Eagler's Nest
General Category => Off Topics and General Interest => Topic started by: s johnson on December 13, 2015, 12:23:17 AM
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https://www.youtube.com/watch?v=F017f7nkWmI (https://www.youtube.com/watch?v=F017f7nkWmI)
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Scott,
Are you planning to close in behind you..? A fastback of some sort will take off all the air that is curling off the top of the wings and around the doors. Thin, thin plexi would seem ideal.
Are you getting an Artic blast right down your shirt collar..? Or no.
Thanks for sharing, and that motor sounds great!
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Hi Dan,
I was thinking about enclosing the back as well but couldn't figure out a good way to do it. I didn't want to interfere with the original structure. All of this is done with adel clamps and tubing. Similar to the way the doors are mounted on the Challenger aircraft.
The left door is fixed and will not open but put in a little window with a hinge so when I start I have access to the throttle and mag switch. Works out pretty well.
Yes I do get a little draft on the back but is soooo much better that with out the doors.. They will come back off when it hits the 50 degree mark.
Now we just need some snow so I can try the skis. I was going to try last year but it was just too cold. Now I think I'm ready to give it a go.
Scott J.
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Scott, those doors look like they work great with that big rounded front windscreen. Seems like you should have picked up some cruise speed. I put the doors on DE Stubby last winter (or two? I forget) and picked up some speed and much comfort. We fly with them all season - just overall more comfortable.
We toyed with the idea of "fastbacking" it, like Dan suggested. We would put a stringer from the trailing edge of the wing at the center to the top longeron tubing joint. Then put a frame at the back edge of the door, and run stringers from that frame to the back trailing stringer. Make all this from thin wood strips, maybe "T" section for stiffness. Cover it all in fabric. We modeled it with temp. wood strips and string, and it looks like it would make a nice streamlined cockpit, and pick up a few more MPH. Especially if we replaced the flat windscreen with one rounded like yours. That would take some more thinking, though.
Maybe this winter . . .
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Hi all new guy in Eau Claire Wi here building an xl.. Scott the doors look great! This is awesome as I was just thinking doors for some skiing would be great!! What if you used that clear stuff they use for ice shack windows to close up the back of the le? Its clear flexable when cold can be sewed could attach with velcro or snaps or lace it on....just a thought..anyways the doors look great!! Jay
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What if you used that clear stuff they use for ice shack windows to close up the back of the le?
Jay
Will have to have something to defrost the windshield if the cabin is completely closed in... No step for a stepper however...
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Hi all new guy in Eau Claire Wi here building an xl.. Scott the doors look great! This is awesome as I was just thinking doors for some skiing would be great!! What if you used that clear stuff they use for ice shack windows to close up the back of the le? Its clear flexable when cold can be sewed could attach with velcro or snaps or lace it on....just a thought..anyways the doors look great!! Jay
Windows in ice shacks are small; the stuff can break quite easily when very cold.
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Hi all new guy in Eau Claire Wi here building an xl.. Scott the doors look great! This is awesome as I was just thinking doors for some skiing would be great!! What if you used that clear stuff they use for ice shack windows to close up the back of the le? Its clear flexable when cold can be sewed could attach with velcro or snaps or lace it on....just a thought..anyways the doors look great!! Jay
Windows in ice shacks are small; the stuff can break quite easily when very cold.
Im not saying take windows out of ice shacks you can buy that material and custom make a rear cover to fully enclose the cockpit I think t-birds had the same type or stuff enclosing them...my iceshack windows certainly dont break at even -20 folding and unfolding my shack as i said its just a thought....Jay
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No, I understand Jay, but I asked my friend who does canvas boat tops and has rolls of it, and in larger pieces the stuff can crack more easily. It is also quite heavy.
Kent
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I added to my DE doors too - made a nicer experience to fly with out a heap of wind
was worth the days work
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Hi, Scott, I was going to suggest that you add a light plywood panel in the triangle behind your head and then extend the fabric to cover the headrest, but I see from these pics from a 2006 EAA Experimenter article that you did have fabric there but removed it. Why the change? Also, why the wingtip change from the previous MiniMax ones? Cheers, Matthew
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Matthew,
I wanted to save weight by removing the original tips and replacing with Leonard's design tips.saved quite a bit allowing me to build doors for use in winter ops .
Scott.
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Scott:
Do you recall the weight of the old wing tips and from what material they were constructed? I have been thinking of experimenting this winter with shaping some Hoerner style tips from rigid pink foam insulation (?polystyrene?) adhered to 4mm plywood. Weight and strength being primary concerns. It may be an exercise in futility but I'd like to explore it anyway.
Vince
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Vince,
Seems to me they weighed around 3lbs s lbs each but not sure . if I can get to them I will weigh them. They are fiberglass.
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I have been thinking of experimenting this winter with shaping some Hoerner style tips from rigid pink foam insulation (?polystyrene?) adhered to 4mm plywood.
Vince
Wing tip devices have a lot of leverage at that distance from the center line of the airplane. Make them absolutely identical side to side, and mounted exactly alike.
Be ready for a heavy wing on the first flight, especially if one side is pushing up more and one side is pushing down more at the same time.
I'm going through this pain right now on a different design. The original builder apparently was oblivious to the need to make the tips the same.
String lines and digital levels are your friends...
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Vince, I made Hoerner wing tips for our LEU Treehugger a number of years ago. Made out of the pink home insulation foam board, covered with fiberglass/epoxy. By the way, the foam is polystyrene, and epoxy has to be used, or the foam will disintegrate. Anyway, from the picture the finish was not great, but we tried them out. We were looking for increased climb during takeoff. We only got a couple flights before ole Treehugger acquired its name, but it seems that they did make an improvement over the flat plates on the tips.
Hope you can get them made and do some more testing.
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Matthew,
I wanted to save weight by removing the original tips and replacing with Leonard's design tips.saved quite a bit allowing me to build doors for use in winter ops .
Scott.
Scott, are you planning on using the rule of -
- at deepest thickness of wing- go out 12"
- what ever angle that gives you (lets say it was 41 degrees)
- use that same angle out from all places of the wing rib profile (thus the top will always be flat across the span-and the bottom angle will always be the same)
- This gives you the predefined curve, and basically a easily to create shape that has a calculated value.
The 12 inch rule was used for cub like aircraft, I don't know if it would be best (could be) for our Eagle sized birds, if this would be the number, remembering the lessor the distance the higher the used angle would be. I guess a person has to start somewhere. Certainly can and perhaps should use the lost foam-bulkhead technique to save weight, as the retained foam-super strength would not be required.
I have done this shape in CAD many times, just never for the XL
Was wondering what formula you were planning on?
cheers
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Well.....
Scott, I honestly had no plan. Just built to fit sort of thing Mostly not what you wanted to hear but..... seems to work just fine so far. Yep... nope as you guessed it. I'm not n engineer But am having loads of fun making things work. :-) By they way, where do you come up with all these formulas, your making me feel kind of stupid.. Haha
Scott J.
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As Leonard says its only and airplane... just build it !
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Tom H,
Thanks for posting the picture and comments on the wing tips. A pictures worth...!
I wonder:
- Did you hollow out the material in the tip or did you somehow form thin sheets of foam to that shape?
- What's the best way to shape the foam [knife/saw/file/abrasive/razor/blow-torch/TNT]?
- Do you think the same material used to cover the wing could also cover the tip [ex. Dacron rather than fiberglass]?
One more thing. Did you make peace with the tree or did you turn it into firewood?
Vince
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Vince, I made the tips sorta like this:
- I saw this technique somewhere on-line
- stacked, glued 2" thick pink foam to make a block somewhat larger than the final tip. Used 5 min epoxy, but made sure that it was only dabbed onto areas that would not have to be cut
- fastened a plywood template of a wing rib to each end of the block with long deck screws
- cut the wing profile using a hot wire. I used SS safety wire in a crude light weight frame. The power supply was an old 10 amp transformer type car battery charger, powered by a Harbor Freight tool speed controller to get just the right temperature on the wire.
- left one template on the end, removed the other. Then attached a narrow strip of 0.025 aluminum sheet to the surface of the foam near what would be the tip end
- hot wired along the bottom of the plywood template and the alum strip. this gave a curved shape to the cut. The leading edge and trailing edge corners need hand shaping, if I remember correctly.
- I noticed that some Hoerner tips look like they have been run through a large vertical band saw set at around 45 degrees. Don't know which way is correct or better. Probably would be easier if run through a large bandsaw, though.
- I used epoxy/fiberglass boat cloth, one layer. The fiberglass cloth is woven in a style that allows it to conform to compound curves. I don't think dacron cloth will do that. Also, some type of dacron is used as a peel ply material with epoxy because it does not stick. Better check the compatibility first. And, if you use the Polyfiber products, they will destroy polystyrene foam because of the MEK. (note, if you want to use the cheaper polystyrene or vinylester resins, as used on boats, you can use urethane foam. But, don't hot wire urethane foam - fumes are toxic.)
- finally, I initially did not plan to hollow out the foam, but did it to reduce weight. I think I used a variety of techniques, knife, hacksaw blade, hand held die grinder, but no TNT. Tried to leave the foam thick enough to support the glass.
Sure wish that I took photos of the build - my recollection would be better. Hope this helps, though.
A limb was amputated from the tree - some would say "a just punishment".
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Well.....
Scott, I honestly had no plan. Just built to fit sort of thing Mostly not what you wanted to hear but..... seems to work just fine so far. Yep... nope as you guessed it. I'm not n engineer But am having loads of fun making things work. :-) By they way, where do you come up with all these formulas, your making me feel kind of stupid.. Haha
Scott J.
Ha, certainly the case for "what ever works" and what is built is 10 times better than what is proposed to be built.
Formula came from a Tip builder in the state of Washington. but he was building for 100 mph aircraft, so I have no idea, if they are to much, or even effective. But certainly liked the established rule that he used, thus he could make the same basic shape, no matter what rib profile was used. Again, this might be completely a pie in the sky approach.
I really liked how you did yours, I don't think any stupid event prevailed for you. It got done. Top notch.
Scott in Iowa