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Quick Question - HS702 relief holes?

aviationgeek84

aviationgeek84

Well Known Member
Hi All,

Quick question... do I need the bend relief holes drilled in the HS-702 (forward HS spar) on the -8? I noticed the -7 has these and the manual explicitly says to drill them, but there is no mention in the -8 manual from what I can see. I *think* there are shown in the plans, but there are no dimensions or callouts that I am seeing (doesn't mean they aren't there) on the plans.

Advice? :)
 
After doing some more research, it does look like I just missed this on the plans. Will do it tomorrow. :) If anyone knows differently, please speak up... :p

Thanks!
 
You're not the only one who has missed it... I did as well. I don't recall that the text instructions mention the relief holes or cuts, but after my HS was done I noticed them on a buddy's RV-7 HS. Then I took a closer look at the drawings... oops. Oh well, I'm flying now 3+ years and 650 hours without, but keeping a close eye on any cracks developing there. If they show up, looks like I build another HS, oh joy!
 
I missed it too...:mad: Here is a great link to see how it's done right... http://www.rv7factory.com/log/050601.html

I just started priming the left side of the HS and have time to do this (I hope)....I hope it's not too late, even though the bend is there?? I also held off in the counter sinking until I get that perfect on a piece of scrap first.
 
I haven't riveted anything together and only have all of the skeleton parts laying on the table - could easily add these if it isn't too late with the bend in. Thoughts from others?

Thanks for the replies so far.:)
 
The link I posted was for the -7....I'm just ooking at mine right now and there is already somewhat aof a relief in the bend already...should I go further in? It is a newer kit (Nov 09) and I'm wondering if they have encorporated it in???

I haven't riveted anything yet either. I'll post a pic in a bit to show what I have and see if there are concerns with it.
 
Don and casey- if the parts are not assembled, i would certainly put the relief radius in, even if the part is already bent. without the relief radius, the stress is concentrated in the corner and the part cracks eventually. I think that might have been where Dan C.'s tail didn't pass one of his annuals- he mentioned replacing it at one point.

edit- i found a chain saw file (round) to work very well for removing aluminium, and leaving a fairly clean surface. of course you want to make sure there are no scratches and the parts are properly polished when you are done. refer to deburring and edge prep in the manual.
 
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Okay, so here is the result....I'm hoping it's sufficient. I looked at the diagrams, measured it and tried to accurately transfer it.

aku8h2.jpg


You will notice an "misshapen" hole 3rd over from the top left. Is this something I should be concerned about? Should I put a larger rivet in it? I can't seem to find much information about an misshapen hole?

Any advise wold be appreciated.

Thanks
 
Don,
Did you make those stress-reliever holes on the HS-702 or did the part come that way? Mine definitely doesn't have those from the factory.
 
I just made them tonight.....after seeing your post and realizing my error, I went into the garage and started to fix it. Put a fresh coat of self-etching primer on it as well as you can see from the gloss...it was still wet!

I gotta pay better attention to those plans!
 
Hi Don,

I'm guessing yours was already bent as well.. what method did you use to get your relief holes in there safely? :) Thanks!
 
casey- when you do yours, you probably don't want to remove as much material as Don. look at the rv7factory blog photo, that one looks ideal.


Don, I don't know enough to recommend a proper course of action for the misshapen hole. if it was my plane i'd make sure the hole was smooth and get the tightest fitting rivet in there i could make a proper shop head with and call it good, but that is just me.

maybe someone with more experience will chime in.
 
Casey, my 702 wasn't bent...I just measured it and bent it myself. I measured the relief hole from the diagram, doubled it and then used a 3/16 circle for my template and matched the lines from my measurements. I centre punched the circle and drilled a #30 and then smoothed it all out with the files and then 600 grit sandpaper. Took about 30 minutes to do the one 702.

Thanks Danny,

I'll send that off to Van's. They were pretty quick with their resposne for what I thought was a MED issue on my HS-404...they said to build on. I'm hoping I'm not becoming to critical of my work. better safe than sorry!
 
Oh, sorry Don... I just meant that you had already bent the 702 before adding your relief holes - is that correct? Or did you catch it before making the bend yourself?

Mine are aren't bent, but I'm planning to add the relief holes tonight or tomorrow.
 
No, I bent it first and added the relief afterward. Danny is right, my relief is probably a little larger than it should be. The right side whille be a little smaller when I do it.
 
Hey guys.

I'm working on the emp kit for the -7, but I thought I might be able to add a little something.

Here's some quoting from my Dec 30, 2009 blog entry.

I marked the bend lines on the HS-702 front spar channels. This takes some careful measurement and marking, so take your time.
Click to expand...

http://n999za.files.wordpress.com/2009/12/12-30-09-011-large.jpg

Then, I strayed from the plans a little. They have you use a 1/8″ bit to create a notch relief hole, then enlarge to 1/4″ using a unibit. I used snips and then a file. The second one turned out better than the first (which I hear is pretty common on everything in the project), and I had some trouble making them look perfect. (I know, things don’t have to be perfect, but it bugs me, anyway.) Biggest lesson learned: cut the flange in the correct place first, then unbend the flange to give you more material to work with. You can see in the top one in the picture below that I didn’t do this, and had to taper into the bend relief notch. (The bottom one below is better, nice straight line back to the relief notch.)
Click to expand...

http://n999za.files.wordpress.com/2009/12/12-31-09-082-large.jpg

Then I bent HS-710, HS-714, and both HS-702s. I created a cardboard template using trigonometry. I took the tangent of 6 degrees. Which is a little over 0.1. (This means fromthe bend line, for every inch you go laterally, the angle will be just over 0.1 inches up.) That’s a little hard to measure, so I took the inverse (to figure out how many inches laterally I need to go for 1 inch up), and got just over 9.5 inches. I have a calibrated 6 inch ruler, so I divided by two, and ended up with Mike Bullock's numbers; 4.75″ over, and 0.5″ up.

Now that I have my template for six degrees, let’s get bending.

After trying a few methods in the vise, I ended up just lining up my bend line with the edge if the table, holding a wooden block over the piece, and putting a little pressure on it. If you go slowly, you can get 6 degrees pretty dead nuts on. I laid everything on top of eachother, and it all lined up very nicely.
Click to expand...

http://n999za.files.wordpress.com/2009/12/12-31-09-083-large.jpg

For the record, I used Brad Oliver's posts as a guide, so I was striving for what he ended up with.
 
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Bend relief hole

Andrew, I'm a bit new here, but wanted to add my thoughts. Depending on where Casey and others are in their build, they may not want to unbend the flanges. If the outboard holes have been drilled thru the 810/814 into the spar, any unbending and rebending of the spar, if not done exactly as the original bend, might result in a mis-alignment of the outboard holes. If the flange has already been bent, I don't see a problem with adding the relief holes to the bent flange. A small rotary file on a dremel would work to contour the holes.

Sky
RV8
Emp.
 
Hi All,

Yeah - I'm definitely not unbending anything.. I will have to add these to what I have right now. At least it isn't riveted together, yet. :)
 
Yes, of course.

The unbending I was mentioning in my original entry was after you cut the flange on the spar (I think this step is particular to the -7). You have to measure and cut the flanges on the spar, then "un-bend" a little bit of the remaining web-to-flange radius that remains after the cut. (If you look at the line I drew in the first picture link above, you can see the line where the -7 spar flanges needs to be trimmed.)

You are both right, don't unbend the web of the spar if you've already bent the 6 degrees.

Sorry, I thought I was helping...didn't mean to add any confusion.
 
Andrea,

Nope, you're fine. Yes - I think trimming the flange of the spar is particular to the -7 ...

I will be adding these this week and then moving on... gotta build an airplane at some point! :D
 
Hi Don,

Haven't done it yet, myself... I'm going to have my EAA Tech Counselor stop by and just have a look - maybe give me some pointers. Since I already put the 6 degree bend in the spar, I'm going to get his suggestions as well. :)
 
I thought I was doing well following the manual until I read this thread. Of course, I already riveted the front spar in place without the reliefs. The written instructions make no mention of the reliefs but they are visible in the picture. Has it ever been determined if there is really an issue here? It appears this problem has been around for several years. If it is an issue, I would have thought that it would have been addressed in the manual by now.
 
DOX8 said:
I thought I was doing well following the manual until I read this thread. Of course, I already riveted the front spar in place without the reliefs. The written instructions make no mention of the reliefs but they are visible in the picture. Has it ever been determined if there is really an issue here? It appears this problem has been around for several years. If it is an issue, I would have thought that it would have been addressed in the manual by now.
Click to expand...

+1.

I finished my HS last week, never noticed the relief in the plans.

This should really be in the instructions, or at least a clearer note in the drawings to make sure this gets done.....
 
You are not alone........

Dave Bernard said:
+1.

I finished my HS last week, never noticed the relief in the plans.

This should really be in the instructions, or at least a clearer note in the drawings to make sure this gets done.....
Click to expand...

So sounds like many of us are in the same boat on this. My HS is done, and I did not notice the relief holes either. However, I made a conscious decision NOT to add them after having an experienced RV builder who had built several RVs over the years basically tell me that if I was concerned about it to add them, but if not, then don't worry about it. He thought that the bend area would be OK, as long as I smoothed out the area as much as possible to prevent any stress risers from forming, which I did. Problem is he never looked over the plans or anything either.

I decided not to add them based in part on his advise, also ebcause they were not mentioned in the book. In fact, until I read this thread I was convinced that they were not on the plans either. So, after looking them over again, and to be a little more specific, here are the issues that I agree Van's should address in their plans:

1. There is no mentioned to create the relief holes for the -8 assembly instructions, but there definitely is in the RV 7 instructions. If needed the instructions should be added to the -8 isntructions.

2. Section A-A view on the HS plans does seem to show a relief hole near the bend, but there is so much other stuff going on in that drawing it is difficult to tell for certain. The other problem I noticed is that the lines are solid instead of dashed, which leads one to think that those lines belong to the angle HS 814 and HS 810 parts in the front, and NOT part of HS 702 flange in the back. The lines should be dashed, and more attention called to the relief holes in that area of the the plans.

3. Best for last, as some of you have indicated, if you look at the isometric view in the HS plans, there they are --discreetly drawn in the center section -- relief holes in the bend line of the HS 702 flange. I think that Vans should add a note to call attention to these.

I guess at this point I would like to hear from any other RV 8 drivers with completed airplanes that also did not apply these relief holes to HS 702 to see if they experienced any cracking in this area over time, and if they had to repair, or worse yet, replace an entire HS as a result.

How frustrating it is to think you managed to address everything correctly in the plans, only to find out about this well after the fact........
 
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I received an e-mail from Van's builder support about this issue. It started by saying that the reliefs are important and ended by saying that if the bend wasn't sharp and less than 90 degrees that it might be OK. So...... I don't know any more than I did before.:confused:
I went ahead and used a tiny file to get a radius in the corners and now moving on......finished the VS tonight.:D
 
Hey Jeff,

The way I looked at it was "do the work now to fix it, or do it later when it cracked"...either way, it needs to get done. Then again, I caught mine before I riveted it, which made it easier for me.

You may be lucky and it never goes south on you, or, you can fix it now with a little bit of work and effort and prevent all that extra work down the road in the event it does go bad on you. I couldn't imagine ripping off my tail section, ripping apart my HS and fixing it..what a nightmare that would be.

I'm guessing you have it riveted on already?

I really don't know why Van's doesn't have that one line step in the manual for this, especially for new builders just learning the ropes and how to read blueprints.

Don
 
Don Patrick said:
I'm guessing you have it riveted on already?

I really don't know why Van's doesn't have that one line step in the manual for this, especially for new builders just learning the ropes and how to read blueprints.

Don
Click to expand...

Yes, the HS is completely riveted together. I have a local AP/IA that has built a couple of RV's. I think I will see what he thinks.

I agree. The assembly of the front HS spar is literally on the first page of the build. I think this should be covered at least once in the manual before it is assumed that I know what I'm doing.
 
the bend

Real quick question...

So in order to bend the spars its advised to put them inbetween 2 wooden blocks and bend them to 6 degrees? If I do this what if the bend of the HS810 and 814s dont exactly match up with the bends of the spars.... will the assembly with rivets take out any small diferences in angle?

Havent done it yet but was wondering what protocol is on that!
 
That's how I did it. As long as the 810 and 814 have the same angle, the spar will adjust itself for small differences. But it's easy got get it fairly close.
 
hendrik said:
That's how I did it. As long as the 810 and 814 have the same angle, the spar will adjust itself for small differences. But it's easy got get it fairly close.
Click to expand...

okay thanks! Guess ill drill the relief holes and bend them tonight~! :)
 
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