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Author Topic: Jimmie Allen Fans  (Read 9209 times)
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crashcaley
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« Reply #75 on: October 08, 2009, 11:57:53 AM »

Al, Again, my thanks for your suggestion. I will use that rubber band trick and move the wing forward to see what happens. I guess I tend to get caught up in the plan and think that the placement of the wing is etched in stone. If your idea doesn't cure the nose heaviness and allow it to fly, then I will just have to do surgery on the stab and fin to add infills to cure that nose heaviness. I've got some pretty hefty balsa that can do the trick.

But for now, the JA Special is on hold until I build a "Big Pussycat" for a young lady that I met at my last flying session. She loved the SortaSenator that I let her wind up and fly once. Figured the Pussycat might be perfect for her.

Caley
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applehoney
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« Reply #76 on: October 08, 2009, 01:59:39 PM »

Even a regular Pussycat would do the job well, Caley.

As for the JA .. I'd hate adding weight to the back, rather scrape the prop and add lightness ... and follow Al's suggestion for wing placing and incidence.
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Maxout
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« Reply #77 on: October 08, 2009, 02:10:15 PM »

Caley,

Looks very nice. For future reference, the JA Special is extremely over built, so you want to use the lightest wood you can possibly find. Don't worry about load bearing capability, the tissue will take care of that. Were I building it, I'd be looking for some 4 lb wood. It just doesn't need the strength. I think it's possible to get this one down to 10-12 g, and with that, you'd probably only need a loop of 1/8 for power with the little prop that the plans probably call for. For comparison, my ~9 g Prairie Bird uses a Peck 7" and a very long loop of 1/8. Gives a modest climb and a 2 1/2 minute motor run.

For the prop, the largest allowed is whatever's shown on the plans or 1/3 span, whichever is larger.

It will fly very well with an 8" prop, but I suspect that's not what's shown on the plans.
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crashcaley
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« Reply #78 on: October 08, 2009, 03:09:29 PM »

Jim, I'll make sure I scrape a little off the prop also, and follow Al's suggestion about the wing and incidence.

Joshua, I kind of thought that this model was a bit overbuilt, but I guess I just like to build according to the plans of these old timers. Is that being a purist? Grin I do have a lot of that 4-5# wood on the shelf, but hesitate to use it for much of anything except infills. With my ham hands, I tend to break the wood. Good example was my SortaSenator in which I had to build the fuse three times. I crushed the first two basically by brushing against them too hard. I'll try to build with the light wood I have in the future to see if I can manage. If nothing else, this being a heavyweight, it should penetrate a breeze pretty easily. Smiley

Caley
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High Point
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« Reply #79 on: October 08, 2009, 07:04:15 PM »

Caley,

Your framework looks great! I'm still finishing up on the wing of mine and then I'll be about ready to start covering.

Curtis
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crashcaley
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« Reply #80 on: October 08, 2009, 07:40:28 PM »

Curtis, Thanks. Look forward to seeing your work. Then the hard part comes, flight (fright) trimming. Grin

Caley
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Maxout
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« Reply #81 on: October 08, 2009, 10:40:12 PM »

Caley,

Nothing wrong with being a purist on these. The rules require it anyway. Grin As far as the light wood, I know what you mean... built a Zephyr (also 3/32 sq longerons) with some of that light wood, and my dad put his finger right through one of them while helping me prep it for flight (motor was wound and loaded by this point, naturally!). He was mighty upset with himself, but we had the bird airborne withing 2 minutes.

Anyway, the light wood really is worth the trouble. You do, of course, have to remember where to not use light wood (rear motor pegs, spar doublers, etc), but by and large, oldtimers really don't need heavy wood. Stuff like the SortaSenator is different. My most recent Bostonian used some pretty stout wood, and I still had to add a big hunk of lead to bring it up to weight. But then, it was plastic covered, so much lighter than doped tissue would have been.
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albackstrom
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« Reply #82 on: October 09, 2009, 11:29:57 AM »

Caley as I said earlier I am not a builder of very light models. When I try and do light all I seem to accomplish is breaking a bunch of sticks. I weighed my JA Special and it comes in at 21 gms, This is not really heavy for a 20" span model with about 49 sq in area. I was last using a 6.5 gm motor so the loading is just over 0.5 gms/sq in. The 1/2 gms per sq. in. is generally a good max loading for indoor scale or scalish models.
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Al Backstrom USA - Will be missed by all that knew him.
crashcaley
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« Reply #83 on: October 09, 2009, 02:48:49 PM »

Al, Yours is a good weight compared to mine. I am figuring 25 grams without rubber. So I will have to use a bit bigger motor to get any kind of climb out. I'm going to experiment with various amounts of 1/16 rubber to find what's best. Of course, I could carve a 6.75 inch prop from balsa and probably lose another gram or so on the nose.

I've asked several times. Does anyone know the recommended CG for this model, or can someone tell me what theirs flys best at. Would be nice to know where to balance it, then I can adjust things to get it there. Only reason I ask is I with my KK Senator that performance was hindered by a bad CG point, and have found that on other models, which I am rehabilitating to proper CG. Sorry to keep asking, but from what I've experience, CG is important to the performance of a model.

Caley
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PeeTee
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« Reply #84 on: October 10, 2009, 03:12:26 AM »

Peter, Could you also inquire about the JA British SE5? I have been trying to locate those plans for a gift to friend who is not on line and not having much luck. Thanks and have fun, Bill

Bill,

No luck with the SE5 I'm afraid. The response was that my chum would like a copy as well!!

Peter
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Aeronut
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« Reply #85 on: October 10, 2009, 01:23:39 PM »

Thanks for asking Peter! Those plans are sure hard to come by Smiley Maybe someone else will have an idea. Anyway, again thanks and will keep looking, Best, Bill
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Maxout
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« Reply #86 on: October 10, 2009, 05:05:09 PM »

Caley, I'm busy at the moment, but will try to get back to you in a while with a CG location. Stay tuned...
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crashcaley
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« Reply #87 on: October 10, 2009, 05:25:41 PM »

Joshua, Many thanks. Know that you're always running for one reason or another. Special is still on hold until I finish all the little model airplanes for the kids for tomorrow. The Big Pussycat is nearly done. Just hope it'll fly even a little bit.

Caley
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Mooney
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« Reply #88 on: October 10, 2009, 06:14:59 PM »

Oh, the Big Pussycat will fly. They're great.
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crashcaley
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« Reply #89 on: October 10, 2009, 06:44:59 PM »

HP, Hope you don't mind a foreign model intrusion on this thread. Just about finished the girls Big Pussycat. The markings you see on the model are from a sticker sheet I purchased from Dollar Tree Store. They're made of aluminum, and are very colourful. Hope she will like it. Just hope this Pussycat wants to fly.

Caley
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Maxout
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« Reply #90 on: October 10, 2009, 09:55:59 PM »

Caley, I compute that the CG should be approximately 1.17" aft of the wing LE with the location shown on the plans. It's approximate because I didn't feel inclined to be exact on the area computations. Anyhow, the formula is conservative, so that should be a safe location.
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crashcaley
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« Reply #91 on: October 10, 2009, 10:25:41 PM »

Joshua, Again, many thanks. I've got two plans, and neither has a CG on it. One is from Easy Built Models and the other is a redraw of the original plans that was posted on one of the Yahoo Groups. I will give that CG (30mm) you gave a try and balance at that point. I may end up having to carve a prop. I figure it has to be at least half the weight of the P-P's 7-incher, and I heard that 6.75 inches is the correct legal size for this model.

Hope you have some time to have fun and maybe fly tomorrow, as I hope for everyone. Get the flying in soon, as winter is on the way. Sad

Caley
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High Point
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« Reply #92 on: October 13, 2009, 02:56:31 PM »

I pretty much finished up the framework on my JA Special over the weekend. A little nose heavy at this point. Start covering next.

Curtis
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crashcaley
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« Reply #93 on: October 13, 2009, 03:31:18 PM »

Curtis, Looks very nice. Did you have the same yips with the wingtips that I had. Took some careful studying and building to get them to plan, for me at least. Mine is noseheavy also, but maybe the covering will help balance things closer. If not, will do surgery on the tail feather covering and add some weight.

Caley
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High Point
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« Reply #94 on: October 13, 2009, 06:47:41 PM »

Caley, there were a few questionable areas I had to work through including the wing tips. I did get some help from our other members on this forum that I posted on Sept 30: http://www.hippocketaeronautics.com/hpa_forum/index.php/topic,2600.0.html

Curtis
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crashcaley
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« Reply #95 on: October 13, 2009, 06:54:36 PM »

Very interesting Curtis. I raised the LE of the wingtip to meet the center of the wing LE, as was suggested. But I added gussets to strengthen the joint a little better. Guess that doings things is much a personal preference, though my method may not be as strong. Bob's suggestion was good.

I'm still in the middle of supplying the local kids with lots of fun flying model airplanes, so my own models are kind of on the back burner. Maybe things with the kids will settle a bit so I can cover my Special.  Smiley

Look forward to seeing what you choose to do with the covering and decorations.

Caley
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High Point
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« Reply #96 on: October 25, 2009, 12:54:15 PM »

Looks like I'm on the home stretch of my JA Special. Question: would you glue the rudder with a few degrees off-set for the usual left turn? That's what I've done in the past on other models.

Thanks,
Curtis
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applehoney
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« Reply #97 on: October 25, 2009, 01:14:33 PM »

the usual left turn?

Why a left turn? The model will climb better in a right spiral.
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High Point
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« Reply #98 on: October 25, 2009, 01:43:43 PM »

Left turn; I guess that is the normal turning tendency as far as the prop torque, also what I've observed in other's models, and read about. So something to think about for sure. Anyway you would still sit in a few degrees to the right if you wanted to trim for a right turn. Right?

Curtis
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applehoney
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« Reply #99 on: October 25, 2009, 02:20:58 PM »

A left turn with torque keeps the nose down... climb out against torgue to the right for altitude.

Indoor models usually turn left to reduce climb to the ceiling - outdoor... to the right.

I don't like offset fins... I'd rather have everything straight, use right thrust primarily for the power pattern and if rudder found necessary, use a strip of balsa on the appropriate side of the TE, adjusting size as required. Glide turn by stab tilt.
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