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Lowrider LSA

Lowrider said:
View attachment 30410
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Lowrider said:
Thanks Sky!

There are no rivets in there yet.

I do have a mushroom set with the rubber around the edges. I'm planning to back-rivet in those areas where I can. I made a 2" round brass bucking bar that works really well for that. It gets beat up some but I just put it in the lathe and "freshen it up" a bit.
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Look outboard of the skin which is clecoed in place. Count outboard to the 2nd and 4th exposed nose ribs. From here it appears that the rivets which are holding the vertical stiffeners are dimpled. This is from not holding the angle stiffener while driving the rivets. If you held the bucking bar in the palm of your hand and held the stiffener with two fingers of that hand while driving the rivets, the dimpling could have been prevented.
 
Right you are! I did those on the table with a plate under the rib and it looks like I must have hit the rivet before it was on the plate...lesson learned.
 
I'm on the 3rd skin piece and that involves the landing/taxi light. I'm putting in a 30 watt LED with a 60* beam which I aimed maybe 100 yds in front of the nose when in an approximate 3 pt landing configuration. I had the wing hung on the fuselage awhile back and estimated where to aim inside my shop with the house lights off so it very well may need some tweaking once real time flying happens. This will probably just be a bright light for recognition purposes. I'm also doing nav and a strobe light.

My plan is to cut the skin in an approximate shape, finish riveting the skin then go back to make the plexiglass lens and trim ring before painting. Is that the usual method or would it be better to put the finish cut and make the trim while I still have access to the inside of the wing? I shouldn't need to get into the light unless it needs re-aiming since it's LED and no bulb to replace (I hope). Thoughts?
 
Lowrider said:
My plan is to cut the skin in an approximate shape, finish riveting the skin then go back to make the plexiglass lens and trim ring before painting. Is that the usual method or would it be better to put the finish cut and make the trim while I still have access to the inside of the wing? I shouldn't need to get into the light unless it needs re-aiming since it's LED and no bulb to replace (I hope). Thoughts?
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It is always better to have access and not use it than to not have it and need it.

Before you cut the leading edge for the landing light make sure that the bend in the leading edge is accurate or just a whisker tighter than desired. If not the skin will spring outward when you cut the hole making a bulge in the skin around the landing light. You will not like this.
 
Hmmm...good thought on the skin springing out. Would it make sense to cut out a "frame" for the light opening, rivet it in place THEN cut the hole? I will have access into the wing by removing the plexi if needed. I was only going to make one ring with nut plates on the inside but making another for the outside would not be a big deal.

The light is a 10 watt not 30 watt as previously mentioned. I bought a 30 watt light for my baby Kubota (the one that bit my hand) and haven't installed it yet. I might put that one inside the engine cowl as a taxi light since it is a 120* flood.
 
You want the "spring out" stress to be removed before you cut the hole. Riveting the frame in first will only fool you into thinking the "bend out" stresses are removed. Bending the leading edge correctly is no more work than doing it wrong. I would prefer a little over-bending than under-bending in this situation as the "outward" puckers will not be present and the riveted frame will counter any inward force.

If you can gain access by removing the landing light lens, you don't need another ring. I agree with minimizing the amount of cutouts, but make sure that you have enough.

IF you make a slight reverse curve aft of the leading edge bend, when you rivet the skin to the ribs it will sit tight and straight between the ribs.
If not the spring back stresses will cause the skin to have a slight hump between the ribs. This can be done after you drill the rivet holes before riveting if you find that the skin raises between the ribs when clecoed. Place a straight edge spanwise across the ribs. Is the skin flat?
 
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skywagon8a said:
...

IF you make a slight reverse curve aft of the leading edge bend, when you rivet the skin to the ribs it will sit tight and straight between the ribs.
If not the spring back stresses will cause the skin to have a slight hump between the ribs. This can be done after you drill the rivet holes before riveting if you find that the skin raises between the ribs when clecoed. Place a straight edge spanwise across the ribs. Is the skin flat?
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Lost me on the reverse curve. Do you mean bending the skin inward slightly? Yes, the skin is flat so far.

I used an 8' straight edge on the ribs top, ends and bottom and adjusted them as needed which wasn't much before I put the wing in the upright frame. I found it necessary to do the same thing after I pulled the forward spar into a straight line using a 3 axis laser level which I can highly recommend to anyone trying to do this with a string and bubble level. It's a Bosch product I bought to use in building my shop/hanger and house but it worked really well for this application too. BTW, my shop stem walls are square and level within 1/4" using that little sucker. It does require early morning or late afternoon use or you can't see the laser. That sure helped when I built the walls, roof and siding.
 
Lowrider said:
Lost me on the reverse curve. Do you mean bending the skin inward slightly? Yes, the skin is flat so far.
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When you drop the prebent skin over the leading edge into the correct position does any part of it touch the ribs or is it sprung away from the ribs? If when you drill and install the clecos they pull the skin into the ribs, the skin can bow up away from the ribs due to the built in stress trying to pull the skin away from the ribs. If the skin has a slight curve away from the ribs, when you pull it down and fasten it there will be no outward stresses raising it up away from the ribs. This can cause the skin to raise away from the rib shape between the ribs. Hmmm? It's a bit difficult to explain. Your pictures of the bottom of the leading edge skin looks good. Have you drilled and clecoed the top yet? When you have that done show me a picture. If it is flat spanwise you may disregard what I'm trying to explain. The top with it's greater curve is more apt to not want to lay flat.
 
Now I got it! I went out and checked all the ribs beyond mid point and found a couple main ribs that protruded maybe an 1/8" on the bottom so I applied a dead blow rubber hammer and solved the problem. The ribs were flat once the edge was bent to a 90* as it should have been. Top was fine.


The skin over the nose ribs fit the rib pretty tightly and when drilled and cleco'd the skin is straight with a 4' straight edge. I could also put a "stiffener" on the inside where the light opening will be...say out of 0.032 2024 to keep the skin from moving when it's cut. I see what you mean since it's 0.020 and there is a pretty large hole without support.


I'm also getting ready for the pitot/static tubes and I'm still thinking inboard of the strut attach point to give it some protection. I need to set it back on the wing anyway since the two tubes are welded together on the one you suggested so it will be difficult to try to bend it down from a farther forward position. Thoughts?
 
pitot_static_tube_2447.jpg


Took awhile to find this picture but this is the pitot/static tubes I have from ACS. This is shown on a Sonics and I want to put it on the first flat area just inboard of the strut attach point to give it some protection from folks taller than me.
 
It looks as though the bottom of the ribs have a slight concave curve. You have three considerations for the location. Well outboard of the prop blast, inboard of the turbulence generated by the strut attachment to the spar and away from banging heads. It wants to be either parallel to the path of flight or pointed down by as much as 10 degrees for slow speed accuracy. Mine is parallel to the flight path (adjustable) and is 100% accurate from 40 - 160 mph. Below 40 - 30 IAS there is a 5+ mph error to the high side.

Is your entrance door on the right side only? Place the pitot under the left wing.

My suggestion based on your picture in post #1858 is adjacent (inboard) to the second exposed rib outboard of the wing skin centered on the web midway between the second and third lightening hole aft of the spar. Cut a scrap of .032" about 2-1/2" - 3" square (or whatever size best fits more than the pitot base). Bend it 90 degrees diagonally (forms two triangles). Bend up each side 3/16" or so to stiffen the edges. Make sure that there is a smooth radius at the 90* bend where the edges are bent up so that no cracks can form. This piece will be riveted (3ea) to the rib (AN470-3) and the bottom skin (AN426-3 or AN470-3) and will reinforce the attachment of the pitot. Also it will prevent the bottom skin from cracking (important) at the base of the pitot due to vibration over time.

Second location choice is to move it forward to the next web on the rib.
 
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Well. I'd like to thank all the folks out there that have been viewing these project reports. We slipped over 300K views this morning and that's incredible to me that so many are interested in my efforts to build a flying machine. I believe in no small part their interest stems from the guidance and advise that is being provided by other builders and mostly Sky who is a constant source of expert information and innovation.

Thanks Skywagon8a (Pete) for all your help and for sticking with this effort!!

I made a 3" diameter 0.032 piece to fit inside the skin and adjacent to the rib at whatever point I choose to put the pitot. My thinking is that the base of the pitot on the outside can then be shimmed to adjust the angle to keep it into the prevailing airflow...maybe 10* down from centerline of the wing chord. Does that make sense?
 
Lowrider said:
I made a 3" diameter 0.032 piece to fit inside the skin and adjacent to the rib at whatever point I choose to put the pitot. My thinking is that the base of the pitot on the outside can then be shimmed to adjust the angle to keep it into the prevailing airflow...maybe 10* down from centerline of the wing chord. Does that make sense?
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If that 3" circle is in the middle of a skin without being attached to a stiffener (rib) it can cause cracks in the skin next to the rivet holes. Any motion caused by vibration must be eliminated or the possibility for cracking exists.

You want the pitot to be parallel to the line of flight. The chord line of the wing may be a few degrees up thus pointing the pitot that many degrees out of line. A pitot tube wants to be +/- 10 degrees to the airflow. Of course zero is the most accurate.
 
I was planning to put two of the attach rivets inside of the rib flange so it won't cause a bulge in the skin. Maybe putting it over the rib on the outside with 2 of the 4 rivets on the rib flange. I could also put an "L" shaped piece on the inside attached to the web of the rib and extend out to support the other 2 rivets. That should stiffen up the skin to reduce/stop vibration. I'm going to try bending the tubes between the base and the 1st weld and see how that goes.
 
Lowrider said:
I was planning to put two of the attach rivets inside of the rib flange so it won't cause a bulge in the skin. Maybe putting it over the rib on the outside with 2 of the 4 rivets on the rib flange. I could also put an "L" shaped piece on the inside attached to the web of the rib and extend out to support the other 2 rivets. That should stiffen up the skin to reduce/stop vibration.
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There are numerous little methods to reduce relative motion, preventing cracks. Just keep them in mind when you are building something.


Lowrider said:
I'm going to try bending the tubes between the base and the 1st weld and see how that goes.
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And what if it doesn't go? I like the shim idea better unless the tubing is soft and pliable.
You could make a little aerodynamic shape to cover the vertical portion to reduce a little drag.
 
Too hard to bend...back to shims. The shape is a good idea...maybe foam covered with epoxy coating.

A wise man once told me I could use a thin layer of silicone on the inside around the area to stop vibration. He crew chiefed Marine One for a couple years so he wasn't concerned about weight. He also told me spit on my finger before I used it to spread silicone...it won't stick to saliva...it works too.
 
No wonder you know so much!!

I got selected for floppy wing driver school at Ft Campbell but at the last minute they stopped the program...just as well I suppose.
 
My friend Wally served on Marine 1 as a maintenance chief for Reagan, Geo H.W. Bush and slick Willies first term. He is now a maintenance supervisor on the Airbus for UPS. He has plenty of stories about the experience.
 
I worked second shift and actually met Igor Sikorsky while I was working there when he walked through the plant one evening.
 
My ailerons do 23* up and 18* down. That said, if I were going to do gap seals for them what would I use that won't eat up the paint on the aileron? Next question, are gap seals really worth it for a pretty low speed plane?

I do plan on something to seal the top of the flaps which will be extended skin to a point...haven't got there yet but know I want them.
 
Before you address aileron gap seals, you need to discuss what type of ailerons you have along with the hinge location. Some types of ailerons want the air to flow up through the slot for more effective control. Can you show a picture of the cross section of the aileron including the hinge location?
 
Yes Sir, I can, just not now as long as I have the wing upright. Guess I'll wait and ask this later. I left 4" of extra top skin on each sheet so I can extend it over the ailerons which should allow the air flow to stay on top of the aileron. I'll check the plans and see if it shows any detail.
 
Starting just before 8:00 minutes. https://youtu.be/q_eMQvDoDWk This shows the airflow through a slot and over the flap helping to hold the airflow in the boundary area on top of the flap. The ailerons work in a similar manner. When the leading edge dips below the bottom of the wing it can direct air through the slot over the top of the aileron helping to push it down. I would not want the gap sealed. If it is a hinged aileron, it would not be as effective. A little time spent looking ought to find more videos showing airflow over the ailerons.
 
Fyi....... When airplanes fly less than, say, 30 mph the airflow acts different than 50 mph air.

Maybe sealed gaps are a good thing.
 
Well, I should have consulted the drawings first...my bad. There is suppose to be skin over the pocket ribs and rearward to maybe 1/2" clearance between the skin and the aileron in the up position...that provides the "gap seal" I was considering. There is no skin on the bottom of the wing that extends beyond the rear spar but I suppose that's less important drag wise than the top. The flaps get essentially the same thing but will extend over the flap in the up condition and allow air flow over top of the flap when deployed.

Thanks Gents for the comments and the info on air flow.
 
Yep

Wayne Mackey stuff....

less than 30 mph a Helio slat aint a slat...unless you give it more gap to flow through

maybe Lowrider wants to seal his aileron gaps...maybe he doesnt.
 
Top skin is on.

Turning to thoughts of the wing tip. The current plan (discussed earlier) is to just square off the tip and install nav/strobe lights and be done with it for the time being. Basically, just a piece of 0.020 screwed to last rib. Thoughts please!

Dave/Sky,

My aileron control stuff is set up to allow normal operation or drooped ailerons by moving one bolt on the control rod. It's the droop position that makes me wonder about air flow over the top of the aileron. I THINK there needs to be some flow over the top at low speed and the planned top skin would reduce or eliminate air flow at high angle of attack...I think. Until I get the control surfaces mounted and set up it's hard to be sure. I will say that the original designer had apparently no intention of offering droops so they are not taken into consideration when the top skin overlap was planned. The conventional pocket ribs provide a pretty good seal on the top, as much as possible while still allowing 23* up aileron.
 
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