With Christmas holidays out of the way, I had an opportunity to get back to the F-48 center hull. I had planned on leaving foam in place, but after reading Jon’s description of foam removal, I tried an idea of “melt-cutting” to remove un-needed/wanted internal foam.
This was a test, so results on first side of main hull are a bit “rough” - but I found it does work. See photos to follow along.
- Took an old Weller soldering gun and removed the solder tip. Fashioned a cutting wire out of some heavy copper wire to form a relatively flat wire. I tried coat hanger, but it didn’t heat up enough to make cuts.
2.Once tip was made, you press the trigger, and as the wire heats up, it will smoke slightly. I made a vertical “plunge” cut to depth of wire (I checked first to make sure I didn’t cut all the way through) and when reaching depth, slowly moved gun/wire toward other side. When I reached the other side I simply lifted the cutter and out popped a chunk of foam. This is simply repeated, although the wider the wire cutter, the larger foam removed and the less cuts required. Since it was done by “eye-ball” you can see in one photo the different depths - leaving a not-so-smooth interior wall. The two large pieces left is where the cross beams will mount. I will still cut an access hole for sheeting and steering connections, but most will remain for strength. Also a fin box will need to be added, a mast step, etc.
- Once the other side is done, I can fit the radio gear in proper location. I can also cut out a hatch area, but may do that after both sides are glued together and glassed.
Last photo is just a pile of the foam chunks that were removed.
Recently continued with the hollow foam trimaran.
Have got most of the major work out of the way (i hope!) Been very time consuming with the fittings and rig. The hulls were the fast and easy part.
pic1 (if I manage to attach OK) shows assembled tri - with a few bits of string holding parts together! Weighs just over 2kg as shown - just missing batteries and foils.
pic3 shows close up of main hull and rig. I decided to use a powerfull servo (probably short term) instead of a winch, and eventually got carried away with 3 hatches.
I will soon know if the wing mast will have enough floatation to prevent inverting when capsizing.
Jon
Jon,
A bit off off-subject (foam hulls)… but BEAUTIFUL SAILS!! Did you make them?
yar
Yar,
Yes, the sails are made “the old way” from draughting film with three slim battens (about 1/16" carbon rod, split in half) sticky-backed to the sail.
Instead of using eyelets for clews etc, I had been taping rings - sail1 and sail2 - but did not have any available yesterday. Instead I made my own “ring” from some fine wire - sail3 - and taped these on - sail4 and sail5.
Jon
To follow up on Yar’s comment, I have to say that the wingmast looks very nice as well.
Please fill us in on the method of construction.
Regards,
Bill K
Bill,
Those masts are quite a bit of work as you would surely know. (yours looks better finished than mine!)
Eventually, I glassed over a foam core (initially started to make a mould) See attachment.
The foam core is a very soft noodle prior to glassing, and I hung it vertically while the resin was curing. The aluminium tube was glued on after glassing, and cut (dremel). The aluminium has not been that successful.
The mast is 1700 x 85 x 21 mm (5’7" x 3.25" x 7/8") and weighs 340g. How does the weight compare to yours (and if yours is much lighter, how did you make yours?)
My next attempt at a mast will be to place directional carbon in a mould - vacuum and let set - place web and track on one side and then join trailing edges together (at this stage anyway!) See second attachment.
Any better way that you know of?
Jon
All too well, I take about 10 hours to build the entire rig (mast, boom, sail & rigging)
Mine are very similar: 68" long, 3.5" chord (base) tapering to 2.25" (tip), 3/4" thickness at base. The weight comes in between 130 & 190g, depending on weight of cloth & generosity of epoxy application.
Well, I’m not sure if its “better”, but I have been building them for my rc iceboats/landyachts for several years. I have posted “build blogs” of 2 different methods on this forum. I also plan to use them on a F-48/Mini 40 “Team Phillips” concept catamaran:
- composite glass/epoxy vacuum bagged over a foam core
http://www.rcsailing.net/forum1/showthread.php?t=3474 - balsa/pine (much simpler than the composite)
http://www.rcsailing.net/forum1/blog.php?b=17
also check out entries #11,13 & 14 for related topcs
Regards,
Bill K
http://www.iceboat.org/RCBoats/rc%20boats.htm
Bill,
Thanks for the info. I had searched for wing mast info, but had not found much.
I was sure my mast was overweight as I used expanded styrene which soaks up resin, and also hand layup, not vacuumed (= heaps of resin). I just decided to try and go sailing at this stage with a quick build.
With your weights, you have set a serious target for me!
Jon
Bill,
There are a lot of good ideas (and a couple of sneaky ones too) in that info. I had not seen the sail in the slit idea before. This means thinking of a cored mast (easier) rather than a hollow one with track. It has been the track idea that has caused me the construction problems.
Thanks again, Jon
Yeah, most of my best ideas are sorta sneaky…
You could probably just leave the track off & use the soldering iron with the sharpened tip, to burn in a slot (like I show in the composite blog.)
Actually, the balsa/pine mast is just about as light & a heck of alot simpler to build. The advantage to the composite is that you can play around with lateral mast bend which helps depower the rig in a gust. I guess you could do the same by shaving the pine leading edge. I just haven’t gotten around to trying that yet.
As far as lightness goes, it helps to taper towards the tip, as weight aloft matters alot more than lower down. The 130g mast was using a skin of only 3oz glass & proved to be too bendy. I almost broke it & ended up adding strips of CF to keep it out of the trash bin. I would say a weight of 175-200g is a reasonable range to shoot for.
Yeah, most of my best ideas are sorta sneaky…
You could probably just leave the track off & use the soldering iron with the sharpened tip, to burn in a slot (like I show in the composite blog.)
Actually, the balsa/pine mast is just about as light & a heck of alot simpler to build. The advantage to the composite is that you can play around with lateral mast bend which helps depower the rig in a gust. I guess you could do the same by shaving the pine leading edge. I haven’t gotten around to trying that yet.
As far as lightness goes, it helps to taper towards the tip, as weight aloft matters alot more than lower down. The 130g mast was using a skin of only 3oz glass & proved to be too bendy. I almost broke it & ended up adding strips of CF to keep it out of the trash bin. I would say a weight of 175-200g is a reasonable range to shoot for.