Monkey Spanker

One for the bottom guys, I have a 236 Rinker Captiva. At 70mph it handles great with no problems. I put a straight edge on the bottom and there is about 1/8"-3/16" gap (hook) about 16" from the transom. What good or bad will come from removing this? and what kind of speed gain (if any) might I see. Thanks.

Mr Gadgets

Monkey.. I am short on time... but I told a long story about hook a while back... maybe a long while back. Do a search and see if it comes up under my name as a post..
Took out too much hook on a 25' Checkmate and it caused some real problems.. It all depends on why the hook is there.. Usually 1/8" wont hurt anything and unless the bow is heavy.. wont help if it is removed.. if you need a bunch of trim to get the bow up.. It may help. How long was your straight edge... 6-10' should be checked to see the real story..

Hope this helps
Dick

Monkey Spanker

Thanks, I will try the longer one. I am waiting on new Rev 4 23 prop to try. I seem to need alot of trim to carry the bow. This prop seems to be the magic cross between the B-1 and M+.

Mr Gadgets

Hook will force the bow down.. If you can't carry it with a different prop, then maybe removing the hook will help.. it may also affect handling... Like I said see my story ...

Dick

Monkey Spanker

The bottom has four lifting strakes. The two lower center ones stop 67" from the transom. The top two run full length. The keel pad starts way up front and ends at the transom about 5 1/4" wide. The boat leaps on plane, my buddys 22 Scarab will run right beside me, but I'll leave him 100 yards back from a hole shot. It looks as though if I take the transom down the bottom will then have a rocker in it. Would filling in the concave area be best? The strakes do not look to be sharp, more like a normal mold. The boat most likely weighs around 4400 with me and fuel. The motor has 521 hp at 5500 and 560 ft lbs from 4000-4400. It runs right around 70 at 4700 with a 25 m+ , 5000 with a 23 M+ I will be trying a 23 rev 4 hopefully tomorrow. The hp numbers were with dyno headers and no accessarys, so most likely somwhere around 475 at the prop.

onesickpantera

My new boat has a slight hook in the last few inches of the hull and it is SUPPOSED to be there. I've heard of hooks being there that weren't suppose to from pulling the molds, trailers, etc. My boat is small and carries the bow decent but stays relatively flat. I could probably pull a couple more mph if I took it out but it would effect the handling of my boat and I don't want that. My boat needs no trim tabs at all in any water conditions. Runs and flies flat.

My blackhawk had rocker in the hull and going from the blackhawk to the Unlimited is night and day. Yeah, I lost a few mph but I've hit rollers and boat wakes in the Unlimited(which is 3' shorter) trimmed out at WFO that would have been DEADLY in my blackhawk. For a micro boat it tears chit up in rough water and I contribute a lot of that to the hook in the hull design.

If the hook isn't suppose to be there then remove it. If it is suppose to be there then I personally wouldn't.

tcelano

Hook is designed into a hull for some of the purposes listed above, but mainly to achieve stable operation, free from porpoising. There are several ways to stop porpoising at a given speed:

1) shift weight forward
2) deflect trim tabs to give stern lift
3) put in hook to give stern lift
4) install a propeller with more stern lift
5) go faster (in some cases)

As most have probably noticed, at lower speeds (i.e. 40-60mph), you have to run your boat with more tab and/or lower drive trim to keep it from porposiing than you do at high speeds. As you go faster, you can trim it up more, which results in less wetted surface, and a center of pressure location farther aft. If your boat has a lot of hook in it, it means that it was designed to run with a CG position pretty far aft in relation to the intended speed (good for avoiding stuffing the nose). If you repower your boat, and want to go faster, you will benefit from taking some hook out, and you'll have to make up the difference at those lower speeds with tab position, but you'll pick up top end. The hook in the hull is more efficient at generating that stern lift than the tabs are.


Hope that helps, if you want more info on this, search through the archives for my screen name, and you'll find excerpts from a paper I published on the topic, in addition to lots of great discussion from some of the forum members.

Dave M

I hate to sound like a wet blanket, but ......

I would just leave it alone. You are already going faster than that hull was ever intended to go. Hook or no hook, that hull is not very efficient if you are only going 70 with 521 HP. If speed is your goal, I would start by getting a fast hull.

Good luck,
Dave M.

AeroSpeedMarine

i took a hook out of a 29 baja outlaw and all it did was porpus its as s off until it hit 70 then would calm down unless you trimed more then half way. also i didnt pick anything up.

Monkey Spanker

You know boys, drag racing is my backround, and just when I started to think I had a handle on making things go fast....... I always told my buddy, "Bottom Smottom" just make more power and the thing will fly! We went on a poker run on Seneca lake In N.Y., the water was really rough that day, 2-3 foot swells with alot of big rollers. While we got the snot pounded out of us, the boat handled well. Everyone should try riding the prop while the whole boat is out of the water, and climbing higher, at least once.(twice if your underpants are still clean after the first time) My buddy with the 22 Scarab had to slow down while I could keep going fast. Especially when his seat ripped out of the floor when he came down from one of the big rollers(god I wish I could have seen his face!) Thankfully we came home in one piece with a new appreciation for big water boating. I think I'm going to leave this boat alone. The Rev 4 prop I got today works exceptionally well. Brett at BBlades said I would love it and I do. While I don't have any gps numbers yet, it pegged the speedo back to the pin just like the 25+ did, and provided alot more bow lift while doing it. Thanks for the frank advice on the bottom. This place is great for getting both sides of an issue. Now if someone made an intercooler that sits on top of a carb in place of the flame arrester.....................HMM just thinking.