TiggerToo
Well-Known Member
What are the advantages and disadvanatges of using pop rivets to fix things to the mast (e.g. a radar-reflector bracket?)
rivets vs self tappers
- Thread starter TiggerToo
- Start date
Csail
N/A
Advantage of rivets is they are less likely to snad or damage ropes, wires etc. and in theory wont become loose.
savageseadog
Well-Known Member
Rivets pull the workpieces very tightly together, tighter than most people can screw a screw down, drill size equals diameter of rivet, easy to get right, The Rivet is a stronger fixing, the flare of the rivet spreads the load behind the fixing. For self tapping screws, drill size is very important, too small, screw is tight, too big, weak fastening . No sharp points inside mast, less liable to corrode into place, rivets can are easy to drill out .
A better compromise would be to drill and tap for machine screws and use Duralac.
A better compromise would be to drill and tap for machine screws and use Duralac.
whipper_snapper
Well-Known Member
I recently attached a ss bracket to a mast with monel rivets and I was very disappointed to see that the work was not pulled up tight as I had expected. It was a very awkward job and I was not able to go back and do it again, and anyway I had no other rivets. It is rigid because of the brackets shape, but there is a 2-3mm space between bracket and mast. Before I riveted I could push it flush by hand. It seems the rivets did not collapse as far as they should have done. I guess that I got rivets too long, is there a guide to the size range of rivet needed for a given final thickness ?
Thanks
Thanks
oldharry
Well-Known Member
Most unusual for pop rivets not to pull in tight, as they will not 'pop' until a quite high pre-set load is applied to the mandrel. The compression load of even a small pop rivet is way above any hand pressure you can apply. Did you start from the middle and work outwards? If not, the first rivets may have pulled the bracket out of shape so that it could not conform to the mast shape. Also If the bracket is likely to have high stress or shock loading as in a rigging component, the rivets could eventually fail if the bracket can move.
Billjratt
Well-Known Member
Whatever you do, use Duralac and the best quality fixings. Our reflector and it's expensive bracket blew away last winter...mainly because deterioration wasn't being considered, even though I was up there for other jobs a few times.
castaway
Well-Known Member
I have used monel 'pop' or 'blind' rivets for mast steps and also for fitting gantry for my (big) Air-X wind generator.
I bought a Draper riviter... the pantograph type , (looks a bit like trellis work).
The mast steps i did as far as the spreaders whilst climbing up the steps as I fitted them .. but I wouldnt recommend this as its quite tricky.. the ones above the spreaders I did when the mast was down for some other work.
The mizzen gantry for the Air-X I did from a ladder but that was also not ideal.. I got a good tight result with both but would not recommend it.
The box the draper tool came in came with all the correct drill/hole sizes and rivet/material thickness guide. I bough from one of those Tool Stop shops near us that sell Draper stuff and it was'nt expensive.
I know another Halberier owner in Australia who had his mast work done by his yard rigger... he did it all with s/s bolts and tapped holes.. and that was very succesful. Personally i would think that as long as you have good access ( ie dont do as I did!) Its pretty easy to use rivets.
Only use Monel.......don't forget to use Zinc Chromate stuff.
Good luck
Nick
One last thing.. if you are planning to use a lot of rivets ..shop around as they dont 'arf tot up !
I bought a Draper riviter... the pantograph type , (looks a bit like trellis work).
The mast steps i did as far as the spreaders whilst climbing up the steps as I fitted them .. but I wouldnt recommend this as its quite tricky.. the ones above the spreaders I did when the mast was down for some other work.
The mizzen gantry for the Air-X I did from a ladder but that was also not ideal.. I got a good tight result with both but would not recommend it.
The box the draper tool came in came with all the correct drill/hole sizes and rivet/material thickness guide. I bough from one of those Tool Stop shops near us that sell Draper stuff and it was'nt expensive.
I know another Halberier owner in Australia who had his mast work done by his yard rigger... he did it all with s/s bolts and tapped holes.. and that was very succesful. Personally i would think that as long as you have good access ( ie dont do as I did!) Its pretty easy to use rivets.
Only use Monel.......don't forget to use Zinc Chromate stuff.
Good luck
Nick
One last thing.. if you are planning to use a lot of rivets ..shop around as they dont 'arf tot up !
whipper_snapper
Well-Known Member
Yes tapped holes and machine screws sound a lot 'nicer' and allows you to snug the whole thing evenly and square. I have never had problems with rivets before, but I think I will drill them out and redo at the next opportunity.
I did use duralac - it was almost liquid, not the paste I was expecting. It ran everywhere and made a right mess.
What drills/taps would I need for say M4 or M6 machine screws ? Is there a 'kit' that a novice can use ?
(Sorry to hijack your thread tiggertoo!)
I did use duralac - it was almost liquid, not the paste I was expecting. It ran everywhere and made a right mess.
What drills/taps would I need for say M4 or M6 machine screws ? Is there a 'kit' that a novice can use ?
(Sorry to hijack your thread tiggertoo!)
PuffTheMagicDragon
Well-Known Member
Next time, before you use the Duralac, 'massage' the tube gently as it does have a tendency to separate; massaging the tube helps to re-establish the consistency. Try to store the tube upside down, not flat.
Tapping drills. For Metric threads, if you subtract the pitch from the diameter and use the result as the size of drill, you will get approximately 80% of the theoretical thread. This is normally good enough for most practical purposes.
Tapping drills. For Metric threads, if you subtract the pitch from the diameter and use the result as the size of drill, you will get approximately 80% of the theoretical thread. This is normally good enough for most practical purposes.
maxi77
Well-Known Member
Our engineers look for a threaded depth equivalent to 1.5 times the diameter of the bolt so on that basis bolting things to the mast is only suitable for relatively small items. That is admitedly for aircraft standards but I would not realy trust something where the bolt was more than the thikness of the mast shell
Spuddy
Well-Known Member
If a tapped hole went into something thick or dense then it would, of course be the best option. Into relatively thin alu though.......I can't really see any advantage over self tappers since the load is spread over thread depth. I used self tappers for a VHF ariel where there is low stress but planning to put some turning blocks on the boom and will go for monel rivets so that load is spread over larger area.
savageseadog
Well-Known Member
[ QUOTE ]
I recently attached a ss bracket to a mast with monel rivets and I was very disappointed to see that the work was not pulled up tight as I had expected. It was a very awkward job and I...............
[/ QUOTE ]Can be caused by rivets that are too short or less often too long.
I recently attached a ss bracket to a mast with monel rivets and I was very disappointed to see that the work was not pulled up tight as I had expected. It was a very awkward job and I...............
[/ QUOTE ]Can be caused by rivets that are too short or less often too long.
Topcat47
Well-Known Member
If you're planning to tap holes drilled in the mast, be aware that most mast extrusions are not of uniform thickness (unlike tubes, say). I would always use monel rivits on mine, unless there was little prospect of the fitting comming under load.
JayBee
Well-Known Member
The length of the rivets should be equal to the diameter of the rivet plus the thickness of the mast section, or whatever the fitting is being riveted to and the fitting itself. It is good practice to progressively tighten rivets, a bit like tightening wheel nuts, to avoid distorting the fitting and finding gaps like the ones you describe. I have found that it is sometimes useful to make an initial fix with self tapping screws, replacing them one at a time with rivets. It also helps on a curved surface to make sure that the rivets are going into the work at right angles to the surface.
BrendanS
Well-Known Member
Great idea. Never thought of that before.
PuffTheMagicDragon
Well-Known Member
[ QUOTE ]
[ QUOTE ]
I recently attached a ss bracket to a mast with monel rivets and I was very disappointed to see that the work was not pulled up tight as I had expected. It was a very awkward job and I...............
[/ QUOTE ]Can be caused by rivets that are too short or less often too long.
[/ QUOTE ]
Can also be caused by not pushing down on the rivet head and not using a 'proper tool'. Typical situation when trying to pop monel rivets without a lazy tong type of rivetter. Almost unavoidable when rivetting something to a mast that is erect - you cannot really put your weight behind it.
To put these steps on the mast:
the only proper way - in my book - was to take the mast down. Those are 5mm monel rivets.
[ QUOTE ]
I recently attached a ss bracket to a mast with monel rivets and I was very disappointed to see that the work was not pulled up tight as I had expected. It was a very awkward job and I...............
[/ QUOTE ]Can be caused by rivets that are too short or less often too long.
[/ QUOTE ]
Can also be caused by not pushing down on the rivet head and not using a 'proper tool'. Typical situation when trying to pop monel rivets without a lazy tong type of rivetter. Almost unavoidable when rivetting something to a mast that is erect - you cannot really put your weight behind it.
To put these steps on the mast:
the only proper way - in my book - was to take the mast down. Those are 5mm monel rivets.
srp
Well-Known Member
I think you've hit the nail on the head with getting some weight behind the rivet gun - if there is a gap between the fitting and the mast when you start squeezing, the rivet can expand at the wrong point, into the gap.
Aircraft engineers use temporary fixtures called (I think) Clecos, which you insert into each hole as you drill it, making it much easier to guarantee alignment and to ensure that the fixture is seated properly on the (in this case) mast. Try someone like LAS Aero or Airworlduk.com.
Aircraft engineers use temporary fixtures called (I think) Clecos, which you insert into each hole as you drill it, making it much easier to guarantee alignment and to ensure that the fixture is seated properly on the (in this case) mast. Try someone like LAS Aero or Airworlduk.com.
PuffTheMagicDragon
Well-Known Member
I just play 'musical chairs' with extra rivets, just drop one into each hole right after you drill. When all holes are drilled (of whatever item is being fitted, e.g., each step) remove them, apply Duralac, reassemble with all the rivets in place, and then start popping. That way you ensure that alignment is maintained.
Bejasus
Well-Known Member
I drill and tap all of my mast fittings and use stainless machine screws and Duralac. However, my masts are not thin extrusions, they are heavy wall aluminium. Tried pulling a 1/4 in. monel rivet in them to mount my radar reflector. Soon gave up. Easier to go up the mast with a drill and tap.