Help trimming boost glider

Discussion in 'Rocket Boosted Gliders' started by Lugnut56, Jul 7, 2018.

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  1. Jul 7, 2018 #1

    Lugnut56

    Lugnut56

    Lugnut56

    What, me worry?

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    I recently completed my first glider (Semroc Hawk Boost Glider), but am having trouble trimming it. When I toss it, it just seems to drop (there was a slight breeze the day I was testing it however). I've read the chapter in "The Handbook of Model Rocketry" about gliders, and it states that sometimes they just won't glide with a toss. What am I doing wrong, or is this a common issue with some gliders?
     
  2. Jul 7, 2018 #2

    Amsterdam

    Amsterdam

    Amsterdam

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    My first starting point if i have a model do that is too plop a gram or so worth of clay to one extreme, aft or nose and see what happens. if it’s performing the same as it did without the clay, switch extremes.

    Trimming is never permanent. And frustrating at first. But you’re starting with a proven model so be confident that it will glide well.
     
  3. Jul 7, 2018 #3

    Lugnut56

    Lugnut56

    Lugnut56

    What, me worry?

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    Thanks for the advice. What about paint? After reading several different reviews about painting vs unpainted, I was planning on just using colored Magic Markers to keep the weight down. Any thoughts or suggestions?
     
  4. Jul 7, 2018 #4

    Amsterdam

    Amsterdam

    Amsterdam

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    All of my gliders are dirty, messy, dinged, and that’s before I’ve even launched it. Painting always makes em look nice with little effect on performance as long as you don’t overdue it. But I’d skip that step for now. Color it. Trim it, fly it. See if it’s something you like
     
  5. Jul 7, 2018 #5

    Lugnut56

    Lugnut56

    Lugnut56

    What, me worry?

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    Ok, sounds like I know what I need to do. Thanks for your input.
     
  6. Jul 7, 2018 #6

    GuyNoir

    GuyNoir

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  7. Jul 9, 2018 #7

    Maxout

    Maxout

    Maxout

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    Find a field full of tall grass. Do a few experiments: throw the model at the horizon good and hard. If it noses up and stalls and drops back down, then you probably just need to add some clay to the tail to get it to glide normally. If it goes straight or worse, noses down when thrown hard, bend the trailing edge of the horizontal stab up to make the model tend to pitch up a little. You don't want it to pitch up super aggressively, but you want a guarantee that the model will pull out of a dive. If the model rolls hard to one side or the other, you can bend the vertical stab a little to correct for that.
     
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  8. Jul 13, 2018 #8

    dwinings

    dwinings

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    For my competition gliders I use contest Balsa (less the 4 lb/cuft for the wings) the lighter the better, Hard balsa for the fusilage and c grain medium balsa for the tail feathers. Then finish by painting with 50% thinned Sig clear light coat and covering with true Jap tissue.
     
  9. Jul 14, 2018 #9

    caveduck

    caveduck

    caveduck

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    As you are starting out in B/G there are very few kits available, and not too much published information on the model rocket side. In general you can find a ton more information about glider construction/flying from the model airplane HLG and DLG (discus launch gliders) world than from the NAR site. But pretty much any good hand launch glider plan can be converted to a rocket glider by putting the rudder on the underside of the boom and adding a motor pod.

    A good HLG build and trimming article by a serious expert that I hadn't found before: http://www.modelresearchlabs.com/legacy.htm and some more articles here http://www.modelresearchlabs.com/applications.htm.
     
  10. Jul 16, 2018 #10

    Maxout

    Maxout

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    This is pretty much what I was trying to get at, but in simplified form. Since we've opened the worm can, here's a video I did on actually implementing Curt Stevens' article you reference.

    I've been using his basic method for the past 15 years and to pretty good effect. One should not overlook, however, that there's some obvious ego showing through in the article and that the general theory he uses is somewhat dated. He downplays the advances made by Lee Hines (a personal friend of mine and one of the top 5 free flight glider guys EVER) and makes no mention of the work done by Stan Buddenbohm (also a friend of mine). While that galls me to no end, it doesn't reduce the value in the trimming section. I take serious issue with some of his construction stuff as he majors on the minors in my opinion. Yes, he's got the right airfoils, etc, but the level of precision he's after is completely unnecessary, and I've got enough free flight contest experience, both indoors and out, to back my claims. There are several videos of my flying rather cobbled together models to 60+ seconds in dead air from a catapult, which is mostly on par with Lee or Stan. I had several 70 second flights in Johnson City back in the day which would have put me in the top 3 had I not managed to use up all my official flights on a more fragile model which kept promising to perform but never did. That' not to toot my own horn, but rather to clarify that you don't need the OCD building philosophy to get good flights. I'm not as good as Stan and Lee and I'm happy to admit that.

    I know a lot of folks use the tissuing method for rocket powered models but I haven't really found it to be necessary unless you're getting into the D-E range. I've had no problems with flutter from my Carbonette 19 R/C BGs and they're built pretty light. I get 2 minutes in dead air on B engines, and that's with the R/C stuff hanging out in the breeze. You could probably do 2:30-3:00 with a free flight version. It borrows pretty heavily from Stan's Swee' Cat, for what that's worth.

    I think someone with good ingenuity could make a pretty competitive no-moving-parts D RG from one of Stan's DLG kits by putting the motor over the wing at the CG. Trim it out as a DLG and it should give a really nice spiral climb under rocket power. One of these days I'll get around to trying that on one of mine.
     
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  11. Jul 16, 2018 #11

    caveduck

    caveduck

    caveduck

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    Agree 100% about not needing stupid levels of precision. For me, building by eye on a decent flat surface does just fine. There are some control authority issues that come into play for the E6 powered models that can reach 150mph on boost. You for sure don't need tissue on the smaller BGs. These days almost everybody uses RC on B BG and up anyway. And small DLGs convert real well...if they're over optimum glide mass you can even remove some structure b/c a rocket boost is a lot easier on the airframe than getting flung at 90mph off a wing tip :)
     
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  12. Jul 21, 2018 #12

    Lugnut56

    Lugnut56

    Lugnut56

    What, me worry?

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    Sorry to be getting back to this thread so late,but between work and both my sons coming to visit, I haven't had much free time. Thanks to all for the information about this subject and I will be doing some reading (and tossing) this weekend.
     
    Last edited: Jul 21, 2018

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