Tmcfarland
User
Very nice. Do you have a name for this glider yet?
Aloft Forums
Welcome to Aloft Forums. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!
Doc's D-Lite - A new thermal build at Aloft
- Thread starter Wayne
- Start date
Tmcfarland
User
Just saw the D-lite title. Looks great.
We are taking a little break from this project as we need to give attention to a number of other projects and production of existing products.
We did suffer a wing failure on the last build. Plane was being launched into the sun, pilot lost orientation and pulled hard to regain sight. Wing folded in the left side near the center. (Think he said it folded to about 45 degrees.) At this point he had no control and it came down pretty hard.
No Aloft crew where there, and sadly we did not get the chance to inspect the wreckage until after the owner had dug into it. Working with the owner and studying photos we think we know the causes. Luckily we have another nearly identical panel here we have been doing some testing on.
In the failed wing section the carbon spar caps separated from the shear webs. Something that should not be able to happen in flight according to the testing we performed. But it did. I suspect the trailing edge spar failed as we have spotted some weakness in it, and this then allowed the wing to twist, and that added in the spar cap failure. The builder has a long building history and know his stuff. He did sand the carbon caps, but thinks he failed to sand enough. He was able to fully remove the carbon caps from the wing after the crash sure points to this being a major contributing issue.
This wing uses the same spar setup as I used in our AH-100, and my prototype on that is 100% thin CA glue. (I might have some medium in there??) I did this to test the worst possible glue joint, and I could not snap that wing in flight. Yes, that is only a 2.5m wing, but the wing on the Delight is built much stronger, and the caps are getting additional layers of plywood. Earlier prototypes had no issues with wing strength in our flight testing. So needless to say this was shocking to us. Not at all expected.
We will be making some changes on the trailing edge spar as it is showing some weakness. We are also going to do some additional glue testing with the carbon caps.
On the plus side, we have ordered up the new longer noses in fiberglass, we had been testing with a 3D printed nose extender during the prototype stages, we finally got some real world results with the last build to give us the exact length needed to balance with a small battery.
Wish I had better news, but that is the way project development goes sometimes.
-Wayne
We did suffer a wing failure on the last build. Plane was being launched into the sun, pilot lost orientation and pulled hard to regain sight. Wing folded in the left side near the center. (Think he said it folded to about 45 degrees.) At this point he had no control and it came down pretty hard.
No Aloft crew where there, and sadly we did not get the chance to inspect the wreckage until after the owner had dug into it. Working with the owner and studying photos we think we know the causes. Luckily we have another nearly identical panel here we have been doing some testing on.
In the failed wing section the carbon spar caps separated from the shear webs. Something that should not be able to happen in flight according to the testing we performed. But it did. I suspect the trailing edge spar failed as we have spotted some weakness in it, and this then allowed the wing to twist, and that added in the spar cap failure. The builder has a long building history and know his stuff. He did sand the carbon caps, but thinks he failed to sand enough. He was able to fully remove the carbon caps from the wing after the crash sure points to this being a major contributing issue.
This wing uses the same spar setup as I used in our AH-100, and my prototype on that is 100% thin CA glue. (I might have some medium in there??) I did this to test the worst possible glue joint, and I could not snap that wing in flight. Yes, that is only a 2.5m wing, but the wing on the Delight is built much stronger, and the caps are getting additional layers of plywood. Earlier prototypes had no issues with wing strength in our flight testing. So needless to say this was shocking to us. Not at all expected.
We will be making some changes on the trailing edge spar as it is showing some weakness. We are also going to do some additional glue testing with the carbon caps.
On the plus side, we have ordered up the new longer noses in fiberglass, we had been testing with a 3D printed nose extender during the prototype stages, we finally got some real world results with the last build to give us the exact length needed to balance with a small battery.
Wish I had better news, but that is the way project development goes sometimes.
-Wayne
Odd having the carbon spar caps come off. I can remember sanding the carbon, cleaning with acetone and using medium CA. Never has any come loose. Was the spar wrapped with Kevlar thread?
Oh well, things like this do happen that is why there are test builds. Always did like the carbon tube for a spar system. That is what all my Polecat Aero planes used and never had any issues. And boy did I stress test some of the those wings.... Going from F3B to electric is quite the change.
Ed
Oh well, things like this do happen that is why there are test builds. Always did like the carbon tube for a spar system. That is what all my Polecat Aero planes used and never had any issues. And boy did I stress test some of the those wings.... Going from F3B to electric is quite the change.
Ed
Hey Ed,
No, we did not wrap with kevlar, we had considered it, and actually have provisions for this in some key areas, but have not found the need in prior testing.
On the plus side, someone suggested a new glue to me I was not aware of, going to give it a test.
No, we did not wrap with kevlar, we had considered it, and actually have provisions for this in some key areas, but have not found the need in prior testing.
On the plus side, someone suggested a new glue to me I was not aware of, going to give it a test.
Tmcfarland
User
Little break is over. Lets get back to work on thisWe are taking a little break from this project as we need to give attention to a number of other projects and production of existing products.
We did suffer a wing failure on the last build. Plane was being launched into the sun, pilot lost orientation and pulled hard to regain sight. Wing folded in the left side near the center. (Think he said it folded to about 45 degrees.) At this point he had no control and it came down pretty hard.
No Aloft crew where there, and sadly we did not get the chance to inspect the wreckage until after the owner had dug into it. Working with the owner and studying photos we think we know the causes. Luckily we have another nearly identical panel here we have been doing some testing on.
In the failed wing section the carbon spar caps separated from the shear webs. Something that should not be able to happen in flight according to the testing we performed. But it did. I suspect the trailing edge spar failed as we have spotted some weakness in it, and this then allowed the wing to twist, and that added in the spar cap failure. The builder has a long building history and know his stuff. He did sand the carbon caps, but thinks he failed to sand enough. He was able to fully remove the carbon caps from the wing after the crash sure points to this being a major contributing issue.
This wing uses the same spar setup as I used in our AH-100, and my prototype on that is 100% thin CA glue. (I might have some medium in there??) I did this to test the worst possible glue joint, and I could not snap that wing in flight. Yes, that is only a 2.5m wing, but the wing on the Delight is built much stronger, and the caps are getting additional layers of plywood. Earlier prototypes had no issues with wing strength in our flight testing. So needless to say this was shocking to us. Not at all expected.
We will be making some changes on the trailing edge spar as it is showing some weakness. We are also going to do some additional glue testing with the carbon caps.
On the plus side, we have ordered up the new longer noses in fiberglass, we had been testing with a 3D printed nose extender during the prototype stages, we finally got some real world results with the last build to give us the exact length needed to balance with a small battery.
Wish I had better news, but that is the way project development goes sometimes.
-Wayne
