Straight bottom Cig lifting strakes
 

A while back I was interested in some of the discussion regarding the straight bottom cigs and their porpoise issues at higher speeds. Saw guys doing the "wedge" mod to the hull, which I imagine helps keep the bow down and the porpoise under control.

My thought was maybe , rather than try to keep the bow down, maybe something to help keep it "up". I was watching a video of a straight bottom 38 Scarab that had big power in it, the boat ran straight, and dry at higher speed. Watched some videos of straight bottom 38 cigs, and noticed at higher speeds, they often appear to run fairly "wet", and a bit of porpoise. Some you can actually watch the boat lift and then land again on and off the inner strakes over and over. I asked some of the straight bottom scarab guys to measure their inner lifting strakes.

From the edge of the transom, to the end of the inner lifting strake, it was 10ft on the scarabs. On the top gun, it was 14ft. One hull measures 37'7", other measures 37'6", but the scarab has 4ft more lifting strake.

Curious if anyone has ever tried extending the lifting strakes on a straight bottom Cig

This straight bottom 38 scarab had side by side 850-950hp blower motors, #5 drives. Boat ran 108 if i recall.

Tres Martin would be one guy worth talking to about this!!

Am I reading this wrong ? or are the boats flipped ?

From transom edge to end of lifting strake, its 10ft on the scarab. 14ft on cig.

I see, so you're thinking shorter strakes eliminates the porpoise ?

The scarabs have longer strakes, 4ft longer.

Im thinking maybe the cigs with bigger power, are outrunning the short strakes so to speak. The props are lifting the hull off the strakes, but cant hold the boat up very long , so the porpoise starts happening.

We all Know why a 388 hustler is so fast with mild power, they have full length strakes all the way to transom. Or pad bottom hulls.

Prob not a mod for a 70mph top gun, but maybe for the guy shooting for 90 plus ? Idk just thinking out loud

Im confused , on the previous post you said they were 14' on the cig ?

he said 14' from the back of the boat, he is asking if a longer inner lifting strake would make the boat ride out of the water more and less of a wetted surface, the short answer is hydro dynamically speaking, yes it would, but being as the boat would be riding higher the propensity to chine walk and fall to the sides instead of down in the front would be more, also with a longer lifted surface it would change the X dim slightly. I dont think that it would be hard to do, didnt Dan do something like that on his?

Dan didnt extend the inner strakes. First, he had someone remove some of the outer strakes, in therory to let the transom settle. Then he had them put back on, and did that tres martin wedge thing. I think the wedge helped the porpoise.

Speedy, the measurement i am speaking of, is if you take a tape measure, and measure from the transom edge, to the end of the inner lifting strake. the longer the distance, the less strake you have.

https://cimg7.ibsrv.net/gimg/www.off...f43a1adbd8.jpg
https://cimg8.ibsrv.net/gimg/www.off...5cc14a1173.jpg

From what i heard about the 388s, was once you were to put big power in them, the full length strakes didnt handle so well at high speeds. However, with a pair of HP500s, theyd pretty much walk past a top gun with 750s on calm waters.

Prob also why the cigs ride so nice. 14ft from the transom theres nothing but a smooth vee . Minimal horizontal surface to land on off waves.

All clear now, :angry-smiley-038: the distance where there is no strake :flag:

After Joe had me measure mine I made a post on FB about this and what you said was explained to me by a buddy that designed Baja hulls, I am also wondering if it has anything to do with the Cig hull being a "rocker" hull?

rocker is different, a rocker hull is like a "rocking chair" that is designed to allow water to travel up to the drives. and certain cig hulls have it and some don't, many hulls with notch's have none. strakes channel water in a specific direction to achieve lift and aren't displacement type hulls. strakes are designed to work under pressure with speed, as joe had mentioned the lifting strake ending at a certain point stops lifting, to extend it further back it lifts more and would raise the hull further based on speed achieved.

if you stop the vid at :16 it looks like the water starts where the strakes end. (further back then any straight bottom cig.)
If there was a way to add temporary strakes I`d try it.

I`d also like to try lowering my extension boxes vs. putting a spacer in the drives.

The Scarab 38 hull is also a rockered hull as is the Scarab 43. Larry Smith built a non-rockered 43 for Tom Gentry, and it didn't work well at all. That was the first 43 built. I believe they added 3-4" of rocker to that boat to get it to run well. As to the inner chines, not only are the Scarabs longer, I was also told they are wider than that of a 38 Cigarette. So not only does it get better lift, it also makes it more stable. I would also measure the width of the inner strakes between the two boats. If I remember right Larry Smith race Scarabs and production Scarabs had the inner strakes in different locations. I think the race version had them placed closer together.

I think Rookie made some temporary strakes for his Panther. PM him and see what he did.

Just saw a thread about this topic from several years ago, someone else was thinking about doing this to their 38 flatdeck..cignificantother replied

I can see that. On the flip side, sucks when you spend a bunch of money and arent happy with the performance or handling of your boat. Guess is depends what you want out of it

I was about to extend the strakes on the Gun, but bought the Tiger and later sold the Gun. I've been contemplating extending the strakes on the Tiger, as it is a similar set up with #6 Drives. Most of the non-stepped Tigers were rigged with 500 HP and Bravos. Longer strakes seem like a better option than adding a wedge near the transom, as Cigs with #6 Drives have plenty transom lift over 70 mph.

Like the Scarab, the strakes on a 41 Apache appear longer than a 42 Tiger. Supposedly, the addition of a single step on the Apache had very mixed reviews. Some stated the modification possibly helped cruising efficiency below 70mph, but not sure that was ever proven.
https://www.offshoreonly.com/forums/...apache-071.jpg

Check out how the old 39 sutphen runs at the 3:30 mark. 39ft straightbottom . Friend of mine that owns the old 39 Cig raceboat " Long Shot" told me the other day after seeing this thread, that the inner strakes on that boat were extended 80 inches. Strakes end 8ft from transom edge.

hmmmm, wonder if any gains on a slug like mine, I wish there was a easy temp way to do it...

I would be willing to do this as I've considered the "wedge" mod. My boat porpoises noticeably without running tab unless you're accelerating or over 70ish mph. You can always take them off.... hmmm. Glassdave, you busy?

Tim, I doubt the mod would be much worth it unless you were getting over 80mph.

Something to consider.
Tres martin said it would make no difference since the strakes are out of the water when running. Guess they`d have to be extended far enough to be in the water.

For sure @ LOTOhttps://cimg5.ibsrv.net/gimg/www.off...3e16005108.jpg

Yes, but these boats run so deep. I remember your videos of you and Joe (MT) posting about how the water breaks just in front of the windscreen, and on newer, stepped, pads, or other hull designs it's considerably aft of that (hulls that run "on top" of the water). I would never really challenge what Tres says as he has all the experience and knows what he's talking about. I guess the $10-20K question is, who has done it on a Top Gun and has it worked?

Only thing I'd be worried about is undesirable handling, turning at high speeds, chine walk, etc. Is there any concern that the strakes come into play when turning the boat? Is there a "race hull" designed 38 TG with extended strakes? You'd think it would be a common modification on the non-stepped boats with 900+ hp to get these things over 100 mph. What about the 41 Apache, same hull right? There's probably a reason we don't see it done....

Edit: ^^^ that LOTO boat looks like it's coming "out" of the water, not necessarily running, or looking at the average time that the hull is in the water.

question is, is that running shot showing it during a porpoise or simply bouncing off waves? I doubt that its from simply the props carrying the boat like that.

I also think that's a 35', no? And x2 what Joe said.

Judging by the picture in post 33 . you would have to extend the strakes at least 7 feet further back to have any impact .
Then the question become what impact does it have on stability ?
ie. chine walk . RG.

wave bounce, main channel Saturday around noon.......I really don't remember much if any porpoise in this boat running on my home lake in calmer water.

Edit: I would think a high number of these boats that have this issue are not in their original configurations, so the question is, did they porpoise when new ?

Who's boat is that