Hydrofoil thoughts ???????
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Category: General Forums
Forum Name: The Boat Shed
Forum Description: Discuss all things boating.
URL: https://www.fishing.net.nz/forum/forum_posts.asp?TID=81559
Printed Date: 29 Jan 2026 at 11:55pm
Topic: Hydrofoil thoughts ???????
Posted By: mowerman
Subject: Hydrofoil thoughts ???????
Date Posted: 17 Aug 2012 at 11:45pm
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Do hydrofoils work? ,no doubt this subject has been raised before . The boat is a 620 aly hardtop with a honda 115/4 stroke.In at my local boat shop who suggested they are worth while fitting..The boat is well balanced ( 90 litres ) fuel under front bunks ,In the past they were in the stern of the boat but it made stern heavy with the honda motor being fairly weighty. No issues with hole shot but a little porpoising at higher speed with dosnt seem to trim out. The motor appears to be set correctly in its depth Whats the thoughts on fitting one..good move ,bad move and waist of time and money ? ..just dont want to drill holes if nothings achieved ..One thought I had is it would be a hell of a job freeing any line that gets wrapped around the prop
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Replies:
Posted By: Bounty Hunter
Date Posted: 18 Aug 2012 at 9:04am
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porpoising is a sign that the fore/aft balance of the boat is wrong. is it still apparent when you are light on fuel? my guess is that moving the tanks that far forward probably wasnt a great idea. a good boat design will have as much of the weight centered as possible, same as cars, bikes, etc. ------------- No disintegrations! |
Posted By: johnybegood
Date Posted: 18 Aug 2012 at 9:17am
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I got one last year, worked great. Did some digging and Burnsco brought it in, it's completely drill-less so and comes off in 5 mins... http://www.stingrayhydrofoils.com/stingray-xr-iii/" rel="nofollow - http://www.stingrayhydrofoils.com/stingray-xr-iii/ ------------- I just want to jig |
Posted By: mowerman
Date Posted: 18 Aug 2012 at 9:17am
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It still was porpoising when fuel tank aft.. The amount of porpoising isnt bad by any means ,just annoying ( flat water going at speed ) Trimming the motor does help a little but that impedes overall performance .. Fuel tanks aft it was far to stern heavy with bow well out on getting up on the plain,also walking up hill all day was a pain in the ass. The overall balance now is fairly well spot on . This week adding an extra battery aft.Have experimented moving weight around but it dosnt go away
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Posted By: M.I.L.F
Date Posted: 18 Aug 2012 at 10:45am
hi guys i had a similar problem then i bought the stingray 300se had my concerns that it was just a flash fin until i tried it out and man what a difference it made got on to the plane faster, lower revs it does work  ------------- KING SMURFIX |
Posted By: Kings Marine
Date Posted: 18 Aug 2012 at 2:10pm
Porpoising is caused by bad hull shape and nothing else, i see a lot of alloy hulls that have poor hull designs or hulls that have warped out of shape. fitting a hydrofoil can help with the hull issue, but will never cure it totally ------------- The Mighty Waikato http://www.facebook.com/pages/Kings-Marine/100476476662857?%3Fref=ts |
mowerman wrote:Posted By: Blue Asparagus
Date Posted: 18 Aug 2012 at 6:18pm
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I used a perma trim I guess it is the same thing, made a huge difference to the boat at rest and under power and helped in a following sea when trimmed right. ------------- Ultimate GAME Fishing Adventures. Northland |
Posted By: family affair
Date Posted: 19 Aug 2012 at 5:54pm
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had then on all my boats made massive difference on my glass boats but didn't do **** to the surtees ------------- mv maui |
Posted By: Denny Boy
Date Posted: 20 Aug 2012 at 3:59pm
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Posted By: Catchelot
Date Posted: 20 Aug 2012 at 5:24pm
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Had Permatrims on most of my boats, made a huge difference to take off without wheelstanding so to speak and could plane at slower revs, much better ride in a following sea going up and over and down the swells without continuously working the throttle. Yep do recommend them IF your boat needs them, helps with boats that porpoise too.
------------- "The sea, once it casts its spell, holds one in its net of wonder forever." - Jacques Cousteau |
Posted By: family affair
Date Posted: 20 Aug 2012 at 6:06pm
------------- mv maui |
Posted By: Lethal
Date Posted: 20 Aug 2012 at 7:19pm
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yep get yourself a permatrim, means bolting it on but then no-ones about to flog it in a hurry... they make different sizes and colours for different boats and outboards.. if your getting knocked around in a head on sea you can push the sea open as well but just make sure your hull is strong enough to take the weight it can apply to your hull if used this way... but like others have said it gets you outa the hole reel smart and stabilizes your boat when trimmed right in a running sea... ------------- Thanks for everything you did for us Eric. may you rest in peace, You were one of the real legends of NZ recreational fishing |
Posted By: Denny Boy
Date Posted: 21 Aug 2012 at 8:47am
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Posted By: Raptor 650
Date Posted: 12 Nov 2012 at 3:22pm
| Have just has a permatrim fitted to my rig and has made the world of difference,, Set up is a Extreme Game King 650 with a 200hp 4 stroke Suzuki on the back. The main issues I had were despite adding weight ( via some lead bricks) to the anchor well and putting on larger trim tabs the boat never really like going at trolling speed of 7 knots without having its ass right down in the water and had a tendency to porpoise at speeds between 18-25 knots unless fully trimmed and tabs down. ( interestingly the porpoising issue used to settle down when over 28 knots) The permatrim has completely sorted these issues out as well as making the hole shot almost instant and can now hold the plane at 16-17 knots heading into sloppy seas or a steep sharp 15-20 knot westerly chop without the pounding it used to have in these situations.Wish I had done it earlier. |
Posted By: Apex Predator
Date Posted: 12 Nov 2012 at 5:29pm
| I wouldn't keep lead bricks anywhere on an aluminium boat as it will quickly corrode the alloy. I imagine in the anchor well with all the seawater that comes in with the warp it would happen faster still. |
Posted By: Tipper
Date Posted: 12 Nov 2012 at 5:42pm
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remember all foils increase drag if they provide lift, basic hydrodynamics. Your fuel bill will go up for the same boat speed. Aeroplanes with fatter wings take off sooner, and land at slower airspeeds, but overall speed and efficiency is compromised. ------------- Please make sure you have the full 'witty' Plug-In installed on your Internet Browser, or the default 'half-witty' output may affect your profile |
Posted By: Raptor 650
Date Posted: 12 Nov 2012 at 8:52pm
Cheers mate I did think of that and had the lead in some thick plastic bags but now going back to the scrap metal yard
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Posted By: Raptor 650
Date Posted: 12 Nov 2012 at 8:59pm
In fact the fuel efficiency at normal cruising speed of 20-30 knots hasnt changed according to the gauges and still 1.1-1.2 liters per nm and is better at the 15-18 kn range as the hull is planing at a more efficient angle.Dont know about top speed as 45 kn is too fast for my liking and sucks the juice big time.
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Posted By: feeder
Date Posted: 12 Nov 2012 at 9:35pm
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Interesting about fuel consumption, I go on a regular basis to spot X, prior to fitting a permatrim would use bang on 20ltrs, now 18.5, that's gas put in, not by gauge. Cheers ------------- The only bar to frequent is the Kawhia Bar |
Posted By: worksux
Date Posted: 13 Nov 2012 at 7:42am
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I put a se 300 on my f115. For some reason it would make my 6m HT lay over, almost as if the hydrofoil was working as a wing. It certainly would get the boat on plane quicker and kept it there longer, Fuel wise I didn't think it was any better quiet possibly from the drag the hydrofoil caused. I have taken it of the boat now and any laying over issues have gone. ------------- http://www.legasea.co.nz" rel="nofollow"> 
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Posted By: Captn Phil
Date Posted: 13 Nov 2012 at 8:10am
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I've just been through the excercise and ended up fitting a permatrim to Reel Life. The results are quite interesting. The boat definitely moves onto the plane easier and rides way more level with a bunch of blokes or weight in the back. Both into a sea and in a following sea the boat is a lot more stable. It is definitely more trim sensative and more inclined to cavitate when trimmed up a little. Lowering the engine by one hole got rid of the cavitation but was a backwards move for the handling and ride. I have not noticed and difference in fuel useage. Line wrapped around the prop is an issue as its no longer possible to clear from the boat. I also wonder about the extra drag created by the plate and the strain on the transom from the extra leverage. Reel Life is a White Pointer and IMO one of the best handling alloy boats made, it was always going to be difficult to improve such an excellent boat, Being an open water charter boat my application and requirements are fairly extreme but the overall result is better than I expected. Would I buy another Permatrim? - yes. The Permatrim people are awesome to deal with. They went out of their way to help me. The product works without doubt and for the money its an excellent addition for any boat. ------------- Taking sportfishing charters to the next level. Blue Water Adventures Ltd Whangaroa / Bay of Islands |
Posted By: CanadianJohn
Date Posted: 13 Nov 2012 at 9:21am
| worksux, theres a bit about this on the net. the hydrofoil acts as a planing surface and raises the boat up enough that you can lose stabilty. with not enough of the hull in the water it flops side to side (chine walks?). can be a safety issues from accounts and not an improvement for all boats. |
Posted By: Fogdog
Date Posted: 13 Nov 2012 at 2:33pm
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Hey Mowerman I have a Buccaneer 735 - F225 that I just cant get the right prop to do what I want - Low speed cruise, hold up in rough head sea, so am planning on putting a permatrim on...will let you know how it all stacks up. not the same problems as you however it is going to be interesting to see how it works on a big rig ------------- www.fogdog.co.nz - Just Add Beer |
Posted By: treedoc
Date Posted: 14 Nov 2012 at 11:00am
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I have also just fitted a permatrim, onto a 6m Atomix glass hardtop with an optimax 150. When trimmed out on glassy water it would porpoise a little, and I wanted to bring my planing speed down in the rough. I had lifted the motor prior to fitting the permatrim, which improved the porporsing, and the cav plate was running at waterlevel on the plane. I was advised to fit the permatrim under the cav plate, and on the first run the first thing I noticed was that it steered true at low speed away from the ramp, with no wandering. I trimmed right down to get onto the plane, but once on the plane the boat leaned to the right slightly, when trimmed down. Once trimmed out correctly the lean dissapeared. The boat certainly held the plane longer before falling off, which was what i wanted, but the motor had a terrible vibration, like a metal on metal sound. I had used a sealant so not sure where it actually came from, I presume the cav plate/permatrim. I lifted the motor another hole and the difference was substantial. The vibration has gone and the boat no longer leans over when trimmed down. It actually looks too high on the boat, but the permatrim is running just above waterlevel on the plane. We went to white island on friday, there was about 15-20kts on the way out and 15kts on the return. There is a definite ideal trim range, too far out and it cavitates, but the ride and handling was an improvement over pre-permatrim days. I am still making up my mind, havent been able to get out since, but initial thoughts are positive, and the permatrim guys have been really helpful. They said if it didnt work out they would refund the purchase price, even after I drilled holes in it, cant ask for more than that. |
Posted By: Catchit
Date Posted: 14 Nov 2012 at 1:05pm
When permatrim first came onto the market, one of the selling points was increased fuel economy. You get up to plane/speed at lower revs, so I suppose.... Had them on all my boats, great things.. ------------- "We gave Sir Peter a knighthood," Mr Key said, "And if we could give him a second one, we would." |
Posted By: Fogdog
Date Posted: 14 Nov 2012 at 1:42pm
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Interesting on height mate Im (when I can get around to it) going to run it with the normal height and see how it it goes. Sneaky feeling I may have to go up one hole..the 735 does have a sort of pod stern. front of skeg is actually 300mm away from hull when trimmed in and around 400mm away from hull when in normal trim. the cav plate is also 70mm above keel.. the yammys doent like to run as high as the mercs! ------------- www.fogdog.co.nz - Just Add Beer |
Posted By: Big -Dave
Date Posted: 17 Nov 2012 at 1:55pm
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Its a whole balancing act of right props, right height, right ability to drive and trim as the conditions dictate. I put a permatrim on my 130hp Honda powered Figlass viscount, it made a difference on the low speed planing and holeshot, plus the ability to hold the nose down in crappy weather and punch through the chop. the addition of a mercury vengeance prop improved things even more. An interesting thing is I am now running the motor nearly 2 holes higher, the cavitation plate is way above the keel line, but I am not getting any cavitation anymore. Am toying with trim tabs for those times when I have a heavy load on board, or when it decides it wants to lean in to the wind and the windward side of the boat wants to slap on the chop. |
Posted By: 2Hulls
Date Posted: 26 Apr 2013 at 8:20am
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I just read this great thread because I was thinking of a hydrofoil for my 4.1 30hp tinny. It is my first boat and I don't think there is anything wrong with the boat but then what would I know. There is a sale on and you can get a plastic hydrofoil for $30, should I get one or put the money into something else. Thanks heaps ------------- I think it is just disgusting how everyone has treated Lance Armstrong, especially after what he achieved wining races while competing on drugs. When I was on drugs, I couldn't even find my bike. |
Posted By: pjc
Date Posted: 26 Apr 2013 at 9:06am
| depends on who you talk too,my outboard shop said yes they work but as they try to lift the stern up they also put pressure on outboard steering,bearing in shaft after about 1yr depending on amount of use,when told me $1200.for shaft bearings they came off real quick,but that is only 1 shops opinion |
Posted By: Moki Marko
Date Posted: 26 Apr 2013 at 5:17pm
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Denny Boy mentioned 'lack of power', I think that in mowerman's situation this could be the case - a 115 isn't a very big motor for a 620 hardtop. A permatrim could help mask a few symptoms, but a V6 engine turning a bigger prop would be the cure. |
Posted By: Catchelot
Date Posted: 26 Apr 2013 at 5:31pm
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I think the Big Fuel Saving factor was due to the fact that you could plane slower so less revs and less fuel sip... other wise yes quicker onto plane and staying power...in both sea states. Know what you mean by is it overloading the leg Mr T but I have not heard of any issues of breaking/bending/stressing... Had them on our family boats and highly recommend, used to work for a firm that fitted some to big Volvo stern legs too and again no probs reported, they all loved the performance with better hole shot and stability at slower speeds if you wanted to cruise. I really think a lot of tinnies with heavy four strokes on them will perform far better with these or similar aerolon fins... ------------- "The sea, once it casts its spell, holds one in its net of wonder forever." - Jacques Cousteau |