Justin's Raven
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Re: Justin's Raven
Could you please post a larger pic? Its a bit difficult to understand what you are talking about in your previous post and the pic covers to small an area to understand the context. Alternatively its just me who is being dof this morning...
Re: Justin's Raven
The end cap on the stabilizer doesn't fill up the whole area. So there is a small triangular piece that's not covered. So he's makin' small triangular pieces to fit in that area.
Justin, is there a rule about how far the rivets must be from the edge of the part? And if, why?
Justin, is there a rule about how far the rivets must be from the edge of the part? And if, why?
Life- I did it my way.....
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The world is not enough!
- Manie Rossouw
Re: Justin's Raven
Thanks wallaby that gives me enough info to understand ... I think
So the trailing edge is formed by folding the Al sheet forwards towards the hinge line and the Al rib that forms the end cap does not run all the way to the training edge - leaving a triangular hole (when looking side on to the trailing edge.
Yes there are rules/guides for how far from the edge the rivit can be installed and also what the distance between rivits must be. This particularly applies to areas which take a lot of load and where multiple rivits are used in a staggered pattern close to each other.
My guess in this case is that its not too critical since the rivit does not carry any significant load. The only stress would be due to flexing of the control-surface but the biggest potential problem would be due to vibration.
My guess is that you could use a small pop-rivit if you are worried that it might come loose, but using a suitable epoxy should be easier and result in a better seal. There should also be suitable joint sealers (similar to Polyurethane or Silicone) which can be used on Al. Just check the compatibility as some silicones contain acids which may not be compatible with Al and could cause corrosion. Something that will bond and still retain a degree of flexability should be ideal. So I would use a bonded joint as a first try - you can always drill and poprivit later if you find that it does not last.
So the trailing edge is formed by folding the Al sheet forwards towards the hinge line and the Al rib that forms the end cap does not run all the way to the training edge - leaving a triangular hole (when looking side on to the trailing edge.
Yes there are rules/guides for how far from the edge the rivit can be installed and also what the distance between rivits must be. This particularly applies to areas which take a lot of load and where multiple rivits are used in a staggered pattern close to each other.
My guess in this case is that its not too critical since the rivit does not carry any significant load. The only stress would be due to flexing of the control-surface but the biggest potential problem would be due to vibration.
My guess is that you could use a small pop-rivit if you are worried that it might come loose, but using a suitable epoxy should be easier and result in a better seal. There should also be suitable joint sealers (similar to Polyurethane or Silicone) which can be used on Al. Just check the compatibility as some silicones contain acids which may not be compatible with Al and could cause corrosion. Something that will bond and still retain a degree of flexability should be ideal. So I would use a bonded joint as a first try - you can always drill and poprivit later if you find that it does not last.
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justin.schoeman
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Re: Justin's Raven
Wallaby has it right. Every trailing edge is folded, and every one leaves a gap (too big to fill with filler) to the end of the outer rib/skin. So I need to do this on the ends of the elevator, rudder and ailerons. There are also some bigger gaps, but I will fill these by removing (drill out the rivets) the Raven parts, and plans building the Zodiac parts.
Will waste a day or two (or three), but should be well worth it in the long run!
The construction standards call for a minimum spacing for the rivets of 3x the hole diameter for the rivet. That is, the centre of the drill hole must be at least 3x the diameter from any edge (including the edge of another rivet hole). I am wary of breaking these rules for any reason, as I do not know enough about why those rules are there. Are they for structural strength? Are they to prevent cracking?
Thanks for the advice Andrew.
Anybody know where to get JB Weld?
Will waste a day or two (or three), but should be well worth it in the long run!
The construction standards call for a minimum spacing for the rivets of 3x the hole diameter for the rivet. That is, the centre of the drill hole must be at least 3x the diameter from any edge (including the edge of another rivet hole). I am wary of breaking these rules for any reason, as I do not know enough about why those rules are there. Are they for structural strength? Are they to prevent cracking?
Thanks for the advice Andrew.
Anybody know where to get JB Weld?
Re: Justin's Raven
Pleasure J
AFAIK the rules are predominantly based on structural strength, so if there is no significant load on a riveted joint there should not be a significal problem if you dont adhere to the rules - ie putting a rivit in close to an edge. Cracking usually occurs when holes have not been properly deburred ( or cleanly drilled) and where a nick or gauge on the edge of the hole can cause a crack to form.
Where you have a cyclical load placed on a joint which is not sufficiently designed for that load, cracking is most likely to occur (i.e. resulting from fatigue). Such a load can be low requency (eg actuation of aileron in the Zenair where the skin is actually the hinge) or high frequency - such as caused by vibration. But in essence its a function of the frequency and magnatude of the load. Higher load causes plastic deformation (holes stretching or rivits tearing out) and low load but high frequency usually causes cracks.
Its very difficult to determine if a part will crack (assuming the hole preparation is done correctly) without fancy vibration testing equipment. Thus its sometimes the best to use something that will dampen vibration - such as a bonded joint which allows a bit of flex & vibration absorption.
When working with something like Alclad, its important to finish off edged which have been cut. E.g. if you cut it with a hacksaw or jigsaw - dont leave the edges rough since each of the grooves/scratches left by the blade is a potential startpoint for a crack - particularly if the part will be exposed to vibration. So in such a case make sure you sand down the cut edges with fine waterpaper and remove the cut marks. For this reason its better to cut with a guillotine and even better to do laser cutting - if you have access to such facilities.
for your application I still think the bonded joint is the best/simplest - assuming of course that you can get a suitable sealer/bonding compound - which is affordable.
I am speaking form a general engineering background - not with specific aviation experience - so I hope I am not too far off the mark
I am working from memory here .... based on Mech Eng studies many moons agoI do not know enough about why those rules are there. Are they for structural strength? Are they to prevent cracking?
AFAIK the rules are predominantly based on structural strength, so if there is no significant load on a riveted joint there should not be a significal problem if you dont adhere to the rules - ie putting a rivit in close to an edge. Cracking usually occurs when holes have not been properly deburred ( or cleanly drilled) and where a nick or gauge on the edge of the hole can cause a crack to form.
Where you have a cyclical load placed on a joint which is not sufficiently designed for that load, cracking is most likely to occur (i.e. resulting from fatigue). Such a load can be low requency (eg actuation of aileron in the Zenair where the skin is actually the hinge) or high frequency - such as caused by vibration. But in essence its a function of the frequency and magnatude of the load. Higher load causes plastic deformation (holes stretching or rivits tearing out) and low load but high frequency usually causes cracks.
Its very difficult to determine if a part will crack (assuming the hole preparation is done correctly) without fancy vibration testing equipment. Thus its sometimes the best to use something that will dampen vibration - such as a bonded joint which allows a bit of flex & vibration absorption.
When working with something like Alclad, its important to finish off edged which have been cut. E.g. if you cut it with a hacksaw or jigsaw - dont leave the edges rough since each of the grooves/scratches left by the blade is a potential startpoint for a crack - particularly if the part will be exposed to vibration. So in such a case make sure you sand down the cut edges with fine waterpaper and remove the cut marks. For this reason its better to cut with a guillotine and even better to do laser cutting - if you have access to such facilities.
for your application I still think the bonded joint is the best/simplest - assuming of course that you can get a suitable sealer/bonding compound - which is affordable.
I am speaking form a general engineering background - not with specific aviation experience - so I hope I am not too far off the mark
Re: Justin's Raven
Mmmm...this was not exactly the understanding I had. The pitch minimums (ie. minimum distance between rivets) is, IMHO, to prevent the structure unzipping when loaded...ie. tearing from rivet hole to rivet hole under the anticipated load.
According to the Zenith standards the edge distance should be 1.5d (which is 1.5 x the diameter of the hole concerned) when measured from the centre of the hole. I cannot see anything in the standards at a glance which covers the minimum distance between rivet holes. On my plans the closest spacing I have is pitch 20 for A5 rivets (come to think of it I remember two A4 rivets on the tip rib of the rudder which are only say 1 to 1.5cms apart).
The area concerned is likely to be a low stress area at the TE so maybe the safe bet would be to bond it in place and like someone else said if this goes pear shaped you can always rivet it later instead. If you do decide to rivet there be careful that when drilling the filler piece doesn't get squished and not holed in the process as you will not be able to support the piece when drilling.
Enjoy
PS. I am not an aircraft engineer so trust your judgement on this one. Would it be an idea to leave them open to allow air circulation and reduce moisture build up? After a quick look at my version (601 XL) in the garage there looks like there is sufficient room if you offset the rivets sufficiently.
According to the Zenith standards the edge distance should be 1.5d (which is 1.5 x the diameter of the hole concerned) when measured from the centre of the hole. I cannot see anything in the standards at a glance which covers the minimum distance between rivet holes. On my plans the closest spacing I have is pitch 20 for A5 rivets (come to think of it I remember two A4 rivets on the tip rib of the rudder which are only say 1 to 1.5cms apart).
The area concerned is likely to be a low stress area at the TE so maybe the safe bet would be to bond it in place and like someone else said if this goes pear shaped you can always rivet it later instead. If you do decide to rivet there be careful that when drilling the filler piece doesn't get squished and not holed in the process as you will not be able to support the piece when drilling.
Enjoy
PS. I am not an aircraft engineer so trust your judgement on this one. Would it be an idea to leave them open to allow air circulation and reduce moisture build up? After a quick look at my version (601 XL) in the garage there looks like there is sufficient room if you offset the rivets sufficiently.
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justin.schoeman
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Re: Justin's Raven
Wow - I am developing new respect for scratch builders. I have just spent 1.5 hours working on ONE bracket, and it isn't even finished yet!
measure, measure (and measure again, just for luck), cut, file, polish. Lather, rinse, repeat...
Two more cuts, and it is ready to be match drilled. Make the next, and I can re-fit the nose gear.
How long must it take to build an entire aeroplane like this? Someone has a lot more patience than me
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Justin
measure, measure (and measure again, just for luck), cut, file, polish. Lather, rinse, repeat...
Two more cuts, and it is ready to be match drilled. Make the next, and I can re-fit the nose gear.
How long must it take to build an entire aeroplane like this? Someone has a lot more patience than me
.Justin
Re: Justin's Raven
found these two sites with some useful info:
Note they use rules of thumb - there are variations in rules of thumb since they are not 100% exact. Their intent is to be safe and easy to remember and apply.
Coincidentally both these sites state that the edge distance should be between 2 and 2.5x rivit diameter (depending on the rivit type used). So in your case Justin if you use a smaller rivit you can put it closer to the edge.
Scotsman - there are rules for Transverse and linear minimum distances as listed below
http://www.experimentalaircraft.info/ar ... ding-4.php
This site also contains useful explanations of how to de-burr holes and other plate edges. Interestingly they aslo state that even guillotine cut edges must be de-burred & filed/sanded
http://www.tpub.com/content/aviation/14 ... 18_547.htm
form the second one:
Note they use rules of thumb - there are variations in rules of thumb since they are not 100% exact. Their intent is to be safe and easy to remember and apply.
Coincidentally both these sites state that the edge distance should be between 2 and 2.5x rivit diameter (depending on the rivit type used). So in your case Justin if you use a smaller rivit you can put it closer to the edge.
Scotsman - there are rules for Transverse and linear minimum distances as listed below
http://www.experimentalaircraft.info/ar ... ding-4.php
This site also contains useful explanations of how to de-burr holes and other plate edges. Interestingly they aslo state that even guillotine cut edges must be de-burred & filed/sanded
http://www.tpub.com/content/aviation/14 ... 18_547.htm
form the second one:
Spacing and edge distance
Rivet spacing, also referred as rivet pitch, is the distance between the rivets in the same row, and is measured from the rivet center to the rivet center. Transverse pitch is the distance between the rows of rivets, and is measured from the rivet center to rivet center. Edge distance is the distance from the center of the rivet to the edge of the material being riveted. Figure 13-43.—Rivet length. There are no specific rules that apply to every case or type of riveting. There are, however, certain general rules that should be followed.
RIVET SPACING.—Rivet spacing (pitch) depends upon several factors, principally the thickness of the sheet, the diameter of the rivets, and the manner in which the sheet will be stressed. Rivet spacing should never be less than three times the rivet diameter. Spacing is seldom less than four times the diameter nor more than eight times the diameter.
TRANSVERSE PITCH.—When two or more rows of rivets are used in a repair job, the rivets should be staggered to obtain maximum strength. The distance between the rows of rivets is called “transverse pitch.” Transverse pitch is normally 75 percent of existing rivet pitch, but should never be less than 2 1/2 times the diameter.
EDGE DISTANCE.—The edge distance for all rivets, except those with a flush head, should not be less than twice the diameter of the rivet shank nor more than four times the diameter of the rivet shank. Flush-head rivets require an edge distance of at least 2 1/2 times the diameter. If rivets are placed to close to the edge of the sheet, the sheet is apt to crack or pull away from the rivets. If they are placed too far away from the edge, the sheet is apt to turn up at the edge.
NOTE: On most repairs, the general practice is to use the same rivet spacing and edge distance that the manufacturer used in the surrounding area, or the structural repair manual for the particular aircraft may be consulted, Figure and edge distance. 13-44 shows rivet spacing .
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Re: Justin's Raven
Boet and Justin I am posting pics of the cubby VW with it's cooling baffels. I would like your opinion on this setup. Is this effective or can it be improved . I must say that we have no problems with our VW (touch wood). she runs very cool (between 60 and 75 degrees). I dont really unnderstand what is required in sofar as cooling. Boet can you please draw on my pics to show where the air is supposed to come in and where it is supposed to exit. Why are the baffels on the top but nothing on the bottom. what is the purpose of the black plate in the front on the cooling fins. Also does it make a differnence that on the cubby the entire cylinder head sticks out into the airflow and is not hidden in the aengine cowl.
Cheers
Craig
Cheers
Craig
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justin.schoeman
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Re: Justin's Raven
OK - back from my holiday. Started out as a long weekend, but accidentally booked an extra night. Got up Wednesday morning, and it was so great, I said ---- this, and booked the rest of the week. So I spent the last week passed out on the beach or snorkelling, and no time building...
As to the lack of bottom baffles, I don't know. Everything I have read says that this is a big no-no, but perhaps the strong airflow under the cylinders creates sufficient suction that this is not required?
I hope Boet jumps in on this too, but I will try to comment from the reading I have done. Firstly, the top baffle looks great - it seems to seal very well all the way around, which is very important. The front baffle is generally used to stop the front cylinders from getting too cold - they have a LOT of cooling air hanging out in the breeze like that. Many cowled installations also end up with a small plate partially shielding the front cylinders, so keep them at more-or-less the same temps as the rears.Giarc64 wrote:Boet and Justin I am posting pics of the cubby VW with it's cooling baffels. I would like your opinion on this setup. Is this effective or can it be improved . I must say that we have no problems with our VW (touch wood). she runs very cool (between 60 and 75 degrees). I dont really unnderstand what is required in sofar as cooling. Boet can you please draw on my pics to show where the air is supposed to come in and where it is supposed to exit. Why are the baffels on the top but nothing on the bottom. what is the purpose of the black plate in the front on the cooling fins. Also does it make a differnence that on the cubby the entire cylinder head sticks out into the airflow and is not hidden in the aengine cowl.
As to the lack of bottom baffles, I don't know. Everything I have read says that this is a big no-no, but perhaps the strong airflow under the cylinders creates sufficient suction that this is not required?
Re: Justin's Raven
More than enough,Vp had the same. Just make sure the little plate between the cylinders at the bottom is in its place!
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Re: Justin's Raven
Yes I agree, the little plate at the bottom ensures that the cooling air flows AROUND the cylinder fins, instead of just straight thru the middle and out. The bottom half of the front cylinder therefore have to have a baffle plate as well. Theoretically...... for I have seen VW installations like the cubby and the red VP in the pic, give many years of trouble-free service. You decide. 
Re: Justin's Raven
Thanks Boet Justin and German for your opinions.
The volla on the cubby is very happy at this stage (touch wood). My only real concern is the belt drive. will be changing the belt every 50 hours. Hope you get the yaris convex right boet, then i will be one of your 1st customers. Clive who owns cubby zu-djz in witbank is keen on building a raven and the yaris should be very suitable for that.
Justin how is the vw engine coming along and are you having success with Barry Turner??
cheers
Craig
The volla on the cubby is very happy at this stage (touch wood). My only real concern is the belt drive. will be changing the belt every 50 hours. Hope you get the yaris convex right boet, then i will be one of your 1st customers. Clive who owns cubby zu-djz in witbank is keen on building a raven and the yaris should be very suitable for that.
Justin how is the vw engine coming along and are you having success with Barry Turner??
cheers
Craig
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justin.schoeman
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Re: Justin's Raven
Whee! Just finished fabricating my first aluminium brackets! Lots of schlepp and false starts, but done, and ready for match drilling. Hope I don't stuff them up now!
My MGL Horizon arrived, and looks really cool. Can't wait to play with it!
Most of the engine parts are ordered (R10k worth!), just looking for oversize main bearings, and new rocker feet (for some reason, 1 or 2 are galled?). Engine parts will hitch a lift in a container in 3 weeks time. A bit of a delay, but cheaper than couriering 30kg of bits and pieces...
Unfortunately, I joined the aircooledvwsa group to hunt for the parts, and accidentally bought a type 4 engine. R8500 for a brand new from the factory (30 years ago) 1800 engine. Only a few available, so I thought I would grab one for the next plane . Fit a 71mm crank, and 105mm cylinder kits, and you have a 2.5L engine that will give you 90hp continuous at 3200rpm (and unlike the type 1, you can actually keep it cool at that power level!).
My MGL Horizon arrived, and looks really cool. Can't wait to play with it!
Most of the engine parts are ordered (R10k worth!), just looking for oversize main bearings, and new rocker feet (for some reason, 1 or 2 are galled?). Engine parts will hitch a lift in a container in 3 weeks time. A bit of a delay, but cheaper than couriering 30kg of bits and pieces...
Unfortunately, I joined the aircooledvwsa group to hunt for the parts, and accidentally bought a type 4 engine. R8500 for a brand new from the factory (30 years ago) 1800 engine. Only a few available, so I thought I would grab one for the next plane
. Fit a 71mm crank, and 105mm cylinder kits, and you have a 2.5L engine that will give you 90hp continuous at 3200rpm (and unlike the type 1, you can actually keep it cool at that power level!).-
justin.schoeman
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Re: Justin's Raven
Here are the results of my efforts so far. Ran out of fine sanding pads, so still some scratches left, but will take care of them when the brackets are drilled and deburred:
Not a hell of a lot to show for 3 evenings of work, but things are going quicker as I get some practice...
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