Presuming Ed
Super Anarchist
Centre of gravity.
Southampton Solent Model Yacht Contest
- Thread starter willp14335
- Start date
LeoV
Super Anarchist
NIce work building that mainsail, did you build the jib too ? Seems a bit flattish, but heck what do I know, I am no model sailor.
Start looked hectic, all 40 boats had to start at once ? Nice.
Oh, and hide a small ham in the Spanish model as a price.
Can you excess old students scripts, the Magnan one was influential for offshore work. At least thats the talk.
Start looked hectic, all 40 boats had to start at once ? Nice.
Oh, and hide a small ham in the Spanish model as a price.
Can you excess old students scripts, the Magnan one was influential for offshore work. At least thats the talk.
willp14335
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- Thread starter
- #23
I was going to share that CG picture this morning. The ballast ratio is 70 percent which is what gave it that stability. The wing structure was designed in 3D and the sections were taken using the Orca section command and then lightening and alignment holes were drawn in Acad. The wing uses 42 total basswood laser cut frames and 5 meters of 2mm diameter paltruded CF rods and one 88 cm length of 7mm od 6mm id carbon tubing for the mast. The total wing height is 1.25 meters and all the structure weighed only 75 grams, which is lighter than some of the masts used in the rest of the fleet. When I did the weight study the CG came out as 22 cm below the DWL. Ironically enough, because of this my light air boat actually reaches her sweet spot above her designed maximum wind speed.
For the skin I used saran wrap from Poundland which cost £1. Then I shrunk it using the radiator in my room to get a tight smooth finish and coated it in parcel tape which also cost £1. I found it quite amusing that my instructors couldn't believe that was what I used for the skin!
I added some pictures of the wing construction below. It took me 5 days to glue together and 2 to put the skin on. As a side note, you can see in one of the pictures my first attempt to put a skin on. It turns out the technique from a popsicle stick boat I built 2 years ago worked better than the more advanced shrink wrap I bought specifically for the job in this project.
I built the wing in 4 pieces to make it easier to build and then assembled the four pieces together in the final stage. The top 37 cm was designed in 3D to telescopically connect with the bottom 88 cm so it can be reefed.
The bottom picture is of my friend Harris and I putting the rig on. It was blowing hard and I needed some help to keep it from flying off while tying the stays down tight.
For the skin I used saran wrap from Poundland which cost £1. Then I shrunk it using the radiator in my room to get a tight smooth finish and coated it in parcel tape which also cost £1. I found it quite amusing that my instructors couldn't believe that was what I used for the skin!
I added some pictures of the wing construction below. It took me 5 days to glue together and 2 to put the skin on. As a side note, you can see in one of the pictures my first attempt to put a skin on. It turns out the technique from a popsicle stick boat I built 2 years ago worked better than the more advanced shrink wrap I bought specifically for the job in this project.
I built the wing in 4 pieces to make it easier to build and then assembled the four pieces together in the final stage. The top 37 cm was designed in 3D to telescopically connect with the bottom 88 cm so it can be reefed.
The bottom picture is of my friend Harris and I putting the rig on. It was blowing hard and I needed some help to keep it from flying off while tying the stays down tight.
willp14335
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- Thread starter
- #24
Here's some more photos of the wing skinning process. Race day ended up being completely different weather than any of my tests and was also in a different pond. The one I tested in was so shallow I had to go in the water after my boat when she got tangled in the weeds.
The actual races did not start with all 40 boats, each race had 13 boats (on may 13th as well). The starts were still chaotic though, in my second race I placed poorly after getting entangled with another boat and in the race after that I was T-boned 3 times and got my rig clothes-lined by a much bigger boat. My hull was the third smallest in the fleet, I thought the boat was about to sink!
I can't figure out how to add video footage here, the files are all too big. Has anyone got any suggestions?
The actual races did not start with all 40 boats, each race had 13 boats (on may 13th as well). The starts were still chaotic though, in my second race I placed poorly after getting entangled with another boat and in the race after that I was T-boned 3 times and got my rig clothes-lined by a much bigger boat. My hull was the third smallest in the fleet, I thought the boat was about to sink!
I can't figure out how to add video footage here, the files are all too big. Has anyone got any suggestions?
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Presuming Ed
Super Anarchist
Upload to YouTube, & C&P the URL.
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willp14335
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- #26
Thanks.
Here are the videos. The wind was not strong enough to rustle the trees in these tests, probably only about 2-3 knots max.
Here are the videos. The wind was not strong enough to rustle the trees in these tests, probably only about 2-3 knots max.
Panoramix
Super Anarchist
That's really cool, I want to be 20 years old again!!!
sculpin
Super Anarchist
Nice!
willp14335
Member
- Thread starter
- #30
I suppose to try and order this a little bit I'll put up build photos in the order I built stuff on the boat, so here are some from the plug construction.
The plug was made from 12mm sheets of polyurethane foam cut out into the hull buttock shapes and bonded together with hot glue. The plug has a 3mm particle board backing plate on the top and along the center-line for extra support. After fairing the foam, a blue automotive vinyl wrap was put on the outside to make the surface smoother.
I'm not allowed to post my hull lines but I can post these pictures of my hull model which were never submitted to the university.
The plug was made from 12mm sheets of polyurethane foam cut out into the hull buttock shapes and bonded together with hot glue. The plug has a 3mm particle board backing plate on the top and along the center-line for extra support. After fairing the foam, a blue automotive vinyl wrap was put on the outside to make the surface smoother.
I'm not allowed to post my hull lines but I can post these pictures of my hull model which were never submitted to the university.
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Bob Perry
Super Anarchist
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This is going to be an exciting ride. Here's young Will working in my office on a hand drawn set of lines. I thought he should get a feel for how the old guys did hull shapes before turning him loose on the computer. Will is a quick learner.
Will was 16 years old when he produced this design. It took him about two days to master acad. It went from."Here's how you do that Will." To "How the hell did you do that Will?"
Will was 16 years old when he produced this design. It took him about two days to master acad. It went from."Here's how you do that Will." To "How the hell did you do that Will?"
willp14335
Member
- Thread starter
- #32
I still love that drawing. I've got the sailplan tacked on my dorm my wall at uni.
willp14335
Member
- Thread starter
- #35
The rule was such that all your boat parameters have to equal 70 or below when input into the rule. For greater length you get a lower ballast ratio and SA/D, for shorter you get a higher ballast ratio and SA/D. The rule also dictates a minimum displacement with my boat being one of the lightest with 2.020 kg displacement and a LOA of 70cm. The heaviest boats were around 2.9 kilos (such as the 86 cm boat that hit mine and almost pulled my rig down.)
I was very worried about stability with a wing so I picked a SA/D ratio from from my model yacht I have back at home (a Northwind 36-600 with a lot of mods) and went down near the small end of the rule to get a ballast ratio of 69%. As it turned out, the wing ended up being feather light and the boat was a lot more stable than I expected. Because of this it could sail with full sail up when a lot of the other boats were getting overpowered in the first race which was in about 12-14 knots of wind. Unfortunately, in the later races the wind tapered off and I had more trouble passing other boats and so ended up getting in a lot of collisions at the start.
The boats have massive amounts of power so if I was to do this again I'd build a boat that is longer with a higher prismatic coefficient, flatter buttock run aft (with an immersed transom, more bow knuckle above the waterline and slightly wider beam to make it more surfboard like. I'd also max out the sail area allowed under the rule to drive this hull faster. The other wing sail boat in the race was a scow with these qualities and sailed very well. (Pic came from the Solent Facebook page)
I was very worried about stability with a wing so I picked a SA/D ratio from from my model yacht I have back at home (a Northwind 36-600 with a lot of mods) and went down near the small end of the rule to get a ballast ratio of 69%. As it turned out, the wing ended up being feather light and the boat was a lot more stable than I expected. Because of this it could sail with full sail up when a lot of the other boats were getting overpowered in the first race which was in about 12-14 knots of wind. Unfortunately, in the later races the wind tapered off and I had more trouble passing other boats and so ended up getting in a lot of collisions at the start.
The boats have massive amounts of power so if I was to do this again I'd build a boat that is longer with a higher prismatic coefficient, flatter buttock run aft (with an immersed transom, more bow knuckle above the waterline and slightly wider beam to make it more surfboard like. I'd also max out the sail area allowed under the rule to drive this hull faster. The other wing sail boat in the race was a scow with these qualities and sailed very well. (Pic came from the Solent Facebook page)
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JMOD
Super Anarchist
very cool! and forget about my previous comment. It was my first thought that sprung to mind.
Cool stuff!
Cool stuff!
willp14335
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- Thread starter
- #37
That's fine, I welcome criticism. It's the only way to get better.
mad
Super Anarchist
willp14335
Member
- Thread starter
- #39
Thank you for all the compliments.
After building the plug I laminated the hull over the plug (so it became a male mould) using 3 layers of 100 GSM e-glass woven roving set in Ampreg 22 resin by Gurit. I was worried this would be too light at first as the rest of the class was using two layers 165 GSM (Or building out of wood/other materials). I has 3 m2 of the fabric for another project that hadn't gotten built yet so I used some of it for this boat. When the hull was released from the mould it was very thin and fairly flexible but luckily not too weak. The entire hull ended up weighing just over 200 grams.
After the resin cured I added nine coats of filler primer, sanding between every three and faired until the hull reflected light. The fairing was part of the reason it took me 180 hours to build the boat when the whole project including the design was supposed to take 100. Most people did not bother fairing their hulls that smooth but I thought it was worth it.
After building the plug I laminated the hull over the plug (so it became a male mould) using 3 layers of 100 GSM e-glass woven roving set in Ampreg 22 resin by Gurit. I was worried this would be too light at first as the rest of the class was using two layers 165 GSM (Or building out of wood/other materials). I has 3 m2 of the fabric for another project that hadn't gotten built yet so I used some of it for this boat. When the hull was released from the mould it was very thin and fairly flexible but luckily not too weak. The entire hull ended up weighing just over 200 grams.
After the resin cured I added nine coats of filler primer, sanding between every three and faired until the hull reflected light. The fairing was part of the reason it took me 180 hours to build the boat when the whole project including the design was supposed to take 100. Most people did not bother fairing their hulls that smooth but I thought it was worth it.
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sledracr
Super Anarchist
this is awesome. Can't wait for the next chapter!
