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General control line discussion => Open Forum => Topic started by: Joe Yau on January 11, 2019, 11:51:38 AM
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Just wondering if anyone have experimented on this.. If you were to seal 1/3 -1/2 or so of the hinge line on left side and right side of the wing. Would you seal mostly the outboard, inboard or the middle portion? or a bit of each. and Yes, I know it's best to seal the whole hinge line, but it gets too stiff and springy off neutral. so, it leads to what would be the min and most effective that works?
Thanks in advance
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One way to seal the gaps friction free is to make what I call "gap flaps". I take clear 3/4 inch cellophane tape lay two strips, glue up, side by side and a third strip in the middle of the first two glue down. Cut down the center to make two strips 3/4 inch wide that has half the sticky covered and half exposed. Stick down a strip on the wing or stab so that the not sticky part is just covering the gap and over the flap/elev about 1/16 inch. As the surface moves the flap will cover the gap sealing it. A flap must be placed top and bottom on the flaps and elev.
The pictures may help.
Pic. 1 shows two strips of tape edge to edge glue up and taped down at each end as the cellophane tape will not sit still. The joint of a drop leaf table is perfect for this step as it gives you a cutting guide.
Pic. 2 has the third strip in the center of the first two glue to glue.
Pic. 3 slice the tapes apart into two usable gap flaps.
Pic. 4 shows the installation on a wing flap. Just enough to overhang the bevel in the flap/elev.
Pic. 5 shows the glare off the clear tape sealing the flap gap full length.
No pinch, no stink, no gap. Replaceable and lasts a long time. Absolutely positively friction free.
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If it's too stiff and springy off neutral, then you are using the wrong tape, applying it wrong, or both. Search the forum for the threads on the subject for the best brands guys use. and how they apply it. You basically deflect the flap or elevator up and apply the tape to one side, then kind of roll it into the gap so the "bend" in the tape is at about the hinge line, then seal it to the other side. I apply the tape from hinge to hinge to avoid it getting stiff there. The hinge create a seal where it is so no need to cover it up. It does take practice to do well, like anything else.
Type at you later,
Dan McEntee
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The hinge create a seal where it is so no need to cover it up.
Type at you later,
Dan McEntee
[/quote]
I respectfully disagree. I have emperical data that suggest that is not the case. I seal all the way, right over the hinges. A touch if oil on the hinge barrel does the trick.
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One way to seal the gaps friction free is to make what I call "gap flaps". I take clear 3/4 inch cellophane tape lay two strips, glue up, side by side and a third strip in the middle of the first two glue down. Cut down the center to make two strips 3/4 inch wide that has half the sticky covered and half exposed. Stick down a strip on the wing or stab so that the not sticky part is just covering the gap and over the flap/elev about 1/16 inch. As the surface moves the flap will cover the gap sealing it. A flap must be placed top and bottom on the flaps and elev.
The pictures may help.
Pic. 1 shows two strips of tape edge to edge glue up and taped down at each end as the cellophane tape will not sit still. The joint of a drop leaf table is perfect for this step as it gives you a cutting guide.
Pic. 2 has the third strip in the center of the first two glue to glue.
Pic. 3 slice the tapes apart into two usable gap flaps.
Pic. 4 shows the installation on a wing flap. Just enough to overhang the bevel in the flap/elev.
Pic. 5 shows the glare off the clear tape sealing the flap gap full length.
No pinch, no stink, no gap. Replaceable and lasts a long time. Absolutely positively friction free.
Hi Perry, Thanks for the detailed illustrations. that's an interesting way of doing it.. will have to look into it. I think the problem is the flap/ wing hinge line is fairly close together, and also it has a 40 degree or so bevel flap edge to straight trailing edge hinge line, which makes the angle even sharper for the tape. (pic#1) On my other plane with more typical hinge line (pic#2) and 1/16"or so gap works just fine with either Dollar store/ Crystal clear or 3M Multitask tape. The problem is there isn't enough room for the tape to flex.
Pic #1
(https://i.postimg.cc/4yKHbmRJ/20190112-082120.jpg) (https://postimages.org/)
Pic#2
(https://i.postimg.cc/rp8dZh2Z/20190112-081726.jpg) (https://postimages.org/)
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If it's too stiff and springy off neutral, then you are using the wrong tape, applying it wrong, or both. Search the forum for the threads on the subject for the best brands guys use. and how they apply it. You basically deflect the flap or elevator up and apply the tape to one side, then kind of roll it into the gap so the "bend" in the tape is at about the hinge line, then seal it to the other side. I apply the tape from hinge to hinge to avoid it getting stiff there. The hinge create a seal where it is so no need to cover it up. It does take practice to do well, like anything else.
Type at you later,
Dan McEntee
I started out with the 3M Multitask tape, then went to the thinner Dollar store/ Crystal Clear tape which is a little thinner then Multitask. and usually works better. but it was still too stiff and springy, and that's with a little break-in work on the tape before applying.
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I started out with the 3M Multitask tape, then went to the thinner Dollar store/ Crystal Clear tape which is a little thinner then Multitask. and usually works better. but it was still too stiff and springy, and that's with a little break-in work on the tape before applying.
If it is too stiff, then you didn't get it all the way to the hinge line. If it crosses the gap in line with the hinge pin, you are just flexing the tape, which is negligible. If not (which is how yours is), then it has to roll the tape up down. I can't tell if that is the problem because your pictures are too small and not enlargeable.
For future work, leave a gap sufficient to make it easier. I use a single hinge pin (and idea I ripped off from Paul), and in that case, you can (and must) have the tape touching the pin, which makes it a snap to apply the seals.
To your original question, yes, you can do partial seals and/or not seal over the hinges. It's not a good idea, generally, but you can certainly do it.
Brett
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If it is too stiff, then you didn't get it all the way to the hinge line. If it crosses the gap in line with the hinge pin, you are just flexing the tape, which is negligible. If not (which is how yours is), then it has to roll the tape up down. I can't tell if that is the problem because your pictures are too small and not enlargeable.
That is probably what is going on, as there is not much of a gap in between the flaps and the wing.
To your original question, yes, you can do partial seals and/or not seal over the hinges. It's not a good idea, generally, but you can certainly do it.
I don't think the hinge line on this particular plane could be sealed with the conventional way method without getting stiff and springy controls, as there is near no gap.. but doing it partially inboard or outboard isn't as bad. Just curious which is more effective. (sealing only inboard or outboard?)
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I vote for the inboard section of the flaps because there is more area there.
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I vote for the inboard section of the flaps because there is more area there.
I surely hope we are talking about inboard/outboard as "distance from the fuselage" instead of the left wing vs the right wing! If it was me, if I had somehow convinced myself to do it partially, I would do the outboard (near the tips rather than near the root), because that has more effect on roll.
This is not about making the flaps or elevator more effective (although it does do that, too) but to reduce the variability of the leaks over the travel, which tends to roll the airplane in ways that you cannot otherwise correct.
There is no gap small enough to not benefit, unless it touches all the time, and there is no gap too small to make it impossible to do without binding up. The smaller gaps does make it more difficult, but I have built gaps that I carefully sanded and measured to be about .010", then sealed them with good effects and no binding. And unless you are doing extensive wind tunnel tests to configure it properly, leaving large gaps *doesn't act like a slotted flap* and doesn't make it more effective, quite the opposite. Leaving a large gap reduced the effect of the control surface - although a 3/32" gap with a .010 variation over the travel does have less differential roll effect than a .011 gap with a .010 variation.
I would also note that those who don't think any of this matters typically end up with much larger flaps.
Brett
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The brand and quality of the tape makes a difference. On a suggestion here I started using Moore Crystal Clear tape which is tough but pliable. Your climate will matter. Cooler weather makes the taped controls more stiff. When I have to fly in cooler weather I’d rather pull the tape off and deal with whatever comes of that than lose the feedback and touch of the controls. The Crystal Clear is a little better when it’s cool.
Dave
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I surely hope we are talking about inboard/outboard as "distance from the fuselage" instead of the left wing vs the right wing!
Yes, it is from the fuse.. not Lt vs Rt wing.
If it was me, if I had somehow convinced myself to do it partially, I would do the outboard (near the tips rather than near the root), because that has more effect on roll.
This is not about making the flaps or elevator more effective (although it does do that, too) but to reduce the variability of the leaks over the travel, which tends to roll the airplane in ways that you cannot otherwise correct.
O.k that's good. I started sealing it from the outboard side (or wing tip end) then work inwards, finding about midway is started to get a little stiff and springy. so I stopped there.
There is no gap small enough to not benefit, unless it touches all the time, and there is no gap too small to make it impossible to do without binding up. The smaller gaps does make it more difficult, but I have built gaps that I carefully sanded and measured to be about .010", then sealed them with good effects and no binding. And unless you are doing extensive wind tunnel tests to configure it properly, leaving large gaps *doesn't act like a slotted flap* and doesn't make it more effective, quite the opposite. Leaving a large gap reduced the effect of the control surface - although a 3/32" gap with a .010 variation over the travel does have less differential roll effect than a .011 gap with a .010 variation.
I would also note that those who don't think any of this matters typically end up with much larger flaps.
Thanks for the insight.. that does make sense.
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The brand and quality of the tape makes a difference. On a suggestion here I started using Moore Crystal Clear tape which is tough but pliable. Your climate will matter. Cooler weather makes the taped controls more stiff. When I have to fly in cooler weather I’d rather pull the tape off and deal with whatever comes of that than lose the feedback and touch of the controls. The Crystal Clear is a little better when it’s cool.
Dave
The temperature has been around 6-8C degrees here. I was tempted to remove all the tapes.. but then thought of maybe leaving on some partially. I'll have to look into the Moore crystal clear tape.
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I generally use Ultrakote covering on many of my models. The relevance to the post is that I also use it to hinge the control surfaces. Not too difficult to do and your surfaces are friction free and durable. Some of mine were 10 years old when I parted with the model.
Walt Umland used to have a very good tutorial on the process and perhaps he can make it available again.
The advantage is that you have made up Ultrakote hinges and then sealed the adjoining surfaces the whole length of the control surfaces.
Obviously it would not be used on your front row model but there are many who are really expert with using plastic film and can do amazing covering jobs that would certainly earn praise from even the most die hard painter.
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how important are sealed hinges on an Old Time ship where all but one maneuver is of round shapes
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The air molecules passing by your OTS airplane care about sealed hinge lines. The model will perform better with sealed hinge lines.
Many OTS models have dope finishes which make cloth hinges a viable option. I used cloth hinges on the last OTS model and permanently sealed the hinge line that way.
BTW, the OTS pattern has a total of 10 corners
Climb and Dive: 4 corners
Wing over: 2 corners
Square loop : 4 corners
Jim Hoffman
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how important are sealed hinges on an Old Time ship where all but one maneuver is of round shapes
I guess that'll probably depends on how serious other competitors are at the contest.. yea but it's just OTS