DaveMarles

Most people would define hook as a concave section in the hull from the transom going forward 4 to 8 " (150 to 180mm) from the transom. This will probably be all the way from keel to chine varying in depth slightly. On a deep V boat with a pronounced V keel line, the keel will probably be OK. This hook will act like big trim tabs, forcing the nose of the boat down causing tremendous drag and erratic steering. The hook is caused by shrinkage of the moulding. Every time you make a mould or make a boat from a mould using polyester, some kind of shrinkage is going to take place and it varies with gel thickness, cloth thickness, resin type, speed of hardening and amount of time a boat is left in the mould. Shrinkage of the main hull near the transom is resisted by the transom itself, which causes the hooking. You cannot stop it. Moulding with carbon fibre might resist it a little but it will still distort. Also a polyester boat is never fully cured and it will distort over a long period of time but usually only a small amount. Some manufacturers will say they have built in certain amounts of hook for trimming/stability etc and they used carbon or kevlar as a reinforcement but its a fallacy. You cannot control the amount of hooking like that and so it will vary from boat to boat. On a sport boat if the original pattern is straight and the mould is made carefully then the hooking will be acceptable for sport use but its still there and it will affect performance. Performance is affected like this..The hooking pushes the nose of the boat down which causes drag and scrubs off speed, also the hooking will not be the same each side and so the boat will try to lean one way or the other. The builder then angles up the strut to get the front of the boat up but actually its also forcing the back down into the water which in itself causes drag although not as much as when the hull is deep in the water.
Hooking can also be present in an epoxy boat but is much less likely especially if the boat is made with a very thin gel in a epoxy carbon or ceramic mould, even then great care must be taken in the way the moulding laid up and the moulding must be fully cured or post cured in an oven. Making an epoxy moulding n a polyester mould is a waste of time because the epoxy mouldings need heat to cure and that heat distorts the polyester mould.
The news is not all bad because the hooking can be filled and sanded to remove it and experienced boat racers will do this although that means the boat will have to be painted to get its good looks back.
If the original plug or pattern for the boat is made very slightly convex near the transom then it is possible to reduce dramatically or virtually eliminate the amount of hook that occurs but in practice I see only one manufacturer of polyester racing boats doing that (not me I only make epoxy racing boats) but I will not name them to protect those who are not using this system plus I have not seen close up every racing boat.
For the kind of boatracing I mainly take part in, the hulls have been epoxy for many years and no one would consider a polyester boat. They are too fragile and too inaccurate for good performance and reasonable life and as they take many hours to put together they are expected to have a racing life of several years in what can be a a contact sport on many occasions.

Dana W

Well said , thanks

martno1fan

Thanks for clearing that up for us Dave very interesting reading!!.

Justaddwata

My Feedback: (3)

On the subject of hull shape / hooking - An interesting addition to a boat I purchased used sometime ago was a built in adjustment screw on the rails near the transom. It is designed to flex the ride surface of the hull similar to trim tabs. I was told this was Rich Ballantines personal boat (though Rich has never confirmed this for me). A lot of work in making it that way and I have yet to run it. Interesting idea though.

Here is the hull (though no inside pics for you yet)

madmodelman

Dave, it's good to read this, I had actually arrived at the same conclusion after adjusting stern drives/trimtabs etc, the symptoms you describe are absolutely correct. That was actually my boat in Wayne's picture. I have to be a bit careful as the hulls are part of a sponsorship thingy so I am in a bit of trouble at the moment. It's nice though that you have confirmed my deepest fears!

mopartybob

LOTS of RESPECT out to you Gary,takes a big guy to go out on the line like that with a sponsorship in the balance,I also have one of these hulls in question,(built-in trim tab)LOL, short of major hull renovation,could'nt you just "skin over" the hook with like a 1\16" ply? i'm still on a learning curve here so please bear with me on my question.......[&:]

martno1fan

would it not be possible to correct the hook by adding some framework inside the hull? i like the idea matt mentioned .Gary can i ask who designed that boat? i know who made it and who sells it etc but arent verns boats all splashed from other designs or has he started designing his own boats now?.it seems a shame a nice looking boat acts like that i hope its a one off and not typical.

madmodelman

Thanks for your comments, I am just sitting here at the moment wondering exactly what to do. It's worse, I have a spare one just finished also!
I will add your idea to my list of possible solutions and post if I can solve, thanks again, Gary.

martno1fan

does the spare one act the same?,if so it puts you in a very awkward position im sorry to hear that.hope you can get it sorted soon mate.

patriktegelberg

I symphatize with your problem. But I can't say that I am very sorry that splashed hulls gets bad credit.

madmodelman

I think it's based on Aeromarines Challenger hull. It's sometimes difficult to know and I don't want to upset anyone but some very reputable hull manufacturers do use other peoples designs, sometimes altered slightly. There is only a limited amount of things you can alter on the actual base hull so it's not really suprising. How many "Challengers" and "Apaches" are on the market just with different decks for example! I hope it's a one or two off also. Regarding framework, the rails are really well put in and very solid, it would be a nightmare I think to attempt it but I am interested in getting as much feedback and as many idea's as possible.
In answer to some members earlier comments, the boat is not heavy, the CG is set up correctly and so is the hardware, my previous boats and results will back that up.

madmodelman

To be fair the second one has not been in the water yet, just finishing off.

mopartybob

Is this a "hook" or what? [:@] the piece of wood is straight as a straight edge by the way....the pics are of the L\R inside\outside chines..... the last picture is what it's currently bein used as since reading this thread.........

madmodelman

Yep, looks about the same, I just measured 2.5mm bow on mine. Is that hull a Cobra? Gary.

mopartybob

yup,cobra 45"gt max......when i went to check on this hook issue,I expected it to be only like 10% of the transom-bow,but DANG !! it stretches to almost 60-65%,that\this is some SERIOUS HOOK!, might be better off making it a HYDROFOIL.............Oh well,live and learn.....as far as correcting it.....tuff one indeed ,but i think the last picture sez it all.....[&o]

wayneuk01

makes a real nice flower pot !!i wonder if the woman would like one ,, nice looking hull though ..but just goes to show Looks Can Be Deceiving

i sure a few of these will pop up on e bay soon but carnt blame u trying to get some money back

DaveMarles

With hook like that over such a large part of the hull it not fixable. Thats really the worse kind of distortion probably caused by moulding off a hooked boat and then remoulding again and again. It just gets worse. It might make a nice static scale model or maybe try a steam engine in it. [sm=72_72.gif]
If the hook is just in the last 6 to 8 inches then it can be filled and flatted but trying to wedge it from in side with bits of wood is not going to be viable.

wayneuk01

. sorry but i nearly bought one but i got advised otherwise thank s to rcu
heres a engine for it

mopartybob

Thanks for trying to RAISE my spirits on this one guyz....[:'(]...LOL....I think I'll keep it as a planter box till my next garage sale.....[:-]

madmodelman

OK, my two stretch over 24"! Dave, looks like the old Apache's out again this year!
That WAS an interesting thread wasn't it! Hey Ho.

patriktegelberg

I set my rails (stringers?) before freeing the boat from the mould. Is this beneficial, or not? I use polyester.

Anbjorn

I am in the finishing stage of my plug for a 170 cm deep V.
I have found that i have a small hook of less than 0.1 mm on the running surface.

My question is: What is the limit to call it a hook?

The first mould will be made out of polyester. I have thought up a way to make the mould adjustable so i can get the correct shape of the finished hull. The boat will be laid up in NM epoxy. Depending on the performance of the boat i will see if it is worth making a better quality mould.

I was also thinking as Patrick mentioned fit the rails during the layup in the mould.

Dana W

Let the boat sit in the mold a few days before setting the rails .

mopartybob

Hey Gary,Dave, I know it may seem like a lost cause with the amount of "hook" thats on these hulls,but Gary,you've already got one runnin,try skinnin the hook out as mentioned earlier,(1\16 ply),I know it's quite a ways from transom to bow,but i'm just a guessin here that it would work,shoot,once up on plane the first 18" will seldom touch water,LOL,what have you got to lose except maybe a few hours tinkering time? GO FOR IT.....[8D]

madmodelman

I really appreciate your comment but the racing season starts in 2 weeks time! Attached some pics to show you how sick I feel at the moment! This morning I dragged my old faithful (Marles) Apache out to get it race prepped. I will take your advice and experiment over the next weeks but I feel it's a lost cause. If I find anything that works I'll keep you informed. The guy on the video and I are going to keep in touch with each other (Wayne's mate) so we'll see. Thanks again, Gary. Makes for an interesting thread though doesn't it, this is what forums should be all about.