lower leading surface?

FWIW, I have started some basic cutting on this one (XP-2c) and will be moving this thread as soon as I get started posting the build.

If the airfoil shape is important, it will be on the plans, and you follow it. Small gliders fly perfectly fine with flat planks. They fly better if you round the leading and trailing edges. They fly even better with some sort of basic airfoil. Based on your posts so far, I don't think you are at the point where you benefit from getting all that finicky about the shape of your airfoils.

If you do want to put in a basic airfoil, then a general rule of thumb is that the high point should be 25-30% back from the leading edge.

For the leading edges on basic airfoils, I do the top section, and then just use my sanding block to knock off the bottom squareness. (I am a TLAR type of glider builder).

For the XP-2, you don't want any airfoils on the parts of the wing that go in between the hinge plates.

kj

kjohnson said:

If the airfoil shape is important, it will be on the plans, and you follow it. Small gliders fly perfectly fine with flat planks. They fly better if you round the leading and trailing edges. They fly even better with some sort of basic airfoil. Based on your posts so far, I don't think you are at the point where you benefit from getting all that finicky about the shape of your airfoils.

If you do want to put in a basic airfoil, then a general rule of thumb is that the high point should be 25-30% back from the leading edge.

For the leading edges on basic airfoils, I do the top section, and then just use my sanding block to knock off the bottom squareness. (I am a TLAR type of glider builder).

For the XP-2, you don't want any airfoils on the parts of the wing that go in between the hinge plates.

kj

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Got it! Thanks.

That last part is the only part I had figured out.

The best nose cone match I could find for this rocket was the Semroc BNC-20LS.

The plan directs that the nose cone be hollowed out. To accomplish this, I chose a drill bit that most closely approximated the void shown on the plan and twirled it between my fingers to slowly hollow out the back of the cone to the depth indicated on the plan.

The plan also showed the NC as having a shorter shoulder than my cone so I marked the length from the plan and used a razor saw to cut it to length.

A piece of BT20 was marked for length from the plan and then wrapped with masking tape to guide the blade. A mandrel was inserted and an X-acto used to cut it to length.

The body tube needed three 1/4" vent holes to release ejection gas. Their position was transferred from the plan and a drill was used to make them. Unfortunately, the result was not at straight is it seemed it would be while the actual drilling was being done.

The hole were cleaned up a bit with a knife and then reinforced, along with the tube ends, with some thin CA.

The location for the engine hook was then marked and a slit made. I inserted a standard engine hook from Semroc but I am unsure whether I will leave it or try to bend some music wire as per the plans.

The instructions set the wing span at 30 inches. With that in mind I cut my 1/8" wing stock into two 15" pieces.

I re-printed the template page of the instructions on some cardstock and then cut out the template for the wing housings.

JAL3 said:

For the C Rocket glider, I have chosen the XP-2c plan on the NAR site.

Click to expand...

Yes. The XP series of swing wings really killed the competition in the 80's. And I suppose if crafted well, trimmed well, would kill even today. And beat the traditional slide wings.

The big thing they had going for them is, well, they were BIG up in the sky and could be seen for very far distances. Given the timers in the NAR cannot use binocs, landing an XP swing wing in a nice thermal meant it could be seen and timed longer.

Their glide speed also tended to be a lot slower than the smaller slide wings and this helped too in timing.

Boost altitudes were a different factor though with the swing wings boosting to maybe half the alt. of the slide wings. I built a lot of these in the 80-early 90's and had lots of success with.

Even got to meet and compare notes with the Greatness himself in a hotel room at one Naram when only an A div....Al Nienest. Chris King, also of WWAR, was a national B div. champion that used swings with lots of success.

Kevin Kuczek

kooch said:

Yes. The XP series of swing wings really killed the competition in the 80's. And I suppose if crafted well, trimmed well, would kill even today. And beat the traditional slide wings.

The big thing they had going for them is, well, they were BIG up in the sky and could be seen for very far distances. Given the timers in the NAR cannot use binocs, landing an XP swing wing in a nice thermal meant it could be seen and timed longer.

Their glide speed also tended to be a lot slower than the smaller slide wings and this helped too in timing.

Boost altitudes were a different factor though with the swing wings boosting to maybe half the alt. of the slide wings. I built a lot of these in the 80-early 90's and had lots of success with.

Even got to meet and compare notes with the Greatness himself in a hotel room at one Naram when only an A div....Al Nienest. Chris King, also of WWAR, was a national B div. champion that used swings with lots of success.

Kevin Kuczek

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Your words are most encouraging!

The "crafted well" part kind of stinks because I know my limitations but I'm taking my time and putting it together as well as my skills allow. The build is a little further along than I've had a chance to post and I have hit some glitches. Cutting BT5 to 1/8" lengths was a big one! I managed to ruin an entire 6" piece without getting one usable hub. Luckily, Semroc came through as always! (THANKS SHERYL! :handshake

My goal in this competition is to turn in qualified flights. After that, its all gravy and maybe my next builds will be better. Right now, though, I am satisfied.


I do have a question about the airfoiling. I was marking the line this evening for the high point on the upper chord. The I thought about the tips where they narrow at the ends. Is the airfoil supposed to go straight at this point or should lit follow the curve?

JAL3 said:

I do have a question about the airfoiling. I was marking the line this evening for the high point on the upper chord. The I thought about the tips where they narrow at the ends. Is the airfoil supposed to go straight at this point or should lit follow the curve?

Click to expand...

Follow the curve. You want your high point at 25-30% of the chord everywhere. Tappering the wings so they are thinner at the tips will also help, though you really need to jig up here if you are sanding balsa to make sure the taper is uniform and the same on each panel. For now, I'd just concentrate on getting a decent airfoil sanded in and then work on the trim.

Like Nienest on these, I would glue the pod and wings/rudder in place and then fine tune the amount of negative incidence on the stab by rubber banding it in place for the hand tosses. You want a slightly nose heavy glide on these and not a glide that "mushes" or is on the verge of a stall. Start with a few degrees of negative incidence on the stab and work out from there by sanding in additional if needed to get a glide slope you like. Note that the whole stab was at a negative angle and not just the aft elevator part of the TE.

Kevin K.

kooch said:

Follow the curve. You want your high point at 25-30% of the chord everywhere. Tappering the wings so they are thinner at the tips will also help, though you really need to jig up here if you are sanding balsa to make sure the taper is uniform and the same on each panel. For now, I'd just concentrate on getting a decent airfoil sanded in and then work on the trim.

Like Nienest on these, I would glue the pod and wings/rudder in place and then fine tune the amount of negative incidence on the stab by rubber banding it in place for the hand tosses. You want a slightly nose heavy glide on these and not a glide that "mushes" or is on the verge of a stall. Start with a few degrees of negative incidence on the stab and work out from there by sanding in additional if needed to get a glide slope you like. Note that the whole stab was at a negative angle and not just the aft elevator part of the TE.

Kevin K.

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I'm afraid you've completely lost me in the second paragraph. If the vertical stabilizer is moveable, I completely missed that and need to go back and look at the plans again.

I know this is too late to be of any help to JAL3. But since the issue of Swing Wing hinges came up, I decided to start a new thread about just that.

There is “just something” about flying 6 to 10.5 foot wingspan swing-wings that tends to make you learn how to make stronger, more robust, (and to me, easier) ways to pivot the wings. And those methods down-scale well too. I even did some 1/4A Swing-wings, long ago.

So, for new discussion of swing wing hinges, check out this thread which includes the 6.5 foot span model below and drawings for what I have used for Swing Wing hinges:

https://www.rocketryforum.com/showthread.php?p=165789

- George Gassaway