|
||
Thread OP
|
Quote:
By 45° there is a force off 154kg on each bolt. The leadbomb is 12kg and 330mm off the kiel. My keel is strong enough to hold my bomb under 0° but is to weak when she's going flat . Stronger bolts, but this isn't easy when youre ship is complet finnished and very difficult to handle, Can't turn it over |
|
|
||
|
|
|
|
lucc,
Maybe instead of 12kg that is 330mm down, try more weight very close to the hull. Syren is only about 1.5m long and the lead keel weight is about 18kg. The keel is held on by 6.3mm threaded rods. So maybe you make a heavier keel and mount it directly to the hull? And add some weight inside the hull. That would reduce the angular force quite a bit. Another idea, maybe. Make an external mounting bracket for the lead keel, and attach it as shown in the sketch. The mounting holes would be visible when the keel is removed, but they would be small and could be disguised somehow. Best, Dan |
|
|
|
|
|
You will greatly reduce the chance of a 90deg knockdown if you reduce sail before the wind picks up. Just like the real ships, our models respond to good (micro) seamanship. Most knockdown's I have experienced (due to not reducing sail in time) have been of the 70-80deg range, not 90deg.
The wind spills off the sails as the ship heels, reducing capsize force. In this regard, reducing the lead weight would help you by letting the ship spill wind earlier. Real ships had to check ballast calculations to be sure they would heel to spill wind before the shrouds were over-stressed, btw. ----------- Another idea for supporting your keel would be to run stays from the weight up to the turn of the bilge of the hull. These could be strong, no-stretch fishing line, eg. Spectra (no stretch if pre-stretched before installation). The attachment point for the lines could be small bolts, which would not be too noticeable if painted same color as hull. This is similar to DanL's recommendation, but uses trigonometry, instead of bracket strength, to support the finkeel's weight. The weight is supported by tension, instead of compression, so the hull strength would have to be checked. Remember, the effective weight of your lead bulb is reduced by the buoyancy of the volume of the lead. This reduction can be significant for small bulbs, or pvc pipe filled with lead shot. btw, you might try the pvc-tube-with-lead-shot bulb as you experiment with your boat's sailing capabilities. You might find that, under the conditions you find at your pond, less weight down low would be perfectly acceptable. These models all sail faster than scale speeds, so the drag of the fishing line stays would likely not be too noticeable. I have stays (running from a cross spar on the end of finkeel up to the top of the finkeel) on my sinkable ships (they activate the sinking mechanism when struck by a submarine). They don't seem to slow the sailboat targets at all, or at least that's what the sub skipper (Capt. Nemo) says. And my pvc bulb finkeels are primitive: the pvc pipe is lashed to the finkeel with ordinary string. The extra drag from the string (compared to a bracket attachment) has never seemed to affect the ships |
|
Last edited by Brooks; Jun 02, 2013 at 08:31 PM.
|
|
|
|
I did a tensile strength calc. for your 6mm bolt. As you say, with regular strength steel it will likely fail at 45deg heel (need 308kg but have only 296kg in a 6mm bolt of regular steel). But high strength steel is twice as strong, and would do the job. Or, you could redesign finkeel support so that it used 2 regular strength bolts per side, with some factor of safety.
-------------- Tensile strength of regular steel = 60,000psi, or 42kg/sq mm Generally, one tries to design using factor of safety of 2, so 60ksi => 30ksi proof load, 42 => 21kg/sq mm 21kg/sq mm of steel x area of solid steel of bolt=design, or proof, strength of the bolt. So, using 4, 6mm regular strength steel bolts per side of the finkeel should work for a "proper engineering safety" support of the 45deg heel. If you can get 4 of them per side into your existing finkeel design, no stays or brackets would be needed for the 45 deg heel. ---------------------- My calc. was rough, with estimates of bolt diameter less thread depth (I guessed 50% loss of diameter due to threads). So, you'd want to calculate strength based on the true, solid steel diameter of your bolt. Incidently, people often wonder if the bolt threads will strip before the bolt breaks while under tension. With modern designed bolts, that can't happen; the bolt will break before it pulls out of the threads. Of course, you can strip threads with a wrench, but even then, often failure mode is the bolt twists apart outside the threads. There is so much surface area, within the threads, supporting the load, that the shaft of the bolt usually fails first. Hope this helps. |
|
Last edited by Brooks; Jun 02, 2013 at 08:24 PM.
|
|
|
Thread OP
|
Thanks guys to think.
There was also a second possibility, which is close to disable. 2 stainless steel wire rods 10M in a tube of inox12/10 would already give much better values. Problem was that the brass tubes of 8mm in the keel of 7cm high and is glued with epoxy got away. Today, in hope of victory, started it and it worked. pictures will follow later. language is dutch now there's 13.92 kg on each stainless wire rod, this is exaptabel. |
|
|
|
|||||
Thread OP
|
thank you Planeur.
Progress. I'm going to copy the dutch item here, it's to difficult to explain this (for me) in Englisch. The photo's are clear. René (Isola2) helpd me with de calculation and program Delftship place off the leadbomb calculated Quote:
Rod's to weak ,are going to bend calc +solution Quote:
Quote:
Best and first solution off René. DE messingbuizen eruit halen en vervangen door inoxbuizen van 12/10. Hierdoor konden er 2 inox draadstangen in van M10. Deze gingen niet meer doorbuigen waardoor de krachten op de kiel totaal anders werden. Quote:
the operation yesterday. on my back on the ground. |
||||
|
|||||
|
||
Thread OP
|
Quote:
2 questions: what is the distance between keel and ship. and the thickness off the keel from the ship ?? |
|
|
Last edited by lucc; Jun 05, 2013 at 04:36 PM.
|
|
|
||
Thread OP
|
Quote:
He's very good in this, I can ask this , but what do you need exact? |
|
|
||
|
|
|
how does one download delftship for win7....?.....i just get a lot of other sites...
|
|
|
|
|
Thread OP
|
|
|
|
|
|
|
got it...thanks....couldn't figure out the spam check thing...if i had trouble figuring out the registration, you can imagine the fun i'll have with the program itself
|
|
|
Thread Tools | |
Similar Threads | |||||
Category | Thread | Thread Starter | Forum | Replies | Last Post |
Scratch-building a 1.8m MDM-1 Fox | Joe Yap | Scale Sailplanes | 27 | Aug 30, 2023 01:37 PM | |
Build Log | Scratch-build, own-design ocean-going salvagetug 1:50 | tweety777 | Scale Boats | 36 | May 04, 2013 10:26 AM |
Discussion | The Santisima Trinidad (scratch) (1 : 50) | lucc | Scale Boats | 79 | Mar 20, 2010 12:06 PM |
Build Log | Scratch built 1:12 salmon | xx29l9 | Scale Boats | 6 | Mar 11, 2010 02:41 PM |
Sold | 50 airplanes for sale in ohio 1 lot or seperate | johnsheri | Aircraft - Fuel - Airplanes (FS/W) | 28 | Mar 04, 2010 10:09 PM |