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๐ฌ Slowly does it.
9 years ago by ๐ฉ๐ช RNinMunich (
Fleet Admiral)โง 19 Views ยท 2 Likes
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That's what it's apparently generally come to mean ๐
What you describe is a Cardan Shaft or double Cardan joint! ▲
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hermank
fid2b
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Remove Ads ๐ฌ Slowly does it.
9 years ago by ๐ฌ๐ง fid2b (
Petty Officer 2nd Class)โง 19 Views ยท 1 Like
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That's interesting, didn't know that! Always thought it only became a cardan when a short shaft had a UJ at each end to to change the drive plane. Live and learn!๐
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hermank
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๐ฌ Slowly does it.
9 years ago by ๐ฉ๐ช RNinMunich (
Fleet Admiral)โง 19 Views ยท 1 Like
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Hi,
Strictly speaking the UJ is a Cardan link! Named after Jerome Cardan (Geronimo Cardano) โ 1576 italian mathematician, its inventor. ๐ Whatever! fid - if it feels good - do it! Main thing is to enjoy what you are doing. ๐ We all just wanted to help you avoid disappointment with the performance.๐ญ Greetings also to Zdenek in Prague. He knows what he's doing folks! Check out some of the magnificent ships he has built - here http://www.inkoust.estranky.cz ๐๐๐ Cheers Doug ๐ ▲
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hermank
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๐ฌ Slowly does it.
9 years ago by ๐ฌ๐ง fid2b (
Petty Officer 2nd Class)โง 19 Views ยท 1 Like
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All getting involved now! I suspect it looks worse in the pictures because the prop thrust will definitely pass over the rudder although perhaps not ideally. And I don't have a cardan shaft, just a uj because as I said, simple appealled for a part time hobby as this is to me. My aim was to see if I could form the wooden hull like my Dad did on the fireboat cos I always admired the shape but of course I would like to finish the job eventually ๐
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hermank
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๐ฌ Slowly does it.
9 years ago by ๐ฌ๐ง fid2b (
Petty Officer 2nd Class)โง 19 Views ยท 1 Like
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Ah well, thanks for that! I think you and Sonar are quite right, and no doubt better qualified to comment. Certainly the motor could be lower but I hesitated about moving it forward because of the weight distribution which I thought would be better at least halfway or more aft. As for prop sizes, again I am largely guessing what might work, on the fireboat I have a fifty mm z two blade which seems to work well without the motor getting hot but that has a slower, torquey motor, so smaller will probably be appropriate with the 750s. in truth I'll leave it as it is until I can trial it, probably a few years away, and if it is a disaster then I can still change it then๐
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hermank
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๐ฌ Slowly does it.
9 years ago by ๐ฉ๐ช RNinMunich (
Fleet Admiral)โง 21 Views ยท 3 Likes
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I would say you've achieved your main objective magnificently ๐ The hull is looking really good.
But the shaft angle is maybe 3 times the optimum, based on looking at my Aerokits Sea Scout layout and Sonar's advice! Looks like there is plenty of scope in the hull to mount the motor further forward and much deeper and still be able to fit a pretty large prop. But bigger isn't always better! Not really my expertise but would guess with 50mm you risk overloading the motor!? I'm sure the experts here can advise you better on that than I. You may also find the boat more responsive to the rudder if the prop thrust is directed at the rudder instead of more below it as it seems to be now? Cheers Doug ๐ ▲
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hermank
Inkoust
cenbeth
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๐ฌ Slowly does it.
9 years ago by ๐ฌ๐ง fid2b (
Petty Officer 2nd Class)โง 19 Views ยท 1 Like
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Mines a bit more than that! in all truth I am no a boat designer so I just look at things in a practical way and while I absolutely agree with what you are saying I also know the old fireboat works ok for me. The other thing I wonder is with a short, light at the bow boat and all the weight aft of the centre could the prop thrust tend to lift the whole boat as much as push the front down? Like I say, just thinking aloud rather than speaking from experience!
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hermank
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๐ฌ Slowly does it.
9 years ago by ๐น๐ณ none (
Chief Petty Officer 1st Class)โง 19 Views ยท 1 Like
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lower the motor mounting as close as you can to the bottom of the hull making sure the propellor does not touch the underside of the external hull if this makes sense
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hermank
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๐ฌ Slowly does it.
9 years ago by ๐น๐ณ none (
Chief Petty Officer 1st Class)โง 19 Views ยท 1 Like
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Or as close as possible depending on the shape of the hull
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hermank
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๐ฌ Slowly does it.
9 years ago by ๐น๐ณ none (
Chief Petty Officer 1st Class)โง 19 Views ยท 1 Like
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should be 8 to 10 degrees.
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hermank
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๐ฌ Slowly does it.
9 years ago by ๐ฌ๐ง fid2b (
Petty Officer 2nd Class)โง 19 Views ยท 1 Like
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I would tend to agree! The more it pushes forward the better of course. But I largely copied my 36" fireboat and to get the prop dia options up to about 50mm it needs quite a angle. I didn't want to complicate the drive line either as my main interest was in forming the hull, just to see if I could really. I suppose the proof will be in the sailing!
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hermank
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๐ฌ Slowly does it.
9 years ago by ๐ฉ๐ช RNinMunich (
Fleet Admiral)โง 20 Views ยท 2 Likes
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Hi, Prop shaft seems, to my eyes, to be at a very steep angle!
Would have thought it reduces forward thrust and / or tends to push the bow down. is this normal for this type of boat? Maybe I'm just more used to displacement hulls, destroyers etc. Cheers Doug ๐ ▲
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hermank
cenbeth
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๐ฌ I have done something, honest...
10 years ago by ๐ฌ๐ง fid2b (
Petty Officer 2nd Class)โง 19 Views ยท 1 Like
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HI thanks for the advice, I have been keeping it clamped down during any work and I agree totally, as the skins go on the risk gets worse! My double skins are going to be one on the outside and doublers between the bulkheads on the inside so should avoid some tension issues there. I am happy to see it coming together though!
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hermank
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๐ฌ I have done something, honest...
10 years ago by ๐ฌ๐ง Dave M (
Vice Admiral)โง 19 Views ยท 1 Like
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Your build is progressing well. You really do need to attach the formers to a solid base or you run the risk of the hull distorting as you apply the side sheets. A length of 5/8 mdf would suffice with small uprights nailed to each former.
The 1/32 wood will be fine and even stronger if you use two skins. You will really need to support the hull if you are double skinning at least until the glue has fully cured - 24hrs at least. Looking forward to seeing how you progress dave ▲
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hermank
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๐ฌ Merry Christmas
10 years ago by ๐ฌ๐ง Deswelham (
Petty Officer 1st Class)โง 19 Views ยท 1 Like
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God idea about using thinner strips and laminating
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hermank
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๐ฌ First steps
10 years ago by ๐ฌ๐ง fid2b (
Petty Officer 2nd Class)โง 19 Views ยท 1 Like
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Slowest reply ever? Sorry,just noticed this, perhaps by now you have the order?
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hermank
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๐ฌ First steps
11 years ago by ๐ฌ๐ง Pav403 (
Petty Officer 1st Class)โง 19 Views ยท 1 Like
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Good luck with the build, hopfully when my kids are old enough I'll get a simlar order for an all singing / dancing super destroyer ๐
Regards Dave ▲
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hermank
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๐ฌ MTGMB
10 years ago by ๐ฌ๐ง DodgyGeezer (
Sub-Lieutenant)โง 19 Views ยท 1 Like
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"...designed for an 8 year old to be able to make themselves..."
(so long as an adult cuts out the parts...) ▲
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hermank
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Remove Ads ๐ฌ MTGMB
10 years ago by ๐ฌ๐ง DodgyGeezer (
Sub-Lieutenant)โง 19 Views ยท 1 Like
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In that case you may be interested in this site, which has free plans for a 20" PT boat. The good things about it are:
1 - it's simple to make, designed for an 8 year old to be able to make themselves 2 - it's designed to be made in a bedroom, with few tools and little disturbance 3 - it's cheap, materials about ยฃ5 4 - it's realistic, so it will look good on the shelf 5 - it's fast, with lots of guns.... ▲
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hermank
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๐ฌ MTGMB
10 years ago by ๐ฌ๐ง fid2b (
Petty Officer 2nd Class)โง 19 Views ยท 1 Like
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I've no doubt he'd love it! if it goes bang, explodes or otherwise creates mayhem it's good for him...
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hermank
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๐ฌ MTGMB
10 years ago by ๐ฌ๐ง DodgyGeezer (
Sub-Lieutenant)โง 19 Views ยท 1 Like
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He probably wants an 80ft Elco American PT boat.
They had several machine guns, several cannon, torpedoes, depth charges and missiles. Also, occasionally, anti-tank guns and mortars... ▲
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hermank
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