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Old 03-25-2019, 03:53 PM
  #51  
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Looks like a wing tip tank on an F-89 Scorpion to me, once the extra wood is sanded off
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Old 03-26-2019, 02:55 AM
  #52  
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But Hydro, tip tanks would look out of place on my 4*! lol
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Old 03-26-2019, 03:04 PM
  #53  
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Tonight's lesson/topic is about hard-points. If you've never hear of hard-points then read on...

One thing that bothers me when I see a nice plane that someone built, is when they don't use hard-points under their control horns. How can you tell their not there? Easy, just look for the crushed balsa under the control horns. Often times their so bad the horn sits at an angle because the balsa is crushed. If hard points were installed under the control horn, it would be nearly impossible to crush the end grain of the hardwood dowel under the horn. When installed properly, hard-points are undetectable under the horn, they should never sit proud of the surface.





Two short lengths of 3/8" hardwood dowel with 1/8" holes drilled in their centers. These will become the hard-points.




After locating and marking the exact position for the hard point on the aileron, a 3/8" hole is drilled. I like to place painters tape over the spot before drilling into soft balsa.




This is what the hole looks like with the tape removed. Time to glue the hard-points in place and let them dry.




Your hard-point should be a smaller diameter than the horn's base.




You probably already know the importance of making sure that the horn's pivot point must be directly over the hinge line for correct linkage geometry.

Last edited by VincentJ; 03-27-2019 at 12:19 AM.
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Old 03-27-2019, 01:16 AM
  #54  
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Unfinished business...




Hard-points installed.




Installed correctly, the hard-point will give a rock solid stable foundation the horn requires without ever being seen.






Last edited by VincentJ; 03-27-2019 at 01:59 AM.
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Old 03-27-2019, 01:56 PM
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Actually, everything I've read, both in books and magazines or in build instructions have never said anything about hard points. In fact, many of the older books I've seen actually recommend a slight crush into the balsa. I know, times and information change but these older books used to be almost like an instruction manual to build an airplane. I do use hardpoints, or something similar, in my boats since they have to withstand much more in the way of stress and pounding while testing and racing since, as we all know, water is almost as hard as concrete when something is skimming across it's surface. That said, I do like the way you install them but, something I'm wondering is, since you're using straight dowels to make them, have you ever had one pull out? With the set up you showed in your picture, it seems to me that using a slightly larger dowel and tapering it down to your 3/8" and installing it from the opposite side might make a stronger assembly since the base, being larger than 3/8", would hold the hard point in while the larger tapered end would preclude it pulling through or, with parallel sides, out.
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Old 03-28-2019, 12:38 AM
  #56  
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I've never had any of my hard-points rip out or even loosen up on any of my planes or planes that I have built for others Hydro. Besides being secured with glue, each hard-point is smaller in diameter than the horn above it and its cap below it so it really is locked into place. I've even used used them on flying wires, struts and under engine mounting bolts without failure. Having said that, I am a firm believer that as in all aspects of building, strength comes from well fitted joints along with good glue penetration. So in other words if one is relying on the glue to hold a hard-point installed in a hole that was drilled too large, then all bets are off!

I like your idea of tapered holes, but for me, making clean straight holes in balsa is challenging enough...lol

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Old 03-28-2019, 10:55 AM
  #57  
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So your hard point is sandwiched? That was something your pictures didn't show. I was under the impression that your horn was screwed in to the hard point. That makes a world of difference since the balsa around the hard point is still having to carry a good part of the load and not just the balsa in contact with the hard point inside the hole
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Old 03-28-2019, 01:54 PM
  #58  
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OK Hydro, this one's for you! Yes the dowel is sandwiched between the upper and lower parts of the control horn. Sorry for the confusion.




I hope this is a little more clear as to how the hard-point is clamped between the upper and lower portion of the horn. The dowel is glued and does not float between the two...




With the majority of the wing's building completed, it's time to put it safely aside and start on the fuselage. In my small shop, this is where I store the wing until I'm ready for it.
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Old 03-28-2019, 02:38 PM
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Originally Posted by VincentJ View Post
OK Hydro, this one's for you! Yes the dowel is sandwiched between the upper and lower parts of the control horn. Sorry for the confusion.




I hope this is a little more clear as to how the hard-point is clamped between the upper and lower portion of the horn. The dowel is glued and does not float between the two...




With the majority of the wing's building completed, it's time to put it safely aside and start on the fuselage. In my small shop, this is where I store the wing until I'm ready for it.
Actually, I was good with your description but the picture will probably help someone that's trying to learn from this thread. What has me curious is who makes that horn assembly since I've never seen it before
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Old 03-29-2019, 12:35 AM
  #60  
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Originally Posted by Hydro Junkie View Post
Actually, I was good with your description but the picture will probably help someone that's trying to learn from this thread. What has me curious is who makes that horn assembly since I've never seen it before
This horn is made by Dubro, here's the link.

https://www.dubro.com/collections/co...horn-for-40-91
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Old 03-29-2019, 06:25 AM
  #61  
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Hard points are the way to go. Been using them for years. I especially like to use them for the wing bolts. They look so clean once the wing is covered and there is zero crush and no plywood plates protruding. Keep up the good work.
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Old 03-29-2019, 07:05 AM
  #62  
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Originally Posted by pmcafee View Post
Hard points are the way to go. Been using them for years. I especially like to use them for the wing bolts. They look so clean once the wing is covered and there is zero crush and no plywood plates protruding. Keep up the good work.
Thanks! I plan on sinking the plywood plates flush into the wing on this project as well...
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Old 03-29-2019, 01:32 PM
  #63  
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Itís very common to use 1/2Ē dowel for horn hard points. I have done them on airplanes up to 40% ( 150cc powered). I use a sharpened brass tube to cut a hole through the bottom balsa skin and foam. The dowel gets glued into place making contact with the upper sheeting, the foam and surface leading edge stock. The dowel gets drilled and a 10-32x2Ē set screw is used as the horn. The set screw self taps and is epoxied into place. Have yet to have one fail in over 20 years.

Great build Vincent, I always enjoy your attention to detail associated with your builds.
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Old 03-29-2019, 03:32 PM
  #64  
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Thanks Speedracerntrixie, happy to have you here to keep me honest! lol





The highlighted area is where the new engine firewall will be located. I had to push it back 5/8" . To handle the additional power of the DLE-20 RA, I increased the thickness as well. The new firewall will be 3/8" thick and is angled 2 degrees down. Everything in front of the new firewall will be cut off, remember that I will be installing a fiberglass cowl.

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Old 03-30-2019, 03:39 PM
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Vincent, you donít need me to keep you honest, you do fine without me. I do have something for you to think about though. Have you considered adding some right thrust? Going with a larger engine that will produce more torque, I would consider right thrust would be quite helpful.
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Old 03-31-2019, 04:53 AM
  #66  
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Originally Posted by speedracerntrixie View Post
Vincent, you donít need me to keep you honest, you do fine without me. I do have something for you to think about though. Have you considered adding some right thrust? Going with a larger engine that will produce more torque, I would consider right thrust would be quite helpful.
I did think about adding right thrust, then decided that I would try flying it without without. I can add a washer behind the left hand side of the engine if need be...
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Old 03-31-2019, 05:05 AM
  #67  
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Time to start on the fuselage. I have all of my pieces ready (including clamps) on my work table.




I took the time to place center lines on both sides of each Former which will help in alignment of the fuselage when the time comes.




Stock firewall on the left and its replacement on the right. Besides the increased thickness, note the angled bottom of the firewall to follow the bottom profile of the fuse.




It isn't the time for glue-up quite yet, its wise to dry assemble the fuse using clamps making sure all the joints fit properly. Now is the time to get it right. The construction method used on this fuselage is a lot like that used when building my Tiger 60.




No surprises with initial clamp-up. Now I need to cut and fit 1/16" birch ply to both insides of the fuselage between the firewall and F-1. This will really give much needed strength in preparation for the DLE-20.

Last edited by VincentJ; 03-31-2019 at 05:13 AM.
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Old 03-31-2019, 10:31 AM
  #68  
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With the 1/16" birch ply in place and epoxied, Former (F-1) is glued in place making sure that it is dead nuts square.

Note- 30 minute epoxy is used in areas indicated. When I use the term "glued", I am referring to Titebond ll being used.





For comparison sake, the right and left fuselage panels are shown. The void in the bottom panel is filled using the same ply removed from the laser cutting sheet.




The plug fits perfectly.




The birch panel it cut and fit into position, now it's time to mix-up some epoxy.




Heavy flat weights are placed on top to ensure good contact between each epoxied panel. Just have to wait for the epoxy to cure...

Last edited by VincentJ; 04-01-2019 at 03:12 AM.
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Old 03-31-2019, 04:17 PM
  #69  
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Firewall is epoxied into the fuselage.




Checking square, should be no surprises.




Front of fuse is spot on to the plans and the revisions I had made. You can see the angle on the bottom of the firewall how it conforms to the bottom.




I decided to pin the firewall in place. It will really lock the firewall to the sides of the fuselage. Here you can see my layout lines.




Four 1/8" holes were drilled using a brad point bit on my drill press.




I cut eight pins roughly about one inch in length. If you look carefully you will see that I chamfered one end of each pin.




A drop of glue was spread into holes using a toothpick, then each pin hammered into its opening and trimmed off.




After a quick sanding here is the final results.

Last edited by VincentJ; 04-01-2019 at 02:38 AM.
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Old 04-01-2019, 02:17 PM
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I like to assemble this type of constructed fuselage in the method that I've shown. I know better than to try and assemble the entire fuselage with rubber bands to hold everything together. The chance of building a "bananna" fuse doing it that way will be your likely result. Use the TOP of the fuselage to your advantage, as it's perfectly flat, which is why you see it placed on my build table in that orientation. Constantly check your square and revisit all the center lines and you will be just fine.




If you recall in an earlier post, I recommended marking the center lines on all the Formers. This is where and when it will become an asset helping you build a straight fuselage.




I have various blocks of steel that are perfectly square that I have collected over the years. Many of them I purchased for next to nothing at yard sales.




I will use the blocks mass to clamp off of it making the side of my fuse plumb.




Additional weight on the top will make sure that the top of the fuse makes contact with my flat build table.




Don't be afraid to be creative using clamps to get the job done...







I couldn't install this Former (F-6), as the top of it which is part of the turtle deck would prevent the fuse from sitting flat on the table. I'll install it after the glue dries on all the other Formers.

Last edited by VincentJ; 04-02-2019 at 02:37 AM.
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Old 04-02-2019, 02:56 AM
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3:30 in the morning is quite early, but that was the time I got out of bed and entered my workshop. I was eager to remove the clamps and weights off the fuselage. As each clamp was removed, I was looking to see if my fuselage would move or twist. With the last of the clamps released I'm, happy to report that my fuselage didn't move and is indeed straight and true! So before going upstairs to make my morning coffee, I turned the fuselage over and glued F-6 (the last Former) into position.

Now for that first cup...

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Old 04-02-2019, 05:40 AM
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Thanks for sharing this. You are an excellent builder!

Ealy
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Old 04-02-2019, 06:18 AM
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Originally Posted by EalyB View Post
Thanks for sharing this. You are an excellent builder!

Ealy
Why thank you Ealy, much appreciated...
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Old 04-02-2019, 07:55 AM
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Originally Posted by EalyB View Post
Thanks for sharing this. You are an excellent builder!

Ealy
Indeed! I haven't built an all balsa and ply kit in 4 years. A few weeks ago I picked up an Andrews Aeromaster Two kit, Vincent is inspiring me to get the bench set up and to start framing it. Glad he shares his Ideas with us as I will be using a few of them.
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Old 04-02-2019, 08:51 AM
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Wow, that's great Speedracerntrixie. I've been wanting to build a Bipe for some time now. Last Bipe I built was about 45 years ago, and that was CL. I think it's about time for another! Maybe in the WW-I era, and thank you as well...

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