Trim Tabs

[Crikey]

I'm thinking of doing a winter mod of putting smart tabs (Nauticus SX type) on the stern of my for a winter mod project. Has anybody explored this subject already?

[Ixneigh]

Im always ready to ignore rogers 40 years design expertise and trollop along my merry way with alterations to the bottom of the boat...however the only ways i could see to improve powering is to keep the boat as light as possible. Mine already runs bow down. What do you hope to gain from these trim tabs?

Ixneigh

[Highlander]

Yep . I was checking them out two yrs ago but that was the smaller model , interesting but pondered on the Idea that they maybe slow the boat down while sailing unless they were disconnected & raised & that might be a pita
Also thought of installing an eng, set back or highjack plate say 12-14" I installed one on my it was a 10" set back with a trim plate attached on the bottom if I done that on my it would solve the problem of me having to raise the seat in order to raise the eng. all the way out of the water while sailing & give me alot more room when going through the eng well !!
Maybe I'll have a look @ them again this winter when I go to the big TO Boat Show in Jan /2012 , I usually go twice & meet up with Beene & Rocky u are more than welcome to join us, of coarse being the new guy u'd get to buy the first & last round of beers, we toss a coin to see who pays for the dinner , I always supply the Looney & have yet too lose !

J

[Crikey]

I go to the big TO Boat Show in Jan /2012 , I usually go twice & meet up with Beene & Rocky u are more than welcome to join us, of coarse being the new guy u'd get to buy the first & last round of beers, we toss a coin to see who pays for the dinner , I always supply the Looney & have yet too lose !

J

Ha! Let's try for that - might have to ditch the admiral though, and I'll bring my double sided Loonie.

I got my ideas about the Smart Tabs when I saw them on the shelf at the Dowsars Macgregor dealer. They are well priced, adjustable and won't corrode. The Nauticus home site lays out the benefits to any planing hull (Macgregor?) pretty well and the SX model uses small ribs which should enhance pointing under power somewhat. There is also an optional attachment bracket that can raise them level when under sail if drag proves problematic - which I doubt would be too severe because of the automatic gas strut design. There is a lot of attachment/adjustment tuning configurations that got me wondering in the first place whether anyone had boldly gone there before ( )
The fore/aft loading of the Mac is a fairly elusive thing especially with other passengers on board and the Admiral in the galley mixing up a fresh cooba. Different points of sail also benefit from different loadings, and perhaps the 'automatic' movement of the tabs could help in that regard as well.
Another thought I had was that tabs (in a small way) effectively extend the length of the hull, and hence its hull speed, without adding extra mass structure.

Could be just another 'north of the border' looney tunes though, but I'm hoping it will complement my outboard foil as well - which I really like. If I'm wrong I could probably pawn them off to some dedicated stinkboater, and cut my losses.

This is a think tank - climb on in guys.

Ross

[Highlander]

Ross

Looks like the mod # to go for would be the SX10512-70 is that the one u were thinking of using !

[aya16]

Tabs will plow the bow more, or do nothing if adjusted all the way up. Like what was said already, the bow already rides a tad low at most speeds.
when you plane you want the bow up some, with the bow now riding even lower than before with the tabs, your going to put your boat in a potential dangerous situation at speeds. Even the power trim on my 115hp will not lift the bow much, so I wouldn't do it. Tabs will lower the bow, not lift it. As for sailing I dont think they will do anything.
Mike

[Crikey]

Tabs will plow the bow more, or do nothing if adjusted all the way up. Like what was said already, the bow already rides a tad low at most speeds.
when you plane you want the bow up some, with the bow now riding even lower than before with the tabs, your going to put your boat in a potential dangerous situation at speeds. Even the power trim on my 115hp will not lift the bow much, so I wouldn't do it. Tabs will lower the bow, not lift it. As for sailing I dont think they will do anything.
Mike

Highlander - that's the one.

Mike, I agree with you to some extent about operating at speed, with the bow too low. However the idea is to level the hull more than raise the stern above the bow. Practically every video I've seen of the Mac at speed is with the nose far too high, trying desperately to climb over the bow (or midrif) wave. I think this is why we've seen so many posts on this board about whether the hull is actually even planing with the recommended factory horsepower, or barging.
The interesting thing about these types is that they auto adjust according to the loading, and the range of adjustments available seem to allow a great range of tunability (not the fish!). I can't quite fathom how your bow could be so low to begin with unless you've overloaded this area to compensate for what must be a very heavy (but good!) engine. That much power should be able to trim you through a back flip..... My 60hp can trim the boat through a very wide range - still the idea is to help the bottom glide better, while keeping the engine thrust pointed in an optimum direction for speed, and fuel efficiency.
You could still be right about the amount of effective help achieved, as the whale bellied hull still allows too much water to displace laterally at speed for a solid locked plane. Strategically placed 'smart rails' http://www.thesmartrail.com/
may alleviate that, but that's another post, for another day!

Ross

[aya16]

All you can do is try, when I said my 115 will hardly raise the bow with the power trim, that's with full ballast, sadly or good I don't know, but my engine will push the mac with full ballast at around 24mph, that's not full throttle though. So the need to empty the ballast hasn't come up, although in calm water the mac should really plane well without the ballast. That compared to 8mph with my old 50, full ballast.

I think you hit it right, those videos of the mac riding high in front under full throttle with a 50 I believe is the boat trying to get over its bow wave, so not really planing. My old 50 used to get over the bow wave sometimes briefly and the rpm's would raise, the boat felt faster, and more stable. This only lasted a few seconds and the boat would go back to trying to get over the bow wave. I don't think trim tabs will help, but try it and see. The X with the flatter hull would plane better at those 50 speeds, than the M with the rounded bottom.

Slap a 90+ hp engine on the M or X and its a game changer. the M anyway will ride really nice at speed, no pounding, no jumping wakes, or falling into holes.
she will spray though. very nice riding boat in swells.

I'm convinced that the almost plane that the mac does with the smaller engines, can only be overcome, with either a stripped boat or a larger engine.
to be realistic and give Mac their do, those engines we run are made for small run abouts, that perform great in those boats, mac designed a boat that will almost plane with those dinky engines, that's a big deal, getting the performance we get in a 26 foot boat.

I believe any mod made to the boat, trying different props, even a miracle mod, will only get a mile or two out of that 50-60 engine, in the case of the etec 60, that's a big improvement, best we 50 owners can expect is maybe get the boat to 16mph or so. The only thing that will give people the performance they seek is more hp.
Like in my case, my prop doesn't have to be perfect, I can run at planeing speeds with full ballast, and burn less gas at mid throttle compared to a 50hp at full throttle, and achieve the same or better performance.

I do not recommend the merc 125, 115, or 90 optimax, as that motor is massive, weight is ok, but the motor will barley fit the mac. I beefed up the transom a lot too. The motor looks big but doesn't weigh that much, when I first put the mac in the water with that 115 I thought the boat would ride level sitting at the dock, nope she didn't budge, same water line as before, and I have nothing in the bow bunks to speak of.

If we want the perfect ride at plane with a big motor, we need to glass the bottom of our M, to a flat step about four feet stern to bow, that will give the mac a planing step. I'm not doing that because i'm happy with the boat now, spray rails like you showed, I would consider instead.

I dont want to push the mac, any way, factory mac, says the boat will do well at 24mph, although my engine could push the mac to speeds of way over 30mph.
Im happy with 24-25. That and keeping the boat at what the factory top speeds, will keep Mike Ingmon from losing to much hair. But its good to know my boat will do well over 25mph. Saved for times I have to outrun, white sharks, killer whales and such.

There are two boats here, with the M. Those that run 50-60hp, and those that run 70+hp. The mac turns into a whole other boat at speeds with the extra hp, and considering, Like my engine, designed for boats in the 16-18 foot class, does a hull of a job on our 26 foot boats. I'm slinging a 15 inch pitch large dia. prop that will redline on my boat with a full ballast tank, doing the math I should get 34-35 mph, never have yet, never tried. I could probably get away with running a 16-17 inch pitch prop, wont redline with full ballast, but might with empty ballast. But I'm happy with the 15, although I could probably pull a single skier up from a deep water start. As I lay the throttle down, full ballast my boat gets on plane quick,and will rev out fast as the boat speed keeps climbing, I back off before the boat hits max speed.

Sorry for jumping in with the performance of my boat, It just solved all the little problems of a little more speed I used to have with my little 50hp, by jumping up my hp. The boat ride is better, the steering isn't fought anymore, the prop doesn't blow out any more, Its just a great mod. As far as sailing, I cant tell the difference as before, she still sails well, and that's what I do most of the time anyway...Gotta love the mac's.
Mike

[aya16]

oooppps

[Crikey]

Great reply Mike

You're logic about motor size is right on, and the source of much envy on my part. I'm very happy with my Suzy DF60A from a technological standpoint but, looking back I wish I'd had been able to afford a bigger bag of cojones when I put my package together. Perhaps this freudian angst is what continues to drive my quest for this holy grail (mod's - this is not discussing religion!).
I had thought earlier about your mention of a step, and in a small way think a rear tab might give some similar benefits without resorting to such a major hull modification which would probably seriously affect sailing pointing. That step, and chines, are of course the common element of any dedicated planing powerboat design, regardless of size. Though the Mac is a hybrid the greatest side of Rogers interest lay with its sailing aspect and the power range had to come second to that. I understand that.
What took me to the 'Smart Rails' was an earlier posting on this board (Ixneigh?) who had glassed on skegs for better directional pointing. It seemed to me these would act as chines somewhat and channel the water rearward, instead of displacing sideways, like I mentioned previously. I had a different approach than him, for a different reason. I still think the rails could simulate this with much less interference to beaching and water resistance, but their outrageous pricing will probably never let me go there. Maybe someone will come up with a competing design that I haven't managed to find yet.

Regards ..... Ross

[uanhanlouee]

On the 50 and 60 try Doel Fins on the cavitation plate. They make a difference.
On anything over 70 hp try Lenco 12x12 or 12 x 14 trim tabs. trim tabs make quite a difference on large underpowered cabin cruisers by allowing boat to rise over the bow waver and lowering bow for proper level trim.

[uanhanlouee]

On the 50 and 60 try Doel Fins on the cavitation plate. They make a difference.
On anything over 70 hp try Lenco 12x12 or 12 x 14 trim tabs. trim tabs make quite a difference on large underpowered cabin cruisers by allowing boat to rise over the bow waver and lowering bow for proper level trim.

[Crikey]

On the 50 and 60 try Doel Fins on the cavitation plate. They make a difference.
On anything over 70 hp try Lenco 12x12 or 12 x 14 trim tabs. trim tabs make quite a difference on large underpowered cabin cruisers by allowing boat to rise over the bow waver and lowering bow for proper level trim.

Got one! This works very well for more and I chose it over the Doels, and other types, more for the advantages of directed thrust though the lift and stability it provides are noticeable too. I made a choice to get the 'senior' model based on my hunch that the Mac's size and weight could work better with it. The hardest part was having to ignore the enormous amount of negative comments, made mostly by people who had no direct experience with them, on the various boards around the web. I would concede that it possibly might knock a half knot or so off the top end, but that's wot country and not the operating range I'm mainly concerned with. I'll have a better answer to that when the 'big speedo' (another post) comes along - finally.

Your info about trim tab size is a little wrong, I thought. Aren't they more related to hull type and aft weight than horsepower ratings? For it's size and weight I think the Mac is pretty svelt and in my case, and in combination with the outboard foil, the two systems should be complementary (I hope!). I really like the automatic aspect if the Nauticus type, along with the other adjustability options.
Ideally - and this may be more pipe dream than reality - I think two inboard, and two outboard of the rudder positions might work fairly well. Going to have to hide the cost of that one from the Admiral though!

Ross

[dlandersson]

Are there any trim tabs/power thrusters that don't require drilling, etc., in order to mount them?

I'm thinking of doing a winter mod of putting smart tabs (Nauticus SX type) on the stern of my for a winter mod project. Has anybody explored this subject already?

[Crikey]

Your looking at one.
http://www.buzzillions.com/reviews/mari ... er-reviews
(sorry I didn't do the company site)
The drill less type was another reason I went for this model type. If you follow other general web inquiry's you'll see the biggest problem encountered is the darn things falling off. I think the company has re-vamped their instructions, and I followed them without anything bad happening this season (so far). Before next year I will have probably worked out some forward strap, or something, just to make sure. Some of the reported losses may possibly have to do with the outboard type as well.
The company gave a warning about hydrofoils in their manual but I think their paranoia was primarily concerned with the lateral wing types and extreme maneuvering. Whatever, They also did the 50hp max caution in the old manual as well - that's sure been overruled!
I'm hoping the combined effects of all my changes can facilitate a stable true plane using my 60hp motor. A little ways to go yet, and it still may not happen in the end, but I'm more than happy with this one!

Ross